message: [kernel_gen] Sprinkle in more Canonicalization and CSE passes.
  More is always better, right?
diff: @@ -95,10 +95,11 @@ Status LowerTFtoGPU(mlir::ModuleOp module, bool gpu_binary_only,
  pm.addNestedPass<mlir::FuncOp>(mlir::createTransformUnrankedHloPass());
  pm.addNestedPass<mlir::FuncOp>(mlir::mhlo::createChloLegalizeToHloPass());
  pm.addNestedPass<mlir::FuncOp>(mlir::createCanonicalizerPass());
  + pm.addNestedPass<mlir::FuncOp>(mlir::createCSEPass());
  pm.addPass(mlir::kernel_gen::transforms::CreateShapeToDescriptorsPass());
  // Clean up the IR created above. In particular, operations on descriptors
  // are simplified here.
  - pm.addPass(mlir::createCanonicalizerPass());
  + pm.addPass(mlir::createCSEPass());
  pm.addPass(mlir::kernel_gen::transforms::CreateBufferizePass());
  pm.addNestedPass<mlir::FuncOp>(
  mlir::kernel_gen::transforms::CreateParallelLoopsToSequential());
  