75 lines
2.6 KiB
C++
75 lines
2.6 KiB
C++
//===- llvm/Transforms/Utils/BypassSlowDivision.h ---------------*- C++ -*-===//
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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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//
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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/ADT/DenseMapInfo.h"
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#include "llvm/IR/ValueHandle.h"
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#include <cstdint>
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namespace llvm {
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class BasicBlock;
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class Value;
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struct DivRemMapKey {
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bool SignedOp;
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AssertingVH<Value> Dividend;
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AssertingVH<Value> Divisor;
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DivRemMapKey() = default;
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DivRemMapKey(bool InSignedOp, Value *InDividend, Value *InDivisor)
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: SignedOp(InSignedOp), Dividend(InDividend), Divisor(InDivisor) {}
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};
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template <> struct DenseMapInfo<DivRemMapKey> {
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static bool isEqual(const DivRemMapKey &Val1, const DivRemMapKey &Val2) {
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return Val1.SignedOp == Val2.SignedOp && Val1.Dividend == Val2.Dividend &&
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Val1.Divisor == Val2.Divisor;
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}
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static DivRemMapKey getEmptyKey() {
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return DivRemMapKey(false, nullptr, nullptr);
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}
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static DivRemMapKey getTombstoneKey() {
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return DivRemMapKey(true, nullptr, nullptr);
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}
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static unsigned getHashValue(const DivRemMapKey &Val) {
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return (unsigned)(reinterpret_cast<uintptr_t>(
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static_cast<Value *>(Val.Dividend)) ^
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reinterpret_cast<uintptr_t>(
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static_cast<Value *>(Val.Divisor))) ^
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(unsigned)Val.SignedOp;
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}
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};
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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 namespace llvm
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#endif // LLVM_TRANSFORMS_UTILS_BYPASSSLOWDIVISION_H
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