[clang] [Clang] Add __builtin_bswapg (PR #162433)

[Nikolas Klauser via cfe-commits]

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@@ -3622,6 +3622,15 @@ RValue CodeGenFunction::EmitBuiltinExpr(const GlobalDecl GD, unsigned BuiltinID,
           Builder.CreateArithmeticFence(ArgValue, ConvertType(ArgType)));
     return RValue::get(ArgValue);
   }
+  case Builtin::BI__builtin_bswapg: {
+    Value *ArgValue = EmitScalarExpr(E->getArg(0));
+    llvm::IntegerType *IntTy = cast<llvm::IntegerType>(ArgValue->getType());
+    assert(IntTy && "LLVM's __builtin_bswapg only supports integer variants");
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philnik777 wrote:

It sounds reasonable, but the llvm intrinsic has the constraint on 16 bits. I don't think we should block introducing the builtin on extending the llvm intrinsic.

https://github.com/llvm/llvm-project/pull/162433