[mlir][drr] NFC: avoid SmallVector when collecting substitution values

[antiagainst]

Summary

Now both Operation::operand_range and Operation::result_range have
.begin() and .end() for ranged-based for loop and we have
ValueRange for wrapping a single Value. We can remove the SmallVector
materialization!

[antiagainst]

Fix accidential line join

[jpienaar]

Yay, thanks

[jpienaar]

This may have caused a breakage: https://buildkite.com/mlir/mlir-core/builds/4411 [first commit post green build that touches MLIR]

mlir/lib/TableGen/Pattern.cpp

case Kind::Result: {
     }
     auto repl = llvm::join(values, separator);
     LLVM_DEBUG(llvm::dbgs() << repl << " (VariadicResult)\n");
     return repl;
   }
   case Kind::Value: {
     assert(index < 0 && "only allowed for symbol bound to result");
     assert(op == nullptr);
-    auto repl = formatv(fmt, formatv("{{{0}}", name));
+    auto repl = formatv(fmt, formatv("ValueRange{{{0}}", name));
     LLVM_DEBUG(llvm::dbgs() << repl << " (Value)\n");
     return std::string(repl);
   }
   }
   llvm_unreachable("unknown kind");
 }
 
 bool tblgen::SymbolInfoMap::bindOpArgument(StringRef symbol, const Operator &op,

mlir/tools/mlir-tblgen/RewriterGen.cpp

void PatternEmitter::emitRewriteLogic() {
   } else {
     // Process replacement result patterns.
     os.indent(4) << "SmallVector<Value, 4> tblgen_repl_values;\n";
     for (int i = replStartIndex; i < numResultPatterns; ++i) {
       DagNode resultTree = pattern.getResultPattern(i);
       auto val = handleResultPattern(resultTree, offsets[i], 0);
       os.indent(4) << "\n";
       // Resolve each symbol for all range use so that we can loop over them.
-      // We need an explicit cast to `SmallVector` to capture the cases where
-      // `{0}` resolves to an `Operation::result_range` as well as cases that
-      // are not iterable (e.g. vector that gets wrapped in additional braces by
-      // RewriterGen).
-      // TODO(b/147096809): Revisit the need for materializing a vector.
       os << symbolInfoMap.getAllRangeUse(
           val,
-          "    for (auto v : SmallVector<Value, 4>{ {0} }) {{ "
-          "tblgen_repl_values.push_back(v); }",
-          "\n");
+          "    for (Value v : {0}) {{ tblgen_repl_values.push_back(v); }\n");
     }
     os.indent(4) << "\n";
     os.indent(4) << "rewriter.replaceOp(op0, tblgen_repl_values);\n";
   }
 
   LLVM_DEBUG(llvm::dbgs() << "--- done emitting rewrite logic ---\n");
 }