1 | //===- LegalizeForExport.cpp - Prepare for translation to LLVM IR ---------===// |
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/LegalizeForExport.h" |
10 | |
11 | #include "mlir/Dialect/LLVMIR/LLVMDialect.h" |
12 | #include "mlir/Dialect/LLVMIR/Transforms/DIExpressionLegalization.h" |
13 | #include "mlir/IR/Block.h" |
14 | #include "mlir/IR/Builders.h" |
15 | #include "mlir/IR/BuiltinOps.h" |
16 | #include "mlir/Pass/Pass.h" |
17 | |
18 | namespace mlir { |
19 | namespace LLVM { |
20 | #define GEN_PASS_DEF_LLVMLEGALIZEFOREXPORT |
21 | #include "mlir/Dialect/LLVMIR/Transforms/Passes.h.inc" |
22 | } // namespace LLVM |
23 | } // namespace mlir |
24 | |
25 | using namespace mlir; |
26 | |
27 | /// If the given block has the same successor with different arguments, |
28 | /// introduce dummy successor blocks so that all successors of the given block |
29 | /// are different. |
30 | static void ensureDistinctSuccessors(Block &bb) { |
31 | // Early exit if the block cannot have successors. |
32 | if (bb.empty() || !bb.back().mightHaveTrait<OpTrait::IsTerminator>()) |
33 | return; |
34 | |
35 | auto *terminator = bb.getTerminator(); |
36 | |
37 | // Find repeated successors with arguments. |
38 | llvm::SmallDenseMap<Block *, SmallVector<int, 4>> successorPositions; |
39 | for (int i = 0, e = terminator->getNumSuccessors(); i < e; ++i) { |
40 | Block *successor = terminator->getSuccessor(index: i); |
41 | // Blocks with no arguments are safe even if they appear multiple times |
42 | // because they don't need PHI nodes. |
43 | if (successor->getNumArguments() == 0) |
44 | continue; |
45 | successorPositions[successor].push_back(i); |
46 | } |
47 | |
48 | // If a successor appears for the second or more time in the terminator, |
49 | // create a new dummy block that unconditionally branches to the original |
50 | // destination, and retarget the terminator to branch to this new block. |
51 | // There is no need to pass arguments to the dummy block because it will be |
52 | // dominated by the original block and can therefore use any values defined in |
53 | // the original block. |
54 | OpBuilder builder(terminator->getContext()); |
55 | for (const auto &successor : successorPositions) { |
56 | // Start from the second occurrence of a block in the successor list. |
57 | for (int position : llvm::drop_begin(successor.second, 1)) { |
58 | Block *dummyBlock = builder.createBlock(bb.getParent()); |
59 | terminator->setSuccessor(dummyBlock, position); |
60 | for (BlockArgument arg : successor.first->getArguments()) |
61 | dummyBlock->addArgument(arg.getType(), arg.getLoc()); |
62 | builder.create<LLVM::BrOp>(terminator->getLoc(), |
63 | dummyBlock->getArguments(), successor.first); |
64 | } |
65 | } |
66 | } |
67 | |
68 | void mlir::LLVM::ensureDistinctSuccessors(Operation *op) { |
69 | op->walk(callback: [](Operation *nested) { |
70 | for (Region ®ion : llvm::make_early_inc_range(Range: nested->getRegions())) { |
71 | for (Block &block : llvm::make_early_inc_range(Range&: region)) { |
72 | ::ensureDistinctSuccessors(bb&: block); |
73 | } |
74 | } |
75 | }); |
76 | } |
77 | |
78 | namespace { |
79 | struct LegalizeForExportPass |
80 | : public LLVM::impl::LLVMLegalizeForExportBase<LegalizeForExportPass> { |
81 | void runOnOperation() override { |
82 | LLVM::ensureDistinctSuccessors(op: getOperation()); |
83 | LLVM::legalizeDIExpressionsRecursively(op: getOperation()); |
84 | } |
85 | }; |
86 | } // namespace |
87 | |
88 | std::unique_ptr<Pass> LLVM::createLegalizeForExportPass() { |
89 | return std::make_unique<LegalizeForExportPass>(); |
90 | } |
91 | |