xref: /freebsd/contrib/llvm-project/llvm/lib/CodeGen/GlobalISel/Combiner.cpp (revision 9f23cbd6cae82fd77edfad7173432fa8dccd0a95)
1 //===-- lib/CodeGen/GlobalISel/Combiner.cpp -------------------------------===//
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 constains common code to combine machine functions at generic
10 // level.
11 //===----------------------------------------------------------------------===//
12 
13 #include "llvm/CodeGen/GlobalISel/Combiner.h"
14 #include "llvm/ADT/PostOrderIterator.h"
15 #include "llvm/ADT/SetVector.h"
16 #include "llvm/CodeGen/GlobalISel/CSEInfo.h"
17 #include "llvm/CodeGen/GlobalISel/CSEMIRBuilder.h"
18 #include "llvm/CodeGen/GlobalISel/CombinerInfo.h"
19 #include "llvm/CodeGen/GlobalISel/GISelChangeObserver.h"
20 #include "llvm/CodeGen/GlobalISel/GISelWorkList.h"
21 #include "llvm/CodeGen/GlobalISel/MachineIRBuilder.h"
22 #include "llvm/CodeGen/GlobalISel/Utils.h"
23 #include "llvm/CodeGen/MachineOptimizationRemarkEmitter.h"
24 #include "llvm/Support/Debug.h"
25 
26 #define DEBUG_TYPE "gi-combiner"
27 
28 using namespace llvm;
29 
30 namespace llvm {
31 cl::OptionCategory GICombinerOptionCategory(
32     "GlobalISel Combiner",
33     "Control the rules which are enabled. These options all take a comma "
34     "separated list of rules to disable and may be specified by number "
35     "or number range (e.g. 1-10)."
36 #ifndef NDEBUG
37     " They may also be specified by name."
38 #endif
39 );
40 } // end namespace llvm
41 
42 namespace {
43 /// This class acts as the glue the joins the CombinerHelper to the overall
44 /// Combine algorithm. The CombinerHelper is intended to report the
45 /// modifications it makes to the MIR to the GISelChangeObserver and the
46 /// observer subclass will act on these events. In this case, instruction
47 /// erasure will cancel any future visits to the erased instruction and
48 /// instruction creation will schedule that instruction for a future visit.
49 /// Other Combiner implementations may require more complex behaviour from
50 /// their GISelChangeObserver subclass.
51 class WorkListMaintainer : public GISelChangeObserver {
52   using WorkListTy = GISelWorkList<512>;
53   WorkListTy &WorkList;
54   /// The instructions that have been created but we want to report once they
55   /// have their operands. This is only maintained if debug output is requested.
56 #ifndef NDEBUG
57   SetVector<const MachineInstr *> CreatedInstrs;
58 #endif
59 
60 public:
61   WorkListMaintainer(WorkListTy &WorkList) : WorkList(WorkList) {}
62   virtual ~WorkListMaintainer() = default;
63 
64   void erasingInstr(MachineInstr &MI) override {
65     LLVM_DEBUG(dbgs() << "Erasing: " << MI << "\n");
66     WorkList.remove(&MI);
67   }
68   void createdInstr(MachineInstr &MI) override {
69     LLVM_DEBUG(dbgs() << "Creating: " << MI << "\n");
70     WorkList.insert(&MI);
71     LLVM_DEBUG(CreatedInstrs.insert(&MI));
72   }
73   void changingInstr(MachineInstr &MI) override {
74     LLVM_DEBUG(dbgs() << "Changing: " << MI << "\n");
75     WorkList.insert(&MI);
76   }
77   void changedInstr(MachineInstr &MI) override {
78     LLVM_DEBUG(dbgs() << "Changed: " << MI << "\n");
79     WorkList.insert(&MI);
80   }
81 
82   void reportFullyCreatedInstrs() {
83     LLVM_DEBUG(for (const auto *MI
84                     : CreatedInstrs) {
85       dbgs() << "Created: ";
86       MI->print(dbgs());
87     });
88     LLVM_DEBUG(CreatedInstrs.clear());
89   }
90 };
91 }
92 
93 Combiner::Combiner(CombinerInfo &Info, const TargetPassConfig *TPC)
94     : CInfo(Info), TPC(TPC) {
95   (void)this->TPC; // FIXME: Remove when used.
96 }
97 
98 bool Combiner::combineMachineInstrs(MachineFunction &MF,
99                                     GISelCSEInfo *CSEInfo) {
100   // If the ISel pipeline failed, do not bother running this pass.
101   // FIXME: Should this be here or in individual combiner passes.
102   if (MF.getProperties().hasProperty(
103           MachineFunctionProperties::Property::FailedISel))
104     return false;
105 
106   Builder =
107       CSEInfo ? std::make_unique<CSEMIRBuilder>() : std::make_unique<MachineIRBuilder>();
108   MRI = &MF.getRegInfo();
109   Builder->setMF(MF);
110   if (CSEInfo)
111     Builder->setCSEInfo(CSEInfo);
112 
113   LLVM_DEBUG(dbgs() << "Generic MI Combiner for: " << MF.getName() << '\n');
114 
115   MachineOptimizationRemarkEmitter MORE(MF, /*MBFI=*/nullptr);
116 
117   bool MFChanged = false;
118   bool Changed;
119   MachineIRBuilder &B = *Builder;
120 
121   do {
122     // Collect all instructions. Do a post order traversal for basic blocks and
123     // insert with list bottom up, so while we pop_back_val, we'll traverse top
124     // down RPOT.
125     Changed = false;
126     GISelWorkList<512> WorkList;
127     WorkListMaintainer Observer(WorkList);
128     GISelObserverWrapper WrapperObserver(&Observer);
129     if (CSEInfo)
130       WrapperObserver.addObserver(CSEInfo);
131     RAIIDelegateInstaller DelInstall(MF, &WrapperObserver);
132     for (MachineBasicBlock *MBB : post_order(&MF)) {
133       for (MachineInstr &CurMI :
134            llvm::make_early_inc_range(llvm::reverse(*MBB))) {
135         // Erase dead insts before even adding to the list.
136         if (isTriviallyDead(CurMI, *MRI)) {
137           LLVM_DEBUG(dbgs() << CurMI << "Is dead; erasing.\n");
138           llvm::salvageDebugInfo(*MRI, CurMI);
139           CurMI.eraseFromParent();
140           continue;
141         }
142         WorkList.deferred_insert(&CurMI);
143       }
144     }
145     WorkList.finalize();
146     // Main Loop. Process the instructions here.
147     while (!WorkList.empty()) {
148       MachineInstr *CurrInst = WorkList.pop_back_val();
149       LLVM_DEBUG(dbgs() << "\nTry combining " << *CurrInst;);
150       Changed |= CInfo.combine(WrapperObserver, *CurrInst, B);
151       Observer.reportFullyCreatedInstrs();
152     }
153     MFChanged |= Changed;
154   } while (Changed);
155 
156 #ifndef NDEBUG
157   if (CSEInfo) {
158     if (auto E = CSEInfo->verify()) {
159       errs() << E << '\n';
160       assert(false && "CSEInfo is not consistent. Likely missing calls to "
161                       "observer on mutations.");
162     }
163   }
164 #endif
165   return MFChanged;
166 }
167