82 lines
2.8 KiB
C++
82 lines
2.8 KiB
C++
//===- Dominance.cpp - Dominator analysis for CFG Functions ---------------===//
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//
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// Copyright 2019 The MLIR Authors.
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//
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// http://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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// =============================================================================
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//
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// Implementation of dominance related classes and instantiations of extern
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// templates.
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//
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//===----------------------------------------------------------------------===//
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#include "mlir/Analysis/Dominance.h"
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#include "llvm/Support/GenericDomTreeConstruction.h"
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using namespace mlir;
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template class llvm::DominatorTreeBase<BasicBlock, false>;
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template class llvm::DominatorTreeBase<BasicBlock, true>;
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template class llvm::DomTreeNodeBase<BasicBlock>;
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/// Compute the immediate-dominators map.
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DominanceInfo::DominanceInfo(CFGFunction *function) : DominatorTreeBase() {
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// Build the dominator tree for the function.
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recalculate(*function);
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}
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/// Return true if instruction A properly dominates instruction B.
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bool DominanceInfo::properlyDominates(const Instruction *a,
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const Instruction *b) {
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auto *aBlock = a->getBlock(), *bBlock = b->getBlock();
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// If the blocks are different, it's as easy as whether A's block
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// dominates B's block.
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if (aBlock != bBlock)
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return properlyDominates(a->getBlock(), b->getBlock());
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// If a/b are the same, then they don't properly dominate each other.
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if (a == b)
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return false;
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// If one is a terminator, then the other dominates it.
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auto *aOp = cast<OperationInst>(a);
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if (aOp->isTerminator())
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return false;
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auto *bOp = cast<OperationInst>(b);
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if (bOp->isTerminator())
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return true;
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// Otherwise, do a linear scan to determine whether B comes after A.
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auto aIter = BasicBlock::const_iterator(aOp);
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auto bIter = BasicBlock::const_iterator(bOp);
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auto fIter = aBlock->begin();
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while (bIter != fIter) {
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--bIter;
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if (aIter == bIter)
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return true;
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}
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return false;
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}
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/// Return true if value A properly dominates instruction B.
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bool DominanceInfo::properlyDominates(const SSAValue *a, const Instruction *b) {
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if (auto *aInst = a->getDefiningInst())
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return properlyDominates(aInst, b);
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// bbarguments properly dominate all instructions in their own block, so we
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// use a dominates check here, not a properlyDominates check.
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return dominates(cast<BBArgument>(a)->getOwner(), b->getBlock());
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}
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