1//===-- StackMapLivenessAnalysis.cpp - StackMap live Out Analysis ----------===//
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 the StackMap Liveness analysis pass. The pass calculates
10// the liveness for each basic block in a function and attaches the register
11// live-out information to a stackmap or patchpoint intrinsic if present.
12//
13//===----------------------------------------------------------------------===//
14
15#include "llvm/ADT/Statistic.h"
16#include "llvm/CodeGen/LivePhysRegs.h"
17#include "llvm/CodeGen/MachineFrameInfo.h"
18#include "llvm/CodeGen/MachineFunction.h"
19#include "llvm/CodeGen/MachineFunctionPass.h"
20#include "llvm/CodeGen/TargetSubtargetInfo.h"
21#include "llvm/InitializePasses.h"
22#include "llvm/Pass.h"
23#include "llvm/Support/CommandLine.h"
24#include "llvm/Support/Debug.h"
25#include "llvm/Support/raw_ostream.h"
26
27using namespace llvm;
28
29#define DEBUG_TYPE "stackmaps"
30
31static cl::opt<bool> EnablePatchPointLiveness(
32 "enable-patchpoint-liveness", cl::Hidden, cl::init(Val: true),
33 cl::desc("Enable PatchPoint Liveness Analysis Pass"));
34
35STATISTIC(NumStackMapFuncVisited, "Number of functions visited");
36STATISTIC(NumStackMapFuncSkipped, "Number of functions skipped");
37STATISTIC(NumBBsVisited, "Number of basic blocks visited");
38STATISTIC(NumBBsHaveNoStackmap, "Number of basic blocks with no stackmap");
39STATISTIC(NumStackMaps, "Number of StackMaps visited");
40
41namespace {
42/// This pass calculates the liveness information for each basic block in
43/// a function and attaches the register live-out information to a patchpoint
44/// intrinsic if present.
45///
46/// This pass can be disabled via the -enable-patchpoint-liveness=false flag.
47/// The pass skips functions that don't have any patchpoint intrinsics. The
48/// information provided by this pass is optional and not required by the
49/// aformentioned intrinsic to function.
50class StackMapLiveness : public MachineFunctionPass {
51 const TargetRegisterInfo *TRI = nullptr;
52 LivePhysRegs LiveRegs;
53
54public:
55 static char ID;
56
57 /// Default construct and initialize the pass.
58 StackMapLiveness();
59
60 /// Tell the pass manager which passes we depend on and what
61 /// information we preserve.
62 void getAnalysisUsage(AnalysisUsage &AU) const override;
63
64 MachineFunctionProperties getRequiredProperties() const override {
65 return MachineFunctionProperties().set(
66 MachineFunctionProperties::Property::NoVRegs);
67 }
68
69 /// Calculate the liveness information for the given machine function.
70 bool runOnMachineFunction(MachineFunction &MF) override;
71
72private:
73 /// Performs the actual liveness calculation for the function.
74 bool calculateLiveness(MachineFunction &MF);
75
76 /// Add the current register live set to the instruction.
77 void addLiveOutSetToMI(MachineFunction &MF, MachineInstr &MI);
78
79 /// Create a register mask and initialize it with the registers from
80 /// the register live set.
81 uint32_t *createRegisterMask(MachineFunction &MF) const;
82};
83} // namespace
84
85char StackMapLiveness::ID = 0;
86char &llvm::StackMapLivenessID = StackMapLiveness::ID;
87INITIALIZE_PASS(StackMapLiveness, "stackmap-liveness",
88 "StackMap Liveness Analysis", false, false)
89
90/// Default construct and initialize the pass.
91StackMapLiveness::StackMapLiveness() : MachineFunctionPass(ID) {
92 initializeStackMapLivenessPass(Registry&: *PassRegistry::getPassRegistry());
93}
94
95/// Tell the pass manager which passes we depend on and what information we
96/// preserve.
97void StackMapLiveness::getAnalysisUsage(AnalysisUsage &AU) const {
98 // We preserve all information.
99 AU.setPreservesAll();
100 AU.setPreservesCFG();
101 MachineFunctionPass::getAnalysisUsage(AU);
102}
103
104/// Calculate the liveness information for the given machine function.
105bool StackMapLiveness::runOnMachineFunction(MachineFunction &MF) {
106 if (!EnablePatchPointLiveness)
107 return false;
108
109 LLVM_DEBUG(dbgs() << "********** COMPUTING STACKMAP LIVENESS: "
110 << MF.getName() << " **********\n");
111 TRI = MF.getSubtarget().getRegisterInfo();
112 ++NumStackMapFuncVisited;
113
114 // Skip this function if there are no patchpoints to process.
115 if (!MF.getFrameInfo().hasPatchPoint()) {
116 ++NumStackMapFuncSkipped;
117 return false;
118 }
119 return calculateLiveness(MF);
120}
121
122/// Performs the actual liveness calculation for the function.
123bool StackMapLiveness::calculateLiveness(MachineFunction &MF) {
124 bool HasChanged = false;
125 // For all basic blocks in the function.
126 for (auto &MBB : MF) {
127 LLVM_DEBUG(dbgs() << "****** BB " << MBB.getName() << " ******\n");
128 LiveRegs.init(TRI: *TRI);
129 LiveRegs.addLiveOuts(MBB);
130 bool HasStackMap = false;
131 // Reverse iterate over all instructions and add the current live register
132 // set to an instruction if we encounter a patchpoint instruction.
133 for (MachineInstr &MI : llvm::reverse(C&: MBB)) {
134 if (MI.getOpcode() == TargetOpcode::PATCHPOINT) {
135 addLiveOutSetToMI(MF, MI);
136 HasChanged = true;
137 HasStackMap = true;
138 ++NumStackMaps;
139 }
140 LLVM_DEBUG(dbgs() << " " << LiveRegs << " " << MI);
141 LiveRegs.stepBackward(MI);
142 }
143 ++NumBBsVisited;
144 if (!HasStackMap)
145 ++NumBBsHaveNoStackmap;
146 }
147 return HasChanged;
148}
149
150/// Add the current register live set to the instruction.
151void StackMapLiveness::addLiveOutSetToMI(MachineFunction &MF,
152 MachineInstr &MI) {
153 uint32_t *Mask = createRegisterMask(MF);
154 MachineOperand MO = MachineOperand::CreateRegLiveOut(Mask);
155 MI.addOperand(MF, Op: MO);
156}
157
158/// Create a register mask and initialize it with the registers from the
159/// register live set.
160uint32_t *StackMapLiveness::createRegisterMask(MachineFunction &MF) const {
161 // The mask is owned and cleaned up by the Machine Function.
162 uint32_t *Mask = MF.allocateRegMask();
163 for (auto Reg : LiveRegs)
164 Mask[Reg / 32] |= 1U << (Reg % 32);
165
166 // Give the target a chance to adjust the mask.
167 TRI->adjustStackMapLiveOutMask(Mask);
168
169 return Mask;
170}
171