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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 |