Patch attached.
Feng
________________________________________
From: Richard Biener <richard.guent...@gmail.com>
Sent: Wednesday, October 23, 2019 5:04 PM
To: Feng Xue OS
Cc: Michael Matz; Philipp Tomsich; gcc-patches@gcc.gnu.org; Christoph Müllner;
erick.oc...@theobroma-systems.com
Subject: Re: [PATCH V3] Loop split upon semi-invariant condition (PR
tree-optimization/89134)
On Wed, Oct 23, 2019 at 5:36 AM Feng Xue OS <f...@os.amperecomputing.com> wrote:
>
> Michael,
>
> > I've only noticed a couple typos, and one minor remark.
> Typos corrected.
>
> > I just wonder why you duplicated these three loops instead of integrating
> > the real body into the existing LI_FROM_INNERMOST loop. I would have
> > expected your "if (!optimize_loop_for_size_p && split_loop_on_cond)" block
> > to simply be the else block of the existing
> > "if (... conditions for normal loop splitting ...)" block.
> Adjusted to do two kinds of loop-split in same LI_FROM_INNERMOST loop.
>
> > From my perspective it's okay, but you still need the okay of a proper
> > reviewer,
> > for which you might want to state the testing/regression state of this
> > patch relative to trunk.
>
> Richard,
>
> Is it ok to commit this patch? Bootstrap and regression test passed. And for
> performance, we can get about 7% improvement on spec2017 omnetpp with this
> patch.
Can you please provide the corresponding ChangeLog entries as well and
attach the patch? It seems to be garbled by some encoding.
Thanks,
Richard.
> Thanks,
> Feng
>
> ---
> diff --git a/gcc/doc/invoke.texi b/gcc/doc/invoke.texi
> index 1407d019d14..d41e5aa0215 100644
> --- a/gcc/doc/invoke.texi
> +++ b/gcc/doc/invoke.texi
> @@ -11481,6 +11481,19 @@ The maximum number of branches unswitched in a
> single loop.
> @item lim-expensive
> The minimum cost of an expensive expression in the loop invariant motion.
>
> +@item max-loop-cond-split-insns
> +In a loop, if a branch of a conditional statement is selected since certain
> +loop iteration, any operand that contributes to computation of the
> conditional
> +expression remains unchanged in all following iterations, the statement is
> +semi-invariant, upon which we can do a kind of loop split transformation.
> +@option{max-loop-cond-split-insns} controls maximum number of insns to be
> +added due to loop split on semi-invariant conditional statement.
> +
> +@item min-loop-cond-split-prob
> +When FDO profile information is available, @option{min-loop-cond-split-prob}
> +specifies minimum threshold for probability of semi-invariant condition
> +statement to trigger loop split.
> +
> @item iv-consider-all-candidates-bound
> Bound on number of candidates for induction variables, below which
> all candidates are considered for each use in induction variable
> diff --git a/gcc/params.def b/gcc/params.def
> index 322c37f8b96..73b59f7465e 100644
> --- a/gcc/params.def
> +++ b/gcc/params.def
> @@ -415,6 +415,20 @@ DEFPARAM(PARAM_MAX_UNSWITCH_LEVEL,
> "The maximum number of unswitchings in a single loop.",
> 3, 0, 0)
>
> +/* The maximum number of increased insns due to loop split on semi-invariant
> + condition statement. */
> +DEFPARAM(PARAM_MAX_LOOP_COND_SPLIT_INSNS,
> + "max-loop-cond-split-insns",
> + "The maximum number of insns to be added due to loop split on "
> + "semi-invariant condition statement.",
> + 100, 0, 0)
> +
> +DEFPARAM(PARAM_MIN_LOOP_COND_SPLIT_PROB,
> + "min-loop-cond-split-prob",
> + "The minimum threshold for probability of semi-invariant condition "
> + "statement to trigger loop split.",
> + 30, 0, 100)
> +
> /* The maximum number of insns in loop header duplicated by the copy loop
> headers pass. */
> DEFPARAM(PARAM_MAX_LOOP_HEADER_INSNS,
>
> diff --git a/gcc/testsuite/g++.dg/tree-ssa/loop-cond-split-1.C
> b/gcc/testsuite/g++.dg/tree-ssa/loop-cond-split-1.C
> new file mode 100644
> index 00000000000..51f9da22fc7
> --- /dev/null
> +++ b/gcc/testsuite/g++.dg/tree-ssa/loop-cond-split-1.C
> @@ -0,0 +1,33 @@
> +/* { dg-do compile } */
> +/* { dg-options "-O3 -fdump-tree-lsplit-details" } */
> +
> +#include <string>
> +#include <map>
> +
> +using namespace std;
> +
> +class A
> +{
> +public:
> + bool empty;
> + void set (string s);
> +};
> +
> +class B
> +{
> + map<int, string> m;
> + void f ();
> +};
> +
> +extern A *ga;
> +
> +void B::f ()
> +{
> + for (map<int, string>::iterator iter = m.begin (); iter != m.end ();
> ++iter)
> + {
> + if (ga->empty)
> + ga->set (iter->second);
> + }
> +}
> +
> +/* { dg-final { scan-tree-dump-times "split loop 1 at branch" 1 "lsplit" } }
> */
> diff --git a/gcc/testsuite/gcc.dg/tree-ssa/loop-cond-split-1.c
> b/gcc/testsuite/gcc.dg/tree-ssa/loop-cond-split-1.c
> new file mode 100644
> index 00000000000..bbd522d6bcd
> --- /dev/null
> +++ b/gcc/testsuite/gcc.dg/tree-ssa/loop-cond-split-1.c
> @@ -0,0 +1,23 @@
> +/* { dg-do compile } */
> +/* { dg-options "-O3 -fdump-tree-lsplit-details" } */
> +
> +__attribute__((pure)) __attribute__((noinline)) int inc (int i)
> +{
> + return i + 1;
> +}
> +
> +extern int do_something (void);
> +extern int b;
> +
> +void test(int n)
> +{
> + int i;
> +
> + for (i = 0; i < n; i = inc (i))
> + {
> + if (b)
> + b = do_something();
> + }
> +}
> +
> +/* { dg-final { scan-tree-dump-times "split loop 1 at branch" 1 "lsplit" } }
> */
> diff --git a/gcc/tree-ssa-loop-split.c b/gcc/tree-ssa-loop-split.c
> index f5f083384bc..5cffd4bb508 100644
> --- a/gcc/tree-ssa-loop-split.c
> +++ b/gcc/tree-ssa-loop-split.c
> @@ -32,7 +32,10 @@ along with GCC; see the file COPYING3. If not see
> #include "tree-ssa-loop.h"
> #include "tree-ssa-loop-manip.h"
> #include "tree-into-ssa.h"
> +#include "tree-inline.h"
> +#include "tree-cfgcleanup.h"
> #include "cfgloop.h"
> +#include "params.h"
> #include "tree-scalar-evolution.h"
> #include "gimple-iterator.h"
> #include "gimple-pretty-print.h"
> @@ -40,7 +43,9 @@ along with GCC; see the file COPYING3. If not see
> #include "gimple-fold.h"
> #include "gimplify-me.h"
>
> -/* This file implements loop splitting, i.e. transformation of loops like
> +/* This file implements two kinds of loop splitting.
> +
> + One transformation of loops like:
>
> for (i = 0; i < 100; i++)
> {
> @@ -487,8 +492,9 @@ compute_new_first_bound (gimple_seq *stmts, class
> tree_niter_desc *niter,
> single exit of LOOP. */
>
> static bool
> -split_loop (class loop *loop1, class tree_niter_desc *niter)
> +split_loop (class loop *loop1)
> {
> + class tree_niter_desc niter;
> basic_block *bbs;
> unsigned i;
> bool changed = false;
> @@ -496,8 +502,28 @@ split_loop (class loop *loop1, class tree_niter_desc
> *niter)
> tree border = NULL_TREE;
> affine_iv iv;
>
> + if (!single_exit (loop1)
> + /* ??? We could handle non-empty latches when we split the latch edge
> + (not the exit edge), and put the new exit condition in the new
> block.
