[ONNX] Support onnx.LSTM (#2969)

This PR only performs a lit test. In lieu of an e2e test, nod-ai/SHARK-TestSuite#142 makede sure that the lowering works & the numbers check out.

Co-authored-by: Xida Ren <xida.ren.dev@gmail.com>

Author: renxida

include/torch-mlir/Conversion/TorchOnnxToTorch/Patterns.h

@@ -191,6 +191,25 @@ struct OpBinder {
     return failure();
   }
 
+  ParseResult stringArrayAttr(llvm::SmallVector<std::string> &values,
+                              StringRef nameSuffix) {
+    SmallString<64> name("torch.onnx.");
+    name.append(nameSuffix);
+    auto attr = op->getAttr(name);
+    if (!attr)
+      return success();
+    if (auto arrayAttr = dyn_cast<ArrayAttr>(attr)) {
+      for (auto element : arrayAttr) {
+        StringAttr stringAttr = element.dyn_cast<StringAttr>();
+        if (!stringAttr)
+          return failure();
+        values.push_back(stringAttr.getValue().str());
+      }
+      return success();
+    }
+    return failure();
+  }
+
   ParseResult denseElementsAttr(ElementsAttr elementsattr,
                                 StringRef nameSuffix) {
     SmallString<64> name("torch.onnx.");

include/torch-mlir/Conversion/TorchOnnxToTorch/Utils.h

@@ -10,7 +10,10 @@
 #ifndef TORCHMLIR_CONVERSION_TORCHONNXTOTORCH_UTILS_H
 #define TORCHMLIR_CONVERSION_TORCHONNXTOTORCH_UTILS_H
 
+#include "mlir/IR/ImplicitLocOpBuilder.h"
 #include "torch-mlir/Conversion/TorchOnnxToTorch/Patterns.h"
+#include "torch-mlir/Dialect/Torch/IR/TorchOps.h"
+#include "torch-mlir/Dialect/Torch/Utils/Utils.h"
 
 namespace mlir::torch::onnx_c {
 
@@ -20,6 +23,9 @@ Value createConstantIntList(OpBinder binder,
 
 Type getQTorchTypeFromTorchIntType(Type ty);
 
+LogicalResult OnnxLstmExpander(OpBinder binder,
+                               ConversionPatternRewriter &rewriter);
+
 bool areAllElementsDistinct(SmallVector<int64_t> array);
 
 } // namespace mlir::torch::onnx_c

lib/Conversion/TorchOnnxToTorch/CMakeLists.txt

@@ -2,6 +2,7 @@ add_mlir_conversion_library(TorchMLIRTorchOnnxToTorch
     DefaultDomainAtoF.cpp
     DefaultDomainGtoP.cpp
     DefaultDomainQtoZ.cpp
+    OnnxLstmExpander.cpp
     Passes.cpp
     Patterns.cpp
     TorchOnnxToTorch.cpp

lib/Conversion/TorchOnnxToTorch/DefaultDomainGtoP.cpp

@@ -195,6 +195,7 @@ void mlir::torch::onnx_c::populateDefaultDomainGtoP(
                       binder.op, resultType, operand);
                   return success();
                 });
+  patterns.onOp("LSTM", 1, onnx_c::OnnxLstmExpander);
   patterns.onOp(
       "LogSoftmax", 13,
       [](OpBinder binder, ConversionPatternRewriter &rewriter) {

lib/Conversion/TorchOnnxToTorch/DefaultDomainQtoZ.cpp

@@ -538,7 +538,7 @@ void mlir::torch::onnx_c::populateDefaultDomainQtoZ(
         return success();
       });
   patterns.onOp(
-      "Squeeze", 13, [](OpBinder binder, ConversionPatternRewriter &rewriter) {
+      "Squeeze", 1, [](OpBinder binder, ConversionPatternRewriter &rewriter) {
         Torch::ValueTensorType resultType;
         Value data;
         Value axes;