[mlir][tosa] Fix `tosa.reshape` folder for quantized constants

[rsuderman]

Summary

It is possible for tosa.const to have a quantized return type.
In these cases we need to retain the expected result type to avoid
potential type mismatches further in the model.

[mehdi_amini]

mlir/test/Dialect/Tosa/canonicalize.mlir

369

This CHECK is ignored, the {literal} modifier does not seem like the right syntax.

mlir/lib/Dialect/Tosa/IR/TosaCanonicalizations.cpp

if (!matchPattern(input, m_Constant(&inputAttr)))
       return rewriter.notifyMatchFailure(op, "Non-constant input.");
 
     // Check if has >1 consumer and is not splat
     if (!input.hasOneUse() && !inputAttr.isSplat())
       return rewriter.notifyMatchFailure(op,
                                          "Used more than once or not-splat");
 
     // Build new const op with correct output shape
-    ShapedType inputShape = input.getType().cast<ShapedType>();
-    DenseElementsAttr outputAttr =
-        inputAttr.reshape(inputShape.clone(op.getNewShape()));
-    rewriter.replaceOpWithNewOp<tosa::ConstOp>(op, outputAttr.getType(),
-                                               outputAttr);
+    DenseElementsAttr outputAttr = inputAttr.reshape(
+        inputAttr.getType().cast<ShapedType>().clone(op.getNewShape()));
+    rewriter.replaceOpWithNewOp<tosa::ConstOp>(op, resultTy, outputAttr);
     return success();
   }
 };
 
 void ReshapeOp::getCanonicalizationPatterns(RewritePatternSet &results,
                                             MLIRContext *context) {
   results.add<ReshapeReshapeOptimization>(context);
   results.add<ReshapeConstOptimization>(context);

mlir/test/Dialect/Tosa/canonicalize.mlir

 // CHECK-LABEL: @reshape_canonicalize_const_sparse
 func.func @reshape_canonicalize_const_sparse() -> (tensor<3xi32>, tensor<1x3xi32>) {
   //CHECK: "tosa.reshape"
   %0 = "tosa.const"() {value = dense<[1, 2, 3]> : tensor<3xi32>} : ()-> tensor<3xi32>
   %1 = "tosa.reshape"(%0) {new_shape = array<i64: 1, 3>} : (tensor<3xi32>) -> tensor<1x3xi32>
   return %0 , %1 : tensor<3xi32>, tensor<1x3xi32>
 }
 
+// CHECK-LABEL: @reshape_canonicalize_quant
+func.func @reshape_canonicalize_quant() -> (tensor<1x3x!quant.uniform<i8:f32, 1.000000e+00>>) {
+  //CHECK{literal}: "tosa.const"() {value = dense<[[1, 2, 3]]> : tensor<3xi8>} : ()-> tensor<3x!quant.uniform<i8:f32, 1.000000e+00>>
+  %0 = "tosa.const"() {value = dense<[1, 2, 3]> : tensor<3xi8>} : ()-> tensor<3x!quant.uniform<i8:f32, 1.000000e+00>>
+  %1 = "tosa.reshape"(%0) {new_shape = array<i64: 1, 3>} : (tensor<3x!quant.uniform<i8:f32, 1.000000e+00>>) -> tensor<1x3x!quant.uniform<i8:f32, 1.000000e+00>>
+  return %1 :  tensor<1x3x!quant.uniform<i8:f32, 1.000000e+00>>
+}
+
+// CHECK-LABEL: @reshape_canonicalize_strip_quant
+func.func @reshape_canonicalize_strip_quant() -> (tensor<1x3xi8>) {
+  //CHECK{literal}: "tosa.const"() {value = dense<[[1, 2, 3]]> : tensor<3xi8>} : ()-> tensor<3x!quant.uniform<i8:f32, 1.000000e+00>>
+  %0 = "tosa.const"() {value = dense<[1, 2, 3]> : tensor<3xi8>} : ()-> tensor<3x!quant.uniform<i8:f32, 1.000000e+00>>
+  %1 = "tosa.reshape"(%0) {new_shape = array<i64: 1, 3>} : (tensor<3x!quant.uniform<i8:f32, 1.000000e+00>>) -> tensor<1x3xi8>
+  return %1 :  tensor<1x3xi8>
+}
+
 // CHECK-LABEL: @slice_fold
 func.func @slice_fold(%arg0: tensor<3x4xf32>) -> tensor<3x4xf32> {
   // CHECK: return %arg0
   %0 = "tosa.slice"(%arg0) { size = array<i64: 3, 4>, start = array<i64: 0, 0>}: (tensor<3x4xf32>) -> tensor<3x4xf32>
   return %0 : tensor<3x4xf32>
 }
 
 // CHECK-LABEL: @slice_nofold