llvm/lib/Target/WebAssembly/WebAssemblyMCLowerPrePass.cpp

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