xref: /llvm-project/llvm/tools/llvm-reduce/deltas/ReduceRegisterUses.cpp (revision 073401e59c8c0e03e06be1d516fe8ea821146d2f)
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 
removeUsesFromFunction(Oracle & O,MachineFunction & MF)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 
removeUsesFromModule(Oracle & O,ReducerWorkItem & WorkItem)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 
reduceRegisterUsesMIRDeltaPass(TestRunner & Test)65 void llvm::reduceRegisterUsesMIRDeltaPass(TestRunner &Test) {
66   runDeltaPass(Test, removeUsesFromModule, "Reducing register uses");
67 }
68