Re-commit r282556, reverted in r282564, with a fix to CallArgList::addFrom to

function correctly when targeting MS ABIs (this appears to have never mattered
prior to this change).

Update test case to always cover both 32-bit and 64-bit Windows ABIs, since
they behave somewhat differently from each other here.

Update test case to also cover operators , && and ||, which it appears are also
affected by P0145R3 (they're not explicitly called out by the design document,
but this is the emergent behavior of the existing wording).


Original commit message:

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: 282619

1 files changed, 5 insertions, 3 deletions

diff --git a/clang/lib/CodeGen/CGCall.cpp b/clang/lib/CodeGen/CGCall.cpp
index 4a24e42..525697c 100644
--- a/clang/lib/CodeGen/CGCall.cpp
+++ b/clang/lib/CodeGen/CGCall.cpp
@@ -3129,7 +3129,7 @@ static void emitWritebackArg(CodeGenFunction &CGF, CallArgList &args,
 }
 
 void CallArgList::allocateArgumentMemory(CodeGenFunction &CGF) {
-  assert(!StackBase && !StackCleanup.isValid());
+  assert(!StackBase);
 
   // Save the stack.
   llvm::Function *F = CGF.CGM.getIntrinsic(llvm::Intrinsic::stacksave);
@@ -3172,7 +3172,8 @@ void CodeGenFunction::EmitNonNullArgCheck(RValue RV, QualType ArgType,
 void CodeGenFunction::EmitCallArgs(
     CallArgList &Args, ArrayRef<QualType> ArgTypes,
     llvm::iterator_range<CallExpr::const_arg_iterator> ArgRange,
-    const FunctionDecl *CalleeDecl, unsigned ParamsToSkip) {
+    const FunctionDecl *CalleeDecl, unsigned ParamsToSkip,
+    bool ForceRightToLeftEvaluation) {
   assert((int)ArgTypes.size() == (ArgRange.end() - ArgRange.begin()));
 
   auto MaybeEmitImplicitObjectSize = [&](unsigned I, const Expr *Arg) {
@@ -3191,7 +3192,8 @@ void CodeGenFunction::EmitCallArgs(
 
   // We *have* to evaluate arguments from right to left in the MS C++ ABI,
   // because arguments are destroyed left to right in the callee.
-  if (CGM.getTarget().getCXXABI().areArgsDestroyedLeftToRightInCallee()) {
+  if (CGM.getTarget().getCXXABI().areArgsDestroyedLeftToRightInCallee() ||
+      ForceRightToLeftEvaluation) {
     // Insert a stack save if we're going to need any inalloca args.
     bool HasInAllocaArgs = false;
     for (ArrayRef<QualType>::iterator I = ArgTypes.begin(), E = ArgTypes.end();