[DirectX] Implement Shader Flags Analysis for ResMayNotAlias (#131070)

Fixes #112270

Completed ACs:
- `-res-may-alias` clang-dxc command-line option added
  - It inserts and sets a module metadata flag `dx.resmayalias` to 1
- Shader flag set appropriately:
- The flag IS NOT set if DXIL Version <= 1.6 OR the command-line option
`-res-may-alias` is specified
  - Otherwise the flag IS set when:
    - DXIL Version > 1.7 AND function uses UAVs, OR
    - DXIL Version <= 1.7 AND UAVs present globally
- Add tests 
- Tests for Shader Models 6.6, 6.7, and 6.8 corresponding to DXIL
Versions 1.6, 1.7, and 1.8
- Tests (`res-may-alias-0.ll`/`res-may-alias-1.ll`) for when the module
metadata flag `dx.resmayalias` is set to 0 or 1 respectively
- A frontend test (`res-may-alias.hlsl`) for testing that that the
command-line option `-res-may-alias` inserts `dx.resmayalias` module
metadata correctly

Author: Icohedron

clang/include/clang/Basic/CodeGenOptions.def

@@ -476,6 +476,9 @@ CODEGENOPT(ImportCallOptimization, 1, 0)
 /// (BlocksRuntime) on Windows.
 CODEGENOPT(StaticClosure, 1, 0)
 
+/// Assume that UAVs/SRVs may alias
+CODEGENOPT(ResMayAlias, 1, 0)
+
 /// FIXME: Make DebugOptions its own top-level .def file.
 #include "DebugOptions.def"
 

clang/include/clang/Driver/Options.td

@@ -9131,6 +9131,11 @@ def dxil_validator_version : Option<["/", "-"], "validator-version", KIND_SEPARA
   HelpText<"Override validator version for module. Format: <major.minor>;"
            "Default: DXIL.dll version or current internal version">,
   MarshallingInfoString<TargetOpts<"DxilValidatorVersion">, "\"1.8\"">;
+def res_may_alias : Option<["/", "-"], "res-may-alias", KIND_FLAG>,
+  Group<dxc_Group>, Flags<[HelpHidden]>,
+  Visibility<[DXCOption, ClangOption, CC1Option]>,
+  HelpText<"Assume that UAVs/SRVs may alias">,
+  MarshallingInfoFlag<CodeGenOpts<"ResMayAlias">>;
 def target_profile : DXCJoinedOrSeparate<"T">, MetaVarName<"<profile>">,
   HelpText<"Set target profile">,
   Values<"ps_6_0, ps_6_1, ps_6_2, ps_6_3, ps_6_4, ps_6_5, ps_6_6, ps_6_7,"

clang/lib/CodeGen/CGHLSLRuntime.cpp

@@ -282,11 +282,14 @@ void CGHLSLRuntime::addHLSLBufferLayoutType(const RecordType *StructType,
 
 void CGHLSLRuntime::finishCodeGen() {
   auto &TargetOpts = CGM.getTarget().getTargetOpts();
+  auto &CodeGenOpts = CGM.getCodeGenOpts();
   auto &LangOpts = CGM.getLangOpts();
   llvm::Module &M = CGM.getModule();
   Triple T(M.getTargetTriple());
   if (T.getArch() == Triple::ArchType::dxil)
     addDxilValVersion(TargetOpts.DxilValidatorVersion, M);
+  if (CodeGenOpts.ResMayAlias)
+    M.setModuleFlag(llvm::Module::ModFlagBehavior::Error, "dx.resmayalias", 1);
 
