MachineRegisterInfo: Remove UsedPhysReg infrastructure

[oota-llvm.git] / lib / CodeGen / VirtRegMap.cpp

diff --git a/lib/CodeGen/VirtRegMap.cpp b/lib/CodeGen/VirtRegMap.cpp
index 2912bdd63426de84d3ac0437b81b02e8a05cd3c4..02341b4d66b8cce7a53c8010004aa6bf67a4e7c9 100644 (file)
--- a/lib/CodeGen/VirtRegMap.cpp
+++ b/lib/CodeGen/VirtRegMap.cpp
@@ -163,7 +163,6 @@ class VirtRegRewriter : public MachineFunctionPass {
   SlotIndexes *Indexes;
   LiveIntervals *LIS;
   VirtRegMap *VRM;
-  SparseSet<unsigned> PhysRegs;
 
   void rewrite();
   void addMBBLiveIns();
@@ -319,54 +318,15 @@ void VirtRegRewriter::rewrite() {
   SmallVector<unsigned, 8> SuperDeads;
   SmallVector<unsigned, 8> SuperDefs;
   SmallVector<unsigned, 8> SuperKills;
-  SmallPtrSet<const MachineInstr *, 4> NoReturnInsts;
-
-  // Here we have a SparseSet to hold which PhysRegs are actually encountered
-  // in the MF we are about to iterate over so that later when we call
-  // setPhysRegUsed, we are only doing it for physRegs that were actually found
-  // in the program and not for all of the possible physRegs for the given
-  // target architecture. If the target has a lot of physRegs, then for a small
-  // program there will be a significant compile time reduction here.
-  PhysRegs.clear();
-  PhysRegs.setUniverse(TRI->getNumRegs());
-
-  // The function with uwtable should guarantee that the stack unwinder
-  // can unwind the stack to the previous frame.  Thus, we can't apply the
-  // noreturn optimization if the caller function has uwtable attribute.
-  bool HasUWTable = MF->getFunction()->hasFnAttribute(Attribute::UWTable);
 
   for (MachineFunction::iterator MBBI = MF->begin(), MBBE = MF->end();
        MBBI != MBBE; ++MBBI) {
     DEBUG(MBBI->print(dbgs(), Indexes));
-    bool IsExitBB = MBBI->succ_empty();
     for (MachineBasicBlock::instr_iterator
            MII = MBBI->instr_begin(), MIE = MBBI->instr_end(); MII != MIE;) {
       MachineInstr *MI = MII;
       ++MII;
 
-      // Check if this instruction is a call to a noreturn function.  If this
-      // is a call to noreturn function and we don't need the stack unwinding
-      // functionality (i.e. this function does not have uwtable attribute and
-      // the callee function has the nounwind attribute), then we can ignore
-      // the definitions set by this instruction.
-      if (!HasUWTable && IsExitBB && MI->isCall()) {
-        for (MachineInstr::mop_iterator MOI = MI->operands_begin(),
-               MOE = MI->operands_end(); MOI != MOE; ++MOI) {
-          MachineOperand &MO = *MOI;
-          if (!MO.isGlobal())
-            continue;
-          const Function *Func = dyn_cast<Function>(MO.getGlobal());
-          if (!Func || !Func->hasFnAttribute(Attribute::NoReturn) ||
-              // We need to keep correct unwind information
-              // even if the function will not return, since the
-              // runtime may need it.
-              !Func->hasFnAttribute(Attribute::NoUnwind))
-            continue;
-          NoReturnInsts.insert(MI);
-          break;
-        }
-      }
-
       for (MachineInstr::mop_iterator MOI = MI->operands_begin(),
            MOE = MI->operands_end(); MOI != MOE; ++MOI) {
         MachineOperand &MO = *MOI;
@@ -375,15 +335,6 @@ void VirtRegRewriter::rewrite() {
         if (MO.isRegMask())
           MRI->addPhysRegsUsedFromRegMask(MO.getRegMask());
 
-        // If we encounter a VirtReg or PhysReg then get at the PhysReg and add
-        // it to the physreg bitset.  Later we use only the PhysRegs that were
-        // actually encountered in the MF to populate the MRI's used physregs.
-        if (MO.isReg() && MO.getReg())
-          PhysRegs.insert(
-              TargetRegisterInfo::isVirtualRegister(MO.getReg()) ?
-              VRM->getPhys(MO.getReg()) :
-              MO.getReg());
-
         if (!MO.isReg() || !TargetRegisterInfo::isVirtualRegister(MO.getReg()))
           continue;
         unsigned VirtReg = MO.getReg();
@@ -470,29 +421,5 @@ void VirtRegRewriter::rewrite() {
       }
     }
   }
-
-  // Tell MRI about physical registers in use.
-  if (NoReturnInsts.empty()) {
-    for (SparseSet<unsigned>::iterator
-        RegI = PhysRegs.begin(), E = PhysRegs.end(); RegI != E; ++RegI)
-      if (!MRI->reg_nodbg_empty(*RegI))
-        MRI->setPhysRegUsed(*RegI);
-  } else {
-    for (SparseSet<unsigned>::iterator
-        I = PhysRegs.begin(), E = PhysRegs.end(); I != E; ++I) {
-      unsigned Reg = *I;
-      if (MRI->reg_nodbg_empty(Reg))
-        continue;
-      // Check if this register has a use that will impact the rest of the
-      // code. Uses in debug and noreturn instructions do not impact the
-      // generated code.
-      for (MachineInstr &It : MRI->reg_nodbg_instructions(Reg)) {
-        if (!NoReturnInsts.count(&It)) {
-          MRI->setPhysRegUsed(Reg);
-          break;
-        }
-      }
-    }
-  }
 }