[clang] [VE] Enable _BitInt support (PR #186587)

[Kazushi Marukawa via cfe-commits]

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@@ -53,6 +53,8 @@ class LLVM_LIBRARY_VISIBILITY VETargetInfo : public TargetInfo {
 
   bool hasSjLjLowering() const override { return true; }
 
+  bool hasBitIntType() const override { return true; }
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jam7 wrote:

The VE backend supports _BitInt from the beginning since there is nothing special to support it.  I just forget to turn it on in frontend.  Recently, libcxx/include/bitset is modified to not compilable without _BitInt and it make me realize that we forget to enable this flag in clang.

I didn't add test since the mechanism in clang is tested throughly by other architectures already.

https://github.com/llvm/llvm-project/pull/186587