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tree-optimization/79333 - fold stmts following SSA edges in VN
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This makes sure to follow SSA edges when folding eliminated stmts.
This reaps the same benefit as forwprop folding all stmts, not
waiting for one to produce copysign in the new testcase.

2021-05-04  Richard Biener  <rguenther@suse.de>

	PR tree-optimization/79333
	* tree-ssa-sccvn.c (eliminate_dom_walker::eliminate_stmt):
	Fold stmt following SSA edges.

	* gcc.dg/tree-ssa/ssa-fre-94.c: New testcase.
	* gcc.dg/graphite/fuse-1.c: Adjust.
	* gcc.dg/pr43864-4.c: Likewise.
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rguenth committed May 5, 2021
1 parent 8ebf6b9 commit d846f22
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Showing 4 changed files with 22 additions and 6 deletions.
4 changes: 2 additions & 2 deletions gcc/testsuite/gcc.dg/graphite/fuse-1.c
Original file line number Diff line number Diff line change
@@ -1,6 +1,6 @@
/* Check that the two loops are fused and that we manage to fold the two xor
operations. */
/* { dg-options "-O2 -floop-nest-optimize -fdump-tree-forwprop-all -fdump-tree-graphite-all" } */
/* { dg-options "-O2 -floop-nest-optimize -fdump-tree-forwprop4 -fdump-tree-graphite-all" } */

/* Make sure we fuse the loops like this:
AST generated by isl:
Expand All @@ -12,7 +12,7 @@ for (int c0 = 0; c0 <= 99; c0 += 1) {
/* { dg-final { scan-tree-dump-times "AST generated by isl:.*for \\(int c0 = 0; c0 <= 99; c0 \\+= 1\\) \\{.*S_.*\\(c0\\);.*S_.*\\(c0\\);.*S_.*\\(c0\\);.*\\}" 1 "graphite" } } */

/* Check that after fusing the loops, the scalar computation is also fused. */
/* { dg-final { scan-tree-dump-times "gimple_simplified to\[^\\n\]*\\^ 12" 1 "forwprop4" } } */
/* { dg-final { scan-tree-dump-times " \\^ 12;" 2 "forwprop4" } } */

#define MAX 100
int A[MAX];
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6 changes: 3 additions & 3 deletions gcc/testsuite/gcc.dg/pr43864-4.c
Original file line number Diff line number Diff line change
Expand Up @@ -22,7 +22,7 @@ int f(int c, int b, int d)
return r - r2;
}

/* { dg-final { scan-tree-dump-times "if " 0 "pre"} } */
/* { dg-final { scan-tree-dump-times "(?n)_.*\\+.*_" 1 "pre"} } */
/* { dg-final { scan-tree-dump-times "(?n)_.*-.*_" 2 "pre"} } */
/* During PRE elimination we should simplify this to return b * 2. */
/* { dg-final { scan-tree-dump-times "if " 0 "pre" } } */
/* { dg-final { scan-tree-dump "_\[0-9\]+ = b_\[0-9\]+\\(D\\) \\* 2;\[\\r\\n\]\[^\\r\\n\]*return _\[0-9\]+;" "pre" } } */
/* { dg-final { scan-tree-dump-not "Invalid sum" "pre"} } */
16 changes: 16 additions & 0 deletions gcc/testsuite/gcc.dg/tree-ssa/ssa-fre-94.c
Original file line number Diff line number Diff line change
@@ -0,0 +1,16 @@
/* PR tree-optimization/79333 */
/* { dg-do compile } */
/* { dg-options "-O -ffinite-math-only -fdump-tree-fre1" } */

extern __inline __attribute__ ((__always_inline__,__gnu_inline__))
double __attribute__ ((__nothrow__ , __leaf__))
fabs (double __x) { return __builtin_fabs (__x); }

double f(float f)
{
double t1 = fabs(f);
double t2 = f / t1;
return t2;
}

/* { dg-final { scan-tree-dump "copysign" "fre1" } } */
2 changes: 1 addition & 1 deletion gcc/tree-ssa-sccvn.c
Original file line number Diff line number Diff line change
Expand Up @@ -6362,7 +6362,7 @@ eliminate_dom_walker::eliminate_stmt (basic_block b, gimple_stmt_iterator *gsi)
recompute_tree_invariant_for_addr_expr (gimple_assign_rhs1 (stmt));
gimple_stmt_iterator prev = *gsi;
gsi_prev (&prev);
if (fold_stmt (gsi))
if (fold_stmt (gsi, follow_all_ssa_edges))
{
/* fold_stmt may have created new stmts inbetween
the previous stmt and the folded stmt. Mark
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