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Use FinishThunk to finish musttail thunks 

FinishThunk, and the invariant of setting and then unsetting
CurCodeDecl, was added in 7f416cc426 (2015). The invariant didn't
exist when I added this musttail codepath in ab2090d107 (2014).
Recently in 28328c3771, I started using this codepath on non-Windows
platforms, and users reported problems during release testing (PR44987).

The issue was already present for users of EH on i686-windows-msvc, so I
added a test for that case as well.

Reviewed By: hans

Differential Revision: https://reviews.llvm.org/D76444
This commit is contained in:
Reid Kleckner 2020-03-19 11:52:22 -07:00
parent ffcc076a2b
commit ce5173c0e1
3 changed files with 59 additions and 2 deletions
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5
clang/lib/CodeGen/CGVTables.cpp
View File

@ -437,7 +437,8 @@ void CodeGenFunction::EmitMustTailThunk(GlobalDecl GD,
// Finish the function to maintain CodeGenFunction invariants.
// FIXME: Don't emit unreachable code.
EmitBlock(createBasicBlock());
FinishFunction();
FinishThunk();
}
void CodeGenFunction::generateThunk(llvm::Function *Fn,
@ -564,7 +565,7 @@ llvm::Constant *CodeGenVTables::maybeEmitThunk(GlobalDecl GD,
CGM.SetLLVMFunctionAttributesForDefinition(GD.getDecl(), ThunkFn);
// Thunks for variadic methods are special because in general variadic
// arguments cannot be perferctly forwarded. In the general case, clang
// arguments cannot be perfectly forwarded. In the general case, clang
// implements such thunks by cloning the original function body. However, for
// thunks with no return adjustment on targets that support musttail, we can
// use musttail to perfectly forward the variadic arguments.

27
clang/test/CodeGenCXX/ms-thunks-ehspec.cpp Normal file
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@ -0,0 +1,27 @@
// RUN: %clang_cc1 -fexceptions -fcxx-exceptions %s -triple=i686-windows-msvc -emit-llvm -o - | FileCheck %s
// When generating thunks using musttail due to inalloca parameters, don't push
// and pop terminate scopes. PR44987
struct NonTrivial {
NonTrivial();
NonTrivial(const NonTrivial &o);
~NonTrivial();
int x;
};
struct A {
virtual void f(NonTrivial o) noexcept;
};
struct B {
virtual void f(NonTrivial o) noexcept;
};
class C : A, B {
virtual void f(NonTrivial o) noexcept;
};
C c;
// CHECK-LABEL: define linkonce_odr dso_local x86_thiscallcc void @"?f@C@@G3AEXUNonTrivial@@@Z"(%class.C* %this, <{ %struct.NonTrivial }>* inalloca %0)
// CHECK-NOT: invoke
// CHECK: musttail call x86_thiscallcc void @"?f@C@@EAEXUNonTrivial@@@Z"(%class.C* %{{.*}}, <{ %struct.NonTrivial }>* inalloca %0)
// CHECK-NEXT ret void

29
clang/test/CodeGenCXX/thunks-ehspec.cpp Normal file
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@ -0,0 +1,29 @@
// RUN: %clang_cc1 -fexceptions -fcxx-exceptions %s -triple=x86_64-pc-linux-gnu -munwind-tables -emit-llvm -o - -O1 -disable-llvm-passes | FileCheck %s
// When generating the thunk for secondary, do not push terminate scopes for
// either the varargs or non-varargs case. Related to PR44987.
struct A {
virtual void primary_key();
};
struct B {
virtual void secondary();
virtual void secondary_vararg(int, ...);
};
class C : A, B {
virtual void primary_key();
void secondary() noexcept;
void secondary_vararg(int, ...) noexcept;
};
void C::primary_key() {}
// CHECK-LABEL: define available_externally void @_ZThn8_N1C9secondaryEv(%class.C* %this)
// CHECK-NOT: invoke
// CHECK: tail call void @_ZN1C9secondaryEv(%class.C* %{{.*}})
// CHECK-NOT: invoke
// CHECK: ret void
// CHECK-LABEL: define available_externally void @_ZThn8_N1C16secondary_varargEiz(%class.C* %this, i32 %0, ...)
// CHECK-NOT: invoke
// CHECK: musttail call void (%class.C*, i32, ...) @_ZN1C16secondary_varargEiz(%class.C* %{{.*}}, i32 %{{.*}}, ...) #2
// CHECK-NEXT: ret void