SCCP instead of CFG since SCCP removes code of unused branches, not CFG (shader-slang#4640)

Author: ArielG-NV

source/slang/slang-emit.cpp

@@ -911,7 +911,7 @@ Result linkAndOptimizeIR(
     legalizeVectorTypes(irModule, sink);
 
     // Legalize `__isTextureAccess` and related.
-    legalizeIsTextureAccess(irModule);
+    legalizeIsTextureAccess(irModule, sink);
 
     // Once specialization and type legalization have been performed,
     // we should perform some of our basic optimization steps again,

source/slang/slang-ir-legalize-is-texture-access.cpp

@@ -8,7 +8,7 @@
 #include "slang-parameter-binding.h"
 #include "slang-ir-legalize-image-subscript.h"
 #include "slang-ir-legalize-varying-params.h"
-#include "slang-ir-simplify-cfg.h"
+#include "slang-ir-sccp.h"
 
 namespace Slang
 {
@@ -17,9 +17,9 @@ namespace Slang
         return as<IRImageSubscript>(getRootAddr(inst->getOperand(0)));
     }
 
-    void legalizeIsTextureAccess(IRModule* module)
+    void legalizeIsTextureAccess(IRModule* module, DiagnosticSink* sink)
     {
-        HashSet<IRFunc*> functionsToSimplifyCFG;
+        HashSet<IRFunc*> functionsToSCCP;
         IRBuilder builder(module);
         for (auto globalInst : module->getModuleInst()->getChildren())
         {
@@ -41,7 +41,7 @@ namespace Slang
                         else
                         {
                             inst->replaceUsesWith(builder.getBoolValue(false));
-                            functionsToSimplifyCFG.add(func);
+                            functionsToSCCP.add(func);
                         }
                         inst->removeAndDeallocate();
                         continue;
@@ -53,7 +53,7 @@ namespace Slang
                         else
                         {
                             inst->replaceUsesWith(builder.getBoolValue(false));
-                            functionsToSimplifyCFG.add(func);
+                            functionsToSCCP.add(func);
                         }
                         inst->removeAndDeallocate();
                         continue;
@@ -66,7 +66,7 @@ namespace Slang
                         else
                         {
                             inst->replaceUsesWith(builder.getBoolValue(false));
-                            functionsToSimplifyCFG.add(func);
+                            functionsToSCCP.add(func);
                         }
                         inst->removeAndDeallocate();
                         continue;
@@ -75,10 +75,11 @@ namespace Slang
                 }   
             }
         }
-        // Requires a simplifyCFG to ensure Slang does not evaluate 'IRTextureType' code path for 
-        // 'inst' for when 'inst' is not a 'IRTextureType'/TextureAccessor
-        for(auto func : functionsToSimplifyCFG)
-            simplifyCFG(func, CFGSimplificationOptions::getFast());
+        // Requires a SCCP to ensure Slang does not evaluate 'IRTextureType' code path
+        // and unresolved 'isTextureAccess' operations for when 'inst' is not a
+        // 'IRTextureType'/`TextureAccessor`
+        for (auto func : functionsToSCCP)
+            applySparseConditionalConstantPropagation(func, sink); 
     }
 }
 

source/slang/slang-ir-legalize-is-texture-access.h

@@ -7,5 +7,5 @@ namespace Slang
 {
     class DiagnosticSink;
 
-    void legalizeIsTextureAccess(IRModule* module);
+    void legalizeIsTextureAccess(IRModule* module, DiagnosticSink* sink);
 }

tests/hlsl-intrinsic/atomic/atomic-intrinsics.slang

@@ -1,6 +1,7 @@
 //DISABLE_TEST(compute):COMPARE_COMPUTE_EX:-cpu -compute -shaderobj -output-using-type
 //TEST(compute):COMPARE_COMPUTE_EX(filecheck-buffer=DX12):-slang -compute -dx12 -profile cs_6_0 -use-dxil -shaderobj -output-using-type -xslang -DDX12
 //TEST(compute, vulkan):COMPARE_COMPUTE_EX(filecheck-buffer=VK):-vk -emit-spirv-directly -compute -shaderobj -output-using-type -render-feature hardware-device -xslang -DVK
+//TEST(compute, vulkan):COMPARE_COMPUTE_EX(filecheck-buffer=VK):-vk -emit-spirv-via-glsl -compute -shaderobj -output-using-type -render-feature hardware-device -xslang -DVK -xslang -minimum-slang-optimization
 //TEST(compute, vulkan):COMPARE_COMPUTE_EX(filecheck-buffer=VK):-vk -emit-spirv-via-glsl -compute -shaderobj -output-using-type -render-feature hardware-device -xslang -DVK
 //DISABLE_TEST(compute):COMPARE_COMPUTE_EX:-cuda -compute -shaderobj -output-using-type