[clang] [clang][bytecode] Handle bitcasts involving bitfields (PR #116843)

[Aaron Ballman via cfe-commits]

================
@@ -0,0 +1,88 @@
+//===-------------------- Bitcastbuffer.cpp ---------------------*- C++ -*-===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+#include "BitcastBuffer.h"
+
+using namespace clang;
+using namespace clang::interp;
+
+void BitcastBuffer::pushData(const std::byte *In, size_t BitOffset,
+                             size_t BitWidth, Endian TargetEndianness) {
+  for (unsigned It = 0; It != BitWidth; ++It) {
+    bool BitValue = bitof(In, It);
+    if (!BitValue)
+      continue;
+
+    unsigned DstBit;
+    if (TargetEndianness == Endian::Little)
+      DstBit = BitOffset + It;
+    else
+      DstBit = size() - BitOffset - BitWidth + It;
+
+    unsigned DstByte = (DstBit / 8);
----------------
AaronBallman wrote:

Someday we're going to have to search the entire code base for the number 8, aren't we? :-D

https://github.com/llvm/llvm-project/pull/116843