https://github.com/ilovepi updated https://github.com/llvm/llvm-project/pull/170518
>From b23585403b26d267cf21fcff4f3c550b1b0dd597 Mon Sep 17 00:00:00 2001 From: Paul Kirth <[email protected]> Date: Tue, 2 Dec 2025 15:14:32 -0800 Subject: [PATCH 1/7] [clang] Use tighter lifetime bounds for C temporary arguments In C, consecutive statements in the same scope are under CompoundStmt/CallExpr, while in C++ they typically fall under CompoundStmt/ExprWithCleanup. This leads to different behavior with respect to where pushFullExprCleanUp inserts the lifetime end markers (e.g., at the end of scope). For these cases, we can track and insert the lifetime end markers right after the call completes. Allowing the stack space to be reused immediately. This partially addresses #109204 and #43598 for improving stack usage. --- clang/lib/CodeGen/CGCall.cpp | 18 ++++++++++++++---- clang/lib/CodeGen/CGCall.h | 19 +++++++++++++++++++ clang/test/CodeGen/stack-usage-lifetimes.c | 12 ++++++------ .../CodeGenCXX/stack-reuse-miscompile.cpp | 2 +- 4 files changed, 40 insertions(+), 11 deletions(-) diff --git a/clang/lib/CodeGen/CGCall.cpp b/clang/lib/CodeGen/CGCall.cpp index 35e237c8eedbe..b6387d63a7657 100644 --- a/clang/lib/CodeGen/CGCall.cpp +++ b/clang/lib/CodeGen/CGCall.cpp @@ -4972,11 +4972,16 @@ void CodeGenFunction::EmitCallArg(CallArgList &args, const Expr *E, RawAddress ArgSlotAlloca = Address::invalid(); ArgSlot = CreateAggTemp(E->getType(), "agg.tmp", &ArgSlotAlloca); - // Emit a lifetime start/end for this temporary at the end of the full - // expression. + // Emit a lifetime start/end for this temporary. If the type has a + // destructor, then we need to keep it alive for the full expression. if (!CGM.getCodeGenOpts().NoLifetimeMarkersForTemporaries && - EmitLifetimeStart(ArgSlotAlloca.getPointer())) - pushFullExprCleanup<CallLifetimeEnd>(NormalAndEHCleanup, ArgSlotAlloca); + EmitLifetimeStart(ArgSlotAlloca.getPointer())) { + if (E->getType().isDestructedType()) { + pushFullExprCleanup<CallLifetimeEnd>(NormalAndEHCleanup, ArgSlotAlloca); + } else { + args.addLifetimeCleanup({ArgSlotAlloca.getPointer()}); + } + } } args.add(EmitAnyExpr(E, ArgSlot), type); @@ -6306,6 +6311,11 @@ RValue CodeGenFunction::EmitCall(const CGFunctionInfo &CallInfo, for (CallLifetimeEnd &LifetimeEnd : CallLifetimeEndAfterCall) LifetimeEnd.Emit(*this, /*Flags=*/{}); + if (!CGM.getCodeGenOpts().NoLifetimeMarkersForTemporaries) + for (const CallArgList::EndLifetimeInfo < : + CallArgs.getLifetimeCleanups()) + EmitLifetimeEnd(LT.Addr); + if (!ReturnValue.isExternallyDestructed() && RetTy.isDestructedType() == QualType::DK_nontrivial_c_struct) pushDestroy(QualType::DK_nontrivial_c_struct, Ret.getAggregateAddress(), diff --git a/clang/lib/CodeGen/CGCall.h b/clang/lib/CodeGen/CGCall.h index 1ef8a3f114573..aab4b64d6a4a8 100644 --- a/clang/lib/CodeGen/CGCall.h +++ b/clang/lib/CodeGen/CGCall.h @@ -299,6 +299,10 @@ class CallArgList : public