Revert [MachineLICM] This reverts commit rL327856

Failing build bots. Revert the commit now.

llvm-svn: 327864

2 files changed, 1 insertions, 103 deletions

diff --git a/llvm/lib/CodeGen/MachineLICM.cpp b/llvm/lib/CodeGen/MachineLICM.cpp
index 2b73d492615..2c1b4f09a32 100644
--- a/llvm/lib/CodeGen/MachineLICM.cpp
+++ b/llvm/lib/CodeGen/MachineLICM.cpp
@@ -71,10 +71,6 @@ SinkInstsToAvoidSpills("sink-insts-to-avoid-spills",
                        cl::desc("MachineLICM should sink instructions into "
                                 "loops to avoid register spills"),
                        cl::init(false), cl::Hidden);
-static cl::opt<bool>
-HoistConstStores("hoist-const-stores",
-                 cl::desc("Hoist invariant stores"),
-                 cl::init(true), cl::Hidden);
 
 STATISTIC(NumHoisted,
           "Number of machine instructions hoisted out of loops");
@@ -86,8 +82,6 @@ STATISTIC(NumCSEed,
           "Number of hoisted machine instructions CSEed");
 STATISTIC(NumPostRAHoisted,
           "Number of machine instructions hoisted out of loops post regalloc");
-STATISTIC(NumStoreConst,
-          "Number of stores of const phys reg hoisted out of loops");
 
 namespace {
 
@@ -732,10 +726,6 @@ void MachineLICMBase::HoistOutOfLoop(MachineDomTreeNode *HeaderN) {
       MachineInstr *MI = &*MII;
       if (!Hoist(MI, Preheader))
         UpdateRegPressure(MI);
-      // If we have hoisted an instruction that may store, it can only be a
-      // constant store.
-      else if (MI->mayStore())
-        NumStoreConst++;
       MII = NextMII;
     }
 
@@ -899,79 +889,13 @@ static bool mayLoadFromGOTOrConstantPool(MachineInstr &MI) {
   return false;
 }
 
-// This function iterates through all the operands of the input store MI and
-// checks that each register operand statisfies isCallerPreservedPhysReg.
-// This means, the value being stored and the address where it is being stored
-// is constant throughout the body of the function (not including prologue and
-// epilogue). When called with an MI that isn't a store, it returns false.
-static bool isInvariantStore(const MachineInstr &MI,
-                             const TargetRegisterInfo *TRI,
-                             const MachineRegisterInfo *MRI) {
-
-  if (!MI.mayStore() || MI.hasUnmodeledSideEffects() ||
-      (MI.getNumOperands() == 0))
-    return false;
-
-  // Check that all register operands are caller-preserved physical registers.
-  for (const MachineOperand &MO : MI.operands()) {
-    if (MO.isReg()) {
-      unsigned Reg = MO.getReg();
-      // If operand is a virtual register, check if it comes from a copy of a
-      // physical register.
-      if (TargetRegisterInfo::isVirtualRegister(Reg))
-        Reg = TRI->lookThruCopyLike(MO.getReg(), MRI);
-      if (TargetRegisterInfo::isVirtualRegister(Reg))
-        return false;
-      if (!TRI->isCallerPreservedPhysReg(Reg, *MI.getMF()))
-        return false;
-    }
-  }
-  return true;
-}
-
-// Return true if the input MI is a copy instruction that feeds an invariant
-// store instruction. This means that the src of the copy has to satisfy
-// isCallerPreservedPhysReg and atleast one of it's users should satisfy
-// isInvariantStore.
-static bool isCopyFeedingInvariantStore(const MachineInstr &MI,
-                                        const MachineRegisterInfo *MRI,
-                                        const TargetRegisterInfo *TRI) {
-
-  // FIXME: If targets would like to look through instructions that aren't
-  // pure copies, this can be updated to a query.
-  if (!MI.isCopy())
-    return false;
-
-  const MachineFunction *MF = MI.getMF();
-  // Check that we are copying a constant physical register.
-  unsigned CopySrcReg = MI.getOperand(1).getReg();
-  if (TargetRegisterInfo::isVirtualRegister(CopySrcReg))
-    return false;
-
-  if (!TRI->isCallerPreservedPhysReg(CopySrcReg, *MF))
-    return false;
-
-  unsigned CopyDstReg = MI.getOperand(0).getReg();
-  // Check if any of the uses of the copy are invariant stores.
-  assert (TargetRegisterInfo::isVirtualRegister(CopyDstReg) &&
-          "copy dst is not a virtual reg");
-
-  for (MachineInstr &UseMI : MRI->use_instructions(CopyDstReg)) {
-    if (UseMI.mayStore() && isInvariantStore(UseMI, TRI, MRI))
-      return true;
-  }
-  return false;
-}
-
 /// Returns true if the instruction may be a suitable candidate for LICM.
 /// e.g. If the instruction is a call, then it's obviously not safe to hoist it.
 bool MachineLICMBase::IsLICMCandidate(MachineInstr &I) {
   // Check if it's safe to move the instruction.
   bool DontMoveAcrossStore = true;
-  if ((!I.isSafeToMove(AA, DontMoveAcrossStore)) &&
-      !(HoistConstStores && isInvariantStore(I, TRI, MRI))) {
+  if (!I.isSafeToMove(AA, DontMoveAcrossStore))
     return false;
-  }
 
   // If it is load then check if it is guaranteed to execute by making sure that
   // it dominates all exiting blocks. If it doesn't, then there is a path out of
@@ -1191,9 +1115,6 @@ bool MachineLICMBase::IsProfitableToHoist(MachineInstr &MI) {
   // - When hoisting the last use of a value in the loop, that value no longer
   //   needs to be live in the loop. This lowers register pressure in the loop.
 
-  if (HoistConstStores &&  isCopyFeedingInvariantStore(MI, MRI, TRI))
-    return true;
-
   bool CheapInstr = IsCheapInstruction(MI);
   bool CreatesCopy = HasLoopPHIUse(&MI);
 
diff --git a/llvm/lib/CodeGen/TargetRegisterInfo.cpp b/llvm/lib/CodeGen/TargetRegisterInfo.cpp
index 8b5cd3e73ac..5db1c58d349 100644
--- a/llvm/lib/CodeGen/TargetRegisterInfo.cpp
+++ b/llvm/lib/CodeGen/TargetRegisterInfo.cpp
@@ -472,29 +472,6 @@ unsigned TargetRegisterInfo::getRegSizeInBits(unsigned Reg,
   return getRegSizeInBits(*RC);
 }
 
-unsigned
-TargetRegisterInfo::lookThruCopyLike(unsigned SrcReg,
-                                     const MachineRegisterInfo *MRI) const {
-  while (true) {
-    const MachineInstr *MI = MRI->getVRegDef(SrcReg);
-    if (!MI->isCopyLike())
-      return SrcReg;
-
-    unsigned CopySrcReg;
-    if (MI->isCopy())
-      CopySrcReg = MI->getOperand(1).getReg();
-    else {
-      assert(MI->isSubregToReg() && "Bad opcode for lookThruCopyLike");
-      CopySrcReg = MI->getOperand(2).getReg();
-    }
-
-    if (!isVirtualRegister(CopySrcReg))
-      return CopySrcReg;
-
-    SrcReg = CopySrcReg;
-  }
-}
-
 #if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
 LLVM_DUMP_METHOD
 void TargetRegisterInfo::dumpReg(unsigned Reg, unsigned SubRegIndex,