1 //===- NVPTXProxyRegErasure.cpp - NVPTX Proxy Register Instruction Erasure -==//
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 // The pass is needed to remove ProxyReg instructions and restore related
11 // registers. The instructions were needed at instruction selection stage to
12 // make sure that callseq_end nodes won't be removed as "dead nodes". This can
13 // happen when we expand instructions into libcalls and the call site doesn't
14 // care about the libcall chain. Call site cares about data flow only, and the
15 // latest data flow node happens to be before callseq_end. Therefore the node
16 // becomes dangling and "dead". The ProxyReg acts like an additional data flow
17 // node *after* the callseq_end in the chain and ensures that everything will be
18 // preserved.
19 //
20 //===----------------------------------------------------------------------===//
21
22 #include "NVPTX.h"
23 #include "llvm/CodeGen/MachineFunctionPass.h"
24 #include "llvm/CodeGen/MachineInstrBuilder.h"
25 #include "llvm/CodeGen/MachineRegisterInfo.h"
26 #include "llvm/CodeGen/TargetInstrInfo.h"
27 #include "llvm/CodeGen/TargetRegisterInfo.h"
28
29 using namespace llvm;
30
31 namespace llvm {
32 void initializeNVPTXProxyRegErasurePass(PassRegistry &);
33 }
34
35 namespace {
36
37 struct NVPTXProxyRegErasure : public MachineFunctionPass {
38 public:
39 static char ID;
NVPTXProxyRegErasure__anone37b4a500111::NVPTXProxyRegErasure40 NVPTXProxyRegErasure() : MachineFunctionPass(ID) {
41 initializeNVPTXProxyRegErasurePass(*PassRegistry::getPassRegistry());
42 }
43
44 bool runOnMachineFunction(MachineFunction &MF) override;
45
getPassName__anone37b4a500111::NVPTXProxyRegErasure46 StringRef getPassName() const override {
47 return "NVPTX Proxy Register Instruction Erasure";
48 }
49
getAnalysisUsage__anone37b4a500111::NVPTXProxyRegErasure50 void getAnalysisUsage(AnalysisUsage &AU) const override {
51 MachineFunctionPass::getAnalysisUsage(AU);
52 }
53
54 private:
55 void replaceMachineInstructionUsage(MachineFunction &MF, MachineInstr &MI);
56
57 void replaceRegisterUsage(MachineInstr &Instr, MachineOperand &From,
58 MachineOperand &To);
59 };
60
61 } // namespace
62
63 char NVPTXProxyRegErasure::ID = 0;
64
65 INITIALIZE_PASS(NVPTXProxyRegErasure, "nvptx-proxyreg-erasure", "NVPTX ProxyReg Erasure", false, false)
66
runOnMachineFunction(MachineFunction & MF)67 bool NVPTXProxyRegErasure::runOnMachineFunction(MachineFunction &MF) {
68 SmallVector<MachineInstr *, 16> RemoveList;
69
70 for (auto &BB : MF) {
71 for (auto &MI : BB) {
72 switch (MI.getOpcode()) {
73 case NVPTX::ProxyRegI1:
74 case NVPTX::ProxyRegI16:
75 case NVPTX::ProxyRegI32:
76 case NVPTX::ProxyRegI64:
77 case NVPTX::ProxyRegF16:
78 case NVPTX::ProxyRegF16x2:
79 case NVPTX::ProxyRegF32:
80 case NVPTX::ProxyRegF64:
81 replaceMachineInstructionUsage(MF, MI);
82 RemoveList.push_back(&MI);
83 break;
84 }
85 }
86 }
87
88 for (auto *MI : RemoveList) {
89 MI->eraseFromParent();
90 }
91
92 return !RemoveList.empty();
93 }
94
replaceMachineInstructionUsage(MachineFunction & MF,MachineInstr & MI)95 void NVPTXProxyRegErasure::replaceMachineInstructionUsage(MachineFunction &MF,
96 MachineInstr &MI) {
97 auto &InOp = *MI.uses().begin();
98 auto &OutOp = *MI.defs().begin();
99
100 assert(InOp.isReg() && "ProxyReg input operand should be a register.");
101 assert(OutOp.isReg() && "ProxyReg output operand should be a register.");
102
103 for (auto &BB : MF) {
104 for (auto &I : BB) {
105 replaceRegisterUsage(I, OutOp, InOp);
106 }
107 }
108 }
109
replaceRegisterUsage(MachineInstr & Instr,MachineOperand & From,MachineOperand & To)110 void NVPTXProxyRegErasure::replaceRegisterUsage(MachineInstr &Instr,
111 MachineOperand &From,
112 MachineOperand &To) {
113 for (auto &Op : Instr.uses()) {
114 if (Op.isReg() && Op.getReg() == From.getReg()) {
115 Op.setReg(To.getReg());
116 }
117 }
118 }
119
createNVPTXProxyRegErasurePass()120 MachineFunctionPass *llvm::createNVPTXProxyRegErasurePass() {
121 return new NVPTXProxyRegErasure();
122 }
123