[clang] [CIR] Add cir.lifetime.start and cir.lifetime.end Op (PR #199599)
Jiahao Guo via cfe-commits
cfe-commits at lists.llvm.org
Mon May 25 21:13:27 PDT 2026
https://github.com/E00N777 created https://github.com/llvm/llvm-project/pull/199599
### summary
part of ：https://github.com/llvm/llvm-project/issues/198961
Adds the `cir.lifetime.start` and `cir.lifetime.end` ops, which mark the beginning and end of an alloca's live range. They mirror the LLVM intrinsics `llvm.lifetime.start` / `llvm.lifetime.end`
>From bf59c69d600f96f24e2f403aa6c841d198dcd546 Mon Sep 17 00:00:00 2001
From: E0N777 <E0N_gjh at 163.com>
Date: Tue, 26 May 2026 12:08:52 +0800
Subject: [PATCH] [CIR] Add cir.lifetime.start and cir.lifetime.end Op
---
clang/include/clang/CIR/Dialect/IR/CIROps.td | 56 +++++++++++++++++++
clang/lib/CIR/CodeGen/CIRGenBuilder.h | 9 +++
.../CIR/Lowering/DirectToLLVM/LowerToLLVM.cpp | 15 +++++
clang/test/CIR/IR/lifetime.cir | 25 +++++++++
clang/test/CIR/Lowering/lifetime.cir | 29 ++++++++++
5 files changed, 134 insertions(+)
create mode 100644 clang/test/CIR/IR/lifetime.cir
create mode 100644 clang/test/CIR/Lowering/lifetime.cir
diff --git a/clang/include/clang/CIR/Dialect/IR/CIROps.td b/clang/include/clang/CIR/Dialect/IR/CIROps.td
index 67ddaa73d9184..d3fb486be8f2e 100644
--- a/clang/include/clang/CIR/Dialect/IR/CIROps.td
+++ b/clang/include/clang/CIR/Dialect/IR/CIROps.td
@@ -4670,6 +4670,62 @@ def CIR_StackRestoreOp : CIR_Op<"stackrestore"> {
let assemblyFormat = "$ptr attr-dict `:` qualified(type($ptr))";
}
+//===----------------------------------------------------------------------===//
+// LifetimeStartOp & LifetimeEndOp
+//===----------------------------------------------------------------------===//
+
+def CIR_LifetimeStartOp : CIR_Op<"lifetime.start"> {
+ let summary = "Marks the beginning of an alloca object's live range";
+ let description = [{
+ The `cir.lifetime.start` operation marks the beginning of the live range
+ of the memory region pointed to by `$ptr`. Between this operation and a
+ matching `cir.lifetime.end` on the same pointer, the underlying storage
+ is considered live; outside that range it is considered dead, and the
+ optimizer is free to reuse the storage for other purposes.
+
+ This operation exhibits undefined behavior if:
+ * `$ptr` does not point to memory allocated by `cir.alloca`; or
+ * no matching `cir.lifetime.end` reaches every control-flow path that
+ follows this operation.
+
+ This operation corresponds to the LLVM intrinsic `llvm.lifetime.start`.
+
+ Example:
+ ```
+ cir.lifetime.start %ptr : !cir.ptr<!void>
+ ```
+ }];
+
+ let arguments = (ins CIR_PointerType:$ptr);
+ let assemblyFormat = "$ptr attr-dict `:` qualified(type($ptr))";
+}
+
+def CIR_LifetimeEndOp : CIR_Op<"lifetime.end"> {
+ let summary = "Marks the end of an alloca object's live range";
+ let description = [{
+ The `cir.lifetime.end` operation marks the end of the live range of the
+ memory region pointed to by `$ptr`. After this operation the underlying
+ storage is considered dead until a subsequent `cir.lifetime.start` on
+ the same pointer; accesses to the storage in the dead range are
+ undefined behavior.
+
+ This operation exhibits undefined behavior if:
+ * `$ptr` does not point to memory allocated by `cir.alloca`; or
+ * it is not preceded by a matching `cir.lifetime.start` on every
+ control-flow path that reaches this operation.
+
+ This operation corresponds to the LLVM intrinsic `llvm.lifetime.end`.
