1 //===-- LiveStacks.cpp - Live Stack Slot 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 live stack slot analysis pass. It is analogous to
10 // live interval analysis except it's analyzing liveness of stack slots rather
13 //===----------------------------------------------------------------------===//
15 #include "llvm/CodeGen/LiveStacks.h"
16 #include "llvm/CodeGen/LiveIntervals.h"
17 #include "llvm/CodeGen/Passes.h"
18 #include "llvm/CodeGen/TargetRegisterInfo.h"
19 #include "llvm/CodeGen/TargetSubtargetInfo.h"
20 #include "llvm/Support/Debug.h"
21 #include "llvm/Support/raw_ostream.h"
24 #define DEBUG_TYPE "livestacks"
26 char LiveStacks::ID
= 0;
27 INITIALIZE_PASS_BEGIN(LiveStacks
, DEBUG_TYPE
,
28 "Live Stack Slot Analysis", false, false)
29 INITIALIZE_PASS_DEPENDENCY(SlotIndexes
)
30 INITIALIZE_PASS_END(LiveStacks
, DEBUG_TYPE
,
31 "Live Stack Slot Analysis", false, false)
33 char &llvm::LiveStacksID
= LiveStacks::ID
;
35 void LiveStacks::getAnalysisUsage(AnalysisUsage
&AU
) const {
37 AU
.addPreserved
<SlotIndexes
>();
38 AU
.addRequiredTransitive
<SlotIndexes
>();
39 MachineFunctionPass::getAnalysisUsage(AU
);
42 void LiveStacks::releaseMemory() {
43 // Release VNInfo memory regions, VNInfo objects don't need to be dtor'd.
44 VNInfoAllocator
.Reset();
49 bool LiveStacks::runOnMachineFunction(MachineFunction
&MF
) {
50 TRI
= MF
.getSubtarget().getRegisterInfo();
51 // FIXME: No analysis is being done right now. We are relying on the
52 // register allocators to provide the information.
57 LiveStacks::getOrCreateInterval(int Slot
, const TargetRegisterClass
*RC
) {
58 assert(Slot
>= 0 && "Spill slot indice must be >= 0");
59 SS2IntervalMap::iterator I
= S2IMap
.find(Slot
);
60 if (I
== S2IMap
.end()) {
63 std::piecewise_construct
, std::forward_as_tuple(Slot
),
64 std::forward_as_tuple(Register::index2StackSlot(Slot
), 0.0F
))
66 S2RCMap
.insert(std::make_pair(Slot
, RC
));
68 // Use the largest common subclass register class.
69 const TargetRegisterClass
*OldRC
= S2RCMap
[Slot
];
70 S2RCMap
[Slot
] = TRI
->getCommonSubClass(OldRC
, RC
);
75 /// print - Implement the dump method.
76 void LiveStacks::print(raw_ostream
&OS
, const Module
*) const {
78 OS
<< "********** INTERVALS **********\n";
79 for (const_iterator I
= begin(), E
= end(); I
!= E
; ++I
) {
82 const TargetRegisterClass
*RC
= getIntervalRegClass(Slot
);
84 OS
<< " [" << TRI
->getRegClassName(RC
) << "]\n";