On Tue, 28 May 2019, Jiufu Guo wrote:
> Hi,
>
> This patch implements a new opportunity of jump threading for PR77820.
> In this optimization, conditional jumps are merged with unconditional
> jump. And then moving CMP result to GPR is eliminated.
>
> This version is based on the proposal of Richard, Jeff and Andrew, and
> refined to incorporate comments. Thanks for the reviews!
>
> Bootstrapped and tested on powerpc64le and powerpc64be with no
> regressions (one case is improved) and new testcases are added. Is this
> ok for trunk?
>
> Example of this opportunity looks like below:
>
> <P0>
> p0 = a CMP b
> goto <X>;
>
> <P1>
> p1 = c CMP d
> goto <X>;
>
> <X>
> # phi = PHI <p0 (P0), p1 (P1)>
> if (phi != 0) goto <Y>; else goto <Z>;
>
> Could be transformed to:
>
> <P0>
> p0 = a CMP b
> if (p0 != 0) goto <Y>; else goto <Z>;
>
> <P1>
> p1 = c CMP d
> if (p1 != 0) goto <Y>; else goto <Z>;
>
>
> This optimization eliminates:
> 1. saving CMP result: p0 = a CMP b.
> 2. additional CMP on branch: if (phi != 0).
> 3. converting CMP result if there is phi = (INT_CONV) p0 if there is.
>
> Thanks!
> Jiufu Guo
>
>
> [gcc]
> 2019-05-28 Jiufu Guo <guoji...@linux.ibm.com>
> Lijia He <heli...@linux.ibm.com>
>
> PR tree-optimization/77820
> * tree-ssa-threadedge.c
> (edge_forwards_cmp_to_conditional_jump_through_empty_bb_p): New
> function.
> (thread_across_edge): Add call to
> edge_forwards_cmp_to_conditional_jump_through_empty_bb_p.
>
> [gcc/testsuite]
> 2019-05-28 Jiufu Guo <guoji...@linux.ibm.com>
> Lijia He <heli...@linux.ibm.com>
>
> PR tree-optimization/77820
> * gcc.dg/tree-ssa/phi_on_compare-1.c: New testcase.
> * gcc.dg/tree-ssa/phi_on_compare-2.c: New testcase.
> * gcc.dg/tree-ssa/phi_on_compare-3.c: New testcase.
> * gcc.dg/tree-ssa/phi_on_compare-4.c: New testcase.
> * gcc.dg/tree-ssa/split-path-6.c: Update testcase.
>
> ---
> gcc/testsuite/gcc.dg/tree-ssa/phi_on_compare-1.c | 30 ++++++++++
> gcc/testsuite/gcc.dg/tree-ssa/phi_on_compare-2.c | 23 +++++++
> gcc/testsuite/gcc.dg/tree-ssa/phi_on_compare-3.c | 25 ++++++++
> gcc/testsuite/gcc.dg/tree-ssa/phi_on_compare-4.c | 40 +++++++++++++
> gcc/testsuite/gcc.dg/tree-ssa/split-path-6.c | 2 +-
> gcc/tree-ssa-threadedge.c | 76
> +++++++++++++++++++++++-
> 6 files changed, 192 insertions(+), 4 deletions(-)
> create mode 100644 gcc/testsuite/gcc.dg/tree-ssa/phi_on_compare-1.c
> create mode 100644 gcc/testsuite/gcc.dg/tree-ssa/phi_on_compare-2.c
> create mode 100644 gcc/testsuite/gcc.dg/tree-ssa/phi_on_compare-3.c
> create mode 100644 gcc/testsuite/gcc.dg/tree-ssa/phi_on_compare-4.c
>
> diff --git a/gcc/testsuite/gcc.dg/tree-ssa/phi_on_compare-1.c
> b/gcc/testsuite/gcc.dg/tree-ssa/phi_on_compare-1.c
> new file mode 100644
> index 0000000..5227c87
> --- /dev/null
> +++ b/gcc/testsuite/gcc.dg/tree-ssa/phi_on_compare-1.c
> @@ -0,0 +1,30 @@
> +/* { dg-do compile } */
> +/* { dg-options "-Ofast -fdump-tree-vrp1" } */
> +
> +void g (int);
> +void g1 (int);
> +
> +void
> +f (long a, long b, long c, long d, long x)
> +{
> + _Bool t;
> + if (x)
> + {
> + g (a + 1);
> + t = a < b;
> + c = d + x;
> + }
> + else
> + {
> + g (b + 1);
> + a = c + d;
> + t = c > d;
> + }
> +
> + if (t)
> + g1 (c);
> +
> + g (a);
> +}
> +
> +/* { dg-final { scan-tree-dump-times "Removing basic block" 1 "vrp1" } } */
> diff --git a/gcc/testsuite/gcc.dg/tree-ssa/phi_on_compare-2.c
> b/gcc/testsuite/gcc.dg/tree-ssa/phi_on_compare-2.c
> new file mode 100644
> index 0000000..eaf89bb
> --- /dev/null
> +++ b/gcc/testsuite/gcc.dg/tree-ssa/phi_on_compare-2.c
