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Merged
merged 6 commits into from
Jul 11, 2025
Merged

[DirectX] Legalize lifetime intrinsics for DXIL #148003

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c9fbdba
Legalize lifetime intrinsics for DXIL
Icohedron Jul 9, 2025
7a2ae37
Add missing include to resolve LifetimeIntrinsic
Icohedron Jul 10, 2025
94fe78c
Fix GEP in lifetimes dxil-dis test
Icohedron Jul 10, 2025
1b0aaef
Destroy temp lifetime ValueNames when done writing
Icohedron Jul 11, 2025
1d81108
Change if-switch into a single if statement
Icohedron Jul 11, 2025
ce3c8d8
Hoist ValueName creation and destruction to a module-level struct
Icohedron Jul 11, 2025
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23 changes: 20 additions & 3 deletions llvm/lib/Target/DirectX/DXILPrepare.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -24,6 +24,7 @@
#include "llvm/IR/AttributeMask.h"
#include "llvm/IR/IRBuilder.h"
#include "llvm/IR/Instruction.h"
#include "llvm/IR/IntrinsicInst.h"
#include "llvm/IR/Module.h"
#include "llvm/InitializePasses.h"
#include "llvm/Pass.h"
Expand Down Expand Up @@ -239,6 +240,11 @@ class DXILPrepareModule : public ModulePass {
for (size_t Idx = 0, End = F.arg_size(); Idx < End; ++Idx)
F.removeParamAttrs(Idx, AttrMask);

// Lifetime intrinsics in LLVM 3.7 do not have the memory FnAttr
if (Intrinsic::ID IID = F.getIntrinsicID();
IID == Intrinsic::lifetime_start || IID == Intrinsic::lifetime_end)
F.removeFnAttr(Attribute::Memory);

for (auto &BB : F) {
IRBuilder<> Builder(&BB);
for (auto &I : make_early_inc_range(BB)) {
Expand All @@ -247,7 +253,7 @@ class DXILPrepareModule : public ModulePass {

// Emtting NoOp bitcast instructions allows the ValueEnumerator to be
// unmodified as it reserves instruction IDs during contruction.
if (auto LI = dyn_cast<LoadInst>(&I)) {
if (auto *LI = dyn_cast<LoadInst>(&I)) {
if (Value *NoOpBitcast = maybeGenerateBitcast(
Builder, PointerTypes, I, LI->getPointerOperand(),
LI->getType())) {
Expand All @@ -257,7 +263,7 @@ class DXILPrepareModule : public ModulePass {
}
continue;
}
if (auto SI = dyn_cast<StoreInst>(&I)) {
if (auto *SI = dyn_cast<StoreInst>(&I)) {
if (Value *NoOpBitcast = maybeGenerateBitcast(
Builder, PointerTypes, I, SI->getPointerOperand(),
SI->getValueOperand()->getType())) {
Expand All @@ -268,7 +274,7 @@ class DXILPrepareModule : public ModulePass {
}
continue;
}
if (auto GEP = dyn_cast<GetElementPtrInst>(&I)) {
if (auto *GEP = dyn_cast<GetElementPtrInst>(&I)) {
if (Value *NoOpBitcast = maybeGenerateBitcast(
Builder, PointerTypes, I, GEP->getPointerOperand(),
GEP->getSourceElementType()))
Expand All @@ -280,6 +286,17 @@ class DXILPrepareModule : public ModulePass {
CB->removeRetAttrs(AttrMask);
for (size_t Idx = 0, End = CB->arg_size(); Idx < End; ++Idx)
CB->removeParamAttrs(Idx, AttrMask);
// LLVM 3.7 Lifetime intrinics require an i8* pointer operand, so we
// insert a bitcast here to ensure that is the case
if (isa<LifetimeIntrinsic>(CB)) {
Value *PtrOperand = CB->getArgOperand(1);
Builder.SetInsertPoint(CB);
PointerType *PtrTy = cast<PointerType>(PtrOperand->getType());
Value *NoOpBitcast = Builder.Insert(
CastInst::Create(Instruction::BitCast, PtrOperand,
Builder.getPtrTy(PtrTy->getAddressSpace())));
CB->setArgOperand(1, NoOpBitcast);
}
continue;
}
}
Expand Down
2 changes: 1 addition & 1 deletion llvm/lib/Target/DirectX/DXILShaderFlags.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -152,7 +152,7 @@ void ModuleShaderFlags::updateFunctionFlags(ComputedShaderFlags &CSF,
if (!CSF.Int64Ops)
CSF.Int64Ops = I.getType()->isIntegerTy(64);

