[DirectX] Legalize lifetime intrinsics for DXIL #148003

Icohedron · 2025-07-10T17:04:00Z

This PR legalizes lifetime intrinsics for DXIL by

Adding a bitcast for the lifetime intrinsics' pointer operand in dxil-prepare to ensure it gets cast to an i8* when written to DXIL
Removing the memory attribute from lifetime intrinsics in dxil-prepare to match DXIL
Making the DXIL bitcode writer write the base/demangled name of lifetime intrinsics to the symbol table
Making lifetime intrinsics an exception to Int64Ops shader flag analysis (otherwise we get error: Flags must match usage. from the validator)

This commit legalizes lifetime intrinsics for DXIL by - Making lifetime intrinsics an exception to Int64Ops shader flag analysis - Adding a bitcast for the lifetime intrinsics' pointer operand in dxil-prepare to ensure it gets cast to an i8* - Making the DXIL bitcode writer write the base/demangled name of lifetime intrinsics to the symbol table

llvmbot · 2025-07-10T17:04:30Z

@llvm/pr-subscribers-backend-directx

Author: Deric C. (Icohedron)

Changes

Fixes #147395

This PR legalizes lifetime intrinsics for DXIL by

Adding a bitcast for the lifetime intrinsics' pointer operand in dxil-prepare to ensure it gets cast to an i8* when written to DXIL
Removing the memory attribute from lifetime intrinsics in dxil-prepare to match DXIL
Making the DXIL bitcode writer write the base/demangled name of lifetime intrinsics to the symbol table
Making lifetime intrinsics an exception to Int64Ops shader flag analysis (otherwise we get error: Flags must match usage. from the validator)

Full diff: https://github.com/llvm/llvm-project/pull/148003.diff

6 Files Affected:

(modified) llvm/lib/Target/DirectX/DXILPrepare.cpp (+21-3)
(modified) llvm/lib/Target/DirectX/DXILShaderFlags.cpp (+1-1)
(modified) llvm/lib/Target/DirectX/DXILWriter/DXILBitcodeWriter.cpp (+15-1)
(added) llvm/test/CodeGen/DirectX/ShaderFlags/lifetimes-noint64op.ll (+36)
(modified) llvm/test/CodeGen/DirectX/legalize-lifetimes-valver-1.6.ll (+25)
(added) llvm/test/tools/dxil-dis/lifetimes.ll (+38)

diff --git a/llvm/lib/Target/DirectX/DXILPrepare.cpp b/llvm/lib/Target/DirectX/DXILPrepare.cpp
index c8866bfefdfc5..d3a8c0bb995c9 100644
--- a/llvm/lib/Target/DirectX/DXILPrepare.cpp
+++ b/llvm/lib/Target/DirectX/DXILPrepare.cpp
@@ -239,6 +239,13 @@ class DXILPrepareModule : public ModulePass {
       for (size_t Idx = 0, End = F.arg_size(); Idx < End; ++Idx)
         F.removeParamAttrs(Idx, AttrMask);
 
+      // Match FnAttrs of lifetime intrinsics in LLVM 3.7
+      if (F.isIntrinsic())
+        switch (F.getIntrinsicID())
+        case Intrinsic::lifetime_start:
+        case Intrinsic::lifetime_end:
+          F.removeFnAttr(Attribute::Memory);
+
       for (auto &BB : F) {
         IRBuilder<> Builder(&BB);
         for (auto &I : make_early_inc_range(BB)) {
@@ -247,7 +254,7 @@ 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())) {
@@ -257,7 +264,7 @@ 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())) {
@@ -268,7 +275,7 @@ 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()))
@@ -280,6 +287,17 @@ 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;
           }
         }
diff --git a/llvm/lib/Target/DirectX/DXILShaderFlags.cpp b/llvm/lib/Target/DirectX/DXILShaderFlags.cpp
index bd3349d2e18c5..eb4adfea5aed6 100644
--- a/llvm/lib/Target/DirectX/DXILShaderFlags.cpp
+++ b/llvm/lib/Target/DirectX/DXILShaderFlags.cpp
@@ -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;
diff --git a/llvm/lib/Target/DirectX/DXILWriter/DXILBitcodeWriter.cpp b/llvm/lib/Target/DirectX/DXILWriter/DXILBitcodeWriter.cpp
index 1d79c3018439e..22736bbd559f0 100644
--- a/llvm/lib/Target/DirectX/DXILWriter/DXILBitcodeWriter.cpp
+++ b/llvm/lib/Target/DirectX/DXILWriter/DXILBitcodeWriter.cpp
@@ -2559,8 +2559,22 @@ void DXILBitcodeWriter::writeFunctionLevelValueSymbolTable(
   // to ensure the binary is the same no matter what values ever existed.
   SmallVector<const ValueName *, 16> SortedTable;
 