   // NativeHalfType corresponds to the -fnative-half-type clang option which is
   // aliased by clang-dxc's -enable-16bit-types option. This option is used to

clang/lib/Driver/ToolChains/Clang.cpp

@@ -3974,6 +3974,7 @@ static void RenderOpenCLOptions(const ArgList &Args, ArgStringList &CmdArgs,
 static void RenderHLSLOptions(const ArgList &Args, ArgStringList &CmdArgs,
                               types::ID InputType) {
   const unsigned ForwardedArguments[] = {options::OPT_dxil_validator_version,
+                                         options::OPT_res_may_alias,
                                          options::OPT_D,
                                          options::OPT_I,
                                          options::OPT_O,

clang/test/CodeGenHLSL/res-may-alias.hlsl

@@ -0,0 +1,7 @@
+// RUN: %clang_dxc -res-may-alias -T lib_6_3 -HV 202x -Vd -Xclang -emit-llvm %s | FileCheck %s --check-prefix=FLAG
+// RUN: %clang_dxc -T lib_6_3 -HV 202x -Vd -Xclang -emit-llvm %s | FileCheck %s --check-prefix=NOFLAG
+
+// FLAG-DAG: ![[RMA:.*]] = !{i32 1, !"dx.resmayalias", i32 1}
+// FLAG-DAG: !llvm.module.flags = !{{{.*}}![[RMA]]{{.*}}}
+
+// NOFLAG-NOT: dx.resmayalias

llvm/lib/Target/DirectX/DXILShaderFlags.cpp

@@ -74,7 +74,8 @@ static bool checkWaveOps(Intrinsic::ID IID) {
 /// \param I Instruction to check.
 void ModuleShaderFlags::updateFunctionFlags(ComputedShaderFlags &CSF,
                                             const Instruction &I,
-                                            DXILResourceTypeMap &DRTM) {
+                                            DXILResourceTypeMap &DRTM,
+                                            const ModuleMetadataInfo &MMDI) {
   if (!CSF.Doubles)
     CSF.Doubles = I.getType()->isDoubleTy();
 
@@ -128,8 +129,15 @@ void ModuleShaderFlags::updateFunctionFlags(ComputedShaderFlags &CSF,
     switch (II->getIntrinsicID()) {
     default:
       break;
-    case Intrinsic::dx_resource_handlefrombinding:
-      switch (DRTM[cast<TargetExtType>(II->getType())].getResourceKind()) {
+    case Intrinsic::dx_resource_handlefrombinding: {
+      dxil::ResourceTypeInfo &RTI = DRTM[cast<TargetExtType>(II->getType())];
+
+      // 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;
+
+      switch (RTI.getResourceKind()) {
       case dxil::ResourceKind::StructuredBuffer:
       case dxil::ResourceKind::RawBuffer:
         CSF.EnableRawAndStructuredBuffers = true;
@@ -138,6 +146,7 @@ void ModuleShaderFlags::updateFunctionFlags(ComputedShaderFlags &CSF,
         break;
       }
       break;
+    }
     case Intrinsic::dx_resource_load_typedbuffer: {
       dxil::ResourceTypeInfo &RTI =
           DRTM[cast<TargetExtType>(II->getArgOperand(0)->getType())];
@@ -163,7 +172,18 @@ void ModuleShaderFlags::updateFunctionFlags(ComputedShaderFlags &CSF,
 
 /// Construct ModuleShaderFlags for module Module M
 void ModuleShaderFlags::initialize(Module &M, DXILResourceTypeMap &DRTM,
+                                   DXILResourceMap &DRM,
                                    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)
+      CanSetResMayNotAlias = false;
+
   CallGraph CG(M);
 
   // Compute Shader Flags Mask for all functions using post-order visit of SCC
@@ -188,6 +208,11 @@ void ModuleShaderFlags::initialize(Module &M, DXILResourceTypeMap &DRTM,
         continue;
       }
 
+      // Set ResMayNotAlias to true if DXIL version < 1.8 and there are UAVs
+      // present globally.
+      if (CanSetResMayNotAlias && MMDI.DXILVersion < VersionTuple(1, 8))
+        SCCSF.ResMayNotAlias = !DRM.uavs().empty();
+
       // Set UseNativeLowPrecision using dx.nativelowprec module metadata
       if (auto *NativeLowPrec = mdconst::extract_or_null<ConstantInt>(
               M.getModuleFlag("dx.nativelowprec")))
@@ -198,7 +223,7 @@ void ModuleShaderFlags::initialize(Module &M, DXILResourceTypeMap &DRTM,
       ComputedShaderFlags CSF;
       for (const auto &BB : *F)
         for (const auto &I : BB)
-          updateFunctionFlags(CSF, I, DRTM);
+          updateFunctionFlags(CSF, I, DRTM, MMDI);
       // Update combined shader flags mask for all functions in this SCC
       SCCSF.merge(CSF);
 
