1 files changed, 26 insertions, 25 deletions

diff --git a/clang/lib/CodeGen/CGCall.cpp b/clang/lib/CodeGen/CGCall.cpp
index 525697c3527..233f6c17d48 100644
--- a/clang/lib/CodeGen/CGCall.cpp
+++ b/clang/lib/CodeGen/CGCall.cpp
@@ -3173,7 +3173,7 @@ void CodeGenFunction::EmitCallArgs(
     CallArgList &Args, ArrayRef<QualType> ArgTypes,
     llvm::iterator_range<CallExpr::const_arg_iterator> ArgRange,
     const FunctionDecl *CalleeDecl, unsigned ParamsToSkip,
-    bool ForceRightToLeftEvaluation) {
+    EvaluationOrder Order) {
   assert((int)ArgTypes.size() == (ArgRange.end() - ArgRange.begin()));
 
   auto MaybeEmitImplicitObjectSize = [&](unsigned I, const Expr *Arg) {
@@ -3191,11 +3191,18 @@ 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() ||
-      ForceRightToLeftEvaluation) {
-    // Insert a stack save if we're going to need any inalloca args.
-    bool HasInAllocaArgs = false;
+  // because arguments are destroyed left to right in the callee. As a special
+  // case, there are certain language constructs that require left-to-right
+  // evaluation, and in those cases we consider the evaluation order requirement
+  // to trump the "destruction order is reverse construction order" guarantee.
+  bool LeftToRight =
+      CGM.getTarget().getCXXABI().areArgsDestroyedLeftToRightInCallee()
+          ? Order == EvaluationOrder::ForceLeftToRight
+          : Order != EvaluationOrder::ForceRightToLeft;
+
+  // Insert a stack save if we're going to need any inalloca args.
+  bool HasInAllocaArgs = false;
+  if (CGM.getTarget().getCXXABI().isMicrosoft()) {
     for (ArrayRef<QualType>::iterator I = ArgTypes.begin(), E = ArgTypes.end();
          I != E && !HasInAllocaArgs; ++I)
       HasInAllocaArgs = isInAllocaArgument(CGM.getCXXABI(), *I);
@@ -3203,30 +3210,24 @@ void CodeGenFunction::EmitCallArgs(
       assert(getTarget().getTriple().getArch() == llvm::Triple::x86);
       Args.allocateArgumentMemory(*this);
     }
+  }
 
-    // Evaluate each argument.
-    size_t CallArgsStart = Args.size();
-    for (int I = ArgTypes.size() - 1; I >= 0; --I) {
-      CallExpr::const_arg_iterator Arg = ArgRange.begin() + I;
-      MaybeEmitImplicitObjectSize(I, *Arg);
-      EmitCallArg(Args, *Arg, ArgTypes[I]);
-      EmitNonNullArgCheck(Args.back().RV, ArgTypes[I], (*Arg)->getExprLoc(),
-                          CalleeDecl, ParamsToSkip + I);
-    }
+  // Evaluate each argument in the appropriate order.
+  size_t CallArgsStart = Args.size();
+  for (unsigned I = 0, E = ArgTypes.size(); I != E; ++I) {
+    unsigned Idx = LeftToRight ? I : E - I - 1;
+    CallExpr::const_arg_iterator Arg = ArgRange.begin() + Idx;
+    if (!LeftToRight) MaybeEmitImplicitObjectSize(Idx, *Arg);
+    EmitCallArg(Args, *Arg, ArgTypes[Idx]);
+    EmitNonNullArgCheck(Args.back().RV, ArgTypes[Idx], (*Arg)->getExprLoc(),
+                        CalleeDecl, ParamsToSkip + Idx);
+    if (LeftToRight) MaybeEmitImplicitObjectSize(Idx, *Arg);
+  }
 
+  if (!LeftToRight) {
     // Un-reverse the arguments we just evaluated so they match up with the LLVM
     // IR function.
     std::reverse(Args.begin() + CallArgsStart, Args.end());
-    return;
-  }
-
-  for (unsigned I = 0, E = ArgTypes.size(); I != E; ++I) {
-    CallExpr::const_arg_iterator Arg = ArgRange.begin() + I;
-    assert(Arg != ArgRange.end());
-    EmitCallArg(Args, *Arg, ArgTypes[I]);
-    EmitNonNullArgCheck(Args.back().RV, ArgTypes[I], (*Arg)->getExprLoc(),
-                        CalleeDecl, ParamsToSkip + I);
-    MaybeEmitImplicitObjectSize(I, *Arg);
   }
 }