From 64c80b4e39bbd4dc2b1b3b9b0a1be1eaa3f9c7ed Mon Sep 17 00:00:00 2001 From: Vitaly Buka Date: Wed, 26 Oct 2016 05:42:30 +0000 Subject: [CodeGen] Don't emit lifetime intrinsics for some local variables Summary: Current generation of lifetime intrinsics does not handle cases like: ``` { char x; l1: bar(&x, 1); } goto l1; ``` We will get code like this: ``` %x = alloca i8, align 1 call void @llvm.lifetime.start(i64 1, i8* nonnull %x) br label %l1 l1: %call = call i32 @bar(i8* nonnull %x, i32 1) call void @llvm.lifetime.end(i64 1, i8* nonnull %x) br label %l1 ``` So the second time bar was called for x which is marked as dead. Lifetime markers here are misleading so it's better to remove them at all. This type of bypasses are rare, e.g. code detects just 8 functions building clang (2329 targets). PR28267 Reviewers: eugenis Subscribers: beanz, mgorny, cfe-commits Differential Revision: https://reviews.llvm.org/D24693 llvm-svn: 285176 --- clang/lib/CodeGen/CodeGenFunction.cpp | 9 ++++++++- 1 file changed, 8 insertions(+), 1 deletion(-) (limited to 'clang/lib/CodeGen/CodeGenFunction.cpp') diff --git a/clang/lib/CodeGen/CodeGenFunction.cpp b/clang/lib/CodeGen/CodeGenFunction.cpp index a4ea7b608e6..538b50d56d4 100644 --- a/clang/lib/CodeGen/CodeGenFunction.cpp +++ b/clang/lib/CodeGen/CodeGenFunction.cpp @@ -1066,6 +1066,13 @@ void CodeGenFunction::GenerateCode(GlobalDecl GD, llvm::Function *Fn, if (SpecDecl->hasBody(SpecDecl)) Loc = SpecDecl->getLocation(); + Stmt *Body = FD->getBody(); + + // Initialize helper which will detect jumps which can cause invalid lifetime + // markers. + if (Body && ShouldEmitLifetimeMarkers) + Bypasses.Init(Body); + // Emit the standard function prologue. StartFunction(GD, ResTy, Fn, FnInfo, Args, Loc, BodyRange.getBegin()); @@ -1095,7 +1102,7 @@ void CodeGenFunction::GenerateCode(GlobalDecl GD, llvm::Function *Fn, // Implicit copy-assignment gets the same special treatment as implicit // copy-constructors. emitImplicitAssignmentOperatorBody(Args); - } else if (Stmt *Body = FD->getBody()) { + } else if (Body) { EmitFunctionBody(Args, Body); } else llvm_unreachable("no definition for emitted function"); -- cgit v1.2.3