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[4/4] rtl-ssa: Avoid creating duplicated phis

Message ID 20231024103000.3334790-5-richard.sandiford@arm.com
State New
Headers show
Series rtl-ssa: Some small, obvious fixes | expand

Commit Message

Richard Sandiford Oct. 24, 2023, 10:30 a.m. UTC 
If make_uses_available was called twice for the same use,
we could end up trying to create duplicate definitions for
the same extended live range.

gcc/
	* rtl-ssa/blocks.cc (function_info::create_degenerate_phi): Check
	whether the requested phi already exists.
---
 gcc/rtl-ssa/blocks.cc | 5 +++++
 1 file changed, 5 insertions(+)
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Patch

diff --git a/gcc/rtl-ssa/blocks.cc b/gcc/rtl-ssa/blocks.cc
index d46cbf1e388..ecce7a68c59 100644
--- a/gcc/rtl-ssa/blocks.cc
+++ b/gcc/rtl-ssa/blocks.cc
@@ -525,6 +525,11 @@  function_info::create_phi (ebb_info *ebb, resource_info resource,
 phi_info *
 function_info::create_degenerate_phi (ebb_info *ebb, set_info *def)
 {
+  // Allow the function to be called twice in succession for the same def.
+  def_lookup dl = find_def (def->resource (), ebb->phi_insn ());
+  if (set_info *set = dl.matching_set ())
+    return as_a<phi_info *> (set);
+
   access_info *input = def;
   phi_info *phi = create_phi (ebb, def->resource (), &input, 1);
   if (def->is_reg ())