@@ -268,10 +293,11 @@ AnalysisKey ShaderFlagsAnalysis::Key;
 ModuleShaderFlags ShaderFlagsAnalysis::run(Module &M,
                                            ModuleAnalysisManager &AM) {
   DXILResourceTypeMap &DRTM = AM.getResult<DXILResourceTypeAnalysis>(M);
+  DXILResourceMap &DRM = AM.getResult<DXILResourceAnalysis>(M);
   const ModuleMetadataInfo MMDI = AM.getResult<DXILMetadataAnalysis>(M);
 
   ModuleShaderFlags MSFI;
-  MSFI.initialize(M, DRTM, MMDI);
+  MSFI.initialize(M, DRTM, DRM, MMDI);
 
   return MSFI;
 }
@@ -301,16 +327,18 @@ PreservedAnalyses ShaderFlagsAnalysisPrinter::run(Module &M,
 bool ShaderFlagsAnalysisWrapper::runOnModule(Module &M) {
   DXILResourceTypeMap &DRTM =
       getAnalysis<DXILResourceTypeWrapperPass>().getResourceTypeMap();
+  DXILResourceMap &DRM = getAnalysis<DXILResourceWrapperPass>().getBindingMap();
   const ModuleMetadataInfo MMDI =
       getAnalysis<DXILMetadataAnalysisWrapperPass>().getModuleMetadata();
 
-  MSFI.initialize(M, DRTM, MMDI);
+  MSFI.initialize(M, DRTM, DRM, MMDI);
   return false;
 }
 
 void ShaderFlagsAnalysisWrapper::getAnalysisUsage(AnalysisUsage &AU) const {
   AU.setPreservesAll();
   AU.addRequiredTransitive<DXILResourceTypeWrapperPass>();
+  AU.addRequiredTransitive<DXILResourceWrapperPass>();
   AU.addRequired<DXILMetadataAnalysisWrapperPass>();
 }
 

llvm/lib/Target/DirectX/DXILShaderFlags.h

@@ -28,6 +28,7 @@ namespace llvm {
 class Module;
 class GlobalVariable;
 class DXILResourceTypeMap;
+class DXILResourceMap;
 
 namespace dxil {
 
@@ -84,20 +85,21 @@ struct ComputedShaderFlags {
 };
 
 struct ModuleShaderFlags {
-  void initialize(Module &, DXILResourceTypeMap &DRTM,
+  void initialize(Module &, DXILResourceTypeMap &DRTM, DXILResourceMap &DRM,
                   const ModuleMetadataInfo &MMDI);
   const ComputedShaderFlags &getFunctionFlags(const Function *) const;
   const ComputedShaderFlags &getCombinedFlags() const { return CombinedSFMask; }
 
 private:
+  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
   DenseMap<const Function *, ComputedShaderFlags> FunctionFlags;
   /// Combined Shader Flag Mask of all functions of the module
   ComputedShaderFlags CombinedSFMask{};
   void updateFunctionFlags(ComputedShaderFlags &, const Instruction &,
-                           DXILResourceTypeMap &);
+                           DXILResourceTypeMap &, const ModuleMetadataInfo &);
 };
 
