[mlir][linalg] Only generate one var for an attrUse.

[hanchung]

Summary

Some variables are unused after D97383 landed. We should generate one symbol for one attrUse.

mlir/test/mlir-linalg-ods-gen/test-linalg-ods-gen.tc

 ) {
   C(b, m, n) = std_addf<k>(C(b, m, n), std_mulf(A(b, m, k), B(k, n)));
 }
 
 // Test attribute usage in affine expressions
 // IMPL-LABEL: ArrayAttr Test5Op::indexing_maps() {
 // IMPL: auto cst0 = getAffineConstantExpr(strides().getValue<int>({ 0 }), context);
 // IMPL: auto cst1 = getAffineConstantExpr(strides().getValue<int>({ 1 }), context);
-// IMPL: auto cst2 = getAffineConstantExpr(strides().getValue<int>({ 0 }), context);
-// IMPL: auto cst3 = getAffineConstantExpr(strides().getValue<int>({ 1 }), context);
 // IMPL: auto map0 = AffineMap::get(7, 9, {d0, d1 * s7 + d4, d2 * s8 + d5, d6}, context);
-// IMPL: map0 = map0.replaceDimsAndSymbols({}, { s0, s1, s2, s3, s4, s5, s6, cst2, cst3 }, 7, 0);
+// IMPL: map0 = map0.replaceDimsAndSymbols({}, { s0, s1, s2, s3, s4, s5, s6, cst0, cst1 }, 7, 0);
 // IMPL: map0 = simplifyAffineMap(map0);
 // IMPL: auto map1 = AffineMap::get(7, 9, {d3, d4, d5, d6}, context);
-// IMPL: map1 = map1.replaceDimsAndSymbols({}, { s0, s1, s2, s3, s4, s5, s6, cst2, cst3 }, 7, 0);
+// IMPL: map1 = map1.replaceDimsAndSymbols({}, { s0, s1, s2, s3, s4, s5, s6, cst0, cst1 }, 7, 0);
 // IMPL: map1 = simplifyAffineMap(map1);
 // IMPL: auto map2 = AffineMap::get(7, 7, {d0, d1, d2, d3}, context);
-// IMPL: map2 = map2.replaceDimsAndSymbols({}, { s0, s1, s2, s3, s4, s5, s6, cst2, cst3 }, 7, 0);
+// IMPL: map2 = map2.replaceDimsAndSymbols({}, { s0, s1, s2, s3, s4, s5, s6, cst0, cst1 }, 7, 0);
 // IMPL: map2 = simplifyAffineMap(map2);
 // IMPL: return {{.+}}.getAffineMapArrayAttr({ map0, map1, map2 });
 //
 ods_def<Test5Op>:
 def test5(I: f32(N, H, W, C), K: f32(F, KH, KW, C)) -> (O: f32(N, H, W, F))
      attr(strides: 2xi32) {
   O(n, h, w, f) = std_addf<kh, kw>(
       std_mulf(std_addf(I(n, h * strides[0] + kh, w * strides[1] + kw, c),

mlir/tools/mlir-linalg-ods-gen/mlir-linalg-ods-gen.cpp

auto tryToParseAttrUse = [&]() -> llvm::Optional<AffineExpr> {
     if (failed(parseAttrUse(result)))
       return llvm::None;
 
     auto symbolIt = registeredAttrUseToSymbol.find(result.getKey());
     if (symbolIt == registeredAttrUseToSymbol.end()) {
       result.symbol = getAffineSymbolExpr(symbols.size(), parser.context);
       symbols.emplace_back("<attr-use>", result.symbol);
       registeredAttrUseToSymbol[result.getKey()] = result.symbol;
+      attrUses.push_back(result);
     } else {
       result.symbol = symbolIt->second;
     }
 
-    attrUses.push_back(result);
-
     return result.symbol;
   };
 
   AffineParser affineParser(parser, createAffineBareId, tryToParseAttrUse, dims,
                             symbols);
   return affineParser.parseAffineExprs(lDelim, rDelim);
 }