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[DirectX] Set Shader Flag DisableOptimizations. #123136

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[DirectX] Set Shader Flag DisableOptimizations. #123136

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1dda593
[DirectX] Set Shader Flag DisableOptimizations.
bharadwajy Jan 15, 2025
ca014db
Delete metadata dx.disable_optimizations, if it exists,
bharadwajy Jan 30, 2025
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1 change: 1 addition & 0 deletions llvm/include/llvm/Analysis/DXILMetadataAnalysis.h
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Expand Up @@ -37,6 +37,7 @@ struct ModuleMetadataInfo {
Triple::EnvironmentType ShaderProfile{Triple::UnknownEnvironment};
VersionTuple ValidatorVersion{};
SmallVector<EntryProperties> EntryPropertyVec{};
bool DisableOptimizations{false};
void print(raw_ostream &OS) const;
};

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31 changes: 31 additions & 0 deletions llvm/lib/Analysis/DXILMetadataAnalysis.cpp
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Expand Up @@ -68,6 +68,37 @@ static ModuleMetadataInfo collectMetadataInfo(Module &M) {
}
MMDAI.EntryPropertyVec.push_back(EFP);
}

// Set shader flags based on Module properties
SmallVector<llvm::Module::ModuleFlagEntry> FlagEntries;
SmallVector<llvm::Module::ModuleFlagEntry> NewFlagEntries;
M.getModuleFlagsMetadata(FlagEntries);
for (const auto &Flag : FlagEntries) {
if ((Flag.Behavior == Module::ModFlagBehavior::Override) &&
(Flag.Key->getString().compare("dx.disable_optimizations") == 0)) {
const auto *V = mdconst::extract<llvm::ConstantInt>(Flag.Val);
if (V->isOne())
MMDAI.DisableOptimizations = true;
} else
// Collect all Module Flags other than dx.disable_optimizations.
NewFlagEntries.push_back(Flag);
}

// "dx.disable_optimizations" is not included in the metadata specified in
// DXIL specification. Hence it needs to be deleted such that it is not
// emitted in the final DXIL output, now that its intent is captured in MMDAI,
// if present.

if (NewFlagEntries.size() != FlagEntries.size()) {
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Do we need to do this here? We have code in DXILPrepare that cleans the module flags.

@bogner, I think the reason the dx.disable_optimizations named metadata wasn't causing issues is because DXIL doesn't use custom module flags at all, so in DXILPrepare we just strip out any non-standard LLVM 3.7 module flags, which will clean this up.

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@bharadwajy bharadwajy Feb 10, 2025 •
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Do we need to do this here? We have code in DXILPrepare that cleans the module flags.

@bogner, I think the reason the dx.disable_optimizations named metadata wasn't causing issues is because DXIL doesn't use custom module flags at all, so in DXILPrepare we just strip out any non-standard LLVM 3.7 module flags, which will clean this up.

@llvm-beanz I proposed a PR to decorate shader entry functions with the attribute optnone as an alternative to using dx.disable_optimizations named metadata - per feedback above.

The idea is to eliminate creation of dx.disable_optimizations metadata and key off the optnone attribute on shader entry functions to set the shader flag DisableOptimizations as implemented here with an expectation of converting it to a follow-on PR to #125937.

I'd appreciate feedback on #125937 in this context as well as the preferred choice compared to this PR.

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This looks like it now needs an update to adjust to #125937 landing.

NamedMDNode *OrigMDFlags = M.getModuleFlagsMetadata();
// Delete all Module flags
OrigMDFlags->eraseFromParent();
// Repopulate Module flags using the list that excludes
// dx.delete_optimizations.
for (const auto &Flag : NewFlagEntries)
M.addModuleFlag(Flag.Behavior, Flag.Key->getString(), Flag.Val);
}

return MMDAI;
}

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15 changes: 12 additions & 3 deletions llvm/lib/Target/DirectX/DXILShaderFlags.cpp
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Expand Up @@ -96,7 +96,8 @@ void ModuleShaderFlags::updateFunctionFlags(ComputedShaderFlags &CSF,
}

/// Construct ModuleShaderFlags for module Module M
void ModuleShaderFlags::initialize(Module &M, DXILResourceTypeMap &DRTM) {
void ModuleShaderFlags::initialize(Module &M, DXILResourceTypeMap &DRTM,
const ModuleMetadataInfo &MMDI) {
CallGraph CG(M);

// Compute Shader Flags Mask for all functions using post-order visit of SCC
Expand Down Expand Up @@ -142,6 +143,9 @@ void ModuleShaderFlags::initialize(Module &M, DXILResourceTypeMap &DRTM) {
// Merge SCCSF with that of F
FunctionFlags[F].merge(SCCSF);
}

