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      1 //===-- SIFixControlFlowLiveIntervals.cpp - Fix CF live intervals ---------===//
      2 //
      3 //                     The LLVM Compiler Infrastructure
      4 //
      5 // This file is distributed under the University of Illinois Open Source
      6 // License. See LICENSE.TXT for details.
      7 //
      8 //===----------------------------------------------------------------------===//
      9 //
     10 /// \file
     11 /// \brief Spilling of EXEC masks used for control flow messes up control flow
     12 /// lowering, so mark all live intervals associated with CF instructions as
     13 /// non-spillable.
     14 ///
     15 //===----------------------------------------------------------------------===//
     16 
     17 #include "AMDGPU.h"
     18 #include "SIInstrInfo.h"
     19 #include "llvm/CodeGen/LiveIntervalAnalysis.h"
     20 #include "llvm/CodeGen/MachineFunctionPass.h"
     21 #include "llvm/CodeGen/MachineRegisterInfo.h"
     22 
     23 using namespace llvm;
     24 
     25 #define DEBUG_TYPE "si-fix-cf-live-intervals"
     26 
     27 namespace {
     28 
     29 class SIFixControlFlowLiveIntervals : public MachineFunctionPass {
     30 public:
     31   static char ID;
     32 
     33 public:
     34   SIFixControlFlowLiveIntervals() : MachineFunctionPass(ID) {
     35     initializeSIFixControlFlowLiveIntervalsPass(*PassRegistry::getPassRegistry());
     36   }
     37 
     38   bool runOnMachineFunction(MachineFunction &MF) override;
     39 
     40   const char *getPassName() const override {
     41     return "SI Fix CF Live Intervals";
     42   }
     43 
     44   void getAnalysisUsage(AnalysisUsage &AU) const override {
     45     AU.addRequired<LiveIntervals>();
     46     AU.setPreservesAll();
     47     MachineFunctionPass::getAnalysisUsage(AU);
     48   }
     49 };
     50 
     51 } // End anonymous namespace.
     52 
     53 INITIALIZE_PASS_BEGIN(SIFixControlFlowLiveIntervals, DEBUG_TYPE,
     54                       "SI Fix CF Live Intervals", false, false)
     55 INITIALIZE_PASS_DEPENDENCY(LiveIntervals)
     56 INITIALIZE_PASS_END(SIFixControlFlowLiveIntervals, DEBUG_TYPE,
     57                     "SI Fix CF Live Intervals", false, false)
     58 
     59 char SIFixControlFlowLiveIntervals::ID = 0;
     60 
     61 char &llvm::SIFixControlFlowLiveIntervalsID = SIFixControlFlowLiveIntervals::ID;
     62 
     63 FunctionPass *llvm::createSIFixControlFlowLiveIntervalsPass() {
     64   return new SIFixControlFlowLiveIntervals();
     65 }
     66 
     67 bool SIFixControlFlowLiveIntervals::runOnMachineFunction(MachineFunction &MF) {
     68   LiveIntervals *LIS = &getAnalysis<LiveIntervals>();
     69 
     70   for (const MachineBasicBlock &MBB : MF) {
     71     for (const MachineInstr &MI : MBB) {
     72       switch (MI.getOpcode()) {
     73         case AMDGPU::SI_IF:
     74         case AMDGPU::SI_ELSE:
     75         case AMDGPU::SI_BREAK:
     76         case AMDGPU::SI_IF_BREAK:
     77         case AMDGPU::SI_ELSE_BREAK:
     78         case AMDGPU::SI_END_CF: {
     79           unsigned Reg = MI.getOperand(0).getReg();
     80           LIS->getInterval(Reg).markNotSpillable();
     81           break;
     82         }
     83         default:
     84           break;
     85       }
     86     }
     87   }
     88 
     89   return false;
     90 }
     91