 class ShaderFlagsAnalysis : public AnalysisInfoMixin<ShaderFlagsAnalysis> {

llvm/test/CodeGen/DirectX/ShaderFlags/res-may-alias-0.ll

@@ -0,0 +1,43 @@
+; RUN: opt -S --passes="print-dx-shader-flags" 2>&1 %s | FileCheck %s
+
+; This test checks to ensure that setting the LLVM module flag "dx.resmayalias"
+; to 0 has no effect on the DXIL shader flag analysis for the flag
+; ResMayNotAlias.
+
+target triple = "dxil-pc-shadermodel6.8-library"
+
+; CHECK:      Combined Shader Flags for Module
+; CHECK-NEXT: Shader Flags Value: 0x200000010
+
+; CHECK: Note: extra DXIL module flags:
+; CHECK:       Raw and Structured buffers
+; CHECK:       Any UAV may not alias any other UAV
+;
+
+; CHECK: Function loadUAV : 0x20000000
+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
+}
+
+!llvm.module.flags = !{!0}
+
+; dx.resmayalias should never appear with a value of 0.
+; But if it does, ensure that it has no effect.
+!0 = !{i32 1, !"dx.resmayalias", i32 0}
+
+attributes #0 = { convergent norecurse nounwind "hlsl.export"}

llvm/test/CodeGen/DirectX/ShaderFlags/res-may-alias-1.ll

@@ -0,0 +1,41 @@
+; RUN: opt -S --passes="print-dx-shader-flags" 2>&1 %s | FileCheck %s
+
+; This test checks to ensure that setting the LLVM module flag "dx.resmayalias"
+; to 1 prevents the DXIL shader flag analysis from setting the flag
+; ResMayNotAlias.
+
+target triple = "dxil-pc-shadermodel6.8-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
+}
+
+!llvm.module.flags = !{!0}
+
+!0 = !{i32 1, !"dx.resmayalias", i32 1}
+
+attributes #0 = { convergent norecurse nounwind "hlsl.export"}

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

@@ -0,0 +1,37 @@
+; RUN: opt -S --passes="print-dx-shader-flags" 2>&1 %s | FileCheck %s
+
+; This test checks to ensure the behavior of the DXIL shader flag analysis
+; for the flag ResMayNotAlias is correct when the DXIL Version is 1.6. The
+; ResMayNotAlias flag (0x20000000) should not be set at all.
+
+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"}

llvm/test/CodeGen/DirectX/ShaderFlags/res-may-not-alias-shadermodel6.7.ll

@@ -0,0 +1,38 @@
+; RUN: opt -S --passes="print-dx-shader-flags" 2>&1 %s | FileCheck %s
+
+; This test checks to ensure the behavior of the DXIL shader flag analysis
+; for the flag ResMayNotAlias is correct when the DXIL Version is 1.7. The
+; ResMayNotAlias flag (0x20000000) should be set on all functions if there are
+; one or more UAVs present globally in the module.
+
+target triple = "dxil-pc-shadermodel6.7-library"
+
+; CHECK:      Combined Shader Flags for Module
+; CHECK-NEXT: Shader Flags Value: 0x200000010
+
+; CHECK: Note: extra DXIL module flags:
+; CHECK:       Raw and Structured buffers
+; CHECK:       Any UAV may not alias any other UAV
+;
+
+; CHECK: Function loadUAV : 0x200000000
+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 : 0x200000010
+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"}

llvm/test/CodeGen/DirectX/ShaderFlags/res-may-not-alias-shadermodel6.8.ll

@@ -0,0 +1,38 @@
+; RUN: opt -S --passes="print-dx-shader-flags" 2>&1 %s | FileCheck %s
+
+; This test checks to ensure the behavior of the DXIL shader flag analysis
+; for the flag ResMayNotAlias is correct when the DXIL Version is 1.8. The
+; ResMayNotAlias flag (0x20000000) should only be set when a function uses a
+; UAV.
+
+target triple = "dxil-pc-shadermodel6.8-library"
+
+; CHECK:      Combined Shader Flags for Module
+; CHECK-NEXT: Shader Flags Value: 0x200000010
+
+; CHECK: Note: extra DXIL module flags:
+; CHECK:       Raw and Structured buffers
+; CHECK:       Any UAV may not alias any other UAV
+;
+
+; CHECK: Function loadUAV : 0x20000000
+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"}