// Set shader flags based on Module properties based on module metadata
CombinedSFMask.DisableOptimizations = MMDI.DisableOptimizations;
}

void ComputedShaderFlags::print(raw_ostream &OS) const {
Expand Down Expand Up @@ -180,9 +184,10 @@ AnalysisKey ShaderFlagsAnalysis::Key;
ModuleShaderFlags ShaderFlagsAnalysis::run(Module &M,
ModuleAnalysisManager &AM) {
DXILResourceTypeMap &DRTM = AM.getResult<DXILResourceTypeAnalysis>(M);
const ModuleMetadataInfo MMDI = AM.getResult<DXILMetadataAnalysis>(M);

ModuleShaderFlags MSFI;
MSFI.initialize(M, DRTM);
MSFI.initialize(M, DRTM, MMDI);

return MSFI;
}
Expand Down Expand Up @@ -212,20 +217,24 @@ PreservedAnalyses ShaderFlagsAnalysisPrinter::run(Module &M,
bool ShaderFlagsAnalysisWrapper::runOnModule(Module &M) {
DXILResourceTypeMap &DRTM =
getAnalysis<DXILResourceTypeWrapperPass>().getResourceTypeMap();
const ModuleMetadataInfo MMDI =
getAnalysis<DXILMetadataAnalysisWrapperPass>().getModuleMetadata();

MSFI.initialize(M, DRTM);
MSFI.initialize(M, DRTM, MMDI);
return false;
}

void ShaderFlagsAnalysisWrapper::getAnalysisUsage(AnalysisUsage &AU) const {
AU.setPreservesAll();
AU.addRequiredTransitive<DXILResourceTypeWrapperPass>();
AU.addRequired<DXILMetadataAnalysisWrapperPass>();
}

char ShaderFlagsAnalysisWrapper::ID = 0;

INITIALIZE_PASS_BEGIN(ShaderFlagsAnalysisWrapper, "dx-shader-flag-analysis",
"DXIL Shader Flag Analysis", true, true)
INITIALIZE_PASS_DEPENDENCY(DXILResourceTypeWrapperPass)
INITIALIZE_PASS_DEPENDENCY(DXILMetadataAnalysisWrapperPass)
INITIALIZE_PASS_END(ShaderFlagsAnalysisWrapper, "dx-shader-flag-analysis",
"DXIL Shader Flag Analysis", true, true)
4 changes: 3 additions & 1 deletion llvm/lib/Target/DirectX/DXILShaderFlags.h
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Expand Up @@ -14,6 +14,7 @@
#ifndef LLVM_TARGET_DIRECTX_DXILSHADERFLAGS_H
#define LLVM_TARGET_DIRECTX_DXILSHADERFLAGS_H

#include "llvm/Analysis/DXILMetadataAnalysis.h"
#include "llvm/IR/Function.h"
#include "llvm/IR/PassManager.h"
#include "llvm/Pass.h"
Expand Down Expand Up @@ -83,7 +84,8 @@ struct ComputedShaderFlags {
};

struct ModuleShaderFlags {
void initialize(Module &, DXILResourceTypeMap &DRTM);
void initialize(Module &, DXILResourceTypeMap &DRTM,
const ModuleMetadataInfo &MMDI);
const ComputedShaderFlags &getFunctionFlags(const Function *) const;
const ComputedShaderFlags &getCombinedFlags() const { return CombinedSFMask; }

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27 changes: 27 additions & 0 deletions llvm/test/CodeGen/DirectX/ShaderFlags/disable-opt.ll
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@@ -0,0 +1,27 @@
; RUN: opt -S --passes="print-dx-shader-flags" 2>&1 %s | FileCheck %s

target triple = "dxilv1.6-unknown-shadermodel6.6-library"

; CHECK: ; Combined Shader Flags for Module
; CHECK-NEXT: ; Shader Flags Value: 0x00000001

; CHECK: ; Note: extra DXIL module flags:
; CHECK-NEXT: ; D3D11_1_SB_GLOBAL_FLAG_SKIP_OPTIMIZATION

; CHECK: ; Shader Flags for Module Functions

target triple = "dxilv1.6-unknown-shadermodel6.6-library"

; CHECK: ; Function main : 0x00000000
define void @main() {
entry:
ret void
}

; CHECK-NOT: llvm.module.flags
!llvm.module.flags = !{!0}

; CHECK-NOT: "dx.disable_optimizations"
!0 = !{i32 4, !"dx.disable_optimizations", i32 1}


2 changes: 1 addition & 1 deletion llvm/test/CodeGen/DirectX/llc-pipeline.ll
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Expand Up @@ -23,8 +23,8 @@
; CHECK-NEXT: Scalarize vector operations
; CHECK-NEXT: DXIL Resource Binding Analysis
; CHECK-NEXT: DXIL resource Information
; CHECK-NEXT: DXIL Shader Flag Analysis
; CHECK-NEXT: DXIL Module Metadata analysis
; CHECK-NEXT: DXIL Shader Flag Analysis
; CHECK-NEXT: DXIL Translate Metadata
; CHECK-NEXT: DXIL Op Lowering
; CHECK-NEXT: DXIL Prepare Module
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