https://github.com/ilovepi updated https://github.com/llvm/llvm-project/pull/170518
>From acdccf174bad71ff21f820660528bcd460bb1f37 Mon Sep 17 00:00:00 2001 From: Paul Kirth <[email protected]> Date: Tue, 2 Dec 2025 15:14:32 -0800 Subject: [PATCH 1/5] [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 80075dd8a4cca..75e3bea3f3237 100644 --- a/clang/lib/CodeGen/CGCall.cpp +++ b/clang/lib/CodeGen/CGCall.cpp @@ -4973,11 +4973,16 @@ 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); @@ -6307,6 +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); + 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 463c2d1abcb9649aa2e78183bd5c670aab770adb Mon Sep 17 00:00:00 2001 From: Paul Kirth <[email protected]> Date: Wed, 3 Dec 2025 14:18:34 -0800 Subject: [PATCH 2/5] 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 75e3bea3f3237..1e4116300bdce 100644 --- a/clang/lib/CodeGen/CGCall.cpp +++ b/clang/lib/CodeGen/CGCall.cpp @@ -4963,12 +4963,10 @@ 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 8799240074b7876f1e689d7551a7049b5578d864 Mon Sep 17 00:00:00 2001 From: Paul Kirth <[email protected]> Date: Wed, 3 Dec 2025 16:37:11 -0800 Subject: [PATCH 3/5] 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 337078cb6b455..440162fd3d238 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 21b9837571a03a24a3185cafbb7c81d18d475916 Mon Sep 17 00:00:00 2001 From: Paul Kirth <[email protected]> Date: Thu, 4 Dec 2025 11:11:21 -0800 Subject: [PATCH 4/5] Add cleanups for the error path and add more tests --- clang/lib/CodeGen/CGCall.cpp | 5 +++- clang/test/CodeGen/lifetime-invoke-c.c | 8 +++--- .../CodeGenCXX/aggregate-lifetime-invoke.cpp | 25 +++++++++---------- 3 files changed, 19 insertions(+), 19 deletions(-) diff --git a/clang/lib/CodeGen/CGCall.cpp b/clang/lib/CodeGen/CGCall.cpp index 1e4116300bdce..4831d55ed0bf0 100644 --- a/clang/lib/CodeGen/CGCall.cpp +++ b/clang/lib/CodeGen/CGCall.cpp @@ -4976,9 +4976,12 @@ 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 a2ab7978cf88d..e5df317dcb376 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-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 440162fd3d238..69dd4d788b70d 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 961297f174b8188aa0360175003f0039a27508f3 Mon Sep 17 00:00:00 2001 From: Paul Kirth <[email protected]> Date: Thu, 4 Dec 2025 13:55:05 -0800 Subject: [PATCH 5/5] 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 4831d55ed0bf0..385713c7219a2 100644 --- a/clang/lib/CodeGen/CGCall.cpp +++ b/clang/lib/CodeGen/CGCall.cpp @@ -6313,10 +6313,11 @@ 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) _______________________________________________ llvm-branch-commits mailing list [email protected] https://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-branch-commits
