Add the PPCCTRLoops pass: a PPC machine-code-level optimization pass to form CTR-based loop branching code.

This pass is derived from the Hexagon HardwareLoops pass. The only significant enhancement over the Hexagon
pass is that PPCCTRLoops will also attempt to delete the replaced add and compare operations if they are
no longer otherwise used. Also, invalid preheader DebugLoc is not used.

llvm-svn: 158204

1 files changed, 71 insertions, 6 deletions

diff --git a/llvm/lib/Target/PowerPC/PPCInstrInfo.cpp b/llvm/lib/Target/PowerPC/PPCInstrInfo.cpp
index c0b9e92c2d0..d6522822432 100644
--- a/llvm/lib/Target/PowerPC/PPCInstrInfo.cpp
+++ b/llvm/lib/Target/PowerPC/PPCInstrInfo.cpp
@@ -186,10 +186,14 @@ void PPCInstrInfo::insertNoop(MachineBasicBlock &MBB,
 
 
 // Branch analysis.
+// Note: If the condition register is set to CTR or CTR8 then this is a
+// BDNZ (imm == 1) or BDZ (imm == 0) branch.
 bool PPCInstrInfo::AnalyzeBranch(MachineBasicBlock &MBB,MachineBasicBlock *&TBB,
                                  MachineBasicBlock *&FBB,
                                  SmallVectorImpl<MachineOperand> &Cond,
                                  bool AllowModify) const {
+  bool isPPC64 = TM.getSubtargetImpl()->isPPC64();
+
   // If the block has no terminators, it just falls into the block after it.
   MachineBasicBlock::iterator I = MBB.end();
   if (I == MBB.begin())
@@ -221,7 +225,26 @@ bool PPCInstrInfo::AnalyzeBranch(MachineBasicBlock &MBB,MachineBasicBlock *&TBB,
       Cond.push_back(LastInst->getOperand(0));
       Cond.push_back(LastInst->getOperand(1));
       return false;
+    } else if (LastInst->getOpcode() == PPC::BDNZ8 ||
+               LastInst->getOpcode() == PPC::BDNZ) {
+      if (!LastInst->getOperand(0).isMBB())
+        return true;
+      TBB = LastInst->getOperand(0).getMBB();
+      Cond.push_back(MachineOperand::CreateImm(1));
+      Cond.push_back(MachineOperand::CreateReg(isPPC64 ? PPC::CTR8 : PPC::CTR,
+                                               true));
+      return false;
+    } else if (LastInst->getOpcode() == PPC::BDZ8 ||
+               LastInst->getOpcode() == PPC::BDZ) {
+      if (!LastInst->getOperand(0).isMBB())
+        return true;
+      TBB = LastInst->getOperand(0).getMBB();
+      Cond.push_back(MachineOperand::CreateImm(0));
+      Cond.push_back(MachineOperand::CreateReg(isPPC64 ? PPC::CTR8 : PPC::CTR,
+                                               true));
+      return false;
     }
+
     // Otherwise, don't know what this is.
     return true;
   }
@@ -245,6 +268,30 @@ bool PPCInstrInfo::AnalyzeBranch(MachineBasicBlock &MBB,MachineBasicBlock *&TBB,
     Cond.push_back(SecondLastInst->getOperand(1));
     FBB = LastInst->getOperand(0).getMBB();
     return false;
+  } else if ((SecondLastInst->getOpcode() == PPC::BDNZ8 ||
+              SecondLastInst->getOpcode() == PPC::BDNZ) &&
+      LastInst->getOpcode() == PPC::B) {
+    if (!SecondLastInst->getOperand(0).isMBB() ||
+        !LastInst->getOperand(0).isMBB())
+      return true;
+    TBB = SecondLastInst->getOperand(0).getMBB();
+    Cond.push_back(MachineOperand::CreateImm(1));
+    Cond.push_back(MachineOperand::CreateReg(isPPC64 ? PPC::CTR8 : PPC::CTR,
+                                             true));
+    FBB = LastInst->getOperand(0).getMBB();
+    return false;
+  } else if ((SecondLastInst->getOpcode() == PPC::BDZ8 ||
+              SecondLastInst->getOpcode() == PPC::BDZ) &&
+      LastInst->getOpcode() == PPC::B) {
+    if (!SecondLastInst->getOperand(0).isMBB() ||
+        !LastInst->getOperand(0).isMBB())
+      return true;
+    TBB = SecondLastInst->getOperand(0).getMBB();
+    Cond.push_back(MachineOperand::CreateImm(0));
+    Cond.push_back(MachineOperand::CreateReg(isPPC64 ? PPC::CTR8 : PPC::CTR,
+                                             true));
+    FBB = LastInst->getOperand(0).getMBB();
+    return false;
   }
 
