Fix DCE on mutable calls in a loop. (#2943)

* Fix DCE on mutable calls in a loop.

* More accurate in-loop test.

* code review  fixes.

* Fix.

---------

Co-authored-by: Yong He <yhe@nvidia.com>

1 files changed, 30 insertions, 34 deletions

diff --git a/source/slang/slang-ir-propagate-func-properties.cpp b/source/slang/slang-ir-propagate-func-properties.cpp
index 7b29aaf14..f530e263d 100644
--- a/source/slang/slang-ir-propagate-func-properties.cpp
+++ b/source/slang/slang-ir-propagate-func-properties.cpp
@@ -14,6 +14,26 @@ public:
     virtual bool propagate(IRBuilder& builder, IRFunc* func) = 0;
 };
 
+static bool isKnownOpCodeWithSideEffect(IROp op)
+{
+    switch (op)
+    {
+    case kIROp_ifElse:
+    case kIROp_unconditionalBranch:
+    case kIROp_Switch:
+    case kIROp_Return:
+    case kIROp_loop:
+    case kIROp_Call:
+    case kIROp_Param:
+    case kIROp_Unreachable:
+    case kIROp_Store:
+    case kIROp_SwizzledStore:
+        return true;
+    default:
+        return false;
+    }
+}
+
 class ReadNoneFuncPropertyPropagationContext : public FuncPropertyPropagationContext
 {
 public:
@@ -40,22 +60,10 @@ public:
             for (auto inst : block->getChildren())
             {
                 // Is this inst known to not have global side effect/analyzable?
-                if (inst->mightHaveSideEffects())
+                if (!isKnownOpCodeWithSideEffect(inst->getOp()))
                 {
-                    switch (inst->getOp())
+                    if (inst->mightHaveSideEffects())
                     {
-                    case kIROp_ifElse:
-                    case kIROp_unconditionalBranch:
-                    case kIROp_Switch:
-                    case kIROp_Return:
-                    case kIROp_loop:
-                    case kIROp_Call:
-                    case kIROp_Param:
-                    case kIROp_Unreachable:
-                    case kIROp_Store:
-                    case kIROp_SwizzledStore:
-                        break;
-                    default:
                         // We have a inst that has side effect and is not understood by this method.
                         // e.g. bufferStore, discard, etc.
                         hasSideEffectCall = true;
@@ -238,33 +246,21 @@ public:
         {
             for (auto inst : block->getChildren())
             {
-                // Is this inst known to not have global side effect/analyzable?
-                if (inst->mightHaveSideEffects())
+                if (!isKnownOpCodeWithSideEffect(inst->getOp()))
                 {
-                    switch (inst->getOp())
+                    // Is this inst known to not have global side effect/analyzable?
+                    if (inst->mightHaveSideEffects())
                     {
-                    case kIROp_ifElse:
-                    case kIROp_unconditionalBranch:
-                    case kIROp_Switch:
-                    case kIROp_Return:
-                    case kIROp_loop:
-                    case kIROp_Call:
-                    case kIROp_Param:
-                    case kIROp_Unreachable:
-                    case kIROp_Store:
-                    case kIROp_SwizzledStore:
-                        break;
-                    default:
                         // We have a inst that has side effect and is not understood by this method.
                         // e.g. bufferStore, discard, etc.
                         hasSideEffectCall = true;
                         break;
                     }
-                }
-                else
-                {
-                    // A side effect free inst can't generate side effects for the function.
-                    continue;
+                    else
+                    {
+                        // A side effect free inst can't generate side effects for the function.
+                        continue;
+                    }
                 }
 
                 if (auto call = as<IRCall>(inst))