if (!CSF.Int64Ops) {
if (!CSF.Int64Ops && !isa<LifetimeIntrinsic>(&I)) {
for (const Value *Op : I.operands()) {
if (Op->getType()->isIntegerTy(64)) {
CSF.Int64Ops = true;
Expand Down
36 changes: 35 additions & 1 deletion llvm/lib/Target/DirectX/DXILWriter/DXILBitcodeWriter.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -2545,6 +2545,25 @@ void DXILBitcodeWriter::writeInstruction(const Instruction &I, unsigned InstID,
Vals.clear();
}

// HLSL Change
namespace {
struct ValueNameCreator {
MallocAllocator Allocator;
SmallVector<ValueName *, 2>
ValueNames; // SmallVector N = 2 because we currently only expect this
// to hold ValueNames for Lifetime intrinsics
~ValueNameCreator() {
for (auto *VN : ValueNames)
VN->Destroy(Allocator);
}
ValueName *create(StringRef Name, Value *V) {
ValueName *VN = ValueName::create(Name, Allocator, V);
ValueNames.push_back(VN);
return VN;
}
};
} // anonymous namespace

// Emit names for globals/functions etc.
void DXILBitcodeWriter::writeFunctionLevelValueSymbolTable(
const ValueSymbolTable &VST) {
Expand All @@ -2559,9 +2578,24 @@ void DXILBitcodeWriter::writeFunctionLevelValueSymbolTable(
// to ensure the binary is the same no matter what values ever existed.
SmallVector<const ValueName *, 16> SortedTable;

// HLSL Change
ValueNameCreator VNC;
for (auto &VI : VST) {
SortedTable.push_back(VI.second->getValueName());
ValueName *VN = VI.second->getValueName();
// Clang mangles lifetime intrinsic names by appending '.p0' to the end,
// making them invalid lifetime intrinsics in LLVM 3.7. We can't
// demangle in dxil-prepare because it would result in invalid IR.
// Therefore we have to do this in the bitcode writer while writing its
// name to the symbol table.
if (const Function *Fn = dyn_cast<Function>(VI.getValue());
Fn && Fn->isIntrinsic()) {
Intrinsic::ID IID = Fn->getIntrinsicID();
if (IID == Intrinsic::lifetime_start || IID == Intrinsic::lifetime_end)
VN = VNC.create(Intrinsic::getBaseName(IID), VI.second);
}
SortedTable.push_back(VN);
}

// The keys are unique, so there shouldn't be stability issues.
llvm::sort(SortedTable, [](const ValueName *A, const ValueName *B) {
return A->first() < B->first();
Expand Down
36 changes: 36 additions & 0 deletions llvm/test/CodeGen/DirectX/ShaderFlags/lifetimes-noint64op.ll
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Original file line number Diff line number Diff line change
@@ -0,0 +1,36 @@
; RUN: opt -S --passes="print-dx-shader-flags" 2>&1 %s | FileCheck %s
; RUN: llc %s --filetype=obj -o - | obj2yaml | FileCheck %s --check-prefix=DXC

target triple = "dxil-pc-shadermodel6.7-library"

