lib/CodeGen/ExpandISelPseudos.cpp

   1 //===-- llvm/CodeGen/ExpandISelPseudos.cpp ----------------------*- C++ -*-===//
   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 // Expand Pseudo-instructions produced by ISel. These are usually to allow
  10 // the expansion to contain control flow, such as a conditional move
  11 // implemented with a conditional branch and a phi, or an atomic operation
  12 // implemented with a loop.
  13 //
  14 //===----------------------------------------------------------------------===//
  15
  16 #include "llvm/CodeGen/MachineFunction.h"
  17 #include "llvm/CodeGen/MachineFunctionPass.h"
  18 #include "llvm/CodeGen/Passes.h"
  19 #include "llvm/CodeGen/TargetLowering.h"
  20 #include "llvm/CodeGen/TargetSubtargetInfo.h"
  21 #include "llvm/Support/Debug.h"
  22 using namespace llvm;
  23
  24 #define DEBUG_TYPE "expand-isel-pseudos"
  25
  26 namespace {
  27   class ExpandISelPseudos : public MachineFunctionPass {
  28   public:
  29     static char ID; // Pass identification, replacement for typeid
  30     ExpandISelPseudos() : MachineFunctionPass(ID) {}
  31
  32   private:
  33     bool runOnMachineFunction(MachineFunction &MF) override;
  34
  35     void getAnalysisUsage(AnalysisUsage &AU) const override {
  36       MachineFunctionPass::getAnalysisUsage(AU);
  37     }
  38   };
  39 } // end anonymous namespace
  40
  41 char ExpandISelPseudos::ID = 0;
  42 char &llvm::ExpandISelPseudosID = ExpandISelPseudos::ID;
  43 INITIALIZE_PASS(ExpandISelPseudos, DEBUG_TYPE,
  44                 "Expand ISel Pseudo-instructions", false, false)
  45
  46 bool ExpandISelPseudos::runOnMachineFunction(MachineFunction &MF) {
  47   bool Changed = false;
  48   const TargetLowering *TLI = MF.getSubtarget().getTargetLowering();
  49
  50   // Iterate through each instruction in the function, looking for pseudos.
  51   for (MachineFunction::iterator I = MF.begin(), E = MF.end(); I != E; ++I) {
  52     MachineBasicBlock *MBB = &*I;
  53     for (MachineBasicBlock::iterator MBBI = MBB->begin(), MBBE = MBB->end();
  54          MBBI != MBBE; ) {
  55       MachineInstr &MI = *MBBI++;
  56
  57       // If MI is a pseudo, expand it.
  58       if (MI.usesCustomInsertionHook()) {
  59         Changed = true;
  60         MachineBasicBlock *NewMBB = TLI->EmitInstrWithCustomInserter(MI, MBB);
  61         // The expansion may involve new basic blocks.
  62         if (NewMBB != MBB) {
  63           MBB = NewMBB;
  64           I = NewMBB->getIterator();
  65           MBBI = NewMBB->begin();
  66           MBBE = NewMBB->end();
  67         }
  68       }
  69     }
  70   }
  71
  72   return Changed;
  73 }