[mlir][tosa] Table did not apply offset before extract on i8 input

[rsuderman]

Summary

Lowering to table was incorrect as it did not apply a 128 offset before
extracting the value from the table. Fixed and correct tensor length on input
table.

[rsuderman]

Rebased to check integration

mlir/lib/Conversion/TosaToLinalg/TosaToLinalg.cpp

rewriter.replaceOp(op, genericOp.getResult(0));
                                TypeRange({inputElementTy, resultElementTy}));
 
       auto inputValue = block->getArgument(0);
       rewriter.setInsertionPointToStart(block);
       if (inputElementTy.isInteger(8) && tableElementTy.isInteger(8) &&
           resultElementTy.isInteger(8)) {
         Value index = rewriter.create<IndexCastOp>(loc, rewriter.getIndexType(),
                                                    inputValue);
+        Value offset = rewriter.create<ConstantIndexOp>(loc, 128);
+        index = rewriter.create<AddIOp>(loc, rewriter.getIndexType(), index,
+                                        offset);
         Value extract =
             rewriter.create<tensor::ExtractOp>(loc, table, ValueRange{index});
         rewriter.create<linalg::YieldOp>(loc, extract);
         return success();
       }
 
       if (inputElementTy.isInteger(16) && tableElementTy.isInteger(16) &&
           resultElementTy.isInteger(32)) {

mlir/test/Conversion/TosaToLinalg/tosa-to-linalg.mlir

func @gather_int(%arg0: tensor<2x3x2xi32>, %arg1: tensor<2x3xi32>) -> () {
   // CHECK:   linalg.yield %[[EXTRACT]]
   %0 = "tosa.gather"(%arg0, %arg1)  : (tensor<2x3x2xi32>, tensor<2x3xi32>)  -> (tensor<2x3x2xi32>)
   return
 }
 
 // -----
 
 // CHECK-LABEL: @table8
-func @table8(%arg0: tensor<6xi8>, %arg1: tensor<513xi8>) -> () {
+func @table8(%arg0: tensor<6xi8>, %arg1: tensor<512xi8>) -> () {
   // CHECK: %[[INIT:.+]] = linalg.init_tensor [6]
   // CHECK: %[[GENERIC:.+]] = linalg.generic {indexing_maps = [#map, #map], iterator_types = ["parallel"]} ins(%arg0 : tensor<6xi8>) outs(%[[INIT]] : tensor<6xi8>)
   // CHECK: ^bb0(%[[ARG_IN:.+]]: i8, %[[ARG_INIT:.+]]: i8)
   // CHECK:   %[[CAST:.+]] = index_cast %[[ARG_IN]]
-  // CHECK:   %[[EXTRACT:.+]] = tensor.extract %arg1[%[[CAST]]]
+  // CHECK:   %[[OFFSET:.+]] = constant 128
+  // CHECK:   %[[ADD:.+]] = addi %[[CAST]], %[[OFFSET]]
+  // CHECK:   %[[EXTRACT:.+]] = tensor.extract %arg1[%[[ADD]]]
   // CHECK:   linalg.yield %[[EXTRACT]]
-  %0 = "tosa.table"(%arg0, %arg1)  : (tensor<6xi8>, tensor<513xi8>)  -> (tensor<6xi8>)
+  %0 = "tosa.table"(%arg0, %arg1)  : (tensor<6xi8>, tensor<512xi8>)  -> (tensor<6xi8>)
   return
 }
 
+// -----
+
 // CHECK-LABEL: @table16
 func @table16(%arg0: tensor<6xi16>, %arg1: tensor<513xi16>) -> () {
   // CHECK: %[[INIT:.+]] = linalg.init_tensor [6]
   // CHECK: %[[GENERIC:.+]] = linalg.generic {indexing_maps = [#map, #map], iterator_types = ["parallel"]} ins(%arg0 : tensor<6xi16>) outs(%[[INIT]] : tensor<6xi32>)
   // CHECK: ^bb0(%arg2: i16, %arg3: i32)
   // CHECK: %[[EXT_IN:.+]] = sexti %arg2
   // CHECK: %[[C32768:.+]] = constant 32768
   // CHECK: %[[C7:.+]] = constant 7