> + OTOH this executes some code unconditionally that might have been
> + skipped by the original exit before. */
> + || !empty_block_p (loop1->latch)
> + || !easy_exit_values (loop1)
> + || !number_of_iterations_exit (loop1, single_exit (loop1), &niter,
> + false, true)
> + || niter.cmp == ERROR_MARK
> + /* We can't yet handle loops controlled by a != predicate. */
> + || niter.cmp == NE_EXPR)
> + return false;
> +
> bbs = get_loop_body (loop1);
>
> + if (!can_copy_bbs_p (bbs, loop1->num_nodes))
> + {
> + free (bbs);
> + return false;
> + }
> +
> /* Find a splitting opportunity. */
> for (i = 0; i < loop1->num_nodes; i++)
> if ((guard_iv = split_at_bb_p (loop1, bbs[i], &border, &iv)))
> @@ -505,8 +531,8 @@ split_loop (class loop *loop1, class tree_niter_desc
> *niter)
> /* Handling opposite steps is not implemented yet. Neither
> is handling different step sizes. */
> if ((tree_int_cst_sign_bit (iv.step)
> - != tree_int_cst_sign_bit (niter->control.step))
> - || !tree_int_cst_equal (iv.step, niter->control.step))
> + != tree_int_cst_sign_bit (niter.control.step))
> + || !tree_int_cst_equal (iv.step, niter.control.step))
> continue;
>
> /* Find a loop PHI node that defines guard_iv directly,
> @@ -575,7 +601,7 @@ split_loop (class loop *loop1, class tree_niter_desc
> *niter)
> Compute the new bound for the guarding IV and patch the
> loop exit to use it instead of original IV and bound. */
> gimple_seq stmts = NULL;
> - tree newend = compute_new_first_bound (&stmts, niter, border,
> + tree newend = compute_new_first_bound (&stmts, &niter, border,
> guard_code, guard_init);
> if (stmts)
> gsi_insert_seq_on_edge_immediate (loop_preheader_edge (loop1),
> @@ -612,6 +638,722 @@ split_loop (class loop *loop1, class tree_niter_desc
> *niter)
> return changed;
> }
>
> +/* Another transformation of loops like:
> +
> + for (i = INIT (); CHECK (i); i = NEXT ())
> + {
> + if (expr (a_1, a_2, ..., a_n)) // expr is pure
> + a_j = ...; // change at least one a_j
> + else
> + S; // not change any a_j
> + }
> +
> + into:
> +
> + for (i = INIT (); CHECK (i); i = NEXT ())
> + {
> + if (expr (a_1, a_2, ..., a_n))
> + a_j = ...;
> + else
> + {
> + S;
> + i = NEXT ();
> + break;
> + }
> + }
> +
> + for (; CHECK (i); i = NEXT ())
> + {
> + S;
> + }
> +
> + */
> +
> +/* Data structure to hold temporary information during loop split upon
> + semi-invariant conditional statement. */
> +class split_info {
> +public:
> + /* Array of all basic blocks in a loop, returned by get_loop_body(). */
> + basic_block *bbs;
> +
> + /* All memory store/clobber statements in a loop. */
> + auto_vec<gimple *> memory_stores;
> +
> + /* Whether above memory stores vector has been filled. */
> + int need_init;
> +
> + split_info () : bbs (NULL), need_init (true) { }
> +
> + ~split_info ()
> + {
> + if (bbs)
> + free (bbs);
> + }
> +};
> +
> +/* Find all statements with memory-write effect in LOOP, including memory
> + store and non-pure function call, and keep those in a vector. This work
> + is only done one time, for the vector should be constant during analysis
> + stage of semi-invariant condition. */
> +
> +static void
> +find_vdef_in_loop (struct loop *loop)
> +{
> + split_info *info = (split_info *) loop->aux;
> + gphi *vphi = get_virtual_phi (loop->header);
> +
> + /* Indicate memory store vector has been filled. */
> + info->need_init = false;
> +
> + /* If loop contains memory operation, there must be a virtual PHI node in
> + loop header basic block. */
> + if (vphi == NULL)
> + return;
> +
> + /* All virtual SSA names inside the loop are connected to be a cyclic
> + graph via virtual PHI nodes. The virtual PHI node in loop header just
> + links the first and the last virtual SSA names, by using the last as
> + PHI operand to define the first. */
> + const edge latch = loop_latch_edge (loop);
> + const tree first = gimple_phi_result (vphi);
> + const tree last = PHI_ARG_DEF_FROM_EDGE (vphi, latch);
> +
> + /* The virtual SSA cyclic graph might consist of only one SSA name, who
> + is defined by itself.
> +
> + .MEM_1 = PHI <.MEM_2(loop entry edge), .MEM_1(latch edge)>
> +
> + This means the loop contains only memory loads, so we can skip it. */
> + if (first == last)
> + return;
> +
> + auto_vec<gimple *> other_stores;
> + auto_vec<tree> worklist;
> + auto_bitmap visited;
> +
> + bitmap_set_bit (visited, SSA_NAME_VERSION (first));
> + bitmap_set_bit (visited, SSA_NAME_VERSION (last));
> + worklist.safe_push (last);
> +
> + do
> + {
> + tree vuse = worklist.pop ();
> + gimple *stmt = SSA_NAME_DEF_STMT (vuse);
> +
> + /* We mark the first and last SSA names as visited at the beginning,
> + and reversely start the process from the last SSA name towards the
> + first, which ensures that this do-while will not touch SSA names
> + defined outside of the loop. */
> + gcc_assert (gimple_bb (stmt)
> + && flow_bb_inside_loop_p (loop, gimple_bb (stmt)));
> +
> + if (gimple_code (stmt) == GIMPLE_PHI)
> + {
> + gphi *phi = as_a <gphi *> (stmt);
> +
> + for (unsigned i = 0; i < gimple_phi_num_args (phi); ++i)
> + {
> + tree arg = gimple_phi_arg_def (stmt, i);
> +
> + if (bitmap_set_bit (visited, SSA_NAME_VERSION (arg)))
> + worklist.safe_push (arg);
> + }
> + }
> + else
> + {
> + tree prev = gimple_vuse (stmt);
> +
> + /* Non-pure call statement is conservatively assumed to impact all
> + memory locations. So place call statements ahead of other memory
> + stores in the vector with an idea of of using them as shortcut
> + terminators to memory alias analysis. */
> + if (gimple_code (stmt) == GIMPLE_CALL)
> + info->memory_stores.safe_push (stmt);
> + else
> + other_stores.safe_push (stmt);
> +
> + if (bitmap_set_bit (visited, SSA_NAME_VERSION (prev)))
> + worklist.safe_push (prev);
> + }
> + } while (!worklist.is_empty ());
> +
> + info->memory_stores.safe_splice (other_stores);
> +}
> +
> +
> +/* Given STMT, memory load or pure call statement, check whether it is
> impacted
> + by some memory store in LOOP, excluding trace starting from SKIP_HEAD (the
> + trace is composed of SKIP_HEAD and those basic block dominated by it,
> always
> + corresponds to one branch of a conditional statement). If SKIP_HEAD is
> + NULL, all basic blocks of LOOP are checked. */
> +
> +static bool
> +vuse_semi_invariant_p (struct loop *loop, gimple *stmt,
> + const_basic_block skip_head)
> +{
> + split_info *info = (split_info *) loop->aux;
> +
> + /* Collect memory store/clobber statements if have not do that. */
> + if (info->need_init)
> + find_vdef_in_loop (loop);
> +
> + tree rhs = is_gimple_assign (stmt) ? gimple_assign_rhs1 (stmt) : NULL_TREE;
> + ao_ref ref;
> + gimple *store;
> + unsigned i;
> +
> + ao_ref_init (&ref, rhs);
> +
> + FOR_EACH_VEC_ELT (info->memory_stores, i, store)
> + {
> + /* Skip basic blocks dominated by SKIP_HEAD, if non-NULL. */
> + if (skip_head
> + && dominated_by_p (CDI_DOMINATORS, gimple_bb (store), skip_head))
> + continue;
> +
> + if (!ref.ref || stmt_may_clobber_ref_p_1 (store, &ref))
> + return false;
> + }
> +
> + return true;
> +}
> +
> +/* Forward declaration. */
> +
> +static bool
> +stmt_semi_invariant_p (struct loop *loop, gimple *stmt,
> + const_basic_block skip_head);
> +
> +/* Suppose one condition branch, led by SKIP_HEAD, is not executed since
> + certain iteration of LOOP, check whether an SSA name (NAME) remains
> + unchanged in next iteration. We call this characteristic semi-
> + invariantness. SKIP_HEAD might be NULL, if so, nothing excluded, all
> + basic blocks and control flows in the loop will be considered. If non-
> + NULL, SSA name to check is supposed to be defined before SKIP_HEAD. */
> +
> +static bool
> +ssa_semi_invariant_p (struct loop *loop, const tree name,
> + const_basic_block skip_head)
> +{
> + gimple *def = SSA_NAME_DEF_STMT (name);
> + const_basic_block def_bb = gimple_bb (def);
> +
> + /* An SSA name defined outside a loop is definitely semi-invariant. */
> + if (!def_bb || !flow_bb_inside_loop_p (loop, def_bb))
> + return true;
> +
> + if (gimple_code (def) == GIMPLE_PHI)
> + {
> + /* For PHI node that is not in loop header, its source operands should
> + be defined inside the loop, which are seen as loop variant. */
> + if (def_bb != loop->header || !skip_head)
> + return false;
> +
> + const_edge latch = loop_latch_edge (loop);
> + tree from = PHI_ARG_DEF_FROM_EDGE (as_a <gphi *> (def), latch);
> +
> + /* A PHI node in loop header contains two source operands, one is
> + initial value, the other is the copy of last iteration through loop
> + latch, we call it latch value. From the PHI node to definition
> + of latch value, if excluding branch trace from SKIP_HEAD, there
> + is no definition of other version of same variable, SSA name defined
> + by the PHI node is semi-invariant.
> +
> + loop entry
> + | .--- latch ---.
> + | | |
> + v v |
> + x_1 = PHI <x_0, x_3> |
> + | |
> + v |
> + .------- if (cond) -------. |
> + | | |
> + | [ SKIP ] |
> + | | |
> + | x_2 = ... |
> + | | |
> + '---- T ---->.<---- F ----' |
> + | |
> + v |
> + x_3 = PHI <x_1, x_2> |
> + | |
> + '----------------------'
> +
> + Suppose in certain iteration, execution flow in above graph goes
> + through true branch, which means that one source value to define
> + x_3 in false branch (x2) is skipped, x_3 only comes from x_1, and
> + x_1 in next iterations is defined by x_3, we know that x_1 will
> + never changed if COND always chooses true branch from then on. */
> +
> + while (from != name)
> + {
> + /* A new value comes from a CONSTANT. */
> + if (TREE_CODE (from) != SSA_NAME)
> + return false;
> +
> + gimple *stmt = SSA_NAME_DEF_STMT (from);
> + const_basic_block bb = gimple_bb (stmt);
> +
> + /* A new value comes from outside of loop. */
> + if (!bb || !flow_bb_inside_loop_p (loop, bb))
> + return false;
> +
> + from = NULL_TREE;
> +
> + if (gimple_code (stmt) == GIMPLE_PHI)
> + {
> + gphi *phi = as_a <gphi *> (stmt);
> +
> + for (unsigned i = 0; i < gimple_phi_num_args (phi); ++i)
> + {
> + const_edge e = gimple_phi_arg_edge (phi, i);
> +
> + /* Don't consider redefinitions in excluded basic blocks.
