Hi!
This is an attempt to extend RTL unroller to allow cases like mentioned in the
PR -
namely when loop has duplicated exit blocks and back edges.
Bootstrapped and regtested on x86_64, also checking wide range of benchmarks -
spec2K, spec2006, EEMBC
Is it ok for trunk in case if no testing issues?
Thanks,
Igor
Changelog:
Gcc:
2014-12-19 Igor Zamyatin <igor.zamya...@intel.com>
PR rtl-optimization/64081
* loop-iv.c (def_pred_latch_p): New function.
(latch_dominating_def): Allow specific cases with non-single
definitions.
(iv_get_reaching_def): Likewise.
(check_complex_exit_p): New function.
(check_simple_exit): Use check_complex_exit_p to allow certain cases
with exits not executing on any iteration.
Testsuite:
2014-12-19 Igor Zamyatin <igor.zamya...@intel.com>
PR rtl-optimization/64081
* gcc.dg/pr64081.c: New test.
diff --git a/gcc/loop-iv.c b/gcc/loop-iv.c
index f55cea2..d5d48f1 100644
--- a/gcc/loop-iv.c
+++ b/gcc/loop-iv.c
@@ -314,34 +314,67 @@ iv_analysis_loop_init (struct loop *loop)
check_iv_ref_table_size ();
}
+/* Checks that def is in an immediate predecessor of the latch block. */
+
+static bool
+def_pred_latch_p (df_ref d_ref)
+{
+ basic_block bb = DF_REF_BB (d_ref);
+ edge_iterator ei;
+ edge e;
+
+ FOR_EACH_EDGE (e, ei, current_loop->latch->preds)
+ {
+ if (e->src == bb)
+ return true;
+ }
+ return false;
+}
+
/* Finds the definition of REG that dominates loop latch and stores
it to DEF. Returns false if there is not a single definition
- dominating the latch. If REG has no definition in loop, DEF
+ dominating the latch or all defs are same and they are on different
+ predecessors of loop latch. If REG has no definition in loop, DEF
is set to NULL and true is returned. */
static bool
latch_dominating_def (rtx reg, df_ref *def)
{
df_ref single_rd = NULL, adef;
- unsigned regno = REGNO (reg);
+ unsigned regno = REGNO (reg), def_num = 0;
struct df_rd_bb_info *bb_info = DF_RD_BB_INFO (current_loop->latch);
for (adef = DF_REG_DEF_CHAIN (regno); adef; adef = DF_REF_NEXT_REG (adef))
{
+ /* Initialize this to true for the very first iteration when
+ SINGLE_RD is NULL. */
+ bool def_pred_latch = true;
+
if (!bitmap_bit_p (df->blocks_to_analyze, DF_REF_BBNO (adef))
|| !bitmap_bit_p (&bb_info->out, DF_REF_ID (adef)))
continue;
- /* More than one reaching definition. */
+ /* More than one reaching definition is ok in case definitions are
+ in predecessors of latch block and those definitions are the same.
+ Probably this could be relaxed and check for sub-dominance instead
+ predecessor. */
if (single_rd)
- return false;
-
- if (!just_once_each_iteration_p (current_loop, DF_REF_BB (adef)))
- return false;
+ {
+ def_num++;
+ if (!(def_pred_latch = def_pred_latch_p (adef))
+ || !rtx_equal_p( PATTERN (DF_REF_INSN (single_rd)),
+ PATTERN (DF_REF_INSN (adef))))
+ return false;
+ }
single_rd = adef;
}
+ /* If we have single definition it has to be excuted on each iteration. */
+ if (!def_num && single_rd
+ && !just_once_each_iteration_p (current_loop, DF_REF_BB (single_rd)))
+ return false;
+
*def = single_rd;
return true;
}
@@ -351,10 +384,10 @@ latch_dominating_def (rtx reg, df_ref *def)
static enum iv_grd_result
iv_get_reaching_def (rtx_insn *insn, rtx reg, df_ref *def)
{
- df_ref use, adef;
+ df_ref use, adef = NULL;
basic_block def_bb, use_bb;
rtx_insn *def_insn;
- bool dom_p;
+ bool dom_p, dom_latch_p = false;
*def = NULL;
if (!simple_reg_p (reg))
@@ -369,11 +402,26 @@ iv_get_reaching_def (rtx_insn *insn, rtx reg, df_ref *def)
if (!DF_REF_CHAIN (use))
return GRD_INVARIANT;
