[Stablehlo] fix aten.arange's lowering to stablehlo (#3138)

* promote to f64 to do division, avoid division on i64 (floor div)
* refactor torch-to-stablehlo-pipeline

lib/Conversion/TorchToStablehlo/Basic.cpp

@@ -1492,15 +1492,17 @@ LogicalResult ConvertAtenOp<AtenArangeStartStepOp>::matchAndRewrite(
 
   // Get length of the 1-d output tensor
   Value subOut = rewriter.create<stablehlo::SubtractOp>(loc, end, start);
-  Value divOut = rewriter.create<stablehlo::DivOp>(loc, subOut, step);
-
-  Value resultLength = rewriter.create<stablehlo::ReshapeOp>(
-      loc, RankedTensorType::get({1}, dtype), divOut);
-  if (dtype.isa<mlir::FloatType>()) {
-    resultLength = rewriter.create<stablehlo::CeilOp>(loc, resultLength);
-    resultLength = rewriter.create<stablehlo::ConvertOp>(
-        loc, RankedTensorType::get({1}, rewriter.getI64Type()), resultLength);
-  }
+  // promote div to f64
+  Type divType = RankedTensorType::get({}, rewriter.getF64Type());
+  Value divOut = rewriter.create<stablehlo::DivOp>(
+      loc, rewriter.create<stablehlo::ConvertOp>(loc, divType, subOut),
+      rewriter.create<stablehlo::ConvertOp>(loc, divType, step));
+  // ceil to i64
+  Value resultLength = rewriter.create<stablehlo::ConvertOp>(
+      loc, RankedTensorType::get({}, rewriter.getI64Type()),
+      rewriter.create<stablehlo::CeilOp>(loc, divOut));
+  resultLength = rewriter.create<stablehlo::ReshapeOp>(
+      loc, RankedTensorType::get({1}, rewriter.getI64Type()), resultLength);
 
   Value window =
       rewriter.create<stablehlo::DynamicIotaOp>(loc, outType, resultLength, 0);

lib/Dialect/TorchConversion/Transforms/Passes.cpp

@@ -142,11 +142,6 @@ void TorchConversion::createTorchBackendToStablehloBackendPipeline(
   // Lowering Chlo ops to Stablehlo
   pm.addNestedPass<func::FuncOp>(
       stablehlo::createChloLegalizeToStablehloPass());
-  // Canonicalize Stablehlo dynamic ops to static ops
-  pm.addNestedPass<func::FuncOp>(
-      stablehlo::createStablehloCanonicalizeDynamismPass());
-  pm.addNestedPass<func::FuncOp>(createCanonicalizerPass());
-
   // Lowering remained ops to Arith
   pm.addNestedPass<func::FuncOp>(createConvertTorchToArithPass());
 
@@ -162,7 +157,17 @@ void TorchConversion::createTorchBackendToStablehloBackendPipeline(
   pm.addNestedPass<func::FuncOp>(
       TorchConversion::createFinalizingBackendTypeConversionPass());
 
-  // Verify that we have lowered to Stablehlo and Chlo ops.
+  // Verify that we have lowered to Stablehlo ops.
   pm.addPass(TorchConversion::createVerifyStablehloBackendContractPass());
+
+  // Canonicalize Stablehlo dynamic ops to static ops
+  pm.addNestedPass<func::FuncOp>(
+      stablehlo::createStablehloCanonicalizeDynamismPass());
+  pm.addNestedPass<func::FuncOp>(createCanonicalizerPass());
+  pm.addPass(stablehlo::createStablehloRefineShapesPass());
+  pm.addNestedPass<func::FuncOp>(createCanonicalizerPass());
+  pm.addNestedPass<func::FuncOp>(
+      stablehlo::createStablehloCanonicalizeDynamismPass());
+  pm.addNestedPass<func::FuncOp>(createCanonicalizerPass());
 }
 #endif

projects/pt1/python/torch_mlir_e2e_test/stablehlo_backends/linalg_on_tensors.py

@@ -18,7 +18,6 @@ __all__ = [
 # The pipeline of func.func passes that lower the STABLEHLO backend contract to the
 # Linalg-on-Tensors backend contract accepted by RefBackend.
 STABLEHLO_TO_LINALG_FUNC_PIPELINE = ",".join([
-    "canonicalize",
     "func.func(stablehlo-aggressive-simplification)",
     "stablehlo-legalize-to-linalg",
     "canonicalize"