[X86_64] fix arg pass error in struct.

In some struct like s67, only one i64 register is used when the structure
parameter is transferred, which is obviously incorrect.So we need
to treat the split case specially, using memory like gcc.

clang/lib/CodeGen/Targets/X86.cpp

@@ -2100,8 +2100,11 @@ void X86_64ABIInfo::classify(QualType Ty, uint64_t OffsetBase, Class &Lo,
         postMerge(Size, Lo, Hi);
         return;
       }
+
+      bool IsInMemory =
+          Offset % getContext().getTypeAlign(i->getType().getCanonicalType());
       // Note, skip this test for bit-fields, see below.
-      if (!BitField && Offset % getContext().getTypeAlign(i->getType())) {
+      if (!BitField && IsInMemory) {
         Lo = Memory;
         postMerge(Size, Lo, Hi);
         return;

clang/test/CodeGen/X86/x86_64-arguments.c

@@ -533,6 +533,24 @@ typedef float t66 __attribute__((__vector_size__(128), __aligned__(128)));
 void f66(t66 a0) {
 }
 
+typedef long long t67 __attribute__((aligned (4)));
+struct s67 {
+  int a;
+  t67 b;
+};
+// CHECK-LABEL: define{{.*}} void @f67(ptr noundef byval(%struct.s67) align 8 %x)
+void f67(struct s67 x) {
+}
+
+typedef double t68 __attribute__((aligned (4)));
+struct s68 {
+  int a;
+  t68 b;
+};
+// CHECK-LABEL: define{{.*}} void @f68(ptr noundef byval(%struct.s68) align 8 %x)
+void f68(struct s68 x) {
+}
+
 /// The synthesized __va_list_tag does not have file/line fields.
 // CHECK:      = distinct !DICompositeType(tag: DW_TAG_structure_type, name: "__va_list_tag",
 // CHECK-NOT:  file: