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().setNoVRegs();
66 }
67
68 /// Calculate the liveness information for the given machine function.
69 bool runOnMachineFunction(MachineFunction &MF) override;
70
71private:
72 /// Performs the actual liveness calculation for the function.
73 bool calculateLiveness(MachineFunction &MF);
74
75 /// Add the current register live set to the instruction.
76 void addLiveOutSetToMI(MachineFunction &MF, MachineInstr &MI);
77
78 /// Create a register mask and initialize it with the registers from
79 /// the register live set.
80 uint32_t *createRegisterMask(MachineFunction &MF) const;
81};
82} // namespace
83
84char StackMapLiveness::ID = 0;
85char &llvm::StackMapLivenessID = StackMapLiveness::ID;
86INITIALIZE_PASS(StackMapLiveness, "stackmap-liveness",
87 "StackMap Liveness Analysis", false, false)
88
89/// Default construct and initialize the pass.
90StackMapLiveness::StackMapLiveness() : MachineFunctionPass(ID) {}
91
92/// Tell the pass manager which passes we depend on and what information we
93/// preserve.
94void StackMapLiveness::getAnalysisUsage(AnalysisUsage &AU) const {
95 // We preserve all information.
96 AU.setPreservesAll();
97 AU.setPreservesCFG();
98 MachineFunctionPass::getAnalysisUsage(AU);
99}
100
101/// Calculate the liveness information for the given machine function.
102bool StackMapLiveness::runOnMachineFunction(MachineFunction &MF) {
103 if (!EnablePatchPointLiveness)
104 return false;
105
106 TRI = MF.getSubtarget().getRegisterInfo();
107 ++NumStackMapFuncVisited;
108
109 // Skip this function if there are no patchpoints to process.
110 if (!MF.getFrameInfo().hasPatchPoint()) {
111 ++NumStackMapFuncSkipped;
112 return false;
113 }
114 return calculateLiveness(MF);
115}
116
117/// Performs the actual liveness calculation for the function.
118bool StackMapLiveness::calculateLiveness(MachineFunction &MF) {
119 LLVM_DEBUG(dbgs() << "********** COMPUTING STACKMAP LIVENESS: "
120 << MF.getName() << " **********\n");
121 bool HasChanged = false;
122 // For all basic blocks in the function.
123 for (auto &MBB : MF) {
124 LLVM_DEBUG(dbgs() << "****** BB " << MBB.getName() << " ******\n");
125 LiveRegs.init(TRI: *TRI);
126 LiveRegs.addLiveOuts(MBB);
127 bool HasStackMap = false;
128 // Reverse iterate over all instructions and add the current live register
129 // set to an instruction if we encounter a patchpoint instruction.
130 for (MachineInstr &MI : llvm::reverse(C&: MBB)) {
131 if (MI.getOpcode() == TargetOpcode::PATCHPOINT) {
132 addLiveOutSetToMI(MF, MI);
133 HasChanged = true;
134 HasStackMap = true;
135 ++NumStackMaps;
136 }
137 LLVM_DEBUG(dbgs() << " " << LiveRegs << " " << MI);
138 LiveRegs.stepBackward(MI);
139 }
140 ++NumBBsVisited;
141 if (!HasStackMap)
142 ++NumBBsHaveNoStackmap;
143 }
144 return HasChanged;
145}
146
147/// Add the current register live set to the instruction.
148void StackMapLiveness::addLiveOutSetToMI(MachineFunction &MF,
149 MachineInstr &MI) {
150 uint32_t *Mask = createRegisterMask(MF);
151 MachineOperand MO = MachineOperand::CreateRegLiveOut(Mask);
152 MI.addOperand(MF, Op: MO);
153}
154
155/// Create a register mask and initialize it with the registers from the
156/// register live set.
157uint32_t *StackMapLiveness::createRegisterMask(MachineFunction &MF) const {
158 // The mask is owned and cleaned up by the Machine Function.
159 uint32_t *Mask = MF.allocateRegMask();
160 for (auto Reg : LiveRegs)
161 Mask[Reg / 32] |= 1U << (Reg % 32);
162
163 // Give the target a chance to adjust the mask.
164 TRI->adjustStackMapLiveOutMask(Mask);
165
166 return Mask;
167}
168