> */
> + if (!dominated_by_p (CDI_DOMINATORS, e->src, skip_head))
> + {
> + /* There are more than one source operands that can
> + provide value to the SSA name, it is variant. */
> + if (from)
> + return false;
> +
> + from = gimple_phi_arg_def (phi, i);
> + }
> + }
> + }
> + else if (gimple_code (stmt) == GIMPLE_ASSIGN)
> + {
> + /* For simple value copy, check its rhs instead. */
> + if (gimple_assign_ssa_name_copy_p (stmt))
> + from = gimple_assign_rhs1 (stmt);
> + }
> +
> + /* Any other kind of definition is deemed to introduce a new value
> + to the SSA name. */
> + if (!from)
> + return false;
> + }
> + return true;
> + }
> +
> + /* Value originated from volatile memory load or return of normal (non-
> + const/pure) call should not be treated as constant in each iteration.
> */
> + if (gimple_has_side_effects (def))
> + return false;
> +
> + /* Check if any memory store may kill memory load at this place. */
> + if (gimple_vuse (def) && !vuse_semi_invariant_p (loop, def, skip_head))
> + return false;
> +
> + /* Check operands of definition statement of the SSA name. */
> + return stmt_semi_invariant_p (loop, def, skip_head);
> +}
> +
> +/* Check whether STMT is semi-invariant in LOOP, iff all its operands are
> + semi-invariant. Trace composed of basic block SKIP_HEAD and basic blocks
> + dominated by it are excluded from the loop. */
> +
> +static bool
> +stmt_semi_invariant_p (struct loop *loop, gimple *stmt,
> + const_basic_block skip_head)
> +{
> + ssa_op_iter iter;
> + tree use;
> +
> + /* Although operand of a statement might be SSA name, CONSTANT or VARDECL,
> + here we only need to check SSA name operands. This is because check on
> + VARDECL operands, which involve memory loads, must have been done
> + prior to invocation of this function in vuse_semi_invariant_p. */
> + FOR_EACH_SSA_TREE_OPERAND (use, stmt, iter, SSA_OP_USE)
> + {
> + if (!ssa_semi_invariant_p (loop, use, skip_head))
> + return false;
> + }
> +
> + return true;
> +}
> +
> +/* Determine when conditional statement never transfers execution to one of
> its
> + branch, whether we can remove the branch's leading basic block (BRANCH_BB)
> + and those basic blocks dominated by BRANCH_BB. */
> +
> +static bool
> +branch_removable_p (basic_block branch_bb)
> +{
> + if (single_pred_p (branch_bb))
> + return true;
> +
> + edge e;
> + edge_iterator ei;
> +
> + FOR_EACH_EDGE (e, ei, branch_bb->preds)
> + {
> + if (dominated_by_p (CDI_DOMINATORS, e->src, branch_bb))
> + continue;
> +
> + if (dominated_by_p (CDI_DOMINATORS, branch_bb, e->src))
> + continue;
> +
> + /* The branch can be reached from opposite branch, or from some
> + statement not dominated by the conditional statement. */
> + return false;
> + }
> +
> + return true;
> +}
> +
> +/* Find out which branch of a conditional statement (COND) is invariant in
> the
> + execution context of LOOP. That is: once the branch is selected in
> certain
> + iteration of the loop, any operand that contributes to computation of the
> + conditional statement remains unchanged in all following iterations. */
> +
> +static edge
> +get_cond_invariant_branch (struct loop *loop, gcond *cond)
> +{
> + basic_block cond_bb = gimple_bb (cond);
> + basic_block targ_bb[2];
> + bool invar[2];
> + unsigned invar_checks;
> +
> + for (unsigned i = 0; i < 2; i++)
> + {
> + targ_bb[i] = EDGE_SUCC (cond_bb, i)->dest;
> +
> + /* One branch directs to loop exit, no need to perform loop split upon
> + this conditional statement. Firstly, it is trivial if the exit
> branch
> + is semi-invariant, for the statement is just to break loop.
> Secondly,
> + if the opposite branch is semi-invariant, it means that the statement
> + is real loop-invariant, which is covered by loop unswitch. */
> + if (!flow_bb_inside_loop_p (loop, targ_bb[i]))
> + return NULL;
> + }
> +
> + invar_checks = 0;
> +
> + for (unsigned i = 0; i < 2; i++)
> + {
> + invar[!i] = false;
> +
> + if (!branch_removable_p (targ_bb[i]))
> + continue;
> +
> + /* Given a semi-invariant branch, if its opposite branch dominates
> + loop latch, it and its following trace will only be executed in
> + final iteration of loop, namely it is not part of repeated body
> + of the loop. Similar to the above case that the branch is loop
> + exit, no need to split loop. */
> + if (dominated_by_p (CDI_DOMINATORS, loop->latch, targ_bb[i]))
> + continue;
> +
> + invar[!i] = stmt_semi_invariant_p (loop, cond, targ_bb[i]);
> + invar_checks++;
> + }
> +
> + /* With both branches being invariant (handled by loop unswitch) or
> + variant is not what we want. */
> + if (invar[0] ^ !invar[1])
> + return NULL;
> +
> + /* Found a real loop-invariant condition, do nothing. */
> + if (invar_checks < 2 && stmt_semi_invariant_p (loop, cond, NULL))
> + return NULL;
> +
> + return EDGE_SUCC (cond_bb, (unsigned) invar[1]);
> +}
> +
> +/* Calculate increased code size measured by estimated insn number if
> applying
> + loop split upon certain branch (BRANCH_EDGE) of a conditional statement.
> */
> +
> +static int
> +compute_added_num_insns (struct loop *loop, const_edge branch_edge)
> +{
> + basic_block cond_bb = branch_edge->src;
> + unsigned branch = EDGE_SUCC (cond_bb, 1) == branch_edge;
> + basic_block opposite_bb = EDGE_SUCC (cond_bb, !branch)->dest;
> + basic_block *bbs = ((split_info *) loop->aux)->bbs;
> + int num = 0;
> +
> + for (unsigned i = 0; i < loop->num_nodes; i++)
> + {
> + /* Do no count basic blocks only in opposite branch. */
> + if (dominated_by_p (CDI_DOMINATORS, bbs[i], opposite_bb))
> + continue;
> +
> + num += estimate_num_insns_seq (bb_seq (bbs[i]), &eni_size_weights);
> + }
> +
> + /* It is unnecessary to evaluate expression of the conditional statement
> + in new loop that contains only invariant branch. This expression should
> + be constant value (either true or false). Exclude code size of insns
> + that contribute to computation of the expression. */
> +
> + auto_vec<gimple *> worklist;
> + hash_set<gimple *> removed;
> + gimple *stmt = last_stmt (cond_bb);
> +
> + worklist.safe_push (stmt);
> + removed.add (stmt);
> + num -= estimate_num_insns (stmt, &eni_size_weights);
> +
> + do
> + {
> + ssa_op_iter opnd_iter;
> + use_operand_p opnd_p;
> +
> + stmt = worklist.pop ();
> + FOR_EACH_PHI_OR_STMT_USE (opnd_p, stmt, opnd_iter, SSA_OP_USE)
> + {
> + tree opnd = USE_FROM_PTR (opnd_p);
> +
> + if (TREE_CODE (opnd) != SSA_NAME || SSA_NAME_IS_DEFAULT_DEF (opnd))
> + continue;
> +
> + gimple *opnd_stmt = SSA_NAME_DEF_STMT (opnd);
> + use_operand_p use_p;
> + imm_use_iterator use_iter;
> +
> + if (removed.contains (opnd_stmt)
> + || !flow_bb_inside_loop_p (loop, gimple_bb (opnd_stmt)))
> + continue;
> +
> + FOR_EACH_IMM_USE_FAST (use_p, use_iter, opnd)
> + {
> + gimple *use_stmt = USE_STMT (use_p);
> +
> + if (!is_gimple_debug (use_stmt) && !removed.contains (use_stmt))
> + {
> + opnd_stmt = NULL;
> + break;
> + }
> + }
> +
> + if (opnd_stmt)
> + {
> + worklist.safe_push (opnd_stmt);
> + removed.add (opnd_stmt);
> + num -= estimate_num_insns (opnd_stmt, &eni_size_weights);
> + }
> + }
> + } while (!worklist.is_empty ());
> +
> + gcc_assert (num >= 0);
> + return num;
> +}
> +
> +/* Find out loop-invariant branch of a conditional statement (COND) if it
> has,
> + and check whether it is eligible and profitable to perform loop split upon
> + this branch in LOOP. */
> +
> +static edge
> +get_cond_branch_to_split_loop (struct loop *loop, gcond *cond)
> +{
> + edge invar_branch = get_cond_invariant_branch (loop, cond);
> +
> + if (!invar_branch)
> + return NULL;
> +
> + profile_probability prob = invar_branch->probability;
> +
> + /* When accurate profile information is available, and execution
> + frequency of the branch is too low, just let it go. */
> + if (prob.reliable_p ())
> + {
> + int thres = PARAM_VALUE (PARAM_MIN_LOOP_COND_SPLIT_PROB);
> +
> + if (prob < profile_probability::always ().apply_scale (thres, 100))
> + return NULL;
> + }
> +
> + /* Add a threshold for increased code size to disable loop split. */
> + if (compute_added_num_insns (loop, invar_branch)
> + > PARAM_VALUE (PARAM_MAX_LOOP_COND_SPLIT_INSNS))
> + return NULL;
> +
> + return invar_branch;
> +}
> +
> +/* Given a loop (LOOP1) with a loop-invariant branch (INVAR_BRANCH) of some
> + conditional statement, perform loop split transformation illustrated
> + as the following graph.
