[clang] [ARM, AArch64] Fix ABI bugs with over-sized bitfields (PR #126774)

[John Brawn via cfe-commits]

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@@ -161,5 +168,62 @@ int test_bitint8(){
 }
 // CHECK:  ret i32 1
 
+// Over-sized bitfield, which results in a 64-bit container type, so 64-bit
+// alignment.
+struct OverSizedBitfield {
+  int x : 64;
+};
+
+unsigned sizeof_OverSizedBitfield = sizeof(OverSizedBitfield);
+unsigned alignof_OverSizedBitfield = alignof(OverSizedBitfield);
+
+// CHECK: define{{.*}} void @g7
+// CHECK: call void @f7(i32 noundef 1, i64 42)
+// CHECK: declare void @f7(i32 noundef, i64)
+void f7(int a, OverSizedBitfield b);
+void g7() {
+  OverSizedBitfield s = {42};
+  f7(1, s);
+}
+
+// There are no 128-bit fundamental data types defined by AAPCS32, so this gets
+// a 64-bit container plus 64 bits of padding, giving it a size of 16 bytes and
+// alignment of 8 bytes.
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john-brawn-arm wrote:

It looks like you've copy-pasted this comment and it's not correct here (we expect a 128-bit container).

https://github.com/llvm/llvm-project/pull/126774