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This function returns whether a block is nested inside of a loop. There can be three kinds of loop: 1) The block is nested inside of a LoopLikeOpInterface 2) The block is nested inside another block which is in a loop 3) There is a cycle in the control flow graph This will be useful for Flang's stack arrays pass, which moves array allocations from the heap to the stack. Special handling is needed when allocations occur inside of loops to ensure additional stack space is not allocated on each loop iteration. Differential Revision: https://reviews.llvm.org/D141401
54 lines
1.7 KiB
C++
54 lines
1.7 KiB
C++
//===- LoopLikeInterface.cpp - Loop-like operations in MLIR ---------------===//
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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/Interfaces/LoopLikeInterface.h"
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#include "mlir/IR/FunctionInterfaces.h"
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#include "llvm/ADT/DenseSet.h"
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using namespace mlir;
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/// Include the definitions of the loop-like interfaces.
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#include "mlir/Interfaces/LoopLikeInterface.cpp.inc"
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bool LoopLikeOpInterface::blockIsInLoop(Block *block) {
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Operation *parent = block->getParentOp();
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// The block could be inside a loop-like operation
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if (isa<LoopLikeOpInterface>(parent) ||
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parent->getParentOfType<LoopLikeOpInterface>())
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return true;
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// This block might be nested inside another block, which is in a loop
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if (!isa<FunctionOpInterface>(parent))
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if (mlir::Block *parentBlock = parent->getBlock())
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if (blockIsInLoop(parentBlock))
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return true;
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// Or the block could be inside a control flow graph loop:
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// A block is in a control flow graph loop if it can reach itself in a graph
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// traversal
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DenseSet<Block *> visited;
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SmallVector<Block *> stack;
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stack.push_back(block);
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while (!stack.empty()) {
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Block *current = stack.pop_back_val();
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auto [it, inserted] = visited.insert(current);
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if (!inserted) {
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// loop detected
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if (current == block)
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return true;
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continue;
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}
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stack.reserve(stack.size() + current->getNumSuccessors());
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for (Block *successor : current->getSuccessors())
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stack.push_back(successor);
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}
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return false;
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}
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