[clang] [clang] Lower _BitInt(129+) to a different type in LLVM IR (PR #91364)

[Mariya Podchishchaeva via cfe-commits]

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@@ -1989,6 +1989,14 @@ llvm::Value *CodeGenFunction::EmitLoadOfScalar(Address Addr, bool Volatile,
     return EmitAtomicLoad(AtomicLValue, Loc).getScalarVal();
   }
 
+  if (const auto *BIT = Ty->getAs<BitIntType>()) {
+    if (BIT->getNumBits() > 128) {
+      // Long _BitInt has array of bytes as in-memory type.
+      llvm::Type *NewTy = ConvertType(Ty);
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Fznamznon wrote:

This patch was mostly intended to fix codegen issues when it comes to big _BitInt types (>128 for 64bit targets), however I'm adding new idea of load/store type, so that seems close.

https://github.com/llvm/llvm-project/pull/91364