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| 14 | pmbaty | 1 | //===- llvm/Transforms/Utils/BypassSlowDivision.h ---------------*- C++ -*-===// |
| 2 | // |
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| 3 | // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions. |
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| 4 | // See https://llvm.org/LICENSE.txt for license information. |
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| 5 | // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception |
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| 6 | // |
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| 7 | //===----------------------------------------------------------------------===// |
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| 8 | // |
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| 9 | // This file contains an optimization for div and rem on architectures that |
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| 10 | // execute short instructions significantly faster than longer instructions. |
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| 11 | // For example, on Intel Atom 32-bit divides are slow enough that during |
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| 12 | // runtime it is profitable to check the value of the operands, and if they are |
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| 13 | // positive and less than 256 use an unsigned 8-bit divide. |
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| 14 | // |
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| 15 | //===----------------------------------------------------------------------===// |
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| 16 | |||
| 17 | #ifndef LLVM_TRANSFORMS_UTILS_BYPASSSLOWDIVISION_H |
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| 18 | #define LLVM_TRANSFORMS_UTILS_BYPASSSLOWDIVISION_H |
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| 19 | |||
| 20 | #include "llvm/ADT/DenseMap.h" |
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| 21 | #include "llvm/ADT/DenseMapInfo.h" |
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| 22 | #include "llvm/IR/ValueHandle.h" |
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| 23 | #include <cstdint> |
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| 24 | |||
| 25 | namespace llvm { |
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| 26 | |||
| 27 | class BasicBlock; |
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| 28 | class Value; |
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| 29 | |||
| 30 | struct DivRemMapKey { |
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| 31 | bool SignedOp; |
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| 32 | AssertingVH<Value> Dividend; |
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| 33 | AssertingVH<Value> Divisor; |
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| 34 | |||
| 35 | DivRemMapKey() = default; |
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| 36 | |||
| 37 | DivRemMapKey(bool InSignedOp, Value *InDividend, Value *InDivisor) |
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| 38 | : SignedOp(InSignedOp), Dividend(InDividend), Divisor(InDivisor) {} |
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| 39 | }; |
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| 40 | |||
| 41 | template <> struct DenseMapInfo<DivRemMapKey> { |
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| 42 | static bool isEqual(const DivRemMapKey &Val1, const DivRemMapKey &Val2) { |
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| 43 | return Val1.SignedOp == Val2.SignedOp && Val1.Dividend == Val2.Dividend && |
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| 44 | Val1.Divisor == Val2.Divisor; |
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| 45 | } |
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| 46 | |||
| 47 | static DivRemMapKey getEmptyKey() { |
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| 48 | return DivRemMapKey(false, nullptr, nullptr); |
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| 49 | } |
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| 50 | |||
| 51 | static DivRemMapKey getTombstoneKey() { |
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| 52 | return DivRemMapKey(true, nullptr, nullptr); |
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| 53 | } |
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| 54 | |||
| 55 | static unsigned getHashValue(const DivRemMapKey &Val) { |
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| 56 | return (unsigned)(reinterpret_cast<uintptr_t>( |
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| 57 | static_cast<Value *>(Val.Dividend)) ^ |
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| 58 | reinterpret_cast<uintptr_t>( |
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| 59 | static_cast<Value *>(Val.Divisor))) ^ |
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| 60 | (unsigned)Val.SignedOp; |
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| 61 | } |
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| 62 | }; |
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| 63 | |||
| 64 | /// This optimization identifies DIV instructions in a BB that can be |
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| 65 | /// profitably bypassed and carried out with a shorter, faster divide. |
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| 66 | /// |
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| 67 | /// This optimization may add basic blocks immediately after BB; for obvious |
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| 68 | /// reasons, you shouldn't pass those blocks to bypassSlowDivision. |
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| 69 | bool bypassSlowDivision( |
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| 70 | BasicBlock *BB, const DenseMap<unsigned int, unsigned int> &BypassWidth); |
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| 71 | |||
| 72 | } // end namespace llvm |
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| 73 | |||
| 74 | #endif // LLVM_TRANSFORMS_UTILS_BYPASSSLOWDIVISION_H |