; CHECK: ; Combined Shader Flags for Module
; CHECK-NEXT: ; Shader Flags Value: 0x00000000
; CHECK-NEXT: ;
; CHECK-NOT: ; Note: shader requires additional functionality:
; CHECK-NOT: ; 64-Bit integer
; CHECK-NOT: ; Note: extra DXIL module flags:
; CHECK-NOT: ;
; CHECK-NEXT: ; Shader Flags for Module Functions
; CHECK-NEXT: ; Function lifetimes : 0x00000000

define void @lifetimes() #0 {
%a = alloca [4 x i32], align 8
call void @llvm.lifetime.start.p0(i64 16, ptr nonnull %a)
call void @llvm.lifetime.end.p0(i64 16, ptr nonnull %a)
ret void
}

; Function Attrs: nounwind memory(argmem: readwrite)
declare void @llvm.lifetime.start.p0(i64, ptr) #1

; Function Attrs: nounwind memory(argmem: readwrite)
declare void @llvm.lifetime.end.p0(i64, ptr) #1

attributes #0 = { convergent norecurse nounwind "hlsl.export"}
attributes #1 = { nounwind memory(argmem: readwrite) }

; DXC: - Name: SFI0
; DXC-NEXT: Size: 8
; DXC-NOT: Flags:
; DXC-NOT: Int64Ops: true
; DXC: ...
25 changes: 25 additions & 0 deletions llvm/test/CodeGen/DirectX/legalize-lifetimes-valver-1.6.ll
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Original file line number Diff line number Diff line change
@@ -1,5 +1,6 @@
; RUN: opt -S -passes='dxil-op-lower' -mtriple=dxil-pc-shadermodel6.3-library %s | FileCheck %s --check-prefixes=CHECK,CHECK-SM63
; RUN: opt -S -passes='dxil-op-lower' -mtriple=dxil-pc-shadermodel6.6-library %s | FileCheck %s --check-prefixes=CHECK,CHECK-SM66
; RUN: opt -S -dxil-op-lower -dxil-prepare -mtriple=dxil-pc-shadermodel6.6-library %s | FileCheck %s --check-prefixes=CHECK,CHECK-PREPARE

; CHECK-LABEL: define void @test_legal_lifetime() {
;
Expand All @@ -15,6 +16,14 @@
; CHECK-SM66-NEXT: store i32 0, ptr [[GEP]], align 4
; CHECK-SM66-NEXT: call void @llvm.lifetime.end.p0(i64 4, ptr nonnull [[ACCUM_I_FLAT]])
;
; CHECK-PREPARE-NEXT: [[ACCUM_I_FLAT:%.*]] = alloca [1 x i32], align 4
; CHECK-PREPARE-NEXT: [[GEP:%.*]] = getelementptr i32, ptr [[ACCUM_I_FLAT]], i32 0
; CHECK-PREPARE-NEXT: [[BITCAST:%.*]] = bitcast ptr [[ACCUM_I_FLAT]] to ptr
; CHECK-PREPARE-NEXT: call void @llvm.lifetime.start.p0(i64 4, ptr nonnull [[BITCAST]])
; CHECK-PREPARE-NEXT: store i32 0, ptr [[GEP]], align 4
; CHECK-PREPARE-NEXT: [[BITCAST:%.*]] = bitcast ptr [[ACCUM_I_FLAT]] to ptr
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Without adding too much complexity to the code, is it possible to re-use this for both lifetimes?

You might be able to just iterate the users of PtrOperand and detect a bitcast to set as the operand.

Happy to just be told no. But wanted to make we thought of it

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dxil-prepare inserts bitcasts for other instructions too, so I think this should be a suggestion for dxil-prepare as a whole and not just bitcasts for lifetimes intrinsics only.

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generally bitcasts are "free" in that they don't have any runtime implementation cost, and for lifetime markers which also have no runtime implementation cost, they're usually not a big deal. They do have some tiny cost on binary size, but I'd say this probably isn't worth fixing.

