[clang] [Clang][AArch64] Fixed incorrect _BitInt alignment (PR #90602)

[Eli Friedman via cfe-commits]

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@@ -518,6 +518,16 @@ class TargetInfo : public TransferrableTargetInfo,
   /// getInt128Align() - Returns the alignment of Int128.
   unsigned getInt128Align() const { return Int128Align; }
 
+  /// getBitIntAlign/Width - Return aligned size of '_BitInt' and
+  /// 'unsigned _BitInt' for this target, in bits.
+  unsigned getBitIntWidth(unsigned NumBits) const {
+    return llvm::alignTo(NumBits, getBitIntAlign(NumBits));
+  }
+  virtual unsigned getBitIntAlign(unsigned NumBits) const {
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efriedma-quic wrote:

Instead of making this virtual, maybe it makes sense to add a field `std::optional<unsigned> BitIntMaxAlign` to TargetInfo?  I expect the logic here besides the max width to be consistent across all targets.

https://github.com/llvm/llvm-project/pull/90602