| //===- LegalizeForExport.cpp - Prepare for translation to LLVM IR ---------===// |
| // |
| // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions. |
| // See https://llvm.org/LICENSE.txt for license information. |
| // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception |
| // |
| //===----------------------------------------------------------------------===// |
| |
| #include "mlir/Dialect/LLVMIR/Transforms/LegalizeForExport.h" |
| #include "PassDetail.h" |
| #include "mlir/Dialect/LLVMIR/LLVMDialect.h" |
| #include "mlir/IR/Block.h" |
| #include "mlir/IR/Builders.h" |
| #include "mlir/IR/BuiltinOps.h" |
| |
| using namespace mlir; |
| |
| static void ensureDistinctSuccessors(Block &bb) { |
| auto *terminator = bb.getTerminator(); |
| |
| // Find repeated successors with arguments. |
| llvm::SmallDenseMap<Block *, SmallVector<int, 4>> successorPositions; |
| for (int i = 0, e = terminator->getNumSuccessors(); i < e; ++i) { |
| Block *successor = terminator->getSuccessor(i); |
| // Blocks with no arguments are safe even if they appear multiple times |
| // because they don't need PHI nodes. |
| if (successor->getNumArguments() == 0) |
| continue; |
| successorPositions[successor].push_back(i); |
| } |
| |
| // If a successor appears for the second or more time in the terminator, |
| // create a new dummy block that unconditionally branches to the original |
| // destination, and retarget the terminator to branch to this new block. |
| // There is no need to pass arguments to the dummy block because it will be |
| // dominated by the original block and can therefore use any values defined in |
| // the original block. |
| OpBuilder builder(terminator->getContext()); |
| for (const auto &successor : successorPositions) { |
| // Start from the second occurrence of a block in the successor list. |
| for (int position : llvm::drop_begin(successor.second, 1)) { |
| Block *dummyBlock = builder.createBlock(bb.getParent()); |
| terminator->setSuccessor(dummyBlock, position); |
| dummyBlock->addArguments(successor.first->getArgumentTypes()); |
| builder.create<LLVM::BrOp>(terminator->getLoc(), |
| dummyBlock->getArguments(), successor.first); |
| } |
| } |
| } |
| |
| void mlir::LLVM::ensureDistinctSuccessors(Operation *op) { |
| op->walk([](LLVMFuncOp f) { |
| for (auto &bb : f) { |
| ::ensureDistinctSuccessors(bb); |
| } |
| }); |
| } |
| |
| namespace { |
| struct LegalizeForExportPass |
| : public LLVMLegalizeForExportBase<LegalizeForExportPass> { |
| void runOnOperation() override { |
| LLVM::ensureDistinctSuccessors(getOperation()); |
| } |
| }; |
| } // end namespace |
| |
| std::unique_ptr<Pass> LLVM::createLegalizeForExportPass() { |
| return std::make_unique<LegalizeForExportPass>(); |
| } |