[mlir][amdgpu] Sink op creation in scaled conversion intrinsics (NFC) (#168542)

Where possible:

* notifyMatchFailure happen first
* then op.emitOpError
* finally assertions / op creation.

---------

Co-authored-by: Jakub Kuderski <[email protected]>

Author: amd-eochoalo

mlir/lib/Conversion/AMDGPUToROCDL/AMDGPUToROCDL.cpp

@@ -1738,15 +1738,11 @@ LogicalResult ScaledExtPacked816OpLowering::matchAndRewrite(
   auto sourceType = cast<VectorType>(op.getSource().getType());
   auto srcElemType = cast<FloatType>(sourceType.getElementType());
   unsigned bitWidth = srcElemType.getWidth();
-  int32_t scaleSel =
-      getScaleSel(blockSize, bitWidth, firstScaleLane, firstScaleByte);
 
   auto targetType = cast<VectorType>(op.getResult().getType());
   auto destElemType = cast<FloatType>(targetType.getElementType());
-  IntegerType i32 = rewriter.getI32Type();
-  Value castedScale =
-      LLVM::BitcastOp::create(rewriter, loc, i32, adaptor.getScale());
 
+  IntegerType i32 = rewriter.getI32Type();
   Value source = adaptor.getSource();
   Type llvmResultType = typeConverter->convertType(op.getResult().getType());
   Type packedType = nullptr;
@@ -1767,15 +1763,19 @@ LogicalResult ScaledExtPacked816OpLowering::matchAndRewrite(
     return rewriter.notifyMatchFailure(op, "type conversion failed");
   }
 
-  Value castedSource =
-      LLVM::BitcastOp::create(rewriter, loc, packedType, source);
-
   std::optional<StringRef> maybeIntrinsic =
       scaledExtPacked816ToIntrinsic(srcElemType, destElemType);
   if (!maybeIntrinsic.has_value())
     return op.emitOpError(
         "no intrinsic matching packed scaled conversion on the given chipset");
 
+  int32_t scaleSel =
+      getScaleSel(blockSize, bitWidth, firstScaleLane, firstScaleByte);
+  Value castedScale =
+      LLVM::BitcastOp::create(rewriter, loc, i32, adaptor.getScale());
+  Value castedSource =
+      LLVM::BitcastOp::create(rewriter, loc, packedType, source);
+
   OperationState loweredOp(loc, *maybeIntrinsic);
   loweredOp.addTypes({llvmResultType});
   loweredOp.addOperands({castedSource, castedScale});