From 1e455c0f3bf789fe6db08fafd54dead214cfe396 Mon Sep 17 00:00:00 2001
From: Jakob Stoklund Olesen <stoklund@2pi.dk>
Date: Thu, 6 Aug 2009 21:19:03 +0000
Subject: [PATCH] Get rid of RegScavenger::backwards() before the bitrot
 spreads.

If we need it one day, there is nothing wrong with putting it back in.

llvm-svn: 78337
---
 .../include/llvm/CodeGen/RegisterScavenging.h | 11 +---
 llvm/lib/CodeGen/RegisterScavenging.cpp       | 64 -------------------
 2 files changed, 3 insertions(+), 72 deletions(-)

diff --git a/llvm/include/llvm/CodeGen/RegisterScavenging.h b/llvm/include/llvm/CodeGen/RegisterScavenging.h
index dbd9032c80b3..b0bcc6724ed0 100644
--- a/llvm/include/llvm/CodeGen/RegisterScavenging.h
+++ b/llvm/include/llvm/CodeGen/RegisterScavenging.h
@@ -90,20 +90,15 @@ public:
   /// passes over/within the same function.
   void initRegState();
 
-  /// forward / backward - Move the internal MBB iterator and update register
-  /// states.
+  /// forward - Move the internal MBB iterator and update register states.
   void forward();
-  void backward();
 
-  /// forward / backward - Move the internal MBB iterator and update register
-  /// states until it has processed the specific iterator.
+  /// forward - Move the internal MBB iterator and update register states until
+  /// it has processed the specific iterator.
   void forward(MachineBasicBlock::iterator I) {
     if (!Tracking && MBB->begin() != I) forward();
     while (MBBI != I) forward();
   }
-  void backward(MachineBasicBlock::iterator I) {
-    while (MBBI != I) backward();
-  }
 
   /// skipTo - Move the internal MBB iterator but do not update register states.
   ///
diff --git a/llvm/lib/CodeGen/RegisterScavenging.cpp b/llvm/lib/CodeGen/RegisterScavenging.cpp
index c3e03ab676e5..79ea579492cd 100644
--- a/llvm/lib/CodeGen/RegisterScavenging.cpp
+++ b/llvm/lib/CodeGen/RegisterScavenging.cpp
@@ -294,70 +294,6 @@ void RegScavenger::forward() {
   }
 }
 
-void RegScavenger::backward() {
-  assert(Tracking && "Not tracking states!");
-  assert(MBBI != MBB->begin() && "Already at start of basic block!");
-  // Move ptr backward.
-  MBBI = prior(MBBI);
-
-  MachineInstr *MI = MBBI;
-  DistanceMap.erase(MI);
-  --CurrDist;
-
-  // Separate register operands into 3 classes: uses, defs, earlyclobbers.
-  SmallVector<std::pair<const MachineOperand*,unsigned>, 4> UseMOs;
-  SmallVector<std::pair<const MachineOperand*,unsigned>, 4> DefMOs;
-  SmallVector<std::pair<const MachineOperand*,unsigned>, 4> EarlyClobberMOs;
-  for (unsigned i = 0, e = MI->getNumOperands(); i != e; ++i) {
-    const MachineOperand &MO = MI->getOperand(i);
-    if (!MO.isReg() || MO.getReg() == 0 || MO.isUndef())
-      continue;
-    if (MO.isUse())
-      UseMOs.push_back(std::make_pair(&MO,i));
-    else if (MO.isEarlyClobber())
-      EarlyClobberMOs.push_back(std::make_pair(&MO,i));
-    else
-      DefMOs.push_back(std::make_pair(&MO,i));
-  }
-
-
-  // Process defs first.
-  unsigned NumECs = EarlyClobberMOs.size();
-  unsigned NumDefs = DefMOs.size();
-  for (unsigned i = 0, e = NumECs + NumDefs; i != e; ++i) {
-    const MachineOperand &MO = (i < NumDefs)
-      ? *DefMOs[i].first : *EarlyClobberMOs[i-NumDefs].first;
-    unsigned Idx = (i < NumECs)
-      ? DefMOs[i].second : EarlyClobberMOs[i-NumDefs].second;
-    if (MO.isUndef())
-      continue;
-
-    // Skip two-address destination operand.
-    if (MI->isRegTiedToUseOperand(Idx))
-      continue;
-
-    unsigned Reg = MO.getReg();
-    assert(isUsed(Reg));
-    if (!isReserved(Reg))
-      setUnused(Reg, MI);
-  }
-
-  // Process uses.
-  BitVector UseRegs(NumPhysRegs);
-  for (unsigned i = 0, e = UseMOs.size(); i != e; ++i) {
-    const MachineOperand MO = *UseMOs[i].first;
-    unsigned Reg = MO.getReg();
-    assert(isUnused(Reg) || isReserved(Reg));
-    UseRegs.set(Reg);
-
-    // Set the sub-registers as "used".
-    for (const unsigned *SubRegs = TRI->getSubRegisters(Reg);
-         unsigned SubReg = *SubRegs; ++SubRegs)
-      UseRegs.set(SubReg);
-  }
-  setUsed(UseRegs);
-}
-
 void RegScavenger::getRegsUsed(BitVector &used, bool includeReserved) {
   if (includeReserved)
     used = ~RegsAvailable;