+  MallocAllocator Allocator;
   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 = ValueName::create(Intrinsic::getBaseName(IID), Allocator,
+                               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) {
diff --git a/llvm/test/CodeGen/DirectX/ShaderFlags/lifetimes-noint64op.ll b/llvm/test/CodeGen/DirectX/ShaderFlags/lifetimes-noint64op.ll
new file mode 100644
index 0000000000000..736c86ebb1299
--- /dev/null
+++ b/llvm/test/CodeGen/DirectX/ShaderFlags/lifetimes-noint64op.ll
@@ -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: ...
diff --git a/llvm/test/CodeGen/DirectX/legalize-lifetimes-valver-1.6.ll b/llvm/test/CodeGen/DirectX/legalize-lifetimes-valver-1.6.ll
index 6552ccddddab4..f77df2d812dfe 100644
--- a/llvm/test/CodeGen/DirectX/legalize-lifetimes-valver-1.6.ll
+++ b/llvm/test/CodeGen/DirectX/legalize-lifetimes-valver-1.6.ll
@@ -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() {
 ; 
@@ -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
+; CHECK-PREPARE-NEXT:    call void @llvm.lifetime.end.p0(i64 4, ptr nonnull [[BITCAST]])
+; 
 ; CHECK-NEXT:    ret void
 ;
 define void @test_legal_lifetime()  {
@@ -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}
diff --git a/llvm/test/tools/dxil-dis/lifetimes.ll b/llvm/test/tools/dxil-dis/lifetimes.ll
new file mode 100644
index 0000000000000..6be523f50895c
--- /dev/null
+++ b/llvm/test/tools/dxil-dis/lifetimes.ll
@@ -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 i32, ptr %a, 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) }
+

inbelic

LGTM implementation wise. Would like a second reviewer based on how this fits into the bigger picture.

llvm/lib/Target/DirectX/DXILPrepare.cpp

inbelic · 2025-07-11T16:00:23Z

llvm/test/CodeGen/DirectX/legalize-lifetimes-valver-1.6.ll

+; 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


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

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.

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.

llvm/lib/Target/DirectX/DXILWriter/DXILBitcodeWriter.cpp

This reverts commit fee27b3.

Reverts #148003 to fix a DirectX backend build breakage due to #149310

…#149883) Reverts llvm/llvm-project#148003 to fix a DirectX backend build breakage due to #149310

Reverts llvm#148003 to fix a DirectX backend build breakage due to llvm#149310

llvmbot added the backend:DirectX label Jul 10, 2025

Icohedron added 2 commits July 10, 2025 17:17

Add missing include to resolve LifetimeIntrinsic

7a2ae37

Fix GEP in lifetimes dxil-dis test

94fe78c

inbelic approved these changes Jul 11, 2025

View reviewed changes

Icohedron added 3 commits July 11, 2025 16:32

Destroy temp lifetime ValueNames when done writing

1b0aaef

Change if-switch into a single if statement

1d81108

Hoist ValueName creation and destruction to a module-level struct

ce3c8d8

llvm-beanz approved these changes Jul 11, 2025

View reviewed changes

Icohedron merged commit fee27b3 into llvm:main Jul 11, 2025
10 checks passed

Icohedron mentioned this pull request Jul 21, 2025

[DirectX] llvm.lifetime.start/.end non-i8* pointers causing Invalid record validation error #147395

Closed

Icohedron added a commit that referenced this pull request Jul 21, 2025

Revert "[DirectX] Legalize lifetime intrinsics for DXIL (#148003)"

905bad8

This reverts commit fee27b3.

Icohedron mentioned this pull request Jul 21, 2025

Revert "[DirectX] Legalize lifetime intrinsics for DXIL" #149883

Merged

Icohedron added a commit that referenced this pull request Jul 21, 2025

Revert "[DirectX] Legalize lifetime intrinsics for DXIL" (#149883)

8f9ed78

Reverts #148003 to fix a DirectX backend build breakage due to #149310

llvm-sync bot pushed a commit to arm/arm-toolchain that referenced this pull request Jul 21, 2025

Automerge: Revert "[DirectX] Legalize lifetime intrinsics for DXIL" (…

24383e2

…#149883) Reverts llvm/llvm-project#148003 to fix a DirectX backend build breakage due to #149310

mahesh-attarde pushed a commit to mahesh-attarde/llvm-project that referenced this pull request Jul 28, 2025

Revert "[DirectX] Legalize lifetime intrinsics for DXIL" (llvm#149883)

30005cb

Reverts llvm#148003 to fix a DirectX backend build breakage due to llvm#149310

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