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