[llvm] [DirectX] Legalize `llvm.lifetime.*` intrinsics in EmbedDXILPass (PR #150100)
Deric C. via llvm-commits
llvm-commits at lists.llvm.org
Tue Jul 22 12:54:25 PDT 2025
https://github.com/Icohedron created https://github.com/llvm/llvm-project/pull/150100
Fixes #147395
This PR:
- Excludes lifetime intrinsics from the Int64Ops shader flags analysis to match DXC behavior and pass DXIL validation.
- Performs legalization of `llvm.lifetime.*` intrinsics in the EmbedDXILPass just before invoking the DXILBitcodeWriter.
- After invoking the DXILBitcodeWriter, all lifetime intrinsics and associated bitcasts are removed from the module to keep the Module Verifier happy. This is fine since lifetime intrinsics are not needed by any passes after the EmbedDXILPass.
>From 7ab0913d694c84897cabd64f7ce14ae9e2a472d1 Mon Sep 17 00:00:00 2001
From: Deric Cheung <dericcheung at microsoft.com>
Date: Tue, 22 Jul 2025 04:05:19 +0000
Subject: [PATCH 1/2] Exclude lifetime intrinsics from the Int64Ops shader flag
---
llvm/lib/Target/DirectX/DXILShaderFlags.cpp | 2 +-
.../ShaderFlags/lifetimes-noint64op.ll | 36 +++++++++++++++++++
2 files changed, 37 insertions(+), 1 deletion(-)
create mode 100644 llvm/test/CodeGen/DirectX/ShaderFlags/lifetimes-noint64op.ll
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/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: ...
>From a782b33a191b795338f0c8f74f21fb64150c22ce Mon Sep 17 00:00:00 2001
From: Deric Cheung <dericcheung at microsoft.com>
Date: Tue, 22 Jul 2025 18:22:48 +0000
Subject: [PATCH 2/2] Legalize lifetime intrinsics in EmbedDXILPass
---
.../DirectX/DXILWriter/DXILWriterPass.cpp | 55 +++++++++++++++++++
llvm/test/tools/dxil-dis/lifetimes.ll | 38 +++++++++++++
2 files changed, 93 insertions(+)
create mode 100644 llvm/test/tools/dxil-dis/lifetimes.ll
diff --git a/llvm/lib/Target/DirectX/DXILWriter/DXILWriterPass.cpp b/llvm/lib/Target/DirectX/DXILWriter/DXILWriterPass.cpp
index dfc79039cb54e..0ea1c5b905a45 100644
--- a/llvm/lib/Target/DirectX/DXILWriter/DXILWriterPass.cpp
+++ b/llvm/lib/Target/DirectX/DXILWriter/DXILWriterPass.cpp
@@ -17,6 +17,7 @@
#include "llvm/Analysis/ModuleSummaryAnalysis.h"
#include "llvm/IR/Constants.h"
#include "llvm/IR/GlobalVariable.h"
+#include "llvm/IR/IntrinsicInst.h"
#include "llvm/IR/Module.h"
#include "llvm/IR/PassManager.h"
#include "llvm/InitializePasses.h"
@@ -52,6 +53,51 @@ class WriteDXILPass : public llvm::ModulePass {
}
};
+static void legalizeLifetimeIntrinsics(Module &M) {
+ for (Function &F : M) {
+ Intrinsic::ID IID = F.getIntrinsicID();
+ if (IID != Intrinsic::lifetime_start && IID != Intrinsic::lifetime_end)
+ continue;
+
+ // Lifetime intrinsics in LLVM 3.7 do not have the memory FnAttr
+ F.removeFnAttr(Attribute::Memory);
+
+ // Lifetime intrinsics in LLVM 3.7 do not have mangled names
+ F.setName(Intrinsic::getBaseName(IID));
+
+ // LLVM 3.7 Lifetime intrinics require an i8* operand, so we insert bitcasts
+ // to ensure that is the case
+ for (auto *User : make_early_inc_range(F.users())) {
+ CallInst *CI = dyn_cast<CallInst>(User);
+ assert(CI && "Expected user of a lifetime intrinsic function to be a "
+ "lifetime intrinsic call");
+ Value *PtrOperand = CI->getArgOperand(1);
+ PointerType *PtrTy = cast<PointerType>(PtrOperand->getType());
+ Value *NoOpBitCast = CastInst::Create(Instruction::BitCast, PtrOperand,
+ PtrTy, "", CI->getIterator());
+ CI->setArgOperand(1, NoOpBitCast);
+ }
+ }
+}
+
+static void removeLifetimeIntrinsics(Module &M) {
+ for (Function &F : make_early_inc_range(M))
+ if (Intrinsic::ID IID = F.getIntrinsicID();
+ IID == Intrinsic::lifetime_start || IID == Intrinsic::lifetime_end) {
+ for (User *U : make_early_inc_range(F.users())) {
+ LifetimeIntrinsic *LI = dyn_cast<LifetimeIntrinsic>(U);
+ assert(LI && "Expected user of lifetime intrinsic function to be "
+ "a LifetimeIntrinsic instruction");
+ BitCastInst *BCI = dyn_cast<BitCastInst>(LI->getArgOperand(1));
+ assert(BCI && "Expected pointer operand of LifetimeIntrinsic to be a "
+ "BitCastInst");
+ LI->eraseFromParent();
+ BCI->eraseFromParent();
+ }
+ F.eraseFromParent();
+ }
+}
+
class EmbedDXILPass : public llvm::ModulePass {
public:
static char ID; // Pass identification, replacement for typeid
@@ -70,8 +116,17 @@ class EmbedDXILPass : public llvm::ModulePass {
// Only the output bitcode need to be DXIL triple.
M.setTargetTriple(Triple("dxil-ms-dx"));
+ // Perform late legalization of lifetime intrinsics that would otherwise
+ // fail the Module Verifier if performed in an earlier pass
+ legalizeLifetimeIntrinsics(M);
+
WriteDXILToFile(M, OS);
+ // We no longer need lifetime intrinsics after bitcode serialization, so we
+ // simply remove them to keep the Module Verifier happy after our
+ // not-so-legal legalizations
+ removeLifetimeIntrinsics(M);
+
// Recover triple.
M.setTargetTriple(OriginalTriple);
diff --git a/llvm/test/tools/dxil-dis/lifetimes.ll b/llvm/test/tools/dxil-dis/lifetimes.ll
new file mode 100644
index 0000000000000..cb3e6291c7bc0
--- /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 [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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