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

   1 //===- ReduceRegisterUses.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 uninteresting register uses from the MachineFunction.
  11 //
  12 //===----------------------------------------------------------------------===//
  13
  14 #include "ReduceRegisterUses.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 removeUsesFromFunction(Oracle &O, MachineFunction &MF) {
  22   MachineRegisterInfo &MRI = MF.getRegInfo();
  23
  24   for (MachineBasicBlock &MBB : MF) {
  25     for (MachineInstr &MI : MBB) {
  26       // Generic instructions are not supposed to have undef operands.
  27       if (isPreISelGenericOpcode(MI.getOpcode()))
  28         continue;
  29
  30       int NumOperands = MI.getNumOperands();
  31       int NumRequiredOps = MI.getNumExplicitOperands() +
  32                            MI.getDesc().implicit_defs().size() +
  33                            MI.getDesc().implicit_uses().size();
  34
  35       for (int I = NumOperands - 1; I >= 0; --I) {
  36         MachineOperand &MO = MI.getOperand(I);
  37         if (!MO.isReg() || !MO.readsReg())
  38           continue;
  39
  40         Register Reg = MO.getReg();
  41         if (Reg.isPhysical() && MRI.isReserved(Reg))
  42           continue;
  43
  44         if (O.shouldKeep())
  45           continue;
  46
  47         // Remove implicit operands. If the register is part of the fixed
  48         // operand list, set to undef.
  49         if (I >= NumRequiredOps)
  50           MI.removeOperand(I);
  51         else
  52           MO.setIsUndef();
  53       }
  54     }
  55   }
  56 }
  57
  58 static void removeUsesFromModule(Oracle &O, ReducerWorkItem &WorkItem) {
  59   for (const Function &F : WorkItem.getModule()) {
  60     if (auto *MF = WorkItem.MMI->getMachineFunction(F))
  61       removeUsesFromFunction(O, *MF);
  62   }
  63 }
  64
  65 void llvm::reduceRegisterUsesMIRDeltaPass(TestRunner &Test) {
  66   runDeltaPass(Test, removeUsesFromModule, "Reducing register uses");
  67 }