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96f0bbf15a
Update some comments to be more explicit. Change bypassSlowDivision and the functions it calls so that they take BasicBlock*s and Instruction*s, rather than Function::iterator&s and BasicBlock::iterator&s. Change the APIs so that the caller is responsible for updating the iterator, rather than the callee. This makes control flow much easier to follow. Patch by Justin Lebar! llvm-svn: 256789
37 lines
1.4 KiB
C++
37 lines
1.4 KiB
C++
//===- llvm/Transforms/Utils/BypassSlowDivision.h --------------*- C++ -*-===//
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//
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// The LLVM Compiler Infrastructure
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//
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// This file is distributed under the University of Illinois Open Source
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// License. See LICENSE.TXT for details.
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//
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//===----------------------------------------------------------------------===//
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//
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// This file contains an optimization for div and rem on architectures that
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// execute short instructions significantly faster than longer instructions.
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// For example, on Intel Atom 32-bit divides are slow enough that during
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// runtime it is profitable to check the value of the operands, and if they are
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// positive and less than 256 use an unsigned 8-bit divide.
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//
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//===----------------------------------------------------------------------===//
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#ifndef LLVM_TRANSFORMS_UTILS_BYPASSSLOWDIVISION_H
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#define LLVM_TRANSFORMS_UTILS_BYPASSSLOWDIVISION_H
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#include "llvm/ADT/DenseMap.h"
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#include "llvm/IR/Function.h"
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namespace llvm {
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/// This optimization identifies DIV instructions in a BB that can be
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/// profitably bypassed and carried out with a shorter, faster divide.
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///
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/// This optimization may add basic blocks immediately after BB; for obvious
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/// reasons, you shouldn't pass those blocks to bypassSlowDivision.
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bool bypassSlowDivision(
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BasicBlock *BB, const DenseMap<unsigned int, unsigned int> &BypassWidth);
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} // End llvm namespace
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#endif
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