Prevent hoisting of non-hoistable instructions in non-function values with code (#4250)

3 files changed, 17 insertions, 2 deletions

diff --git a/source/slang/slang-ir-redundancy-removal.cpp b/source/slang/slang-ir-redundancy-removal.cpp
index c7986cfbc..b679d8438 100644
--- a/source/slang/slang-ir-redundancy-removal.cpp
+++ b/source/slang/slang-ir-redundancy-removal.cpp
@@ -25,9 +25,9 @@ struct RedundancyRemovalContext
                 for (UInt i = 0; i < inst->getOperandCount(); i++)
                 {
                     auto operand = inst->getOperand(i);
-                    if (getParentFunc(operand) != func)
+                    if (!hasDescendent(func, operand))
                     {
-                        // Global value won't prevent hoisting.
+                        // Only prevent hoisting from operands local to this function
                         continue;
                     }
                     auto operandParent = as<IRBlock>(operand->getParent());
diff --git a/source/slang/slang-ir.cpp b/source/slang/slang-ir.cpp
index 3e96d61eb..b6d000d20 100644
--- a/source/slang/slang-ir.cpp
+++ b/source/slang/slang-ir.cpp
@@ -8530,6 +8530,18 @@ namespace Slang
         return nullptr;
     }
 
+    bool hasDescendent(IRInst* inst, IRInst* child)
+    {
+        auto parent = child->getParent();
+        while (parent)
+        {
+            if (inst == parent)
+                return true;
+            parent = parent->getParent();
+        }
+        return false;
+    }
+
     IRInst* getGenericReturnVal(IRInst* inst)
     {
         if (auto gen = as<IRGeneric>(inst))
diff --git a/source/slang/slang-ir.h b/source/slang/slang-ir.h
index 3a5384e8d..9e8be7fc5 100644
--- a/source/slang/slang-ir.h
+++ b/source/slang/slang-ir.h
@@ -2538,6 +2538,9 @@ bool isBuiltin(IRInst* inst);
     // Get the enclosuing function of an instruction.
 IRFunc* getParentFunc(IRInst* inst);
 
+    // Is child a descendent of inst
+bool hasDescendent(IRInst* inst, IRInst* child);
+
     // True if moving this inst will not change the semantics of the program
 bool isMovableInst(IRInst* inst);