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       1             : //===- llvm/Transforms/Utils/BypassSlowDivision.h ---------------*- C++ -*-===//
       2             : //
       3             : //                     The LLVM Compiler Infrastructure
       4             : //
       5             : // This file is distributed under the University of Illinois Open Source
       6             : // License. See LICENSE.TXT for details.
       7             : //
       8             : //===----------------------------------------------------------------------===//
       9             : //
      10             : // This file contains an optimization for div and rem on architectures that
      11             : // execute short instructions significantly faster than longer instructions.
      12             : // For example, on Intel Atom 32-bit divides are slow enough that during
      13             : // runtime it is profitable to check the value of the operands, and if they are
      14             : // positive and less than 256 use an unsigned 8-bit divide.
      15             : //
      16             : //===----------------------------------------------------------------------===//
      17             : 
      18             : #ifndef LLVM_TRANSFORMS_UTILS_BYPASSSLOWDIVISION_H
      19             : #define LLVM_TRANSFORMS_UTILS_BYPASSSLOWDIVISION_H
      20             : 
      21             : #include "llvm/ADT/DenseMap.h"
      22             : #include "llvm/ADT/DenseMapInfo.h"
      23             : #include <cstdint>
      24             : 
      25             : namespace llvm {
      26             : 
      27             : class BasicBlock;
      28             : class Value;
      29             : 
      30             : struct DivRemMapKey {
      31             :   bool SignedOp;
      32             :   Value *Dividend;
      33             :   Value *Divisor;
      34             : 
      35             :   DivRemMapKey(bool InSignedOp, Value *InDividend, Value *InDivisor)
      36        1005 :       : SignedOp(InSignedOp), Dividend(InDividend), Divisor(InDivisor) {}
      37             : };
      38             : 
      39             : template <> struct DenseMapInfo<DivRemMapKey> {
      40             :   static bool isEqual(const DivRemMapKey &Val1, const DivRemMapKey &Val2) {
      41        5594 :     return Val1.SignedOp == Val2.SignedOp && Val1.Dividend == Val2.Dividend &&
      42        2893 :            Val1.Divisor == Val2.Divisor;
      43             :   }
      44             : 
      45             :   static DivRemMapKey getEmptyKey() {
      46             :     return DivRemMapKey(false, nullptr, nullptr);
      47             :   }
      48             : 
      49             :   static DivRemMapKey getTombstoneKey() {
      50             :     return DivRemMapKey(true, nullptr, nullptr);
      51             :   }
      52             : 
      53             :   static unsigned getHashValue(const DivRemMapKey &Val) {
      54        2722 :     return (unsigned)(reinterpret_cast<uintptr_t>(Val.Dividend) ^
      55        1361 :                       reinterpret_cast<uintptr_t>(Val.Divisor)) ^
      56        1361 :            (unsigned)Val.SignedOp;
      57             :   }
      58             : };
      59             : 
      60             : /// This optimization identifies DIV instructions in a BB that can be
      61             : /// profitably bypassed and carried out with a shorter, faster divide.
      62             : ///
      63             : /// This optimization may add basic blocks immediately after BB; for obvious
      64             : /// reasons, you shouldn't pass those blocks to bypassSlowDivision.
      65             : bool bypassSlowDivision(
      66             :     BasicBlock *BB, const DenseMap<unsigned int, unsigned int> &BypassWidth);
      67             : 
      68             : } // end namespace llvm
      69             : 
      70             : #endif // LLVM_TRANSFORMS_UTILS_BYPASSSLOWDIVISION_H