1 //===- NVPTXProxyRegErasure.cpp - NVPTX Proxy Register Instruction Erasure -==//
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 // The pass is needed to remove ProxyReg instructions and restore related
10 // registers. The instructions were needed at instruction selection stage to
11 // make sure that callseq_end nodes won't be removed as "dead nodes". This can
12 // happen when we expand instructions into libcalls and the call site doesn't
13 // care about the libcall chain. Call site cares about data flow only, and the
14 // latest data flow node happens to be before callseq_end. Therefore the node
15 // becomes dangling and "dead". The ProxyReg acts like an additional data flow
16 // node *after* the callseq_end in the chain and ensures that everything will be
17 // preserved.
18 //
19 //===----------------------------------------------------------------------===//
20
21 #include "NVPTX.h"
22 #include "llvm/CodeGen/MachineFunctionPass.h"
23 #include "llvm/CodeGen/MachineInstrBuilder.h"
24 #include "llvm/CodeGen/MachineRegisterInfo.h"
25 #include "llvm/CodeGen/TargetInstrInfo.h"
26 #include "llvm/CodeGen/TargetRegisterInfo.h"
27
28 using namespace llvm;
29
30 namespace llvm {
31 void initializeNVPTXProxyRegErasurePass(PassRegistry &);
32 }
33
34 namespace {
35
36 struct NVPTXProxyRegErasure : public MachineFunctionPass {
37 public:
38 static char ID;
NVPTXProxyRegErasure__anonc87c85950111::NVPTXProxyRegErasure39 NVPTXProxyRegErasure() : MachineFunctionPass(ID) {
40 initializeNVPTXProxyRegErasurePass(*PassRegistry::getPassRegistry());
41 }
42
43 bool runOnMachineFunction(MachineFunction &MF) override;
44
getPassName__anonc87c85950111::NVPTXProxyRegErasure45 StringRef getPassName() const override {
46 return "NVPTX Proxy Register Instruction Erasure";
47 }
48
getAnalysisUsage__anonc87c85950111::NVPTXProxyRegErasure49 void getAnalysisUsage(AnalysisUsage &AU) const override {
50 MachineFunctionPass::getAnalysisUsage(AU);
51 }
52
53 private:
54 void replaceMachineInstructionUsage(MachineFunction &MF, MachineInstr &MI);
55
56 void replaceRegisterUsage(MachineInstr &Instr, MachineOperand &From,
57 MachineOperand &To);
58 };
59
60 } // namespace
61
62 char NVPTXProxyRegErasure::ID = 0;
63
64 INITIALIZE_PASS(NVPTXProxyRegErasure, "nvptx-proxyreg-erasure", "NVPTX ProxyReg Erasure", false, false)
65
runOnMachineFunction(MachineFunction & MF)66 bool NVPTXProxyRegErasure::runOnMachineFunction(MachineFunction &MF) {
67 SmallVector<MachineInstr *, 16> RemoveList;
68
69 for (auto &BB : MF) {
70 for (auto &MI : BB) {
71 switch (MI.getOpcode()) {
72 case NVPTX::ProxyRegI1:
73 case NVPTX::ProxyRegI16:
74 case NVPTX::ProxyRegI32:
75 case NVPTX::ProxyRegI64:
76 case NVPTX::ProxyRegF16:
77 case NVPTX::ProxyRegF16x2:
78 case NVPTX::ProxyRegF32:
79 case NVPTX::ProxyRegF64:
80 replaceMachineInstructionUsage(MF, MI);
81 RemoveList.push_back(&MI);
82 break;
83 }
84 }
85 }
86
87 for (auto *MI : RemoveList) {
88 MI->eraseFromParent();
89 }
90
91 return !RemoveList.empty();
92 }
93
replaceMachineInstructionUsage(MachineFunction & MF,MachineInstr & MI)94 void NVPTXProxyRegErasure::replaceMachineInstructionUsage(MachineFunction &MF,
95 MachineInstr &MI) {
96 auto &InOp = *MI.uses().begin();
97 auto &OutOp = *MI.defs().begin();
98
99 assert(InOp.isReg() && "ProxyReg input operand should be a register.");
100 assert(OutOp.isReg() && "ProxyReg output operand should be a register.");
101
102 for (auto &BB : MF) {
103 for (auto &I : BB) {
104 replaceRegisterUsage(I, OutOp, InOp);
105 }
106 }
107 }
108
replaceRegisterUsage(MachineInstr & Instr,MachineOperand & From,MachineOperand & To)109 void NVPTXProxyRegErasure::replaceRegisterUsage(MachineInstr &Instr,
110 MachineOperand &From,
111 MachineOperand &To) {
112 for (auto &Op : Instr.uses()) {
113 if (Op.isReg() && Op.getReg() == From.getReg()) {
114 Op.setReg(To.getReg());
115 }
116 }
117 }
118
createNVPTXProxyRegErasurePass()119 MachineFunctionPass *llvm::createNVPTXProxyRegErasurePass() {
120 return new NVPTXProxyRegErasure();
121 }
122