> @@ -0,0 +1,23 @@
> +/* { dg-do compile } */
> +/* { dg-options "-Ofast -fdump-tree-vrp1" } */
> +
> +void g (void);
> +void g1 (void);
> +
> +void
> +f (long a, long b, long c, long d, int x)
> +{
> + _Bool t;
> + if (x)
> + t = c < d;
> + else
> + t = a < b;
> +
> + if (t)
> + {
> + g1 ();
> + g ();
> + }
> +}
> +
> +/* { dg-final { scan-tree-dump-times "Removing basic block" 1 "vrp1" } } */
> diff --git a/gcc/testsuite/gcc.dg/tree-ssa/phi_on_compare-3.c
> b/gcc/testsuite/gcc.dg/tree-ssa/phi_on_compare-3.c
> new file mode 100644
> index 0000000..d5a1e0b
> --- /dev/null
> +++ b/gcc/testsuite/gcc.dg/tree-ssa/phi_on_compare-3.c
> @@ -0,0 +1,25 @@
> +/* { dg-do compile } */
> +/* { dg-options "-Ofast -fdump-tree-vrp1" } */
> +
> +void g (void);
> +void g1 (void);
> +
> +void
> +f (long a, long b, long c, long d, int x)
> +{
> + int t;
> + if (x)
> + t = a < b;
> + else if (d == x)
> + t = c < b;
> + else
> + t = d > c;
> +
> + if (t)
> + {
> + g1 ();
> + g ();
> + }
> +}
> +
> +/* { dg-final { scan-tree-dump-times "Removing basic block" 1 "vrp1" } } */
> diff --git a/gcc/testsuite/gcc.dg/tree-ssa/phi_on_compare-4.c
> b/gcc/testsuite/gcc.dg/tree-ssa/phi_on_compare-4.c
> new file mode 100644
> index 0000000..53acabc
> --- /dev/null
> +++ b/gcc/testsuite/gcc.dg/tree-ssa/phi_on_compare-4.c
> @@ -0,0 +1,40 @@
> +/* { dg-do compile } */
> +/* { dg-options "-Ofast -fdump-tree-vrp1" } */
> +
> +void g (int);
> +void g1 (int);
> +
> +void
> +f (long a, long b, long c, long d, int x)
> +{
> + int t;
> + _Bool l1 = 0, l2 = 0;
> + if (x)
> + {
> + g (a);
> + c = a + b;
> + t = a < b;
> + l1 = 1;
> + }
> + else
> + {
> + g1 (b);
> + t = c > d;
> + d = c + b;
> + l2 = 1;
> + }
> +
> + if (t)
> + {
> + if (l1 | l2)
> + g1 (c);
> + }
> + else
> + {
> + g (d);
> + g1 (a + b);
> + }
> + g (c + d);
> +}
> +
> +/* { dg-final { scan-tree-dump-times "Removing basic block" 1 "vrp1" } } */
> diff --git a/gcc/testsuite/gcc.dg/tree-ssa/split-path-6.c
> b/gcc/testsuite/gcc.dg/tree-ssa/split-path-6.c
> index e9b4f26..1d7b587 100644
> --- a/gcc/testsuite/gcc.dg/tree-ssa/split-path-6.c
> +++ b/gcc/testsuite/gcc.dg/tree-ssa/split-path-6.c
> @@ -69,4 +69,4 @@ lookharder (string)
> }
> }
>
> -/* { dg-final { scan-tree-dump-times "Duplicating join block" 3
> "split-paths" } } */
> +/* { dg-final { scan-tree-dump-times "Duplicating join block" 2
> "split-paths" } } */
> diff --git a/gcc/tree-ssa-threadedge.c b/gcc/tree-ssa-threadedge.c
> index c3ea2d6..36c413a 100644
> --- a/gcc/tree-ssa-threadedge.c
> +++ b/gcc/tree-ssa-threadedge.c
> @@ -1157,6 +1157,74 @@ thread_through_normal_block (edge e,
> return 0;
> }
>
> +/* There are basic blocks look like:
> + <P0>
> + p0 = a CMP b ; or p0 = (INT) (a CMP b)
> + goto <X>;
> +
> + <P1>
> + p1 = c CMP d
> + goto <X>;
> +
> + <X>
> + # phi = PHI <p0 (P0), p1 (P1)>
> + if (phi != 0) goto <Y>; else goto <Z>;
> +
> + Then, edge (P0,X) or (P1,X) could be marked as EDGE_START_JUMP_THREAD
> + And edge (X,Y), (X,Z) is EDGE_COPY_SRC_JOINER_BLOCK
> +
> + Return true if E is (P0,X) or (P1,X) */
> +
> +bool
> +edge_forwards_cmp_to_conditional_jump_through_empty_bb_p (edge e)
> +{
> + basic_block bb = e->dest;
> +
> + /* See if there is only one stmt which is gcond. */
> + gimple *gs = last_and_only_stmt (bb);
> + if (gs == NULL || gimple_code (gs) != GIMPLE_COND)
> + return false;
gcond *gs;
if (!(gs = safe_dyn_cast <gcond *> (last_and_only_stmt (bb))))
return false;
makes the following gimple_cond_ accesses more efficient when
checking is enabled.
