llvm/tools/llvm-reduce/deltas/ReduceRegisterMasks.cpp

   1 //===- ReduceRegisterMasks.cpp - Specialized Delta Pass -------------------===//
   2 //
   3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
   4 // See https://llvm.org/LICENSE.txt for license information.
   5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
   6 //
   7 //===----------------------------------------------------------------------===//
   8 //
   9 // This file implements a function which calls the Generic Delta pass in order
  10 // to reduce custom register masks from the MachineFunction.
  11 //
  12 //===----------------------------------------------------------------------===//
  13
  14 #include "ReduceRegisterMasks.h"
  15 #include "llvm/CodeGen/MachineFunction.h"
  16 #include "llvm/CodeGen/MachineModuleInfo.h"
  17 #include "llvm/CodeGen/MachineRegisterInfo.h"
  18
  19 using namespace llvm;
  20
  21 static void reduceMasksInFunction(Oracle &O, MachineFunction &MF) {
  22   DenseSet<const uint32_t *> ConstRegisterMasks;
  23   const auto *TRI = MF.getSubtarget().getRegisterInfo();
  24
  25   // Track predefined/named regmasks which we ignore.
  26   const unsigned NumRegs = TRI->getNumRegs();
  27   for (const uint32_t *Mask : TRI->getRegMasks())
  28     ConstRegisterMasks.insert(Mask);
  29
  30   for (MachineBasicBlock &MBB : MF) {
  31     for (MachineInstr &MI : MBB) {
  32       for (MachineOperand &MO : MI.operands()) {
  33         if (!MO.isRegMask())
  34           continue;
  35
  36         const uint32_t *OldRegMask = MO.getRegMask();
  37         // We're only reducing custom reg masks.
  38         if (ConstRegisterMasks.count(OldRegMask))
  39           continue;
  40         unsigned RegMaskSize =
  41             MachineOperand::getRegMaskSize(TRI->getNumRegs());
  42         std::vector<uint32_t> NewMask(RegMaskSize);
  43
  44         bool MadeChange = false;
  45         for (unsigned I = 0; I != NumRegs; ++I) {
  46           if (OldRegMask[I / 32] & (1u << (I % 32))) {
  47             if (O.shouldKeep())
  48               NewMask[I / 32] |= 1u << (I % 32);
  49           } else
  50             MadeChange = true;
  51         }
  52
  53         if (MadeChange) {
  54           uint32_t *UpdatedMask = MF.allocateRegMask();
  55           std::memcpy(UpdatedMask, NewMask.data(),
  56                       RegMaskSize * sizeof(*OldRegMask));
  57           MO.setRegMask(UpdatedMask);
  58         }
  59       }
  60     }
  61   }
  62 }
  63
  64 static void reduceMasksInModule(Oracle &O, ReducerWorkItem &WorkItem) {
  65   for (const Function &F : WorkItem.getModule()) {
  66     if (auto *MF = WorkItem.MMI->getMachineFunction(F))
  67       reduceMasksInFunction(O, *MF);
  68   }
  69 }
  70
  71 void llvm::reduceRegisterMasksMIRDeltaPass(TestRunner &Test) {
  72   runDeltaPass(Test, reduceMasksInModule, "Reducing register masks");
  73 }