ARM byval: when type alignment is bigger than ABI alignment, instead of

disabling byval, we set realign to true.

It will perform an aligned alloca, and call memcpy to copy the byval
argument to the local variable.
Change the size threshold back to 64 bytes.

rdar://12596507

llvm-svn: 167440

1 files changed, 4 insertions, 5 deletions

diff --git a/clang/lib/CodeGen/TargetInfo.cpp b/clang/lib/CodeGen/TargetInfo.cpp
index 90603371805..22292603f69 100644
--- a/clang/lib/CodeGen/TargetInfo.cpp
+++ b/clang/lib/CodeGen/TargetInfo.cpp
@@ -3221,16 +3221,15 @@ ABIArgInfo ARMABIInfo::classifyArgumentType(QualType Ty, int *VFPRegs,
 
   // Support byval for ARM.
   // The ABI alignment for APCS is 4-byte and for AAPCS at least 4-byte and at most 8-byte.
-  // Byval can't handle the case where type alignment is bigger than ABI alignment.
-  // We also increase the threshold for byval due to its overhead.
+  // We realign the indirect argument if type alignment is bigger than ABI alignment.
   uint64_t ABIAlign = 4;
   uint64_t TyAlign = getContext().getTypeAlign(Ty) / 8;
   if (getABIKind() == ARMABIInfo::AAPCS_VFP ||
       getABIKind() == ARMABIInfo::AAPCS)
     ABIAlign = std::min(std::max(TyAlign, (uint64_t)4), (uint64_t)8);
-  if (getContext().getTypeSizeInChars(Ty) > CharUnits::fromQuantity(64*8) &&
-      TyAlign <= ABIAlign) {
-    return ABIArgInfo::getIndirect(0, /*ByVal=*/true);
+  if (getContext().getTypeSizeInChars(Ty) > CharUnits::fromQuantity(64)) {
+    return ABIArgInfo::getIndirect(0, /*ByVal=*/true,
+           /*Realign=*/TyAlign <= ABIAlign ? false : true);
   }
 
   // Otherwise, pass by coercing to a structure of the appropriate size.