> +
> + /* See if gcond's cond is "(phi !=/== 0/1)" in the basic block. */
> + tree cond = gimple_cond_lhs (gs);
> + enum tree_code code = gimple_cond_code (gs);
> + tree rhs = gimple_cond_rhs (gs);
> + if (TREE_CODE (cond) != SSA_NAME
> + || (code != NE_EXPR && code != EQ_EXPR)
> + || (!integer_onep (rhs) && !integer_zerop (rhs)))
> + return false;
> + gphi *phi = dyn_cast <gphi *> (SSA_NAME_DEF_STMT (cond));
> + if (phi == NULL || gimple_bb (phi) != bb)
> + return false;
> +
> + /* Check if phi's incoming value is CMP. */
> + gimple *def;
> + tree value = PHI_ARG_DEF_FROM_EDGE (phi, e);
> + if (TREE_CODE (value) == SSA_NAME
> + && has_single_use (value)
> + && is_gimple_assign (SSA_NAME_DEF_STMT (value)))
> + def = SSA_NAME_DEF_STMT (value);
Same is true here and below if you rewrite to
gassign *def;
tree value = PHI_ARG_DEF_FROM_EDGE (phi, e);
if (TREE_CODE (value) != SSA_NAME
|| !has_single_use (value)
|| !(def = dyn_cast <gassign *> (SSA_NAME_DEF_STMT (value))))
return false;
Otherwise it looks good. I'd like to have Jeffs opinion and
final ACK here because we touch jump-threading and he's most
familiar with that detail and the place you hook into.
Thanks,
Richard.
> + else
> + return false;
> +
> + /* Or if it is (INT) (a CMP b). */
> + if (CONVERT_EXPR_CODE_P (gimple_assign_rhs_code (def)))
> + {
> + value = gimple_assign_rhs1 (def);
> + if (TREE_CODE (value) == SSA_NAME
> + && has_single_use (value)
> + && is_gimple_assign (SSA_NAME_DEF_STMT (value)))
> + def = SSA_NAME_DEF_STMT (value);
> + else
> + return false;
> + }
> +
> + if (TREE_CODE_CLASS (gimple_assign_rhs_code (def)) != tcc_comparison)
> + return false;
> +
> + return true;
> +}
> +
> /* We are exiting E->src, see if E->dest ends with a conditional
> jump which has a known value when reached via E.
>
> @@ -1317,10 +1385,12 @@ thread_across_edge (gcond *dummy_cond,
>
> /* If we were able to thread through a successor of E->dest, then
> record the jump threading opportunity. */
> - if (found)
> + if (found
> + || edge_forwards_cmp_to_conditional_jump_through_empty_bb_p (e))
> {
> - propagate_threaded_block_debug_into (path->last ()->e->dest,
> - taken_edge->dest);
> + if (taken_edge->dest != path->last ()->e->dest)
> + propagate_threaded_block_debug_into (path->last ()->e->dest,
> + taken_edge->dest);
> register_jump_thread (path);
> }
> else
>
--
Richard Biener <rguent...@suse.de>
SUSE Linux GmbH, Maxfeldstrasse 5, 90409 Nuernberg, Germany;
GF: Felix Imendörffer, Mary Higgins, Sri Rasiah; HRB 21284 (AG Nürnberg)