; CHECK-PREPARE-NEXT: call void @llvm.lifetime.end.p0(i64 4, ptr nonnull [[BITCAST]])
;
; CHECK-NEXT: ret void
;
define void @test_legal_lifetime() {
Expand All @@ -26,6 +35,22 @@ define void @test_legal_lifetime() {
ret void
}

; CHECK-PREPARE-DAG: attributes [[LIFETIME_ATTRS:#.*]] = { nounwind }

; CHECK-PREPARE-DAG: ; Function Attrs: nounwind
; CHECK-PREPARE-DAG: declare void @llvm.lifetime.start.p0(i64, ptr) [[LIFETIME_ATTRS]]

; CHECK-PREPARE-DAG: ; Function Attrs: nounwind
; CHECK-PREPARE-DAG: declare void @llvm.lifetime.end.p0(i64, ptr) [[LIFETIME_ATTRS]]

; Function Attrs: nounwind memory(argmem: readwrite)
declare void @llvm.lifetime.end.p0(i64, ptr) #0

; Function Attrs: nounwind memory(argmem: readwrite)
declare void @llvm.lifetime.start.p0(i64, ptr) #0

attributes #0 = { nounwind memory(argmem: readwrite) }

; Set the validator version to 1.6
!dx.valver = !{!0}
!0 = !{i32 1, i32 6}
38 changes: 38 additions & 0 deletions llvm/test/tools/dxil-dis/lifetimes.ll
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Original file line number Diff line number Diff line change
@@ -0,0 +1,38 @@
; RUN: llc --filetype=obj %s -o - | dxil-dis -o - | FileCheck %s
target triple = "dxil-unknown-shadermodel6.7-library"

define void @test_lifetimes() {
; CHECK-LABEL: test_lifetimes
; CHECK-NEXT: [[ALLOCA:%.*]] = alloca [2 x i32], align 4
; CHECK-NEXT: [[GEP:%.*]] = getelementptr [2 x i32], [2 x i32]* [[ALLOCA]], i32 0, i32 0
; CHECK-NEXT: [[BITCAST:%.*]] = bitcast [2 x i32]* [[ALLOCA]] to i8*
; CHECK-NEXT: call void @llvm.lifetime.start(i64 4, i8* nonnull [[BITCAST]])
; CHECK-NEXT: store i32 0, i32* [[GEP]], align 4
; CHECK-NEXT: [[BITCAST:%.*]] = bitcast [2 x i32]* [[ALLOCA]] to i8*
; CHECK-NEXT: call void @llvm.lifetime.end(i64 4, i8* nonnull [[BITCAST]])
; CHECK-NEXT: ret void
;
%a = alloca [2 x i32], align 4
%gep = getelementptr [2 x i32], ptr %a, i32 0, i32 0
call void @llvm.lifetime.start.p0(i64 4, ptr nonnull %a)
store i32 0, ptr %gep, align 4
call void @llvm.lifetime.end.p0(i64 4, ptr nonnull %a)
ret void
}

; CHECK-DAG: attributes [[LIFETIME_ATTRS:#.*]] = { nounwind }

; CHECK-DAG: ; Function Attrs: nounwind
; CHECK-DAG: declare void @llvm.lifetime.start(i64, i8* nocapture) [[LIFETIME_ATTRS]]

; CHECK-DAG: ; Function Attrs: nounwind
; CHECK-DAG: declare void @llvm.lifetime.end(i64, i8* nocapture) [[LIFETIME_ATTRS]]

; Function Attrs: nounwind memory(argmem: readwrite)
declare void @llvm.lifetime.end.p0(i64, ptr) #0

; Function Attrs: nounwind memory(argmem: readwrite)
declare void @llvm.lifetime.start.p0(i64, ptr) #0

attributes #0 = { nounwind memory(argmem: readwrite) }

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