> +
> + .-------T------ if (true) ------F------.
> + | .---------------. |
> + | | | |
> + v | v v
> + pre-header | pre-header
> + | .------------. | | .------------.
> + | | | | | | |
> + | v | | | v |
> + header | | header |
> + | | | | |
> + [ bool r = cond; ] | | | |
> + | | | | |
> + .---- if (r) -----. | | .--- if (true) ---. |
> + | | | | | | |
> + invariant | | | invariant | |
> + | | | | | | |
> + '---T--->.<---F---' | | '---T--->.<---F---' |
> + | | / | |
> + stmts | / stmts |
> + | | / | |
> + / \ | / / \ |
> + .-------* * [ if (!r) ] .-------* * |
> + | | | | | |
> + | latch | | latch |
> + | | | | | |
> + | '------------' | '------------'
> + '------------------------. .-----------'
> + loop1 | | loop2
> + v v
> + exits
> +
> + In the graph, loop1 represents the part derived from original one, and
> + loop2 is duplicated using loop_version (), which corresponds to the part
> + of original one being splitted out. In loop1, a new bool temporary (r)
> + is introduced to keep value of the condition result. In original latch
> + edge of loop1, we insert a new conditional statement whose value comes
> + from previous temporary (r), one of its branch goes back to loop1 header
> + as a latch edge, and the other branch goes to loop2 pre-header as an entry
> + edge. And also in loop2, we abandon the variant branch of the conditional
> + statement candidate by setting a constant bool condition, based on which
> + branch is semi-invariant. */
> +
> +static bool
> +do_split_loop_on_cond (struct loop *loop1, edge invar_branch)
> +{
> + basic_block cond_bb = invar_branch->src;
> + bool true_invar = !!(invar_branch->flags & EDGE_TRUE_VALUE);
> + gcond *cond = as_a <gcond *> (last_stmt (cond_bb));
> +
> + gcc_assert (cond_bb->loop_father == loop1);
> +
> + if (dump_file && (dump_flags & TDF_DETAILS))
> + {
> + fprintf (dump_file, "In %s(), split loop %d at branch<%s>, BB %d\n",
> + current_function_name (), loop1->num,
> + true_invar ? "T" : "F", cond_bb->index);
> + print_gimple_stmt (dump_file, cond, 0, TDF_SLIM | TDF_VOPS);
> + }
> +
> + initialize_original_copy_tables ();
> +
> + struct loop *loop2 = loop_version (loop1, boolean_true_node, NULL,
> + profile_probability::always (),
> + profile_probability::never (),
> + profile_probability::always (),
> + profile_probability::always (),
> + true);
> + if (!loop2)
> + {
> + free_original_copy_tables ();
> + return false;
> + }
> +
> + /* Generate a bool type temporary to hold result of the condition. */
> + tree tmp = make_ssa_name (boolean_type_node);
> + gimple_stmt_iterator gsi = gsi_last_bb (cond_bb);
> + gimple *stmt = gimple_build_assign (tmp,
> + gimple_cond_code (cond),
> + gimple_cond_lhs (cond),
> + gimple_cond_rhs (cond));
> +
> + gsi_insert_before (&gsi, stmt, GSI_NEW_STMT);
> + gimple_cond_set_condition (cond, EQ_EXPR, tmp, boolean_true_node);
> + update_stmt (cond);
> +
> + basic_block cond_bb_copy = get_bb_copy (cond_bb);
> + gcond *cond_copy = as_a<gcond *> (last_stmt (cond_bb_copy));
> +
> + /* Replace the condition in loop2 with a bool constant to let PassManager
> + remove the variant branch after current pass completes. */
> + if (true_invar)
> + gimple_cond_make_true (cond_copy);
> + else
> + gimple_cond_make_false (cond_copy);
> +
> + update_stmt (cond_copy);
> +
> + /* Insert a new conditional statement on latch edge of loop1. This
> + statement acts as a switch to transfer execution from loop1 to loop2,
> + when loop1 enters into invariant state. */
> + basic_block latch_bb = split_edge (loop_latch_edge (loop1));
> + basic_block break_bb = split_edge (single_pred_edge (latch_bb));
> + gimple *break_cond = gimple_build_cond (EQ_EXPR, tmp, boolean_true_node,
> + NULL_TREE, NULL_TREE);
> +
> + gsi = gsi_last_bb (break_bb);
> + gsi_insert_after (&gsi, break_cond, GSI_NEW_STMT);
> +
> + edge to_loop1 = single_succ_edge (break_bb);
> + edge to_loop2 = make_edge (break_bb, loop_preheader_edge (loop2)->src, 0);
> +
> + to_loop1->flags &= ~EDGE_FALLTHRU;
> + to_loop1->flags |= true_invar ? EDGE_FALSE_VALUE : EDGE_TRUE_VALUE;
> + to_loop2->flags |= true_invar ? EDGE_TRUE_VALUE : EDGE_FALSE_VALUE;
> +
> + update_ssa (TODO_update_ssa);
> +
> + /* Due to introduction of a control flow edge from loop1 latch to loop2
> + pre-header, we should update PHIs in loop2 to reflect this connection
> + between loop1 and loop2. */
> + connect_loop_phis (loop1, loop2, to_loop2);
> +
> + free_original_copy_tables ();
> +
> + rewrite_into_loop_closed_ssa_1 (NULL, 0, SSA_OP_USE, loop1);
> +
> + return true;
> +}
> +
> +/* Traverse all conditional statements in LOOP, to find out a good candidate
> + upon which we can do loop split. */
> +
> +static bool
> +split_loop_on_cond (struct loop *loop)
> +{
> + split_info *info = new split_info ();
> + basic_block *bbs = info->bbs = get_loop_body (loop);
> + bool do_split = false;
> +
> + /* Allocate an area to keep temporary info, and associate its address
> + with loop aux field. */
> + loop->aux = info;
> +
> + for (unsigned i = 0; i < loop->num_nodes; i++)
> + {
> + basic_block bb = bbs[i];
> +
> + /* We only consider conditional statement, which be executed at most
> once
> + in each iteration of the loop. So skip statements in inner loops.
> */
> + if ((bb->loop_father != loop) || (bb->flags & BB_IRREDUCIBLE_LOOP))
> + continue;
> +
> + /* Actually this check is not a must constraint. With it, we can
> ensure
> + conditional statement will always be executed in each iteration. */
> + if (!dominated_by_p (CDI_DOMINATORS, loop->latch, bb))
> + continue;
> +
> + gimple *last = last_stmt (bb);
> +
> + if (!last || gimple_code (last) != GIMPLE_COND)
> + continue;
> +
> + gcond *cond = as_a <gcond *> (last);
> + edge branch_edge = get_cond_branch_to_split_loop (loop, cond);
> +
> + if (branch_edge)
> + {
> + do_split_loop_on_cond (loop, branch_edge);
> + do_split = true;
> + break;
> + }
> + }
> +
> + delete info;
> + loop->aux = NULL;
> +
> + return do_split;
> +}
> +
> /* Main entry point. Perform loop splitting on all suitable loops. */
>
> static unsigned int
> @@ -627,7 +1369,6 @@ tree_ssa_split_loops (void)
> /* Go through all loops starting from innermost. */
> FOR_EACH_LOOP (loop, LI_FROM_INNERMOST)
> {
> - class tree_niter_desc niter;
> if (loop->aux)
> {
> /* If any of our inner loops was split, don't split us,
> @@ -636,29 +1377,14 @@ tree_ssa_split_loops (void)
> continue;
> }
>
> - if (single_exit (loop)
> - /* ??? We could handle non-empty latches when we split
> - the latch edge (not the exit edge), and put the new
> - exit condition in the new block. OTOH this executes some
> - code unconditionally that might have been skipped by the
> - original exit before. */
> - && empty_block_p (loop->latch)
> - && !optimize_loop_for_size_p (loop)
> - && easy_exit_values (loop)
> - && number_of_iterations_exit (loop, single_exit (loop), &niter,
> - false, true)
> - && niter.cmp != ERROR_MARK
> - /* We can't yet handle loops controlled by a != predicate. */
> - && niter.cmp != NE_EXPR
> - && can_duplicate_loop_p (loop))
> + if (optimize_loop_for_size_p (loop))
> + continue;
> +
> + if (split_loop (loop) || split_loop_on_cond (loop))
> {
> - if (split_loop (loop, &niter))
> - {
> - /* Mark our containing loop as having had some split inner
> - loops. */
> - loop_outer (loop)->aux = loop;
> - changed = true;
> - }
> + /* Mark our containing loop as having had some split inner loops.
