[mlir][tosa] Handle unsigned constants in TosaConvertIntegerTypeToSignless (llvm#156483)

This commit fixes handling of unsigned constant data in the
`TosaConvertIntegerTypeToSignless` pass. Previously, the type of the
"values" attribute would remain unsigned, which caused an error in the
const ops verifier:
```
error: 'tosa.const' op expected same attr/result element types
  %input_zp = "tosa.const"() {values = dense<17> : tensor<1xui8>} : () -> tensor<1xui8>
              ^
note: see current operation: %0 = "tosa.const"() <{values = dense<17> : tensor<1xui8>}> : () -> tensor<1xi8>
```
Now the constant data in "values" is transformed to signless as well.

Author: lhutton1

mlir/lib/Dialect/Tosa/Transforms/TosaConvertIntegerTypeToSignless.cpp

@@ -103,6 +103,32 @@ class ConvertGenericOpWithIntegerTensorType : public ConversionPattern {
   }
 };
 
+class ConvertTosaConstWithIntegerTensorType
+    : public OpConversionPattern<tosa::ConstOp> {
+  using OpConversionPattern::OpConversionPattern;
+
+  LogicalResult
+  matchAndRewrite(tosa::ConstOp op, OpAdaptor adaptor,
+                  ConversionPatternRewriter &rewriter) const final {
+    const ElementsAttr oldAttr = op.getValues();
+    const auto oldTy = llvm::cast<ShapedType>(oldAttr.getType());
+    const auto newTy =
+        llvm::cast<ShapedType>(typeConverter->convertType(oldTy));
+    if (oldTy == newTy)
+      return success();
+
+    ElementsAttr newAttr = oldAttr;
+    if (auto denseAttr = llvm::dyn_cast<DenseElementsAttr>(oldAttr)) {
+      newAttr = DenseElementsAttr::get(newTy, denseAttr.getRawData());
+    } else {
+      return rewriter.notifyMatchFailure(op, "unknown elements attribute type");
+    }
+
+    rewriter.replaceOpWithNewOp<tosa::ConstOp>(op, newTy, newAttr);
+    return success();
+  }
+};
+
 class TosaConvertIntegerTypeToSignless
     : public impl::TosaConvertIntegerTypeToSignlessBase<
           TosaConvertIntegerTypeToSignless> {
@@ -116,6 +142,10 @@ class TosaConvertIntegerTypeToSignless
       return typeConverter.isSignatureLegal(op.getFunctionType()) &&
              typeConverter.isLegal(&op.getBody());
     });
+    target.addDynamicallyLegalOp<tosa::ConstOp>([&](tosa::ConstOp op) {
+      return typeConverter.isLegal(op.getType()) &&
+             typeConverter.isLegal(op.getValues().getType());
+    });
     target.markUnknownOpDynamicallyLegal([&](Operation *op) {
       return typeConverter.isLegal(op->getOperandTypes()) &&
              typeConverter.isLegal(op->getResultTypes());
@@ -125,6 +155,7 @@ class TosaConvertIntegerTypeToSignless
     populateFunctionOpInterfaceTypeConversionPattern<func::FuncOp>(
         patterns, typeConverter);
     patterns.add<ConvertGenericOpWithIntegerTensorType>(typeConverter, context);
+    patterns.add<ConvertTosaConstWithIntegerTensorType>(typeConverter, context);
 
     if (failed(
             applyFullConversion(getOperation(), target, std::move(patterns))))

mlir/test/Dialect/Tosa/tosa-convert-integer-type-to-signless.mlir

@@ -32,6 +32,21 @@ func.func @test_rescale_input_unsigned(%arg0: tensor<1x1xui16>) -> (tensor<1x1xi
 
 // -----
 
+// CHECK-LABEL: test_rescale_unsigned_zp
+// CHECK: %[[ZP_IN:.*]] = "tosa.const"() <{values = dense<-2> : tensor<1xi8>}> : () -> tensor<1xi8>
+// CHECK: %[[ZP_OUT:.*]] = "tosa.const"() <{values = dense<2> : tensor<1xi8>}> : () -> tensor<1xi8>
+// CHECK: tosa.rescale %arg0, %0, %1, %[[ZP_IN]], %[[ZP_OUT]] {input_unsigned = true, output_unsigned = false, per_channel = false, rounding_mode = SINGLE_ROUND, scale32 = true} : (tensor<1x1xi8>, tensor<1xi32>, tensor<1xi8>, tensor<1xi8>, tensor<1xi8>)
+func.func @test_rescale_unsigned_zp(%arg0: tensor<1x1xui8>) -> tensor<1x1xi8> {
+  %0 = "tosa.const"() <{values = dense<2> : tensor<1xi32>}> : () -> tensor<1xi32>
+  %1 = "tosa.const"() <{values = dense<1> : tensor<1xi8>}> : () -> tensor<1xi8>
+  %2 = "tosa.const"() <{values = dense<254> : tensor<1xui8>}> : () -> tensor<1xui8>
+  %3 = "tosa.const"() <{values = dense<2> : tensor<1xi8>}> : () -> tensor<1xi8>
+  %r = tosa.rescale %arg0, %0, %1, %2, %3 {input_unsigned = true, output_unsigned = false, per_channel = false, rounding_mode = SINGLE_ROUND, scale32 = true} : (tensor<1x1xui8>, tensor<1xi32>, tensor<1xi8>, tensor<1xui8>, tensor<1xi8>) -> tensor<1x1xi8>
+  return %r : tensor<1x1xi8>
+}
+
+// -----
+
 // CHECK-LABEL: test_unsigned_function_signature
 // CHECK: %arg0: tensor<1xi8>, %arg1: tensor<1xi8>
 func.func @test_unsigned_function_signature(%arg0: tensor<1xui8>, %arg1: tensor<1xui8>) -> (tensor<1xui8>, tensor<1xui8>) {
@@ -41,6 +56,15 @@ func.func @test_unsigned_function_signature(%arg0: tensor<1xui8>, %arg1: tensor<
 
 // -----
 
+// CHECK-LABEL: test_unsigned_const_data
+// CHECK: "tosa.const"() <{values = dense<[-1, -2, 0, 1, -128]> : tensor<5xi8>}> : () -> tensor<5xi8>
+func.func @test_unsigned_const_data() -> tensor<5xui8> {
+  %0 = "tosa.const"() <{values = dense<[255, 254, 0, 1, 128]> : tensor<5xui8>}> : () -> tensor<5xui8>
+  return %0 : tensor<5xui8>
+}
+
+// -----
+
 // CHECK-LABEL: test_no_change
 // CHECK: %arg0: tensor<13x21x3xi8>
 func.func @test_no_change(%arg0: tensor<13x21x3xi8>) -> tensor<13x21x3xi8> {