+
+ Example:
+ ```
+ cir.lifetime.end %ptr : !cir.ptr<!void>
+ ```
+ }];
+
+ let arguments = (ins CIR_PointerType:$ptr);
+ let assemblyFormat = "$ptr attr-dict `:` qualified(type($ptr))";
+}
+
//===----------------------------------------------------------------------===//
// InlineAsmOp
//===----------------------------------------------------------------------===//
diff --git a/clang/lib/CIR/CodeGen/CIRGenBuilder.h b/clang/lib/CIR/CodeGen/CIRGenBuilder.h
index aeb1a122429e2..82ec04e1c1b3a 100644
--- a/clang/lib/CIR/CodeGen/CIRGenBuilder.h
+++ b/clang/lib/CIR/CodeGen/CIRGenBuilder.h
@@ -758,6 +758,15 @@ class CIRGenBuilderTy : public cir::CIRBaseBuilderTy {
return cir::StackRestoreOp::create(*this, loc, v);
}
+ cir::LifetimeStartOp createLifetimeStart(mlir::Location loc,
+ mlir::Value ptr) {
+ return cir::LifetimeStartOp::create(*this, loc, ptr);
+ }
+
+ cir::LifetimeEndOp createLifetimeEnd(mlir::Location loc, mlir::Value ptr) {
+ return cir::LifetimeEndOp::create(*this, loc, ptr);
+ }
+
cir::CmpThreeWayOp createThreeWayCmpTotalOrdering(
mlir::Location loc, mlir::Value lhs, mlir::Value rhs,
const llvm::APSInt <Res, const llvm::APSInt &eqRes,
diff --git a/clang/lib/CIR/Lowering/DirectToLLVM/LowerToLLVM.cpp b/clang/lib/CIR/Lowering/DirectToLLVM/LowerToLLVM.cpp
index c4e98e299dfc1..7fdf6ce101303 100644
--- a/clang/lib/CIR/Lowering/DirectToLLVM/LowerToLLVM.cpp
+++ b/clang/lib/CIR/Lowering/DirectToLLVM/LowerToLLVM.cpp
@@ -4193,6 +4193,21 @@ mlir::LogicalResult CIRToLLVMStackRestoreOpLowering::matchAndRewrite(
return mlir::success();
}
+mlir::LogicalResult CIRToLLVMLifetimeStartOpLowering::matchAndRewrite(
+ cir::LifetimeStartOp op, OpAdaptor adaptor,
+ mlir::ConversionPatternRewriter &rewriter) const {
+ rewriter.replaceOpWithNewOp<mlir::LLVM::LifetimeStartOp>(op,
+ adaptor.getPtr());
+ return mlir::success();
+}
+
+mlir::LogicalResult CIRToLLVMLifetimeEndOpLowering::matchAndRewrite(
+ cir::LifetimeEndOp op, OpAdaptor adaptor,
+ mlir::ConversionPatternRewriter &rewriter) const {
+ rewriter.replaceOpWithNewOp<mlir::LLVM::LifetimeEndOp>(op, adaptor.getPtr());
+ return mlir::success();
+}
+
mlir::LogicalResult CIRToLLVMVecCreateOpLowering::matchAndRewrite(
cir::VecCreateOp op, OpAdaptor adaptor,
mlir::ConversionPatternRewriter &rewriter) const {
diff --git a/clang/test/CIR/IR/lifetime.cir b/clang/test/CIR/IR/lifetime.cir
new file mode 100644
index 0000000000000..06b153e9c9919
--- /dev/null
+++ b/clang/test/CIR/IR/lifetime.cir
@@ -0,0 +1,25 @@
+// Test the CIR operations can parse and print correctly (roundtrip)
+
+// RUN: cir-opt %s --verify-roundtrip | FileCheck %s
+
+!s32i = !cir.int<s, 32>
+
+module {
+ cir.func @lifetime_start_end() {
+ %0 = cir.alloca !s32i, !cir.ptr<!s32i>, ["x"] {alignment = 4 : i64}
+ cir.lifetime.start %0 : !cir.ptr<!s32i>
+ cir.lifetime.end %0 : !cir.ptr<!s32i>
+ cir.return
+ }
+}
+
+//CHECK: module {
+
+//CHECK-NEXT: cir.func @lifetime_start_end() {
+//CHECK-NEXT: %0 = cir.alloca !s32i, !cir.ptr<!s32i>, ["x"] {alignment = 4 : i64}
+//CHECK-NEXT: cir.lifetime.start %0 : !cir.ptr<!s32i>
+//CHECK-NEXT: cir.lifetime.end %0 : !cir.ptr<!s32i>
+//CHECK-NEXT: cir.return
+//CHECK-NEXT: }
+
+//CHECK-NEXT: }
diff --git a/clang/test/CIR/Lowering/lifetime.cir b/clang/test/CIR/Lowering/lifetime.cir
new file mode 100644
index 0000000000000..3589bed554e5a
--- /dev/null
+++ b/clang/test/CIR/Lowering/lifetime.cir
@@ -0,0 +1,29 @@
+// RUN: cir-opt %s -cir-to-llvm -o - | FileCheck %s -check-prefix=MLIR
+// RUN: cir-opt %s -cir-to-llvm -o - | mlir-translate -mlir-to-llvmir | FileCheck %s -check-prefix=LLVM
+
+!s32i = !cir.int<s, 32>
+
+module {
+ cir.func @lifetime_markers() {
+ %0 = cir.alloca !s32i, !cir.ptr<!s32i>, ["x"] {alignment = 4 : i64}
+ cir.lifetime.start %0 : !cir.ptr<!s32i>
+ cir.lifetime.end %0 : !cir.ptr<!s32i>
+ cir.return
+ }
+}
+
+// MLIR: module {
+// MLIR-NEXT: llvm.func @lifetime_markers
+// MLIR: %[[ALLOCA:.*]] = llvm.alloca {{.*}} x i32
+// MLIR: llvm.intr.lifetime.start %[[ALLOCA]] : !llvm.ptr
+// MLIR: llvm.intr.lifetime.end %[[ALLOCA]] : !llvm.ptr
+// MLIR: llvm.return
+// MLIR-NEXT: }
+// MLIR-NEXT: }
+
+// LLVM: define void @lifetime_markers() {
+// LLVM: %[[X:.*]] = alloca i32
+// LLVM: call void @llvm.lifetime.start.p0(ptr %[[X]])
+// LLVM: call void @llvm.lifetime.end.p0(ptr %[[X]])
+// LLVM: ret void
+// LLVM: }
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