Fix Phi simplification bug (#3325)

Fixes https://github.com/shader-slang/slang/issues/3323

1 files changed, 5 insertions, 2 deletions

diff --git a/source/slang/slang-ir-peephole.cpp b/source/slang/slang-ir-peephole.cpp
index d7713618e..6cabbe8d4 100644
--- a/source/slang/slang-ir-peephole.cpp
+++ b/source/slang/slang-ir-peephole.cpp
@@ -845,8 +845,11 @@ struct PeepholeContext : InstPassBase
                 {
                     if (inst->hasUses())
                     {
-                        // Is argValue a global constant?
-                        if (isChildInstOf(inst, argValue->getParent()))
+                        // Is argValue not a local value, i.e. it's not a child
+                        // of a block, and it's 'visible' from inst because
+                        // inst is a descendent of argValue's parent
+                        if (!as<IRBlock>(argValue->getParent())
+                            && isChildInstOf(inst, argValue->getParent()))
                         {
                             inst->replaceUsesWith(argValue);
                             // Never remove param inst.