1 //===-- StackMapLivenessAnalysis.cpp - StackMap live Out Analysis ----------===//
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
7 //===----------------------------------------------------------------------===//
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.
13 //===----------------------------------------------------------------------===//
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"
29 #define DEBUG_TYPE "stackmaps"
31 static cl::opt
<bool> EnablePatchPointLiveness(
32 "enable-patchpoint-liveness", cl::Hidden
, cl::init(true),
33 cl::desc("Enable PatchPoint Liveness Analysis Pass"));
35 STATISTIC(NumStackMapFuncVisited
, "Number of functions visited");
36 STATISTIC(NumStackMapFuncSkipped
, "Number of functions skipped");
37 STATISTIC(NumBBsVisited
, "Number of basic blocks visited");
38 STATISTIC(NumBBsHaveNoStackmap
, "Number of basic blocks with no stackmap");
39 STATISTIC(NumStackMaps
, "Number of StackMaps visited");
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.
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.
50 class StackMapLiveness
: public MachineFunctionPass
{
51 const TargetRegisterInfo
*TRI
= nullptr;
52 LivePhysRegs LiveRegs
;
57 /// Default construct and initialize the pass.
60 /// Tell the pass manager which passes we depend on and what
61 /// information we preserve.
62 void getAnalysisUsage(AnalysisUsage
&AU
) const override
;
64 MachineFunctionProperties
getRequiredProperties() const override
{
65 return MachineFunctionProperties().set(
66 MachineFunctionProperties::Property::NoVRegs
);
69 /// Calculate the liveness information for the given machine function.
70 bool runOnMachineFunction(MachineFunction
&MF
) override
;
73 /// Performs the actual liveness calculation for the function.
74 bool calculateLiveness(MachineFunction
&MF
);
76 /// Add the current register live set to the instruction.
77 void addLiveOutSetToMI(MachineFunction
&MF
, MachineInstr
&MI
);
79 /// Create a register mask and initialize it with the registers from
80 /// the register live set.
81 uint32_t *createRegisterMask(MachineFunction
&MF
) const;
85 char StackMapLiveness::ID
= 0;
86 char &llvm::StackMapLivenessID
= StackMapLiveness::ID
;
87 INITIALIZE_PASS(StackMapLiveness
, "stackmap-liveness",
88 "StackMap Liveness Analysis", false, false)
90 /// Default construct and initialize the pass.
91 StackMapLiveness::StackMapLiveness() : MachineFunctionPass(ID
) {
92 initializeStackMapLivenessPass(*PassRegistry::getPassRegistry());
95 /// Tell the pass manager which passes we depend on and what information we
97 void StackMapLiveness::getAnalysisUsage(AnalysisUsage
&AU
) const {
98 // We preserve all information.
100 AU
.setPreservesCFG();
101 MachineFunctionPass::getAnalysisUsage(AU
);
104 /// Calculate the liveness information for the given machine function.
105 bool StackMapLiveness::runOnMachineFunction(MachineFunction
&MF
) {
106 if (!EnablePatchPointLiveness
)
109 LLVM_DEBUG(dbgs() << "********** COMPUTING STACKMAP LIVENESS: "
110 << MF
.getName() << " **********\n");
111 TRI
= MF
.getSubtarget().getRegisterInfo();
112 ++NumStackMapFuncVisited
;
114 // Skip this function if there are no patchpoints to process.
115 if (!MF
.getFrameInfo().hasPatchPoint()) {
116 ++NumStackMapFuncSkipped
;
119 return calculateLiveness(MF
);
122 /// Performs the actual liveness calculation for the function.
123 bool 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");
129 // FIXME: This should probably be addLiveOuts().
130 LiveRegs
.addLiveOutsNoPristines(MBB
);
131 bool HasStackMap
= false;
132 // Reverse iterate over all instructions and add the current live register
133 // set to an instruction if we encounter a patchpoint instruction.
134 for (MachineInstr
&MI
: llvm::reverse(MBB
)) {
135 if (MI
.getOpcode() == TargetOpcode::PATCHPOINT
) {
136 addLiveOutSetToMI(MF
, MI
);
141 LLVM_DEBUG(dbgs() << " " << LiveRegs
<< " " << MI
);
142 LiveRegs
.stepBackward(MI
);
146 ++NumBBsHaveNoStackmap
;
151 /// Add the current register live set to the instruction.
152 void StackMapLiveness::addLiveOutSetToMI(MachineFunction
&MF
,
154 uint32_t *Mask
= createRegisterMask(MF
);
155 MachineOperand MO
= MachineOperand::CreateRegLiveOut(Mask
);
156 MI
.addOperand(MF
, MO
);
159 /// Create a register mask and initialize it with the registers from the
160 /// register live set.
161 uint32_t *StackMapLiveness::createRegisterMask(MachineFunction
&MF
) const {
162 // The mask is owned and cleaned up by the Machine Function.
163 uint32_t *Mask
= MF
.allocateRegMask();
164 for (auto Reg
: LiveRegs
)
165 Mask
[Reg
/ 32] |= 1U << (Reg
% 32);
167 // Give the target a chance to adjust the mask.
168 TRI
->adjustStackMapLiveOutMask(Mask
);