SmallVector<CallArg, 8> { llvm::Instruction *IsActiveIP; }; + struct EndLifetimeInfo { + llvm::Value *Addr; + }; + void add(RValue rvalue, QualType type) { push_back(CallArg(rvalue, type)); } void addUncopiedAggregate(LValue LV, QualType type) { @@ -312,6 +316,9 @@ class CallArgList : public SmallVector<CallArg, 8> { llvm::append_range(*this, other); llvm::append_range(Writebacks, other.Writebacks); llvm::append_range(CleanupsToDeactivate, other.CleanupsToDeactivate); + LifetimeCleanups.insert(LifetimeCleanups.end(), + other.LifetimeCleanups.begin(), + other.LifetimeCleanups.end()); assert(!(StackBase && other.StackBase) && "can't merge stackbases"); if (!StackBase) StackBase = other.StackBase; @@ -352,6 +359,14 @@ class CallArgList : public SmallVector<CallArg, 8> { /// memory. bool isUsingInAlloca() const { return StackBase; } + void addLifetimeCleanup(EndLifetimeInfo Info) { + LifetimeCleanups.push_back(Info); + } + + ArrayRef<EndLifetimeInfo> getLifetimeCleanups() const { + return LifetimeCleanups; + } + // Support reversing writebacks for MSVC ABI. void reverseWritebacks() { std::reverse(Writebacks.begin(), Writebacks.end()); @@ -365,6 +380,10 @@ class CallArgList : public SmallVector<CallArg, 8> { /// occurs. SmallVector<CallArgCleanup, 1> CleanupsToDeactivate; + /// Lifetime information needed to call llvm.lifetime.end for any temporary + /// argument allocas. + SmallVector<EndLifetimeInfo, 2> LifetimeCleanups; + /// The stacksave call. It dominates all of the argument evaluation. llvm::CallInst *StackBase = nullptr; }; diff --git a/clang/test/CodeGen/stack-usage-lifetimes.c b/clang/test/CodeGen/stack-usage-lifetimes.c index 3787a29e4ce7d..189bc9c229ca4 100644 --- a/clang/test/CodeGen/stack-usage-lifetimes.c +++ b/clang/test/CodeGen/stack-usage-lifetimes.c @@ -40,11 +40,11 @@ void t1(int c) { } void t2(void) { - // x86-precise-remark@-1 {{72 stack bytes}} + // x86-precise-remark@-1 {{40 stack bytes}} // x86-sloppy-remark@-2 {{72 stack bytes}} - // aarch64-precise-remark@-3 {{80 stack bytes}} + // aarch64-precise-remark@-3 {{48 stack bytes}} // aarch64-sloppy-remark@-4 {{80 stack bytes}} - // riscv-precise-remark@-5 {{80 stack bytes}} + // riscv-precise-remark@-5 {{48 stack bytes}} // riscv-sloppy-remark@-6 {{80 stack bytes}} useA(genA()); @@ -52,11 +52,11 @@ void t2(void) { } void t3(void) { - // x86-precise-remark@-1 {{72 stack bytes}} + // x86-precise-remark@-1 {{40 stack bytes}} // x86-sloppy-remark@-2 {{72 stack bytes}} - // aarch64-precise-remark@-3 {{80 stack bytes}} + // aarch64-precise-remark@-3 {{48 stack bytes}} // aarch64-sloppy-remark@-4 {{80 stack bytes}} - // riscv-precise-remark@-5 {{80 stack bytes}} + // riscv-precise-remark@-5 {{48 stack bytes}} // riscv-sloppy-remark@-6 {{80 stack bytes}} useB(genB()); diff --git a/clang/test/CodeGenCXX/stack-reuse-miscompile.cpp b/clang/test/CodeGenCXX/stack-reuse-miscompile.cpp index 50c374d2710f4..4aef39119c94a 100644 --- a/clang/test/CodeGenCXX/stack-reuse-miscompile.cpp +++ b/clang/test/CodeGenCXX/stack-reuse-miscompile.cpp @@ -38,10 +38,10 @@ const char * f(S s) // CHECK: call void @llvm.lifetime.start.p0(ptr [[T3]]) // CHECK: call void @llvm.lifetime.start.p0(ptr [[AGG]]) // CHECK: [[T5:%.