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

[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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clingfei wrote:

As @philnik777 described in https://github.com/llvm/llvm-project/issues/160266, bswapg should work on any integral types that have a multiple of 16 bits as well as a single byte. Thus, the condition should be (getBitWidth() % 16 == 0 and getBitWidth() > 0) or getBitWidth() == 8?

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