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Reinstall the patch "Use EmitPointerWithAlignment to get alignment information of the pointer used in atomic expr" after fixing PR31620. 

This is to fix PR34347. EmitAtomicExpr now only uses alignment information from
Type, instead of Decl, so when the declaration of an atomic variable is marked
to have the alignment equal as its size, EmitAtomicExpr doesn't know about it and
will generate libcall instead of atomic op. The patch uses EmitPointerWithAlignment
to get the precise alignment information.

Differential Revision: https://reviews.llvm.org/D37310


git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@314145 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Wei Mi 2017-09-25 19:57:59 +00:00
parent 2d4bdbc5f5
commit 5572f1b64d
2 changed files with 38 additions and 8 deletions
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16
lib/CodeGen/CGAtomic.cpp
View File

@ -745,19 +745,19 @@ RValue CodeGenFunction::EmitAtomicExpr(AtomicExpr *E) {
QualType MemTy = AtomicTy;
if (const AtomicType *AT = AtomicTy->getAs<AtomicType>())
MemTy = AT->getValueType();
CharUnits sizeChars, alignChars;
std::tie(sizeChars, alignChars) = getContext().getTypeInfoInChars(AtomicTy);
uint64_t Size = sizeChars.getQuantity();
unsigned MaxInlineWidthInBits = getTarget().getMaxAtomicInlineWidth();
bool UseLibcall = (sizeChars != alignChars ||
getContext().toBits(sizeChars) > MaxInlineWidthInBits);
llvm::Value *IsWeak = nullptr, *OrderFail = nullptr;
Address Val1 = Address::invalid();
Address Val2 = Address::invalid();
Address Dest = Address::invalid();
Address Ptr(EmitScalarExpr(E->getPtr()), alignChars);
Address Ptr = EmitPointerWithAlignment(E->getPtr());
CharUnits sizeChars, alignChars;
std::tie(sizeChars, alignChars) = getContext().getTypeInfoInChars(AtomicTy);
uint64_t Size = sizeChars.getQuantity();
unsigned MaxInlineWidthInBits = getTarget().getMaxAtomicInlineWidth();
bool UseLibcall = ((Ptr.getAlignment() % sizeChars) != 0 ||
getContext().toBits(sizeChars) > MaxInlineWidthInBits);
if (E->getOp() == AtomicExpr::AO__c11_atomic_init ||
E->getOp() == AtomicExpr::AO__opencl_atomic_init) {

30
test/CodeGenCXX/atomic-align.cpp Normal file
View File

@ -0,0 +1,30 @@
// RUN: %clang_cc1 %s -std=c++11 -emit-llvm -o - -triple=x86_64-linux-gnu | FileCheck %s
struct AM {
int f1, f2;
};
alignas(8) AM m;
AM load1() {
AM am;
// m is declared to align to 8bytes, so generate load atomic instead
// of libcall.
// CHECK-LABEL: @_Z5load1v
// CHECK: load atomic {{.*}} monotonic
__atomic_load(&m, &am, 0);
return am;
}
struct BM {
int f1;
alignas(8) AM f2;
};
BM bm;
AM load2() {
AM am;
// BM::f2 is declared to align to 8bytes, so generate load atomic instead
// of libcall.
// CHECK-LABEL: @_Z5load2v
// CHECK: load atomic {{.*}} monotonic
__atomic_load(&bm.f2, &am, 0);
return am;
}