2 files changed, 17 insertions, 6 deletions

diff --git a/clang/lib/CodeGen/CGCall.cpp b/clang/lib/CodeGen/CGCall.cpp
index 0ba6789367f..dfe9049add1 100644
--- a/clang/lib/CodeGen/CGCall.cpp
+++ b/clang/lib/CodeGen/CGCall.cpp
@@ -36,6 +36,8 @@ static unsigned ClangCallConvToLLVMCallConv(CallingConv CC) {
   case CC_X86StdCall: return llvm::CallingConv::X86_StdCall;
   case CC_X86FastCall: return llvm::CallingConv::X86_FastCall;
   case CC_X86ThisCall: return llvm::CallingConv::X86_ThisCall;
+  case CC_AAPCS: return llvm::CallingConv::ARM_AAPCS;
+  case CC_AAPCS_VFP: return llvm::CallingConv::ARM_AAPCS_VFP;
   // TODO: add support for CC_X86Pascal to llvm
   }
 }
@@ -104,6 +106,9 @@ static CallingConv getCallingConventionForDecl(const Decl *D) {
   if (D->hasAttr<PascalAttr>())
     return CC_X86Pascal;
 
+  if (PcsAttr *PCS = D->getAttr<PcsAttr>())
+    return (PCS->getPCS() == PcsAttr::AAPCS ? CC_AAPCS : CC_AAPCS_VFP);
+
   return CC_C;
 }
 
diff --git a/clang/lib/CodeGen/TargetInfo.cpp b/clang/lib/CodeGen/TargetInfo.cpp
index 5db9a8e640b..cab60ee5b58 100644
--- a/clang/lib/CodeGen/TargetInfo.cpp
+++ b/clang/lib/CodeGen/TargetInfo.cpp
@@ -2271,27 +2271,33 @@ void ARMABIInfo::computeInfo(CGFunctionInfo &FI) const {
        it != ie; ++it)
     it->info = classifyArgumentType(it->type);
 
-  const llvm::Triple &Triple(getContext().Target.getTriple());
+  // Always honor user-specified calling convention.
+  if (FI.getCallingConvention() != llvm::CallingConv::C)
+    return;
+
+  // Calling convention as default by an ABI.
   llvm::CallingConv::ID DefaultCC;
-  if (Triple.getEnvironmentName() == "gnueabi" ||
-      Triple.getEnvironmentName() == "eabi")
+  llvm::StringRef Env = getContext().Target.getTriple().getEnvironmentName();
+  if (Env == "gnueabi" || Env == "eabi")
     DefaultCC = llvm::CallingConv::ARM_AAPCS;
   else
     DefaultCC = llvm::CallingConv::ARM_APCS;
 
+  // If user did not ask for specific calling convention explicitly (e.g. via
+  // pcs attribute), set effective calling convention if it's different than ABI
+  // default.
   switch (getABIKind()) {
   case APCS:
     if (DefaultCC != llvm::CallingConv::ARM_APCS)
       FI.setEffectiveCallingConvention(llvm::CallingConv::ARM_APCS);
     break;
-
   case AAPCS:
     if (DefaultCC != llvm::CallingConv::ARM_AAPCS)
       FI.setEffectiveCallingConvention(llvm::CallingConv::ARM_AAPCS);
     break;
-
   case AAPCS_VFP:
-    FI.setEffectiveCallingConvention(llvm::CallingConv::ARM_AAPCS_VFP);
+    if (DefaultCC != llvm::CallingConv::ARM_AAPCS_VFP)
+      FI.setEffectiveCallingConvention(llvm::CallingConv::ARM_AAPCS_VFP);
     break;
   }
 }