   // If the block ends with two PPC:Bs, handle it.  The second one is not
@@ -273,7 +320,9 @@ unsigned PPCInstrInfo::RemoveBranch(MachineBasicBlock &MBB) const {
       return 0;
     --I;
   }
-  if (I->getOpcode() != PPC::B && I->getOpcode() != PPC::BCC)
+  if (I->getOpcode() != PPC::B && I->getOpcode() != PPC::BCC &&
+      I->getOpcode() != PPC::BDNZ8 && I->getOpcode() != PPC::BDNZ &&
+      I->getOpcode() != PPC::BDZ8  && I->getOpcode() != PPC::BDZ)
     return 0;
 
   // Remove the branch.
@@ -283,7 +332,9 @@ unsigned PPCInstrInfo::RemoveBranch(MachineBasicBlock &MBB) const {
 
   if (I == MBB.begin()) return 1;
   --I;
-  if (I->getOpcode() != PPC::BCC)
+  if (I->getOpcode() != PPC::BCC &&
+      I->getOpcode() != PPC::BDNZ8 && I->getOpcode() != PPC::BDNZ &&
+      I->getOpcode() != PPC::BDZ8  && I->getOpcode() != PPC::BDZ)
     return 1;
 
   // Remove the branch.
@@ -301,10 +352,16 @@ PPCInstrInfo::InsertBranch(MachineBasicBlock &MBB, MachineBasicBlock *TBB,
   assert((Cond.size() == 2 || Cond.size() == 0) &&
          "PPC branch conditions have two components!");
 
+  bool isPPC64 = TM.getSubtargetImpl()->isPPC64();
+
   // One-way branch.
   if (FBB == 0) {
     if (Cond.empty())   // Unconditional branch
       BuildMI(&MBB, DL, get(PPC::B)).addMBB(TBB);
+    else if (Cond[1].getReg() == PPC::CTR || Cond[1].getReg() == PPC::CTR8)
+      BuildMI(&MBB, DL, get(Cond[0].getImm() ?
+                              (isPPC64 ? PPC::BDNZ8 : PPC::BDNZ) :
+                              (isPPC64 ? PPC::BDZ8  : PPC::BDZ))).addMBB(TBB);
     else                // Conditional branch
       BuildMI(&MBB, DL, get(PPC::BCC))
         .addImm(Cond[0].getImm()).addReg(Cond[1].getReg()).addMBB(TBB);
@@ -312,8 +369,13 @@ PPCInstrInfo::InsertBranch(MachineBasicBlock &MBB, MachineBasicBlock *TBB,
   }
 
   // Two-way Conditional Branch.
-  BuildMI(&MBB, DL, get(PPC::BCC))
-    .addImm(Cond[0].getImm()).addReg(Cond[1].getReg()).addMBB(TBB);
+  if (Cond[1].getReg() == PPC::CTR || Cond[1].getReg() == PPC::CTR8)
+    BuildMI(&MBB, DL, get(Cond[0].getImm() ?
+                            (isPPC64 ? PPC::BDNZ8 : PPC::BDNZ) :
+                            (isPPC64 ? PPC::BDZ8  : PPC::BDZ))).addMBB(TBB);
+  else
+    BuildMI(&MBB, DL, get(PPC::BCC))
+      .addImm(Cond[0].getImm()).addReg(Cond[1].getReg()).addMBB(TBB);
   BuildMI(&MBB, DL, get(PPC::B)).addMBB(FBB);
   return 2;
 }
@@ -665,8 +727,11 @@ PPCInstrInfo::emitFrameIndexDebugValue(MachineFunction &MF,
 bool PPCInstrInfo::
 ReverseBranchCondition(SmallVectorImpl<MachineOperand> &Cond) const {
   assert(Cond.size() == 2 && "Invalid PPC branch opcode!");
-  // Leave the CR# the same, but invert the condition.
-  Cond[0].setImm(PPC::InvertPredicate((PPC::Predicate)Cond[0].getImm()));
+  if (Cond[1].getReg() == PPC::CTR8 || Cond[1].getReg() == PPC::CTR)
+    Cond[0].setImm(Cond[0].getImm() == 0 ? 1 : 0);
+  else
+    // Leave the CR# the same, but invert the condition.
+    Cond[0].setImm(PPC::InvertPredicate((PPC::Predicate)Cond[0].getImm()));
   return false;
 }