[Atomics] warn about atomic accesses using libcalls
If an atomic variable is misaligned (and that suspicion is why Clang emits
libcalls at all) the runtime support library will have to use a lock to safely
access it, with potentially very bad performance consequences. There's a very
good chance this is unintentional so it makes sense to issue a warning.
Also give it a named group so people can promote it to an error, or disable it
if they really don't care.
llvm-svn: 330566
diff --git a/clang/lib/CodeGen/CGAtomic.cpp b/clang/lib/CodeGen/CGAtomic.cpp
index efc7089..47a82b6 100644
--- a/clang/lib/CodeGen/CGAtomic.cpp
+++ b/clang/lib/CodeGen/CGAtomic.cpp
@@ -18,6 +18,7 @@
#include "TargetInfo.h"
#include "clang/AST/ASTContext.h"
#include "clang/CodeGen/CGFunctionInfo.h"
+#include "clang/Sema/SemaDiagnostic.h"
#include "llvm/ADT/DenseMap.h"
#include "llvm/IR/DataLayout.h"
#include "llvm/IR/Intrinsics.h"
@@ -751,6 +752,13 @@
Address Dest = Address::invalid();
Address Ptr = EmitPointerWithAlignment(E->getPtr());
+ if (E->getOp() == AtomicExpr::AO__c11_atomic_init ||
+ E->getOp() == AtomicExpr::AO__opencl_atomic_init) {
+ LValue lvalue = MakeAddrLValue(Ptr, AtomicTy);
+ EmitAtomicInit(E->getVal1(), lvalue);
+ return RValue::get(nullptr);
+ }
+
CharUnits sizeChars, alignChars;
std::tie(sizeChars, alignChars) = getContext().getTypeInfoInChars(AtomicTy);
uint64_t Size = sizeChars.getQuantity();
@@ -758,12 +766,8 @@
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) {
- LValue lvalue = MakeAddrLValue(Ptr, AtomicTy);
- EmitAtomicInit(E->getVal1(), lvalue);
- return RValue::get(nullptr);
- }
+ if (UseLibcall)
+ CGM.getDiags().Report(E->getLocStart(), diag::warn_atomic_op_misaligned);
llvm::Value *Order = EmitScalarExpr(E->getOrder());
llvm::Value *Scope =