[clang] [Clang] Fix oversized bit-field layout on big-endian targets (PR #225494)

[via cfe-commits]

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@@ -15917,12 +15917,15 @@ struct PaddingCalculator {
 
     const uint64_t DeclaredSizeInBits = Field->getBitWidthValue();
 
-    // Handle over-sized bitfields:
-    //   unsigned char a : 12;
-    // In this case, DeclaredSizeInBits is 12, but the actually occupied bit
-    // size is 8, while the remaining 4 bits are padding.
+    // Oversized bit-fields (declared width larger than the field type) keep
+    // only the type's width as the value container. The extra declared bits
+    // are padding and follow that container (Itanium C++ ABI 2.4).
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xiongzile wrote:

Sorry I missed it. Now the entire reference is added

https://github.com/llvm/llvm-project/pull/225494