Do not set ResMayNotAlias if DXIL Ver <= 1.6

Author: Icohedron

llvm/lib/Target/DirectX/DXILShaderFlags.cpp

@@ -120,10 +120,9 @@ void ModuleShaderFlags::updateFunctionFlags(ComputedShaderFlags &CSF,
     case Intrinsic::dx_resource_handlefrombinding: {
       dxil::ResourceTypeInfo &RTI = DRTM[cast<TargetExtType>(II->getType())];
 
-      // If -res-may-alias is NOT specified, and DXIL Ver > 1.7.
-      // Then set ResMayNotAlias if function uses UAVs.
-      if (!CSF.ResMayNotAlias && !ResMayAlias &&
-          MMDI.DXILVersion > VersionTuple(1, 7) && RTI.isUAV()) {
+      // Set ResMayNotAlias if DXIL version >= 1.8 and function uses UAVs
+      if (!CSF.ResMayNotAlias && CanSetResMayNotAlias &&
+          MMDI.DXILVersion >= VersionTuple(1, 8) && RTI.isUAV()) {
         CSF.ResMayNotAlias = true;
       }
 
@@ -165,12 +164,14 @@ void ModuleShaderFlags::initialize(Module &M, DXILResourceTypeMap &DRTM,
                                    DXILBindingMap &DBM,
                                    const ModuleMetadataInfo &MMDI) {
 
+  CanSetResMayNotAlias = MMDI.DXILVersion >= VersionTuple(1, 7);
+
   // Check if -res-may-alias was provided on the command line.
   // The command line option will set the dx.resmayalias module flag to 1.
   if (auto *RMA = mdconst::extract_or_null<ConstantInt>(
           M.getModuleFlag("dx.resmayalias"))) {
     if (RMA->getValue() != 0)
-      ResMayAlias = true;
+      CanSetResMayNotAlias = false;
   }
 
   CallGraph CG(M);
@@ -197,9 +198,9 @@ void ModuleShaderFlags::initialize(Module &M, DXILResourceTypeMap &DRTM,
         continue;
       }
 
-      // If -res-may-alias is NOT specified, and DXIL Ver <= 1.7.
-      // Then set ResMayNotAlias to true if there are UAVs present globally.
-      if (!ResMayAlias && MMDI.DXILVersion <= VersionTuple(1, 7)) {
+      // Set ResMayNotAlias to true if DXIL version < 1.8 and there are UAVs
+      // present globally.
+      if (CanSetResMayNotAlias && MMDI.DXILVersion < VersionTuple(1, 8)) {
         SCCSF.ResMayNotAlias = !DBM.uavs().empty();
       }
 

llvm/lib/Target/DirectX/DXILShaderFlags.h

@@ -91,10 +91,7 @@ struct ModuleShaderFlags {
   const ComputedShaderFlags &getCombinedFlags() const { return CombinedSFMask; }
 
 private:
-  // A bool to indicate if the -res-may-alias flag was passed to clang-dxc.
-  // A module flag "dx.resmayalias" is set to 1 if true.
-  // This bool is used in the logic for setting the flag ResMayNotAlias.
-  bool ResMayAlias = false;
+  bool CanSetResMayNotAlias;
   /// Map of Function-Shader Flag Mask pairs representing properties of each of
   /// the functions in the module. Shader Flags of each function represent both
   /// module-level and function-level flags

llvm/test/CodeGen/DirectX/ShaderFlags/res-may-not-alias-shadermodel6.6.ll

@@ -0,0 +1,33 @@
+; RUN: opt -S --passes="print-dx-shader-flags" 2>&1 %s | FileCheck %s
+
+target triple = "dxil-pc-shadermodel6.6-library"
+
+; CHECK:      Combined Shader Flags for Module
+; CHECK-NEXT: Shader Flags Value: 0x00000010
+
+; CHECK: Note: extra DXIL module flags:
+; CHECK:       Raw and Structured buffers
+; CHECK-NOT:   Any UAV may not alias any other UAV
+;
+
+; CHECK: Function loadUAV : 0x00000000
+define float @loadUAV() #0 {
+  %res = call target("dx.TypedBuffer", float, 1, 0, 0)
+      @llvm.dx.resource.handlefrombinding(i32 0, i32 0, i32 1, i32 0, i1 false)
+  %load = call {float, i1} @llvm.dx.resource.load.typedbuffer(
+      target("dx.TypedBuffer", float, 1, 0, 0) %res, i32 0)
+  %val = extractvalue {float, i1} %load, 0
+  ret float %val
+}
+
+; CHECK: Function loadSRV : 0x00000010
+define float @loadSRV() #0 {
+  %res = tail call target("dx.RawBuffer", float, 0, 0)
+      @llvm.dx.resource.handlefrombinding(i32 0, i32 0, i32 1, i32 0, i1 false)
+  %load = call {float, i1} @llvm.dx.resource.load.rawbuffer(
+      target("dx.RawBuffer", float, 0, 0) %res, i32 0, i32 0)
+  %val = extractvalue { float, i1 } %load, 0
+  ret float %val
+}
+
+attributes #0 = { convergent norecurse nounwind "hlsl.export"}