*]] = call noundef ptr @_ZN1TC1E1S(ptr {{[^,]*}} [[T3]], [2 x i32] %{{.*}}) +// CHECK: call void @llvm.lifetime.end.p0(ptr [[AGG]]) // // CHECK: call void @_ZNK1T6concatERKS_(ptr dead_on_unwind writable sret(%class.T) align 4 [[T1]], ptr {{[^,]*}} [[T2]], ptr noundef nonnull align 4 dereferenceable(16) [[T3]]) // CHECK: [[T6:%.*]] = call noundef ptr @_ZNK1T3strEv(ptr {{[^,]*}} [[T1]]) -// CHECK: call void @llvm.lifetime.end.p0(ptr [[AGG]]) // // CHECK: call void @llvm.lifetime.end.p0( // CHECK: call void @llvm.lifetime.end.p0( >From 785603068a9b0a3f2b8d75aaedbf3e948cebd238 Mon Sep 17 00:00:00 2001 From: Paul Kirth <[email protected]> Date: Wed, 3 Dec 2025 14:18:34 -0800 Subject: [PATCH 2/7] Update comment to be more accurate --- clang/lib/CodeGen/CGCall.cpp | 8 +++----- 1 file changed, 3 insertions(+), 5 deletions(-) diff --git a/clang/lib/CodeGen/CGCall.cpp b/clang/lib/CodeGen/CGCall.cpp index b6387d63a7657..11bc21c334d75 100644 --- a/clang/lib/CodeGen/CGCall.cpp +++ b/clang/lib/CodeGen/CGCall.cpp @@ -4962,12 +4962,10 @@ void CodeGenFunction::EmitCallArg(CallArgList &args, const Expr *E, AggValueSlot ArgSlot = AggValueSlot::ignored(); // For arguments with aggregate type, create an alloca to store - // the value. If the argument's type has a destructor, that destructor + // the value. If the argument's type has a destructor, that destructor // will run at the end of the full-expression; emit matching lifetime - // markers. - // - // FIXME: For types which don't have a destructor, consider using a - // narrower lifetime bound. + // markers. For types which don't have a destructor, we use a narrower + // lifetime bound. if (hasAggregateEvaluationKind(E->getType())) { RawAddress ArgSlotAlloca = Address::invalid(); ArgSlot = CreateAggTemp(E->getType(), "agg.tmp", &ArgSlotAlloca); >From c2d60ae28f176b9079243711e3c663ad1c38b94a Mon Sep 17 00:00:00 2001 From: Paul Kirth <[email protected]> Date: Wed, 3 Dec 2025 16:37:11 -0800 Subject: [PATCH 3/7] Update invoke test for tighter lifetimes --- .../CodeGenCXX/aggregate-lifetime-invoke.cpp | 26 +++++++++---------- 1 file changed, 12 insertions(+), 14 deletions(-) diff --git a/clang/test/CodeGenCXX/aggregate-lifetime-invoke.cpp b/clang/test/CodeGenCXX/aggregate-lifetime-invoke.cpp index 32af6b51fe9c8..026f8cb97de2d 100644 --- a/clang/test/CodeGenCXX/aggregate-lifetime-invoke.cpp +++ b/clang/test/CodeGenCXX/aggregate-lifetime-invoke.cpp @@ -15,29 +15,27 @@ void test() { // CHECK: call void @llvm.lifetime.start.p0(ptr{{.*}} %[[AGG1]]) // CHECK: invoke void @func_that_throws(ptr{{.*}} %[[AGG1]]) - // CHECK-NEXT: to label %[[CONT1:.*]] unwind label %[[LPAD1:.*]] + // CHECK-NEXT: to label %[[CONT1:.