> */
> + loop_outer (loop)->aux = loop;
> + changed = true;
> }
> }
>
> --
> 2.17.1
From 3cb899240b28e46457728bd9a6f2957d873e8dff Mon Sep 17 00:00:00 2001
From: Feng Xue <feng....@amperecomputing.com>
Date: Tue, 12 Mar 2019 11:46:19 +0800
Subject: [PATCH] Loop split on semi-invariant conditional statement
---
gcc/ChangeLog | 16 +
gcc/doc/invoke.texi | 13 +
gcc/params.def | 14 +
gcc/testsuite/ChangeLog | 6 +
.../g++.dg/tree-ssa/loop-cond-split-1.C | 33 +
.../gcc.dg/tree-ssa/loop-cond-split-1.c | 23 +
gcc/tree-ssa-loop-split.c | 782 +++++++++++++++++-
7 files changed, 859 insertions(+), 28 deletions(-)
create mode 100644 gcc/testsuite/g++.dg/tree-ssa/loop-cond-split-1.C
create mode 100644 gcc/testsuite/gcc.dg/tree-ssa/loop-cond-split-1.c
diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index 8ec312d7470..780060b8698 100644
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,3 +1,19 @@
+2019-10-23 Feng Xue <f...@os.amperecomputing.com>
+
+ PR tree-optimization/89134
+ * doc/invoke.texi (max-loop-cond-split-insns): Document new --params.
+ (min-loop-cond-split-prob): Likewise.
+ * params.def: Add max-loop-cond-split-insns, min-loop-cond-split-prob.
+ * tree-ssa-loop-split.c (split_loop): Remove niter parameter, move some
+ outside checks on loop into the function.
+ (split_info): New class.
+ (find_vdef_in_loop, vuse_semi_invariant_p): New functions.
+ (ssa_semi_invariant_p, stmt_semi_invariant_p): Likewise.
+ (branch_removable_p, get_cond_invariant_branch): Likewise.
+ (compute_added_num_insns, get_cond_branch_to_split_loop): Likewise.
+ (do_split_loop_on_cond, split_loop_on_cond): Likewise.
+ (tree_ssa_split_loops): Add loop split on conditional statement.
+
2019-10-23 Iain Sandoe <i...@sandoe.co.uk>
* config/rs6000/darwin.h (ASM_OUTPUT_MAX_SKIP_ALIGN): Guard
diff --git a/gcc/doc/invoke.texi b/gcc/doc/invoke.texi
index 1407d019d14..d41e5aa0215 100644
--- a/gcc/doc/invoke.texi
+++ b/gcc/doc/invoke.texi
@@ -11481,6 +11481,19 @@ The maximum number of branches unswitched in a single loop.
@item lim-expensive
The minimum cost of an expensive expression in the loop invariant motion.
+@item max-loop-cond-split-insns
+In a loop, if a branch of a conditional statement is selected since certain
+loop iteration, any operand that contributes to computation of the conditional
+expression remains unchanged in all following iterations, the statement is
+semi-invariant, upon which we can do a kind of loop split transformation.
+@option{max-loop-cond-split-insns} controls maximum number of insns to be
+added due to loop split on semi-invariant conditional statement.
+
+@item min-loop-cond-split-prob
+When FDO profile information is available, @option{min-loop-cond-split-prob}
+specifies minimum threshold for probability of semi-invariant condition
+statement to trigger loop split.
+
@item iv-consider-all-candidates-bound
Bound on number of candidates for induction variables, below which
all candidates are considered for each use in induction variable
diff --git a/gcc/params.def b/gcc/params.def
index 322c37f8b96..73b59f7465e 100644
--- a/gcc/params.def
+++ b/gcc/params.def
@@ -415,6 +415,20 @@ DEFPARAM(PARAM_MAX_UNSWITCH_LEVEL,
"The maximum number of unswitchings in a single loop.",
3, 0, 0)
+/* The maximum number of increased insns due to loop split on semi-invariant
+ condition statement. */
+DEFPARAM(PARAM_MAX_LOOP_COND_SPLIT_INSNS,
+ "max-loop-cond-split-insns",
+ "The maximum number of insns to be added due to loop split on "
+ "semi-invariant condition statement.",
+ 100, 0, 0)
+
+DEFPARAM(PARAM_MIN_LOOP_COND_SPLIT_PROB,
+ "min-loop-cond-split-prob",
+ "The minimum threshold for probability of semi-invariant condition "
+ "statement to trigger loop split.",
+ 30, 0, 100)
+
/* The maximum number of insns in loop header duplicated by the copy loop
headers pass. */
DEFPARAM(PARAM_MAX_LOOP_HEADER_INSNS,
diff --git a/gcc/testsuite/ChangeLog b/gcc/testsuite/ChangeLog
index fd272807d0b..892cf457b8d 100644
--- a/gcc/testsuite/ChangeLog
+++ b/gcc/testsuite/ChangeLog
@@ -1,3 +1,9 @@
+2019-10-23 Feng Xue <f...@os.amperecomputing.com>
+
+ PR tree-optimization/89134
+ * gcc.dg/tree-ssa/loop-cond-split-1.c: New test.
+ * g++.dg/tree-ssa/loop-cond-split-1.C: New test.
+
2019-10-22 Marc Glisse <marc.gli...@inria.fr>
PR c++/85746
diff --git a/gcc/testsuite/g++.dg/tree-ssa/loop-cond-split-1.C b/gcc/testsuite/g++.dg/tree-ssa/loop-cond-split-1.C
new file mode 100644
index 00000000000..51f9da22fc7
--- /dev/null
+++ b/gcc/testsuite/g++.dg/tree-ssa/loop-cond-split-1.C
@@ -0,0 +1,33 @@
+/* { dg-do compile } */
+/* { dg-options "-O3 -fdump-tree-lsplit-details" } */
+
+#include <string>
+#include <map>
+
+using namespace std;
+
+class A
+{
+public:
+ bool empty;
+ void set (string s);
+};
+
+class B
+{
+ map<int, string> m;
+ void f ();
+};
+
+extern A *ga;
+
+void B::f ()
+{
+ for (map<int, string>::iterator iter = m.begin (); iter != m.end (); ++iter)
+ {
+ if (ga->empty)
+ ga->set (iter->second);
+ }
+}
+
+/* { dg-final { scan-tree-dump-times "split loop 1 at branch" 1 "lsplit" } } */
diff --git a/gcc/testsuite/gcc.dg/tree-ssa/loop-cond-split-1.c b/gcc/testsuite/gcc.dg/tree-ssa/loop-cond-split-1.c
new file mode 100644
index 00000000000..bbd522d6bcd
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/tree-ssa/loop-cond-split-1.c
@@ -0,0 +1,23 @@
+/* { dg-do compile } */
+/* { dg-options "-O3 -fdump-tree-lsplit-details" } */
+
+__attribute__((pure)) __attribute__((noinline)) int inc (int i)
+{
+ return i + 1;
+}
+
+extern int do_something (void);
+extern int b;
+
+void test(int n)
+{
+ int i;
+
+ for (i = 0; i < n; i = inc (i))
+ {
+ if (b)
+ b = do_something();
+ }
+}
+
+/* { dg-final { scan-tree-dump-times "split loop 1 at branch" 1 "lsplit" } } */
diff --git a/gcc/tree-ssa-loop-split.c b/gcc/tree-ssa-loop-split.c
index f5f083384bc..5cffd4bb508 100644
--- a/gcc/tree-ssa-loop-split.c
+++ b/gcc/tree-ssa-loop-split.c
@@ -32,7 +32,10 @@ along with GCC; see the file COPYING3. If not see
#include "tree-ssa-loop.h"
#include "tree-ssa-loop-manip.h"
#include "tree-into-ssa.h"
+#include "tree-inline.h"
+#include "tree-cfgcleanup.h"
#include "cfgloop.h"
+#include "params.h"
#include "tree-scalar-evolution.h"
#include "gimple-iterator.h"
#include "gimple-pretty-print.h"
@@ -40,7 +43,9 @@ along with GCC; see the file COPYING3. If not see
#include "gimple-fold.h"
#include "gimplify-me.h"
-/* This file implements loop splitting, i.e. transformation of loops like
+/* This file implements two kinds of loop splitting.
+
+ One transformation of loops like:
for (i = 0; i < 100; i++)
{
@@ -487,8 +492,9 @@ compute_new_first_bound (gimple_seq *stmts, class tree_niter_desc *niter,
single exit of LOOP. */
static bool
-split_loop (class loop *loop1, class tree_niter_desc *niter)
+split_loop (class loop *loop1)
{
+ class tree_niter_desc niter;
basic_block *bbs;
unsigned i;
bool changed = false;
@@ -496,8 +502,28 @@ split_loop (class loop *loop1, class tree_niter_desc *niter)
tree border = NULL_TREE;
affine_iv iv;
+ if (!single_exit (loop1)
+ /* ??? We could handle non-empty latches when we split the latch edge
+ (not the exit edge), and put the new exit condition in the new block.
