[CodeGen] Ignore unnamed bitfields before handling vector fields

We processed unnamed bitfields after our logic for non-vector field
elements in records larger than 128 bits.  The vector logic would
determine that the bit-field disqualifies the record from occupying a
register despite the unnamed bit-field not participating in the record
size nor its alignment.

N.B. This behavior matches GCC and ICC.

llvm-svn: 278656

2 files changed, 14 insertions, 4 deletions

diff --git a/clang/lib/CodeGen/TargetInfo.cpp b/clang/lib/CodeGen/TargetInfo.cpp
index 7b22ddc431c..bdf3e4b1eae 100644
--- a/clang/lib/CodeGen/TargetInfo.cpp
+++ b/clang/lib/CodeGen/TargetInfo.cpp
@@ -2589,6 +2589,10 @@ void X86_64ABIInfo::classify(QualType Ty, uint64_t OffsetBase,
       uint64_t Offset = OffsetBase + Layout.getFieldOffset(idx);
       bool BitField = i->isBitField();
 
+      // Ignore padding bit-fields.
+      if (BitField && i->isUnnamedBitfield())
+        continue;
+
       // 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.
       //
@@ -2621,10 +2625,7 @@ void X86_64ABIInfo::classify(QualType Ty, uint64_t OffsetBase,
       // structure to be passed in memory even if unaligned, and
       // therefore they can straddle an eightbyte.
       if (BitField) {
-        // Ignore padding bit-fields.
-        if (i->isUnnamedBitfield())
-          continue;
-
+        assert(!i->isUnnamedBitfield());
         uint64_t Offset = OffsetBase + Layout.getFieldOffset(idx);
         uint64_t Size = i->getBitWidthValue(getContext());
 
diff --git a/clang/test/CodeGen/x86_64-arguments.c b/clang/test/CodeGen/x86_64-arguments.c
index de7cfd9d579..9f375d780c9 100644
--- a/clang/test/CodeGen/x86_64-arguments.c
+++ b/clang/test/CodeGen/x86_64-arguments.c
@@ -536,3 +536,12 @@ void f64() {
   f64_helper(x64, x64, 1.0, 1.0, 1.0, 1.0, 1.0, 1.0i);
   f64_helper(x64, x64, 1.0, 1.0, 1.0, 1.0, 1.0, 1.0, 1.0i);
 }
+
+struct t65 {
+  __m256 m;
+  int : 0;
+};
+// SSE-LABEL: @f65(%struct.t65* byval align 32 %{{[^,)]+}})
+// AVX: @f65(<8 x float> %{{[^,)]+}})
+void f65(struct t65 a0) {
+}