APInt fix (#4070)

`ConvertAtenOp<ValueTensorLiteralOp>` triggers newly added assertions
around `APInt` construction (see
[llvm/llvm-project#106524](llvm/llvm-project#106524))
when `isSigned == false` and we pass the result of `v.getSExtValue()`
that doesn't fit within the specified bit-width. For example, if we
build a 32-bit `APInt` using a value of `-1` (returned by
`v.getSExtValue()`), that negative number is stored in a `uint64-t`
representation as `0xFF FF FF FF FF FF FF FF`. Since we are treating it
as unsigned, it obviously doesn't fit into 32-bits, causing the new
assertion to fail.

lib/Conversion/TorchToTosa/TorchToTosa.cpp

@@ -2913,7 +2913,7 @@ LogicalResult ConvertAtenOp<ValueTensorLiteralOp>::matchAndRewrite(
       unsigned bitWidth = builtinTensorElemTy.getIntOrFloatBitWidth();
       DenseElementsAttr valueAttr =
           elements.mapValues(builtinTensorElemTy, [&](const APInt &v) {
-            return APInt(bitWidth, v.getSExtValue());
+            return APInt(bitWidth, v.getSExtValue(), /*isSigned=*/true);
           });
       rewriter.replaceOpWithNewOp<tosa::ConstOp>(op, outputTy, valueAttr);
       return success();

test/Conversion/TorchToTosa/basic.mlir

@@ -1025,6 +1025,18 @@ func.func @torch.vtensor.literal_si64$basic() -> !torch.vtensor<[1,512],si64> {
 }
 
 // -----
+
+// CHECK-LABEL: @torch.vtensor.literal_si32$basic(
+// CHECK: %[[VAL_0:.*]] = "tosa.const"() <{value = dense<-1> : tensor<1x512xi32>}> : () -> tensor<1x512xi32>
+// CHECK: %[[VAL_1:.*]] = torch_c.from_builtin_tensor %[[VAL_0]] : tensor<1x512xi32> -> !torch.vtensor<[1,512],si32>
+// CHECK: return %[[VAL_1]] : !torch.vtensor<[1,512],si32>
+func.func @torch.vtensor.literal_si32$basic() -> !torch.vtensor<[1,512],si32> {
+  %0 = torch.vtensor.literal(dense<-1> : tensor<1x512xsi32>) : !torch.vtensor<[1,512],si32>
+  return %0 : !torch.vtensor<[1,512],si32>
+}
+
+// -----
+
 // CHECK-LABEL:   func.func @torch.aten.arange.start_step() -> !torch.vtensor<[5],si64> {
 // CHECK:           %[[VAL_0:.*]] = torch.constant.none
 // CHECK:           %[[VAL_1:.*]] = torch.constant.int 0