+ OTOH this executes some code unconditionally that might have been
+ skipped by the original exit before. */
+ || !empty_block_p (loop1->latch)
+ || !easy_exit_values (loop1)
+ || !number_of_iterations_exit (loop1, single_exit (loop1), &niter,
+ false, true)
+ || niter.cmp == ERROR_MARK
+ /* We can't yet handle loops controlled by a != predicate. */
+ || niter.cmp == NE_EXPR)
+ return false;
+
bbs = get_loop_body (loop1);
+ if (!can_copy_bbs_p (bbs, loop1->num_nodes))
+ {
+ free (bbs);
+ return false;
+ }
+
/* Find a splitting opportunity. */
for (i = 0; i < loop1->num_nodes; i++)
if ((guard_iv = split_at_bb_p (loop1, bbs[i], &border, &iv)))
@@ -505,8 +531,8 @@ split_loop (class loop *loop1, class tree_niter_desc *niter)
/* Handling opposite steps is not implemented yet. Neither
is handling different step sizes. */
if ((tree_int_cst_sign_bit (iv.step)
- != tree_int_cst_sign_bit (niter->control.step))
- || !tree_int_cst_equal (iv.step, niter->control.step))
+ != tree_int_cst_sign_bit (niter.control.step))
+ || !tree_int_cst_equal (iv.step, niter.control.step))
continue;
/* Find a loop PHI node that defines guard_iv directly,
@@ -575,7 +601,7 @@ split_loop (class loop *loop1, class tree_niter_desc *niter)
Compute the new bound for the guarding IV and patch the
loop exit to use it instead of original IV and bound. */
gimple_seq stmts = NULL;
- tree newend = compute_new_first_bound (&stmts, niter, border,
+ tree newend = compute_new_first_bound (&stmts, &niter, border,
guard_code, guard_init);
if (stmts)
gsi_insert_seq_on_edge_immediate (loop_preheader_edge (loop1),
@@ -612,6 +638,722 @@ split_loop (class loop *loop1, class tree_niter_desc *niter)
return changed;
}
+/* Another transformation of loops like:
+
+ for (i = INIT (); CHECK (i); i = NEXT ())
+ {
+ if (expr (a_1, a_2, ..., a_n)) // expr is pure
+ a_j = ...; // change at least one a_j
+ else
+ S; // not change any a_j
+ }
+
+ into:
+
+ for (i = INIT (); CHECK (i); i = NEXT ())
+ {
+ if (expr (a_1, a_2, ..., a_n))
+ a_j = ...;
+ else
+ {
+ S;
+ i = NEXT ();
+ break;
+ }
+ }
+
+ for (; CHECK (i); i = NEXT ())
+ {
+ S;
+ }
+
+ */
+
+/* Data structure to hold temporary information during loop split upon
+ semi-invariant conditional statement. */
+class split_info {
+public:
+ /* Array of all basic blocks in a loop, returned by get_loop_body(). */
+ basic_block *bbs;
+
+ /* All memory store/clobber statements in a loop. */
+ auto_vec<gimple *> memory_stores;
+
+ /* Whether above memory stores vector has been filled. */
+ int need_init;
+
+ split_info () : bbs (NULL), need_init (true) { }
+
+ ~split_info ()
+ {
+ if (bbs)
+ free (bbs);
+ }
+};
+
+/* Find all statements with memory-write effect in LOOP, including memory
+ store and non-pure function call, and keep those in a vector. This work
+ is only done one time, for the vector should be constant during analysis
+ stage of semi-invariant condition. */
+
+static void
+find_vdef_in_loop (struct loop *loop)
+{
+ split_info *info = (split_info *) loop->aux;
+ gphi *vphi = get_virtual_phi (loop->header);
+
+ /* Indicate memory store vector has been filled. */
+ info->need_init = false;
+
+ /* If loop contains memory operation, there must be a virtual PHI node in
+ loop header basic block. */
+ if (vphi == NULL)
+ return;
+
+ /* All virtual SSA names inside the loop are connected to be a cyclic
+ graph via virtual PHI nodes. The virtual PHI node in loop header just
+ links the first and the last virtual SSA names, by using the last as
+ PHI operand to define the first. */
+ const edge latch = loop_latch_edge (loop);
+ const tree first = gimple_phi_result (vphi);
+ const tree last = PHI_ARG_DEF_FROM_EDGE (vphi, latch);
+
+ /* The virtual SSA cyclic graph might consist of only one SSA name, who
+ is defined by itself.
+
+ .MEM_1 = PHI <.MEM_2(loop entry edge), .MEM_1(latch edge)>
+
+ This means the loop contains only memory loads, so we can skip it. */
+ if (first == last)
+ return;
+
+ auto_vec<gimple *> other_stores;
+ auto_vec<tree> worklist;
+ auto_bitmap visited;
+
+ bitmap_set_bit (visited, SSA_NAME_VERSION (first));
+ bitmap_set_bit (visited, SSA_NAME_VERSION (last));
+ worklist.safe_push (last);
+
+ do
+ {
+ tree vuse = worklist.pop ();
+ gimple *stmt = SSA_NAME_DEF_STMT (vuse);
+
+ /* We mark the first and last SSA names as visited at the beginning,
+ and reversely start the process from the last SSA name towards the
+ first, which ensures that this do-while will not touch SSA names
+ defined outside of the loop. */
+ gcc_assert (gimple_bb (stmt)
+ && flow_bb_inside_loop_p (loop, gimple_bb (stmt)));
+
+ if (gimple_code (stmt) == GIMPLE_PHI)
+ {
+ gphi *phi = as_a <gphi *> (stmt);
+
+ for (unsigned i = 0; i < gimple_phi_num_args (phi); ++i)
+ {
+ tree arg = gimple_phi_arg_def (stmt, i);
+
+ if (bitmap_set_bit (visited, SSA_NAME_VERSION (arg)))
+ worklist.safe_push (arg);
+ }
+ }
+ else
+ {
+ tree prev = gimple_vuse (stmt);
+
+ /* Non-pure call statement is conservatively assumed to impact all
+ memory locations. So place call statements ahead of other memory
+ stores in the vector with an idea of of using them as shortcut
+ terminators to memory alias analysis. */
+ if (gimple_code (stmt) == GIMPLE_CALL)
+ info->memory_stores.safe_push (stmt);
+ else
+ other_stores.safe_push (stmt);
+
+ if (bitmap_set_bit (visited, SSA_NAME_VERSION (prev)))
+ worklist.safe_push (prev);
+ }
+ } while (!worklist.is_empty ());
+
+ info->memory_stores.safe_splice (other_stores);
+}
+
+
+/* Given STMT, memory load or pure call statement, check whether it is impacted
+ by some memory store in LOOP, excluding trace starting from SKIP_HEAD (the
+ trace is composed of SKIP_HEAD and those basic block dominated by it, always
+ corresponds to one branch of a conditional statement). If SKIP_HEAD is
+ NULL, all basic blocks of LOOP are checked. */
+
+static bool
+vuse_semi_invariant_p (struct loop *loop, gimple *stmt,
+ const_basic_block skip_head)
+{
+ split_info *info = (split_info *) loop->aux;
+
+ /* Collect memory store/clobber statements if have not do that. */
+ if (info->need_init)
+ find_vdef_in_loop (loop);
+
+ tree rhs = is_gimple_assign (stmt) ? gimple_assign_rhs1 (stmt) : NULL_TREE;
+ ao_ref ref;
+ gimple *store;
+ unsigned i;
+
+ ao_ref_init (&ref, rhs);
+
+ FOR_EACH_VEC_ELT (info->memory_stores, i, store)
+ {
+ /* Skip basic blocks dominated by SKIP_HEAD, if non-NULL. */
+ if (skip_head
+ && dominated_by_p (CDI_DOMINATORS, gimple_bb (store), skip_head))
+ continue;
+
+ if (!ref.ref || stmt_may_clobber_ref_p_1 (store, &ref))
+ return false;
+ }
+
+ return true;
+}
+
+/* Forward declaration. */
+
+static bool
+stmt_semi_invariant_p (struct loop *loop, gimple *stmt,
+ const_basic_block skip_head);
+
+/* Suppose one condition branch, led by SKIP_HEAD, is not executed since
+ certain iteration of LOOP, check whether an SSA name (NAME) remains
+ unchanged in next iteration. We call this characteristic semi-
+ invariantness. SKIP_HEAD might be NULL, if so, nothing excluded, all
+ basic blocks and control flows in the loop will be considered. If non-
+ NULL, SSA name to check is supposed to be defined before SKIP_HEAD. */
+
+static bool
+ssa_semi_invariant_p (struct loop *loop, const tree name,
+ const_basic_block skip_head)
+{
+ gimple *def = SSA_NAME_DEF_STMT (name);
+ const_basic_block def_bb = gimple_bb (def);
+
+ /* An SSA name defined outside a loop is definitely semi-invariant. */
+ if (!def_bb || !flow_bb_inside_loop_p (loop, def_bb))
+ return true;
+
+ if (gimple_code (def) == GIMPLE_PHI)
+ {
+ /* For PHI node that is not in loop header, its source operands should
+ be defined inside the loop, which are seen as loop variant. */
+ if (def_bb != loop->header || !skip_head)
+ return false;
+
+ const_edge latch = loop_latch_edge (loop);
+ tree from = PHI_ARG_DEF_FROM_EDGE (as_a <gphi *> (def), latch);
+
+ /* A PHI node in loop header contains two source operands, one is
+ initial value, the other is the copy of last iteration through loop
+ latch, we call it latch value. From the PHI node to definition
+ of latch value, if excluding branch trace from SKIP_HEAD, there
+ is no definition of other version of same variable, SSA name defined
+ by the PHI node is semi-invariant.
+
+ loop entry
+ | .--- latch ---.
