tree-optimization/107569 - avoid wrecking earlier folding in FRE/PRE
Commit Message
The following avoids picking up dead code left over from folding
during FRE/PRE, effectively undoing propagations.
Bootstrapped and tested on x86_64-unknown-linux-gnu, pushed.
PR tree-optimization/107569
* tree-ssa-sccvn.cc (eliminate_dom_walker::eliminate_stmt):
Do not push SSA names with zero uses as available leader.
(process_bb): Likewise.
* g++.dg/opt/pr107569.C: New testcase.
---
gcc/testsuite/g++.dg/opt/pr107569.C | 29 +++++++++++++++++++++++++++++
gcc/tree-ssa-sccvn.cc | 17 +++++++++++------
2 files changed, 40 insertions(+), 6 deletions(-)
create mode 100644 gcc/testsuite/g++.dg/opt/pr107569.C
new file mode 100644
@@ -0,0 +1,29 @@
+// { dg-do compile }
+// { dg-require-effective-target c++20 }
+// { dg-options "-O2 -fdump-tree-evrp -fdump-tree-vrp1" }
+
+namespace std
+{
+ constexpr bool isfinite (float x) { return __builtin_isfinite (x); }
+ constexpr bool isfinite (double x) { return __builtin_isfinite (x); }
+ constexpr bool isfinite (long double x) { return __builtin_isfinite (x); }
+}
+
+bool
+foo (double x)
+{
+ if (!std::isfinite (x))
+ __builtin_unreachable ();
+
+ return std::isfinite (x);
+}
+
+bool
+bar (double x)
+{
+ [[assume (std::isfinite (x))]];
+ return std::isfinite (x);
+}
+
+/* { dg-final { scan-tree-dump "return 1;" "evrp" } } */
+/* { dg-final { scan-tree-dump-times "return 1;" 2 "vrp1" } } */
@@ -7197,10 +7197,14 @@ eliminate_dom_walker::eliminate_stmt (basic_block b, gimple_stmt_iterator *gsi)
}
/* Make new values available - for fully redundant LHS we
- continue with the next stmt above and skip this. */
- def_operand_p defp;
- FOR_EACH_SSA_DEF_OPERAND (defp, stmt, iter, SSA_OP_DEF)
- eliminate_push_avail (b, DEF_FROM_PTR (defp));
+ continue with the next stmt above and skip this.
+ But avoid picking up dead defs. */
+ tree def;
+ FOR_EACH_SSA_TREE_OPERAND (def, stmt, iter, SSA_OP_DEF)
+ if (! has_zero_uses (def)
+ || (inserted_exprs
+ && bitmap_bit_p (inserted_exprs, SSA_NAME_VERSION (def))))
+ eliminate_push_avail (b, def);
}
/* Perform elimination for the basic-block B during the domwalk. */
@@ -8046,9 +8050,10 @@ process_bb (rpo_elim &avail, basic_block bb,
avail.eliminate_stmt (bb, &gsi);
else
/* If not eliminating, make all not already available defs
- available. */
+ available. But avoid picking up dead defs. */
FOR_EACH_SSA_TREE_OPERAND (op, gsi_stmt (gsi), i, SSA_OP_DEF)
- if (! avail.eliminate_avail (bb, op))
+ if (! has_zero_uses (op)
+ && ! avail.eliminate_avail (bb, op))
avail.eliminate_push_avail (bb, op);
}