1 //===- DIExpressionRewriter.cpp - Rewriter for DIExpression operators -----===//
2 //
3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4 // See https://llvm.org/LICENSE.txt for license information.
5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6 //
7 //===----------------------------------------------------------------------===//
8
9 #include "mlir/Dialect/LLVMIR/Transforms/DIExpressionRewriter.h"
10 #include "mlir/Transforms/GreedyPatternRewriteDriver.h"
11 #include "llvm/Support/Debug.h"
12
13 using namespace mlir;
14 using namespace LLVM;
15
16 #define DEBUG_TYPE "llvm-di-expression-simplifier"
17
18 //===----------------------------------------------------------------------===//
19 // DIExpressionRewriter
20 //===----------------------------------------------------------------------===//
21
addPattern(std::unique_ptr<ExprRewritePattern> pattern)22 void DIExpressionRewriter::addPattern(
23 std::unique_ptr<ExprRewritePattern> pattern) {
24 patterns.emplace_back(std::move(pattern));
25 }
26
27 DIExpressionAttr
simplify(DIExpressionAttr expr,std::optional<uint64_t> maxNumRewrites) const28 DIExpressionRewriter::simplify(DIExpressionAttr expr,
29 std::optional<uint64_t> maxNumRewrites) const {
30 ArrayRef<OperatorT> operators = expr.getOperations();
31
32 // `inputs` contains the unprocessed postfix of operators.
33 // `result` contains the already finalized prefix of operators.
34 // Invariant: concat(result, inputs) is equivalent to `operators` after some
35 // application of the rewrite patterns.
36 // Using a deque for inputs so that we have efficient front insertion and
37 // removal. Random access is not necessary for patterns.
38 std::deque<OperatorT> inputs(operators.begin(), operators.end());
39 SmallVector<OperatorT> result;
40
41 uint64_t numRewrites = 0;
42 while (!inputs.empty() &&
43 (!maxNumRewrites || numRewrites < *maxNumRewrites)) {
44 bool foundMatch = false;
45 for (const std::unique_ptr<ExprRewritePattern> &pattern : patterns) {
46 ExprRewritePattern::OpIterT matchEnd = pattern->match(inputs);
47 if (matchEnd == inputs.begin())
48 continue;
49
50 foundMatch = true;
51 SmallVector<OperatorT> replacement =
52 pattern->replace(llvm::make_range(inputs.cbegin(), matchEnd));
53 inputs.erase(inputs.begin(), matchEnd);
54 inputs.insert(inputs.begin(), replacement.begin(), replacement.end());
55 ++numRewrites;
56 break;
57 }
58
59 if (!foundMatch) {
60 // If no match, pass along the current operator.
61 result.push_back(inputs.front());
62 inputs.pop_front();
63 }
64 }
65
66 if (maxNumRewrites && numRewrites >= *maxNumRewrites) {
67 LLVM_DEBUG(llvm::dbgs()
68 << "LLVMDIExpressionSimplifier exceeded max num rewrites ("
69 << maxNumRewrites << ")\n");
70 // Skip rewriting the rest.
71 result.append(inputs.begin(), inputs.end());
72 }
73
74 return LLVM::DIExpressionAttr::get(expr.getContext(), result);
75 }
76