1 //===-- WebAssemblyMCLowerPrePass.cpp - Prepare for MC lower --------------===//
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 /// \file
10 /// Some information in MC lowering / asm printing gets generated as
11 /// instructions get emitted, but may be necessary at the start, such as for
12 /// .globaltype declarations. This pass collects this information.
13 ///
14 //===----------------------------------------------------------------------===//
15 
16 #include "MCTargetDesc/WebAssemblyMCTargetDesc.h"
17 #include "Utils/WebAssemblyUtilities.h"
18 #include "WebAssembly.h"
19 #include "WebAssemblyMachineFunctionInfo.h"
20 #include "WebAssemblySubtarget.h"
21 #include "llvm/ADT/SCCIterator.h"
22 #include "llvm/CodeGen/MachineFrameInfo.h"
23 #include "llvm/CodeGen/MachineFunction.h"
24 #include "llvm/CodeGen/MachineInstrBuilder.h"
25 #include "llvm/CodeGen/MachineLoopInfo.h"
26 #include "llvm/CodeGen/MachineModuleInfoImpls.h"
27 #include "llvm/CodeGen/MachineRegisterInfo.h"
28 #include "llvm/CodeGen/Passes.h"
29 #include "llvm/Support/Debug.h"
30 #include "llvm/Support/raw_ostream.h"
31 using namespace llvm;
32 
33 #define DEBUG_TYPE "wasm-mclower-prepass"
34 
35 namespace {
36 class WebAssemblyMCLowerPrePass final : public ModulePass {
37   StringRef getPassName() const override {
38     return "WebAssembly MC Lower Pre Pass";
39   }
40 
41   void getAnalysisUsage(AnalysisUsage &AU) const override {
42     AU.setPreservesCFG();
43     ModulePass::getAnalysisUsage(AU);
44   }
45 
46   bool runOnModule(Module &M) override;
47 
48 public:
49   static char ID; // Pass identification, replacement for typeid
50   WebAssemblyMCLowerPrePass() : ModulePass(ID) {}
51 };
52 } // end anonymous namespace
53 
54 char WebAssemblyMCLowerPrePass::ID = 0;
55 INITIALIZE_PASS(
56     WebAssemblyMCLowerPrePass, DEBUG_TYPE,
57     "Collects information ahead of time for MC lowering",
58     false, false)
59 
60 ModulePass *llvm::createWebAssemblyMCLowerPrePass() {
61   return new WebAssemblyMCLowerPrePass();
62 }
63 
64 // NOTE: this is a ModulePass since we need to enforce that this code has run
65 // for all functions before AsmPrinter. If this way of doing things is ever
66 // suboptimal, we could opt to make it a MachineFunctionPass and instead use
67 // something like createBarrierNoopPass() to enforce ordering.
68 //
69 // The information stored here is essential for emitExternalDecls in the Wasm
70 // AsmPrinter
71 bool WebAssemblyMCLowerPrePass::runOnModule(Module &M) {
72   auto *MMIWP = getAnalysisIfAvailable<MachineModuleInfoWrapperPass>();
73   if (!MMIWP)
74     return true;
75 
76   MachineModuleInfo &MMI = MMIWP->getMMI();
77   MachineModuleInfoWasm &MMIW = MMI.getObjFileInfo<MachineModuleInfoWasm>();
78 
79   for (Function &F : M) {
80     MachineFunction *MF = MMI.getMachineFunction(F);
81     if (!MF)
82       continue;
83 
84     LLVM_DEBUG(dbgs() << "********** MC Lower Pre Pass **********\n"
85                          "********** Function: "
86                       << MF->getName() << '\n');
87 
88     for (MachineBasicBlock &MBB : *MF) {
89       for (auto &MI : MBB) {
90         // FIXME: what should all be filtered out beyond these?
91         if (MI.isDebugInstr() || MI.isInlineAsm())
92           continue;
93         for (MachineOperand &MO : MI.uses()) {
94           if (MO.isSymbol()) {
95             MMIW.MachineSymbolsUsed.insert(MO.getSymbolName());
96           }
97         }
98       }
99     }
100   }
101   return true;
102 }
103