[TORCH] Modified fx_importer to support hop_while_loop

lib/Conversion/TorchToSCF/TorchToSCF.cpp

@@ -150,6 +150,10 @@ class ConvertTorchPrimLoopWhileLikeOp : public OpConversionPattern<PrimLoopOp> {
           targetType = Torch::IntType::get(op->getContext());
         torchArg = typeConverter->materializeSourceConversion(
             rewriter, scfWhileOp.getLoc(), targetType, {to});
+      } else if (auto tty = dyn_cast<RankedTensorType>(targetType)) {
+        targetType = op.getIterArgsInit()[barg.index()].getType();
+        torchArg = typeConverter->materializeSourceConversion(
+            rewriter, scfWhileOp.getLoc(), targetType, {to});
       }
       if (!torchArg)
         return rewriter.notifyMatchFailure(op,
@@ -173,14 +177,6 @@ class ConvertTorchPrimLoopWhileLikeOp : public OpConversionPattern<PrimLoopOp> {
                                              "unsupported type of the operand");
         loopConditionIterArgs.push_back(shouldContinue);
         for (auto torchArg : primLoopConditionOp.getIterArgs()) {
-          Type torchType = torchArg.getType();
-
-          // If the argument is a torch tensor, directly add it in the list of
-          // iter args.
-          if (isa<Torch::BaseTensorType>(torchType)) {
-            loopConditionIterArgs.push_back(torchArg);
-            continue;
-          }
           Value arg = typeConverter->materializeTargetConversion(
               rewriter, scfWhileOp->getLoc(),
               typeConverter->convertType(torchArg.getType()), {torchArg});

lib/Dialect/Torch/Transforms/Passes.cpp

@@ -70,6 +70,9 @@ void mlir::torch::Torch::createTorchScriptModuleToTorchBackendPipeline(
 
 void mlir::torch::Torch::createTorchDynamoExportToTorchBackendPipeline(
     OpPassManager &pm, const TorchLoweringPipelineOptions &options) {
+  // Inline func.call operations created by higher-order ops like while_loop
+  // to conform to the linalg-on-tensors backend contract.
+  pm.addPass(createInlinerPass());
   pm.addNestedPass<func::FuncOp>(
       createReduceOpVariantsPass(options.extraLibrary));
   pm.addNestedPass<func::FuncOp>(createCanonicalizerPass());

projects/pt1/e2e_testing/xfail_sets.py

@@ -246,6 +246,8 @@
     "IsFloatingPointInt_False",
     "TorchPrimLoopForLikeModule_basic",
     "TorchPrimLoopWhileLikeModule_basic",
+    # torch._dynamo.exc.BackendCompilerFailed: Unsupported op: get_attr
+    "TorchPrimLoopWhileLikeHOPModule_basic",
     "ScalarConstantTupleModule_basic",
     # END tests failing due to: empty graph in dynamo
     # ERROR due to: backend never runs because of empty frame
@@ -481,6 +483,7 @@
     "TensorToBoolZeroRank_basic",
     "TensorToBool_basic",
     "ThresholdBackward2dMixedModule_basic",
+    "TorchPrimLoopWhileLikeHOPModule_basic",  # Compilation error: failed to legalize operation 'func.call'
     "UnsafeViewCollapseDynamicWithAtenSizeIntModule_basic",
     "UpSampleNearest2dDynamicFactor_basic",
     "ViewCollapseDynamicWithAtenSizeIntModule_basic",
@@ -993,6 +996,8 @@
     "ElementwiseClampMinModule_bfloat16",
     "ElementwiseClampModule_bfloat16",
     "ElementwiseReluModule_bfloat16",
+    # Runtime error: failed to legalize operation 'torch.constant.int'
+    "TorchPrimLoopWhileLikeHOPModule_basic",
 }
 
 FX_IMPORTER_STABLEHLO_CRASHING_SET = {
@@ -2575,6 +2580,7 @@
 
 LTC_XFAIL_SET = {
     "TorchPrimLoopForLikeTensorArgModule_basic" "CollapseAllDimensionsModule_basic",
+    "TorchPrimLoopWhileLikeHOPModule_basic",
     "CollapseRank1DynamicModule_basic",
     "CollapseStaticModule_basic",
     "CollapsePartialDynamicModule_basic",
@@ -3261,6 +3267,8 @@
     "ToCopyWithDTypeModule_basic",
     "TorchPrimLoopForLikeModule_basic",
     "TorchPrimLoopWhileLikeModule_basic",
+    # RuntimeError: Detected that you are using FX to torch.jit.trace a dynamo-optimized function
+    "TorchPrimLoopWhileLikeHOPModule_basic",
     "TraceModule_basic",
     "TraceModule_empty",
     "TraceModule_nonsquare",
@@ -3957,6 +3965,8 @@
     "ThresholdBackward2dMixedModule_basic",
     "TorchPrimLoopForLikeModule_basic",
     "TorchPrimLoopWhileLikeModule_basic",
+    # Runtime error: failed to legalize operation 'torch.aten.Bool.Tensor'
+    "TorchPrimLoopWhileLikeHOPModule_basic",
     "TraceModule_empty",
     "TraceUnsignedIntModule_empty",
     "TransposedConv1dNegativePadding_basic",
@@ -5036,6 +5046,8 @@
     "ToDtypeFloatFromIntModule_basic",
     "TorchPrimLoopForLikeModule_basic",
     "TorchPrimLoopWhileLikeModule_basic",
+    # RuntimeError: Detected that you are using FX to torch.jit.trace a dynamo-optimized function
+    "TorchPrimLoopWhileLikeHOPModule_basic",
     "TraceModule_basic",
     "TraceModule_empty",
     "TraceModule_nonsquare",

projects/pt1/python/torch_mlir_e2e_test/test_suite/control_flow.py

@@ -10,6 +10,7 @@
 from torch_mlir_e2e_test.framework import TestUtils
 from torch_mlir_e2e_test.registry import register_test_case
 from torch_mlir_e2e_test.annotations import annotate_args, export
+from torch._higher_order_ops.while_loop import while_loop
 
 # ==============================================================================
 
@@ -78,3 +79,36 @@ def TorchPrimLoopForLikeTensorArgModule_basic(module, tu: TestUtils):
     x_test = torch.zeros([7, 9]).float()
 
     module.forward(x_test)
+
+
+# ==============================================================================
+
+
+class TorchPrimLoopWhileLikeHOPModule(torch.nn.Module):
+    def __init__(self):
+        super().__init__()
+
+    def body_fn(self, i, x):
+        return i + 1, x + 1
+
+    def cond_fn(self, i, x):
+        return i < 3
+
+    @export
+    @annotate_args(
+        [
+            None,
+            ([7, 9], torch.float32, True),
+        ]
+    )
+    def forward(self, x: torch.Tensor) -> torch.Tensor:
+        i0 = torch.tensor(0)
+        out_i, out_x = while_loop(self.cond_fn, self.body_fn, (i0, x))
+        return out_i, out_x
+
+
+@register_test_case(module_factory=lambda: TorchPrimLoopWhileLikeHOPModule())
+def TorchPrimLoopWhileLikeHOPModule_basic(module, tu: TestUtils):
+    x_test = torch.zeros([7, 9]).float()
+
+    module.forward(x_test)