P0145R3 (C++17 evaluation order tweaks): evaluate the right-hand side of
assignment and compound-assignment operators before the left-hand side. (Even
if it's an overloaded operator.)
This completes the implementation of P0145R3 + P0400R0 for all targets except
Windows, where the evaluation order guarantees for <<, >>, and ->* are
unimplementable as the ABI requires the function arguments are evaluated from
right to left (because parameter destructors are run from left to right in the
callee).
llvm-svn: 282556
diff --git a/clang/lib/CodeGen/CGExprCXX.cpp b/clang/lib/CodeGen/CGExprCXX.cpp
index 1dfe437..34ab6ad 100644
--- a/clang/lib/CodeGen/CGExprCXX.cpp
+++ b/clang/lib/CodeGen/CGExprCXX.cpp
@@ -28,7 +28,7 @@
commonEmitCXXMemberOrOperatorCall(CodeGenFunction &CGF, const CXXMethodDecl *MD,
llvm::Value *This, llvm::Value *ImplicitParam,
QualType ImplicitParamTy, const CallExpr *CE,
- CallArgList &Args) {
+ CallArgList &Args, CallArgList *RtlArgs) {
assert(CE == nullptr || isa<CXXMemberCallExpr>(CE) ||
isa<CXXOperatorCallExpr>(CE));
assert(MD->isInstance() &&
@@ -61,7 +61,12 @@
RequiredArgs required = RequiredArgs::forPrototypePlus(FPT, Args.size(), MD);
// And the rest of the call args.
- if (CE) {
+ if (RtlArgs) {
+ // Special case: if the caller emitted the arguments right-to-left already
+ // (prior to emitting the *this argument), we're done. This happens for
+ // assignment operators.
+ Args.addFrom(*RtlArgs);
+ } else if (CE) {
// Special case: skip first argument of CXXOperatorCall (it is "this").
unsigned ArgsToSkip = isa<CXXOperatorCallExpr>(CE) ? 1 : 0;
CGF.EmitCallArgs(Args, FPT, drop_begin(CE->arguments(), ArgsToSkip),
@@ -77,11 +82,11 @@
RValue CodeGenFunction::EmitCXXMemberOrOperatorCall(
const CXXMethodDecl *MD, llvm::Value *Callee, ReturnValueSlot ReturnValue,
llvm::Value *This, llvm::Value *ImplicitParam, QualType ImplicitParamTy,
- const CallExpr *CE) {
+ const CallExpr *CE, CallArgList *RtlArgs) {
const FunctionProtoType *FPT = MD->getType()->castAs<FunctionProtoType>();
CallArgList Args;
RequiredArgs required = commonEmitCXXMemberOrOperatorCall(
- *this, MD, This, ImplicitParam, ImplicitParamTy, CE, Args);
+ *this, MD, This, ImplicitParam, ImplicitParamTy, CE, Args, RtlArgs);
return EmitCall(CGM.getTypes().arrangeCXXMethodCall(Args, FPT, required),
Callee, ReturnValue, Args, MD);
}
@@ -92,7 +97,7 @@
StructorType Type) {
CallArgList Args;
commonEmitCXXMemberOrOperatorCall(*this, DD, This, ImplicitParam,
- ImplicitParamTy, CE, Args);
+ ImplicitParamTy, CE, Args, nullptr);
return EmitCall(CGM.getTypes().arrangeCXXStructorDeclaration(DD, Type),
Callee, ReturnValueSlot(), Args, DD);
}
@@ -170,6 +175,19 @@
}
}
+ // C++17 demands that we evaluate the RHS of a (possibly-compound) assignment
+ // operator before the LHS.
+ CallArgList RtlArgStorage;
+ CallArgList *RtlArgs = nullptr;
+ if (auto *OCE = dyn_cast<CXXOperatorCallExpr>(CE)) {
+ if (OCE->isAssignmentOp()) {
+ RtlArgs = &RtlArgStorage;
+ EmitCallArgs(*RtlArgs, MD->getType()->castAs<FunctionProtoType>(),
+ drop_begin(CE->arguments(), 1), CE->getDirectCallee(),
+ /*ParamsToSkip*/0, /*ForceRightToLeftEvaluation*/true);
+ }
+ }
+
Address This = Address::invalid();
if (IsArrow)
This = EmitPointerWithAlignment(Base);
@@ -187,10 +205,12 @@
if (MD->isCopyAssignmentOperator() || MD->isMoveAssignmentOperator()) {
// We don't like to generate the trivial copy/move assignment operator
// when it isn't necessary; just produce the proper effect here.
- // Special case: skip first argument of CXXOperatorCall (it is "this").
- unsigned ArgsToSkip = isa<CXXOperatorCallExpr>(CE) ? 1 : 0;
- Address RHS = EmitLValue(*(CE->arg_begin() + ArgsToSkip)).getAddress();
- EmitAggregateAssign(This, RHS, CE->getType());
+ LValue RHS = isa<CXXOperatorCallExpr>(CE)
+ ? MakeNaturalAlignAddrLValue(
+ (*RtlArgs)[0].RV.getScalarVal(),
+ (*(CE->arg_begin() + 1))->getType())
+ : EmitLValue(*CE->arg_begin());
+ EmitAggregateAssign(This, RHS.getAddress(), CE->getType());
return RValue::get(This.getPointer());
}
@@ -249,7 +269,8 @@
Callee = CGM.GetAddrOfFunction(GlobalDecl(DDtor, Dtor_Complete), Ty);
}
EmitCXXMemberOrOperatorCall(MD, Callee, ReturnValue, This.getPointer(),
- /*ImplicitParam=*/nullptr, QualType(), CE);
+ /*ImplicitParam=*/nullptr, QualType(), CE,
+ nullptr);
}
return RValue::get(nullptr);
}
@@ -282,7 +303,8 @@
}
return EmitCXXMemberOrOperatorCall(MD, Callee, ReturnValue, This.getPointer(),
- /*ImplicitParam=*/nullptr, QualType(), CE);
+ /*ImplicitParam=*/nullptr, QualType(), CE,
+ RtlArgs);
}
RValue