+ | | |
+ v v |
+ x_1 = PHI <x_0, x_3> |
+ | |
+ v |
+ .------- if (cond) -------. |
+ | | |
+ | [ SKIP ] |
+ | | |
+ | x_2 = ... |
+ | | |
+ '---- T ---->.<---- F ----' |
+ | |
+ v |
+ x_3 = PHI <x_1, x_2> |
+ | |
+ '----------------------'
+
+ Suppose in certain iteration, execution flow in above graph goes
+ through true branch, which means that one source value to define
+ x_3 in false branch (x2) is skipped, x_3 only comes from x_1, and
+ x_1 in next iterations is defined by x_3, we know that x_1 will
+ never changed if COND always chooses true branch from then on. */
+
+ while (from != name)
+ {
+ /* A new value comes from a CONSTANT. */
+ if (TREE_CODE (from) != SSA_NAME)
+ return false;
+
+ gimple *stmt = SSA_NAME_DEF_STMT (from);
+ const_basic_block bb = gimple_bb (stmt);
+
+ /* A new value comes from outside of loop. */
+ if (!bb || !flow_bb_inside_loop_p (loop, bb))
+ return false;
+
+ from = NULL_TREE;
+
+ if (gimple_code (stmt) == GIMPLE_PHI)
+ {
+ gphi *phi = as_a <gphi *> (stmt);
+
+ for (unsigned i = 0; i < gimple_phi_num_args (phi); ++i)
+ {
+ const_edge e = gimple_phi_arg_edge (phi, i);
+
+ /* Don't consider redefinitions in excluded basic blocks. */
+ if (!dominated_by_p (CDI_DOMINATORS, e->src, skip_head))
+ {
+ /* There are more than one source operands that can
+ provide value to the SSA name, it is variant. */
+ if (from)
+ return false;
+
+ from = gimple_phi_arg_def (phi, i);
+ }
+ }
+ }
+ else if (gimple_code (stmt) == GIMPLE_ASSIGN)
+ {
+ /* For simple value copy, check its rhs instead. */
+ if (gimple_assign_ssa_name_copy_p (stmt))
+ from = gimple_assign_rhs1 (stmt);
+ }
+
+ /* Any other kind of definition is deemed to introduce a new value
+ to the SSA name. */
+ if (!from)
+ return false;
+ }
+ return true;
+ }
+
+ /* Value originated from volatile memory load or return of normal (non-
+ const/pure) call should not be treated as constant in each iteration. */
+ if (gimple_has_side_effects (def))
+ return false;
+
+ /* Check if any memory store may kill memory load at this place. */
+ if (gimple_vuse (def) && !vuse_semi_invariant_p (loop, def, skip_head))
+ return false;
+
+ /* Check operands of definition statement of the SSA name. */
+ return stmt_semi_invariant_p (loop, def, skip_head);
+}
+
+/* Check whether STMT is semi-invariant in LOOP, iff all its operands are
+ semi-invariant. Trace composed of basic block SKIP_HEAD and basic blocks
+ dominated by it are excluded from the loop. */
+
+static bool
+stmt_semi_invariant_p (struct loop *loop, gimple *stmt,
+ const_basic_block skip_head)
+{
+ ssa_op_iter iter;
+ tree use;
+
+ /* Although operand of a statement might be SSA name, CONSTANT or VARDECL,
+ here we only need to check SSA name operands. This is because check on
+ VARDECL operands, which involve memory loads, must have been done
+ prior to invocation of this function in vuse_semi_invariant_p. */
+ FOR_EACH_SSA_TREE_OPERAND (use, stmt, iter, SSA_OP_USE)
+ {
+ if (!ssa_semi_invariant_p (loop, use, skip_head))
+ return false;
+ }
+
+ return true;
+}
+
+/* Determine when conditional statement never transfers execution to one of its
+ branch, whether we can remove the branch's leading basic block (BRANCH_BB)
+ and those basic blocks dominated by BRANCH_BB. */
+
+static bool
+branch_removable_p (basic_block branch_bb)
+{
+ if (single_pred_p (branch_bb))
+ return true;
+
+ edge e;
+ edge_iterator ei;
+
+ FOR_EACH_EDGE (e, ei, branch_bb->preds)
+ {
+ if (dominated_by_p (CDI_DOMINATORS, e->src, branch_bb))
+ continue;
+
+ if (dominated_by_p (CDI_DOMINATORS, branch_bb, e->src))
+ continue;
+
+ /* The branch can be reached from opposite branch, or from some
+ statement not dominated by the conditional statement. */
+ return false;
+ }
+
+ return true;
+}
+
+/* Find out which branch of a conditional statement (COND) is invariant in the
+ execution context of LOOP. That is: once the branch is selected in certain
+ iteration of the loop, any operand that contributes to computation of the
+ conditional statement remains unchanged in all following iterations. */
+
+static edge
+get_cond_invariant_branch (struct loop *loop, gcond *cond)
+{
+ basic_block cond_bb = gimple_bb (cond);
+ basic_block targ_bb[2];
+ bool invar[2];
+ unsigned invar_checks;
+
+ for (unsigned i = 0; i < 2; i++)
+ {
+ targ_bb[i] = EDGE_SUCC (cond_bb, i)->dest;
+
+ /* One branch directs to loop exit, no need to perform loop split upon
+ this conditional statement. Firstly, it is trivial if the exit branch
+ is semi-invariant, for the statement is just to break loop. Secondly,
+ if the opposite branch is semi-invariant, it means that the statement
+ is real loop-invariant, which is covered by loop unswitch. */
+ if (!flow_bb_inside_loop_p (loop, targ_bb[i]))
+ return NULL;
+ }
+
+ invar_checks = 0;
+
+ for (unsigned i = 0; i < 2; i++)
+ {
+ invar[!i] = false;
+
+ if (!branch_removable_p (targ_bb[i]))
+ continue;
+
+ /* Given a semi-invariant branch, if its opposite branch dominates
+ loop latch, it and its following trace will only be executed in
+ final iteration of loop, namely it is not part of repeated body
+ of the loop. Similar to the above case that the branch is loop
+ exit, no need to split loop. */
+ if (dominated_by_p (CDI_DOMINATORS, loop->latch, targ_bb[i]))
+ continue;
+
+ invar[!i] = stmt_semi_invariant_p (loop, cond, targ_bb[i]);
+ invar_checks++;
+ }
+
+ /* With both branches being invariant (handled by loop unswitch) or
+ variant is not what we want. */
+ if (invar[0] ^ !invar[1])
+ return NULL;
+
+ /* Found a real loop-invariant condition, do nothing. */
+ if (invar_checks < 2 && stmt_semi_invariant_p (loop, cond, NULL))
+ return NULL;
+
+ return EDGE_SUCC (cond_bb, (unsigned) invar[1]);
+}
+
+/* Calculate increased code size measured by estimated insn number if applying
+ loop split upon certain branch (BRANCH_EDGE) of a conditional statement. */
+
+static int
+compute_added_num_insns (struct loop *loop, const_edge branch_edge)
+{
+ basic_block cond_bb = branch_edge->src;
+ unsigned branch = EDGE_SUCC (cond_bb, 1) == branch_edge;
+ basic_block opposite_bb = EDGE_SUCC (cond_bb, !branch)->dest;
+ basic_block *bbs = ((split_info *) loop->aux)->bbs;
+ int num = 0;
+
+ for (unsigned i = 0; i < loop->num_nodes; i++)
+ {
+ /* Do no count basic blocks only in opposite branch. */
+ if (dominated_by_p (CDI_DOMINATORS, bbs[i], opposite_bb))
+ continue;
+
+ num += estimate_num_insns_seq (bb_seq (bbs[i]), &eni_size_weights);
+ }
+
+ /* It is unnecessary to evaluate expression of the conditional statement
+ in new loop that contains only invariant branch. This expression should
+ be constant value (either true or false). Exclude code size of insns
+ that contribute to computation of the expression. */
+
+ auto_vec<gimple *> worklist;
+ hash_set<gimple *> removed;
+ gimple *stmt = last_stmt (cond_bb);
+
+ worklist.safe_push (stmt);
+ removed.add (stmt);
+ num -= estimate_num_insns (stmt, &eni_size_weights);
+
+ do
+ {
+ ssa_op_iter opnd_iter;
+ use_operand_p opnd_p;
+
+ stmt = worklist.pop ();
+ FOR_EACH_PHI_OR_STMT_USE (opnd_p, stmt, opnd_iter, SSA_OP_USE)
+ {
+ tree opnd = USE_FROM_PTR (opnd_p);
+
+ if (TREE_CODE (opnd) != SSA_NAME || SSA_NAME_IS_DEFAULT_DEF (opnd))
+ continue;
+
+ gimple *opnd_stmt = SSA_NAME_DEF_STMT (opnd);
+ use_operand_p use_p;
+ imm_use_iterator use_iter;
+
+ if (removed.contains (opnd_stmt)
+ || !flow_bb_inside_loop_p (loop, gimple_bb (opnd_stmt)))
+ continue;
+
+ FOR_EACH_IMM_USE_FAST (use_p, use_iter, opnd)
+ {
+ gimple *use_stmt = USE_STMT (use_p);
+
+ if (!is_gimple_debug (use_stmt) && !removed.contains (use_stmt))
+ {
+ opnd_stmt = NULL;
+ break;
+ }
+ }
+
+ if (opnd_stmt)
+ {
+ worklist.safe_push (opnd_stmt);
+ removed.add (opnd_stmt);
+ num -= estimate_num_insns (opnd_stmt, &eni_size_weights);
+ }
+ }
+ } while (!worklist.is_empty ());
+
+ gcc_assert (num >= 0);
+ return num;
+}
+
+/* Find out loop-invariant branch of a conditional statement (COND) if it has,
+ and check whether it is eligible and profitable to perform loop split upon
+ this branch in LOOP. */
+
+static edge
+get_cond_branch_to_split_loop (struct loop *loop, gcond *cond)
+{
+ edge invar_branch = get_cond_invariant_branch (loop, cond);
+
+ if (!invar_branch)
+ return NULL;
+
+ profile_probability prob = invar_branch->probability;
+
+ /* When accurate profile information is available, and execution
+ frequency of the branch is too low, just let it go. */
+ if (prob.reliable_p ())
+ {
+ int thres = PARAM_VALUE (PARAM_MIN_LOOP_COND_SPLIT_PROB);
+
+ if (prob < profile_probability::always ().apply_scale (thres, 100))
+ return NULL;
+ }
+
+ /* Add a threshold for increased code size to disable loop split. */
+ if (compute_added_num_insns (loop, invar_branch)
+ > PARAM_VALUE (PARAM_MAX_LOOP_COND_SPLIT_INSNS))
+ return NULL;
+
+ return invar_branch;
+}
+
+/* Given a loop (LOOP1) with a loop-invariant branch (INVAR_BRANCH) of some
+ conditional statement, perform loop split transformation illustrated
+ as the following graph.