*]] unwind label %[[LPAD:.*]] // CHECK: [[CONT1]]: + + // CHECK-NEXT: call void @llvm.lifetime.end.p0(ptr{{.*}} %[[AGG1]]) // CHECK-NEXT: call void @llvm.lifetime.start.p0(ptr{{.*}} %[[AGG2]]) - // CHECK: invoke void @func_that_throws(ptr{{.*}} %[[AGG2]]) - // CHECK-NEXT: to label %[[CONT2:.*]] unwind label %[[LPAD2:.*]] + // CHECK: invoke void @_func_that_throws(ptr{{.*}} %[[AGG2]]) + // CHECK-NEXT: to label %[[CONT2:.*]] unwind label %[[LPAD]] // CHECK: [[CONT2]]: - // CHECK-DAG: call void @llvm.lifetime.end.p0(ptr{{.*}} %[[AGG2]]) - // CHECK-DAG: call void @llvm.lifetime.end.p0(ptr{{.*}} %[[AGG1]]) + // CHECK-NEXT: call void @llvm.lifetime.end.p0(ptr{{.*}} %[[AGG2]]) // CHECK: br label %[[TRY_CONT:.*]] - // CHECK: [[LPAD1]]: - // CHECK: landingpad - // CHECK: br label %[[EHCLEANUP:.*]] - - // CHECK: [[LPAD2]]: + // CHECK: [[LPAD]]: // CHECK: landingpad - // CHECK: call void @llvm.lifetime.end.p0(ptr{{.*}} %[[AGG2]]) - // CHECK: br label %[[EHCLEANUP]] + // CHECK-NOT: call void @llvm.lifetime.end.p0(ptr{{.*}} %[[AGG1]]) + // CHECK-NOT: call void @llvm.lifetime.end.p0(ptr{{.*}} %[[AGG2]]) + // CHECK: br label %[[TRY_CONT]] - // CHECK: [[EHCLEANUP]]: - // CHECK: call void @llvm.lifetime.end.p0(ptr{{.*}} %[[AGG1]]) + // CHECK: [[TRY_CONT]]: + // CHECK-NEXT: ret void try { func_that_throws(Trivial{0}); func_that_throws(Trivial{0}); >From 9dc7e8d5a95e0e27ebf53e2657fb931ca2e38ecc Mon Sep 17 00:00:00 2001 From: Paul Kirth <[email protected]> Date: Thu, 4 Dec 2025 11:11:21 -0800 Subject: [PATCH 4/7] Add cleanups for the error path and add more tests --- clang/lib/CodeGen/CGCall.cpp | 5 +++- clang/test/CodeGen/lifetime-invoke-c.c | 12 ++++----- .../CodeGenCXX/aggregate-lifetime-invoke.cpp | 25 +++++++++---------- 3 files changed, 21 insertions(+), 21 deletions(-) diff --git a/clang/lib/CodeGen/CGCall.cpp b/clang/lib/CodeGen/CGCall.cpp index 11bc21c334d75..86d3bf0a847a6 100644 --- a/clang/lib/CodeGen/CGCall.cpp +++ b/clang/lib/CodeGen/CGCall.cpp @@ -4975,9 +4975,12 @@ void CodeGenFunction::EmitCallArg(CallArgList &args, const Expr *E, if (!CGM.getCodeGenOpts().NoLifetimeMarkersForTemporaries && EmitLifetimeStart(ArgSlotAlloca.getPointer())) { if (E->getType().isDestructedType()) { - pushFullExprCleanup<CallLifetimeEnd>(NormalAndEHCleanup, ArgSlotAlloca); + pushFullExprCleanup<CallLifetimeEnd>(NormalEHLifetimeMarker, ArgSlotAlloca); } else { args.addLifetimeCleanup({ArgSlotAlloca.getPointer()}); + if (getInvokeDest()) + pushFullExprCleanup<CallLifetimeEnd>(CleanupKind::EHCleanup, + ArgSlotAlloca); } } } diff --git a/clang/test/CodeGen/lifetime-invoke-c.c b/clang/test/CodeGen/lifetime-invoke-c.c index f3573f4b2ec17..95aadf9d2babf 100644 --- a/clang/test/CodeGen/lifetime-invoke-c.c +++ b/clang/test/CodeGen/lifetime-invoke-c.c @@ -22,16 +22,14 @@ void test() { // CHECK-NEXT: to label %[[CONT1:.*]] unwind label %[[LPAD1:.