1 //===-- LiveStacks.cpp - Live Stack Slot 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 live stack slot analysis pass. It is analogous to
10 // live interval analysis except it's analyzing liveness of stack slots rather
11 // than registers.
12 //
13 //===----------------------------------------------------------------------===//
14
15 #include "llvm/CodeGen/LiveStacks.h"
16 #include "llvm/CodeGen/TargetRegisterInfo.h"
17 #include "llvm/CodeGen/TargetSubtargetInfo.h"
18 #include "llvm/InitializePasses.h"
19 using namespace llvm;
20
21 #define DEBUG_TYPE "livestacks"
22
23 char LiveStacks::ID = 0;
24 INITIALIZE_PASS_BEGIN(LiveStacks, DEBUG_TYPE,
25 "Live Stack Slot Analysis", false, false)
26 INITIALIZE_PASS_DEPENDENCY(SlotIndexesWrapperPass)
27 INITIALIZE_PASS_END(LiveStacks, DEBUG_TYPE,
28 "Live Stack Slot Analysis", false, false)
29
30 char &llvm::LiveStacksID = LiveStacks::ID;
31
getAnalysisUsage(AnalysisUsage & AU) const32 void LiveStacks::getAnalysisUsage(AnalysisUsage &AU) const {
33 AU.setPreservesAll();
34 AU.addPreserved<SlotIndexesWrapperPass>();
35 AU.addRequiredTransitive<SlotIndexesWrapperPass>();
36 MachineFunctionPass::getAnalysisUsage(AU);
37 }
38
releaseMemory()39 void LiveStacks::releaseMemory() {
40 // Release VNInfo memory regions, VNInfo objects don't need to be dtor'd.
41 VNInfoAllocator.Reset();
42 S2IMap.clear();
43 S2RCMap.clear();
44 }
45
runOnMachineFunction(MachineFunction & MF)46 bool LiveStacks::runOnMachineFunction(MachineFunction &MF) {
47 TRI = MF.getSubtarget().getRegisterInfo();
48 // FIXME: No analysis is being done right now. We are relying on the
49 // register allocators to provide the information.
50 return false;
51 }
52
53 LiveInterval &
getOrCreateInterval(int Slot,const TargetRegisterClass * RC)54 LiveStacks::getOrCreateInterval(int Slot, const TargetRegisterClass *RC) {
55 assert(Slot >= 0 && "Spill slot indice must be >= 0");
56 SS2IntervalMap::iterator I = S2IMap.find(Slot);
57 if (I == S2IMap.end()) {
58 I = S2IMap
59 .emplace(
60 std::piecewise_construct, std::forward_as_tuple(Slot),
61 std::forward_as_tuple(Register::index2StackSlot(Slot), 0.0F))
62 .first;
63 S2RCMap.insert(std::make_pair(Slot, RC));
64 } else {
65 // Use the largest common subclass register class.
66 const TargetRegisterClass *OldRC = S2RCMap[Slot];
67 S2RCMap[Slot] = TRI->getCommonSubClass(OldRC, RC);
68 }
69 return I->second;
70 }
71
72 /// print - Implement the dump method.
print(raw_ostream & OS,const Module *) const73 void LiveStacks::print(raw_ostream &OS, const Module*) const {
74
75 OS << "********** INTERVALS **********\n";
76 for (const_iterator I = begin(), E = end(); I != E; ++I) {
77 I->second.print(OS);
78 int Slot = I->first;
79 const TargetRegisterClass *RC = getIntervalRegClass(Slot);
80 if (RC)
81 OS << " [" << TRI->getRegClassName(RC) << "]\n";
82 else
83 OS << " [Unknown]\n";
84 }
85 }
86