+
+ .-------T------ if (true) ------F------.
+ | .---------------. |
+ | | | |
+ v | v v
+ pre-header | pre-header
+ | .------------. | | .------------.
+ | | | | | | |
+ | v | | | v |
+ header | | header |
+ | | | | |
+ [ bool r = cond; ] | | | |
+ | | | | |
+ .---- if (r) -----. | | .--- if (true) ---. |
+ | | | | | | |
+ invariant | | | invariant | |
+ | | | | | | |
+ '---T--->.<---F---' | | '---T--->.<---F---' |
+ | | / | |
+ stmts | / stmts |
+ | | / | |
+ / \ | / / \ |
+ .-------* * [ if (!r) ] .-------* * |
+ | | | | | |
+ | latch | | latch |
+ | | | | | |
+ | '------------' | '------------'
+ '------------------------. .-----------'
+ loop1 | | loop2
+ v v
+ exits
+
+ In the graph, loop1 represents the part derived from original one, and
+ loop2 is duplicated using loop_version (), which corresponds to the part
+ of original one being splitted out. In loop1, a new bool temporary (r)
+ is introduced to keep value of the condition result. In original latch
+ edge of loop1, we insert a new conditional statement whose value comes
+ from previous temporary (r), one of its branch goes back to loop1 header
+ as a latch edge, and the other branch goes to loop2 pre-header as an entry
+ edge. And also in loop2, we abandon the variant branch of the conditional
+ statement candidate by setting a constant bool condition, based on which
+ branch is semi-invariant. */
+
+static bool
+do_split_loop_on_cond (struct loop *loop1, edge invar_branch)
+{
+ basic_block cond_bb = invar_branch->src;
+ bool true_invar = !!(invar_branch->flags & EDGE_TRUE_VALUE);
+ gcond *cond = as_a <gcond *> (last_stmt (cond_bb));
+
+ gcc_assert (cond_bb->loop_father == loop1);
+
+ if (dump_file && (dump_flags & TDF_DETAILS))
+ {
+ fprintf (dump_file, "In %s(), split loop %d at branch<%s>, BB %d\n",
+ current_function_name (), loop1->num,
+ true_invar ? "T" : "F", cond_bb->index);
+ print_gimple_stmt (dump_file, cond, 0, TDF_SLIM | TDF_VOPS);
+ }
+
+ initialize_original_copy_tables ();
+
+ struct loop *loop2 = loop_version (loop1, boolean_true_node, NULL,
+ profile_probability::always (),
+ profile_probability::never (),
+ profile_probability::always (),
+ profile_probability::always (),
+ true);
+ if (!loop2)
+ {
+ free_original_copy_tables ();
+ return false;
+ }
+
+ /* Generate a bool type temporary to hold result of the condition. */
+ tree tmp = make_ssa_name (boolean_type_node);
+ gimple_stmt_iterator gsi = gsi_last_bb (cond_bb);
+ gimple *stmt = gimple_build_assign (tmp,
+ gimple_cond_code (cond),
+ gimple_cond_lhs (cond),
+ gimple_cond_rhs (cond));
+
+ gsi_insert_before (&gsi, stmt, GSI_NEW_STMT);
+ gimple_cond_set_condition (cond, EQ_EXPR, tmp, boolean_true_node);
+ update_stmt (cond);
+
+ basic_block cond_bb_copy = get_bb_copy (cond_bb);
+ gcond *cond_copy = as_a<gcond *> (last_stmt (cond_bb_copy));
+
+ /* Replace the condition in loop2 with a bool constant to let PassManager
+ remove the variant branch after current pass completes. */
+ if (true_invar)
+ gimple_cond_make_true (cond_copy);
+ else
+ gimple_cond_make_false (cond_copy);
+
+ update_stmt (cond_copy);
+
+ /* Insert a new conditional statement on latch edge of loop1. This
+ statement acts as a switch to transfer execution from loop1 to loop2,
+ when loop1 enters into invariant state. */
+ basic_block latch_bb = split_edge (loop_latch_edge (loop1));
+ basic_block break_bb = split_edge (single_pred_edge (latch_bb));
+ gimple *break_cond = gimple_build_cond (EQ_EXPR, tmp, boolean_true_node,
+ NULL_TREE, NULL_TREE);
+
+ gsi = gsi_last_bb (break_bb);
+ gsi_insert_after (&gsi, break_cond, GSI_NEW_STMT);
+
+ edge to_loop1 = single_succ_edge (break_bb);
+ edge to_loop2 = make_edge (break_bb, loop_preheader_edge (loop2)->src, 0);
+
+ to_loop1->flags &= ~EDGE_FALLTHRU;
+ to_loop1->flags |= true_invar ? EDGE_FALSE_VALUE : EDGE_TRUE_VALUE;
+ to_loop2->flags |= true_invar ? EDGE_TRUE_VALUE : EDGE_FALSE_VALUE;
+
+ update_ssa (TODO_update_ssa);
+
+ /* Due to introduction of a control flow edge from loop1 latch to loop2
+ pre-header, we should update PHIs in loop2 to reflect this connection
+ between loop1 and loop2. */
+ connect_loop_phis (loop1, loop2, to_loop2);
+
+ free_original_copy_tables ();
+
+ rewrite_into_loop_closed_ssa_1 (NULL, 0, SSA_OP_USE, loop1);
+
+ return true;
+}
+
+/* Traverse all conditional statements in LOOP, to find out a good candidate
+ upon which we can do loop split. */
+
+static bool
+split_loop_on_cond (struct loop *loop)
+{
+ split_info *info = new split_info ();
+ basic_block *bbs = info->bbs = get_loop_body (loop);
+ bool do_split = false;
+
+ /* Allocate an area to keep temporary info, and associate its address
+ with loop aux field. */
+ loop->aux = info;
+
+ for (unsigned i = 0; i < loop->num_nodes; i++)
+ {
+ basic_block bb = bbs[i];
+
+ /* We only consider conditional statement, which be executed at most once
+ in each iteration of the loop. So skip statements in inner loops. */
+ if ((bb->loop_father != loop) || (bb->flags & BB_IRREDUCIBLE_LOOP))
+ continue;
+
+ /* Actually this check is not a must constraint. With it, we can ensure
+ conditional statement will always be executed in each iteration. */
+ if (!dominated_by_p (CDI_DOMINATORS, loop->latch, bb))
+ continue;
+
+ gimple *last = last_stmt (bb);
+
+ if (!last || gimple_code (last) != GIMPLE_COND)
+ continue;
+
+ gcond *cond = as_a <gcond *> (last);
+ edge branch_edge = get_cond_branch_to_split_loop (loop, cond);
+
+ if (branch_edge)
+ {
+ do_split_loop_on_cond (loop, branch_edge);
+ do_split = true;
+ break;
+ }
+ }
+
+ delete info;
+ loop->aux = NULL;
+
+ return do_split;
+}
+
/* Main entry point. Perform loop splitting on all suitable loops. */
static unsigned int
@@ -627,7 +1369,6 @@ tree_ssa_split_loops (void)
/* Go through all loops starting from innermost. */
FOR_EACH_LOOP (loop, LI_FROM_INNERMOST)
{
- class tree_niter_desc niter;
if (loop->aux)
{
/* If any of our inner loops was split, don't split us,
@@ -636,29 +1377,14 @@ tree_ssa_split_loops (void)
continue;
}
- if (single_exit (loop)
- /* ??? We could handle non-empty latches when we split
- the latch edge (not the exit edge), and put the new
- exit condition in the new block. OTOH this executes some
- code unconditionally that might have been skipped by the
- original exit before. */
- && empty_block_p (loop->latch)
- && !optimize_loop_for_size_p (loop)
- && easy_exit_values (loop)
- && number_of_iterations_exit (loop, single_exit (loop), &niter,
- false, true)
- && niter.cmp != ERROR_MARK
- /* We can't yet handle loops controlled by a != predicate. */
- && niter.cmp != NE_EXPR
- && can_duplicate_loop_p (loop))
+ if (optimize_loop_for_size_p (loop))
+ continue;
+
+ if (split_loop (loop) || split_loop_on_cond (loop))
{
- if (split_loop (loop, &niter))
- {
- /* Mark our containing loop as having had some split inner
- loops. */
- loop_outer (loop)->aux = loop;
- changed = true;
- }
+ /* Mark our containing loop as having had some split inner loops. */
+ loop_outer (loop)->aux = loop;
+ changed = true;
}
}
--
2.17.1