*]] // CHECK: [[CONT1]]: - // CHECK-NOT: call void @llvm.lifetime.end.p0(ptr %[[AGG1]]) - - // CHECK: call void @llvm.lifetime.start.p0(ptr %[[AGG2]]) - // CHECK: invoke void @gen(ptr{{.*}} sret(%struct.Trivial){{.*}} %[[AGG2]]) - // CHECK: invoke void @func(ptr{{.*}} %[[AGG2]]) + // CHECK-NEXT: call void @llvm.lifetime.end.p0(ptr %[[AGG1]]) + // CHECK-NEXT: call void @llvm.lifetime.start.p0(ptr %[[AGG2]]) + // CHECK: invoke void @gen(ptr{{.*}} sret(%struct.Trivial) align 4 %[[AGG2]]) + // CHECK: invoke void @func(ptr{{.*}} byval(%struct.Trivial) align 8 %[[AGG2]]) // CHECK-NEXT: to label %[[CONT2:.*]] unwind label %[[LPAD2:.*]] // CHECK: [[CONT2]]: - // CHECK-DAG: call void @llvm.lifetime.end.p0(ptr %[[AGG2]]) - // CHECK-DAG: call void @llvm.lifetime.end.p0(ptr %[[AGG1]]) + // CHECK-NEXT: call void @llvm.lifetime.end.p0(ptr %[[AGG2]]) // CHECK: [[LPAD1]]: // CHECK: landingpad diff --git a/clang/test/CodeGenCXX/aggregate-lifetime-invoke.cpp b/clang/test/CodeGenCXX/aggregate-lifetime-invoke.cpp index 026f8cb97de2d..adcc357cb2e45 100644 --- a/clang/test/CodeGenCXX/aggregate-lifetime-invoke.cpp +++ b/clang/test/CodeGenCXX/aggregate-lifetime-invoke.cpp @@ -15,27 +15,26 @@ void test() { // CHECK: call void @llvm.lifetime.start.p0(ptr{{.*}} %[[AGG1]]) // CHECK: invoke void @func_that_throws(ptr{{.*}} %[[AGG1]]) - // CHECK-NEXT: to label %[[CONT1:.*]] unwind label %[[LPAD:.*]] - - // CHECK: [[CONT1]]: + // CHECK: [[CONT1:.*]]: // CHECK-NEXT: call void @llvm.lifetime.end.p0(ptr{{.*}} %[[AGG1]]) // CHECK-NEXT: call void @llvm.lifetime.start.p0(ptr{{.*}} %[[AGG2]]) - // CHECK: invoke void @_func_that_throws(ptr{{.*}} %[[AGG2]]) - // CHECK-NEXT: to label %[[CONT2:.*]] unwind label %[[LPAD]] + // CHECK: invoke void @func_that_throws(ptr{{.*}} %[[AGG2]]) - // CHECK: [[CONT2]]: + // CHECK: [[CONT2:.*]]: // CHECK-NEXT: call void @llvm.lifetime.end.p0(ptr{{.*}} %[[AGG2]]) - // CHECK: br label %[[TRY_CONT:.*]] - // CHECK: [[LPAD]]: + // CHECK: [[LPAD1:lpad.*]]: + // CHECK: landingpad + // CHECK: br label %[[EHCLEANUP:.*]] + + // CHECK: [[LPAD2:lpad.*]]: // CHECK: landingpad - // CHECK-NOT: call void @llvm.lifetime.end.p0(ptr{{.*}} %[[AGG1]]) - // CHECK-NOT: call void @llvm.lifetime.end.p0(ptr{{.*}} %[[AGG2]]) - // CHECK: br label %[[TRY_CONT]] + // CHECK: call void @llvm.lifetime.end.p0(ptr{{.*}} %[[AGG2]]) + // CHECK: br label %[[EHCLEANUP]] - // CHECK: [[TRY_CONT]]: - // CHECK-NEXT: ret void + // CHECK: [[EHCLEANUP]]: + // CHECK: call void @llvm.lifetime.end.p0(ptr{{.*}} %[[AGG1]]) try { func_that_throws(Trivial{0}); func_that_throws(Trivial{0}); >From 1f7a5a32c47b41748d43db15589f061d1e81707e Mon Sep 17 00:00:00 2001 From: Paul Kirth <[email protected]> Date: Thu, 4 Dec 2025 13:55:05 -0800 Subject: [PATCH 5/7] Avoid checking NoLifetimeMarkersForTemporaries --- clang/lib/CodeGen/CGCall.cpp | 9 +++++---- 1 file changed, 5 insertions(+), 4 deletions(-) diff --git a/clang/lib/CodeGen/CGCall.cpp b/clang/lib/CodeGen/CGCall.cpp index 86d3bf0a847a6..bd0b4513d4ddd 100644 --- a/clang/lib/CodeGen/CGCall.cpp +++ b/clang/lib/CodeGen/CGCall.cpp @@ -6312,10 +6312,11 @@ RValue CodeGenFunction::EmitCall(const CGFunctionInfo &CallInfo, for (CallLifetimeEnd &LifetimeEnd : CallLifetimeEndAfterCall) LifetimeEnd.Emit(*this, /*Flags=*/{}); - if (!CGM.getCodeGenOpts().NoLifetimeMarkersForTemporaries) - for (const CallArgList::EndLifetimeInfo < : - CallArgs.getLifetimeCleanups()) - EmitLifetimeEnd(LT.Addr); + // Add lifetime end markers for any temporary aggregates. Under + // NoLifetimeMarkersForTemporaries LifetimeCleanups will be empty, so this is + // still correct. + for (const CallArgList::EndLifetimeInfo < : CallArgs.getLifetimeCleanups()) + EmitLifetimeEnd(LT.Addr); if (!ReturnValue.isExternallyDestructed() && RetTy.isDestructedType() == QualType::DK_nontrivial_c_struct) >From eb19707ea5a954e864f15e748f7edc21c4b319a4 Mon Sep 17 00:00:00 2001 From: Paul Kirth <[email protected]> Date: Thu, 4 Dec 2025 13:57:15 -0800 Subject: [PATCH 6/7] git clang-format --- clang/lib/CodeGen/CGCall.cpp | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/clang/lib/CodeGen/CGCall.cpp b/clang/lib/CodeGen/CGCall.cpp index bd0b4513d4ddd..779c372613488 100644 --- a/clang/lib/CodeGen/CGCall.cpp +++ b/clang/lib/CodeGen/CGCall.cpp @@ -4975,7 +4975,8 @@ void CodeGenFunction::EmitCallArg(CallArgList &args, const Expr *E, if (!CGM.getCodeGenOpts().NoLifetimeMarkersForTemporaries && EmitLifetimeStart(ArgSlotAlloca.getPointer())) { if (E->getType().isDestructedType()) { - pushFullExprCleanup<CallLifetimeEnd>(NormalEHLifetimeMarker, ArgSlotAlloca); + pushFullExprCleanup<CallLifetimeEnd>(NormalEHLifetimeMarker, + ArgSlotAlloca); } else { args.addLifetimeCleanup({ArgSlotAlloca.getPointer()}); if (getInvokeDest()) >From 4f509487ab392442ae418a9353c819d3fbb034a6 Mon Sep 17 00:00:00 2001 From: Paul Kirth <[email protected]> Date: Thu, 4 Dec 2025 14:35:38 -0800 Subject: [PATCH 7/7] Fix test checks --- clang/test/CodeGen/lifetime-invoke-c.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/clang/test/CodeGen/lifetime-invoke-c.c b/clang/test/CodeGen/lifetime-invoke-c.c index 95aadf9d2babf..5d38ad9e0c408 100644 --- a/clang/test/CodeGen/lifetime-invoke-c.c +++ b/clang/test/CodeGen/lifetime-invoke-c.c @@ -24,8 +24,8 @@ void test() { // CHECK: [[CONT1]]: // CHECK-NEXT: call void @llvm.lifetime.end.p0(ptr %[[AGG1]]) // CHECK-NEXT: call void @llvm.lifetime.start.p0(ptr %[[AGG2]]) - // CHECK: invoke void @gen(ptr{{.*}} sret(%struct.Trivial) align 4 %[[AGG2]]) - // CHECK: invoke void @func(ptr{{.*}} byval(%struct.Trivial) align 8 %[[AGG2]]) + // CHECK: invoke void @gen(ptr{{.*}} sret(%struct.Trivial){{.*}} %[[AGG2]]) + // CHECK: invoke void @func(ptr{{.*}} %[[AGG2]]) // CHECK-NEXT: to label %[[CONT2:.*]] unwind label %[[LPAD2:.*]] // CHECK: [[CONT2]]: _______________________________________________ llvm-branch-commits mailing list [email protected] https://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-branch-commits