- /* More than one reaching def. */
+ adef = DF_REF_CHAIN (use)->ref;
+ /* Having more than one reaching def is ok once all defs are in blocks which
+ are latch's predecessors. */
if (DF_REF_CHAIN (use)->next)
- return GRD_INVALID;
+ {
+ df_link* defs;
+ unsigned int def_num = 0;
- adef = DF_REF_CHAIN (use)->ref;
+ for (defs = DF_REF_CHAIN (use); defs; defs = defs->next)
+ {
+ if (!def_pred_latch_p (defs->ref))
+ return GRD_INVALID;
+ def_num++;
+ }
+ /* Make sure all preds contain definitions. */
+ if (def_num != EDGE_COUNT (current_loop->latch->preds))
+ return GRD_INVALID;
+
+ dom_latch_p = true;
+ }
/* We do not handle setting only part of the register. */
if (DF_REF_FLAGS (adef) & DF_REF_READ_WRITE)
@@ -396,8 +444,8 @@ iv_get_reaching_def (rtx_insn *insn, rtx reg, df_ref *def)
/* The definition does not dominate the use. This is still OK if
this may be a use of a biv, i.e. if the def_bb dominates loop
- latch. */
- if (just_once_each_iteration_p (current_loop, def_bb))
+ latch or all defs are in latch's predecessors. */
+ if (dom_latch_p || just_once_each_iteration_p (current_loop, def_bb))
return GRD_MAYBE_BIV;
return GRD_INVALID;
@@ -2910,6 +2958,49 @@ fail:
return;
}
+/* Check whether exit is not simple but still good for further analysis.
+ Looks like such loops mostly are a result of jump threading. */
+
+static bool
+check_complex_exit_p (struct loop* loop, basic_block bb)
+{
+ edge e;
+ basic_block pred, exit;
+
+ if (EDGE_COUNT (bb->preds) > 1)
+ return false;
+
+ e = EDGE_PRED (bb, 0);
+
+ pred = e->src;
+ if (EDGE_COUNT (pred->succs) != 2)
+ return false;
+
+ /* Predecessor must be tested (at least) once during any iteration. */
+ if (!dominated_by_p (CDI_DOMINATORS, loop->latch, pred))
+ return false;
+
+ if (EDGE_SUCC (pred, 0)->dest == bb)
+ exit = EDGE_SUCC (pred, 1)->dest;
+ else
+ exit = EDGE_SUCC (pred, 0)->dest;
+
+ /* Check that EXIT is really loop exit. */
+ if (flow_bb_inside_loop_p (loop, exit))
+ {
+ edge_iterator eei;
+ edge ee;
+
+ FOR_EACH_EDGE (ee, eei, exit->succs)
+ {
+ if (!flow_bb_inside_loop_p (loop, ee->dest))
+ return true;
+ }
+ }
+ return false;
+
+}
+
/* Checks whether E is a simple exit from LOOP and stores its description
into DESC. */
@@ -2929,7 +3020,8 @@ check_simple_exit (struct loop *loop, edge e, struct
niter_desc *desc)
return;
/* It must be tested (at least) once during any iteration. */
- if (!dominated_by_p (CDI_DOMINATORS, loop->latch, exit_bb))
+ if (!dominated_by_p (CDI_DOMINATORS, loop->latch, exit_bb)
+ && !check_complex_exit_p (loop, exit_bb))
return;
/* It must end in a simple conditional jump. */
diff --git a/gcc/testsuite/gcc.dg/pr64081.c b/gcc/testsuite/gcc.dg/pr64081.c
new file mode 100644
index 0000000..6151d00
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/pr64081.c
@@ -0,0 +1,41 @@
+/* PR rtl-optimization/64081 */
+/* { dg-do compile } */
+/* { dg-options "-O2 -funroll-loops -fdump-rtl-loop2_unroll" } */
+
+long token;
+long *data;
+long *arr1;
+long *arr2;
+
+int main (int argc, const char* argv[])
+{
+ unsigned long i;
+ static long pos, start, count;
+ static int dir;
+
+ pos = 0;
+ dir = 1;
+
+ for (i = 0; i < argc; i++)
+ {
+ start = pos;
+ for (count = 0; count <= 400; count++)
+ {
+ if (token == data[pos])
+ break;
+ if (dir == 1)
+ pos = arr1[pos];
+ else
+ pos = arr2[pos];
+ if (pos == -1)
+ {
+ pos = start;
+ dir = !dir;
+ }
+ }
+ }
+ return pos + dir;
+}
+
+/* { dg-final { scan-rtl-dump "loop unrolled 7 times" "loop2_unroll" } } */
+/* { dg-final { cleanup-rtl-dump "loop*" } } */
