Reapply r134946 with fixes. Tested on Benjamin testcase and other test-suite failures.

llvm-svn: 135091

1 files changed, 10 insertions, 2 deletions

diff --git a/clang/lib/CodeGen/TargetInfo.cpp b/clang/lib/CodeGen/TargetInfo.cpp
index 199ce251a10..a1a1412ea1e 100644
--- a/clang/lib/CodeGen/TargetInfo.cpp
+++ b/clang/lib/CodeGen/TargetInfo.cpp
@@ -1275,9 +1275,17 @@ void X86_64ABIInfo::classify(QualType Ty, uint64_t OffsetBase,
       uint64_t Offset = OffsetBase + Layout.getFieldOffset(idx);
       bool BitField = i->isBitField();
 
-      // AMD64-ABI 3.2.3p2: Rule 1. If ..., or it contains unaligned
-      // fields, it has class MEMORY.
+      // AMD64-ABI 3.2.3p2: Rule 1. If the size of an object is larger than
+      // four eightbytes, or it contains unaligned fields, it has class MEMORY.
       //
+      // The only case a 256-bit wide vector could be used is when the struct
+      // contains a single 256-bit element. Since Lo and Hi logic isn't extended
+      // to work for sizes wider than 128, early check and fallback to memory.
+      //
+      if (Size > 128 && getContext().getTypeSize(i->getType()) != 256) {
+        Lo = Memory;
+        return;
+      }
       // Note, skip this test for bit-fields, see below.
       if (!BitField && Offset % getContext().getTypeAlign(i->getType())) {
         Lo = Memory;