Implement AnalyzeBranch in Sparc Backend.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@123561 91177308-0d34-0410-b5e6-96231b3b80d8

2 files changed, 199 insertions, 7 deletions

diff --git a/lib/Target/Sparc/SparcInstrInfo.cpp b/lib/Target/Sparc/SparcInstrInfo.cpp
index 7ede8e7..afa3c1f 100644
--- a/lib/Target/Sparc/SparcInstrInfo.cpp
+++ b/lib/Target/Sparc/SparcInstrInfo.cpp
@@ -66,15 +66,200 @@ unsigned SparcInstrInfo::isStoreToStackSlot(const MachineInstr *MI,
   return 0;
 }
 
+static bool IsIntegerCC(unsigned CC)
+{
+  return  (CC <= SPCC::ICC_VC);
+}
+
+
+static SPCC::CondCodes GetOppositeBranchCondition(SPCC::CondCodes CC)
+{
+  switch(CC) {
+  default: llvm_unreachable("Unknown condition code");
+  case SPCC::ICC_NE:   return SPCC::ICC_E;
+  case SPCC::ICC_E:    return SPCC::ICC_NE;
+  case SPCC::ICC_G:    return SPCC::ICC_LE;
+  case SPCC::ICC_LE:   return SPCC::ICC_G;
+  case SPCC::ICC_GE:   return SPCC::ICC_L;
+  case SPCC::ICC_L:    return SPCC::ICC_GE;
+  case SPCC::ICC_GU:   return SPCC::ICC_LEU;
+  case SPCC::ICC_LEU:  return SPCC::ICC_GU;
+  case SPCC::ICC_CC:   return SPCC::ICC_CS;
+  case SPCC::ICC_CS:   return SPCC::ICC_CC;
+  case SPCC::ICC_POS:  return SPCC::ICC_NEG;
+  case SPCC::ICC_NEG:  return SPCC::ICC_POS;
+  case SPCC::ICC_VC:   return SPCC::ICC_VS;
+  case SPCC::ICC_VS:   return SPCC::ICC_VC;
+
+  case SPCC::FCC_U:    return SPCC::FCC_O;
+  case SPCC::FCC_O:    return SPCC::FCC_U;
+  case SPCC::FCC_G:    return SPCC::FCC_LE;
+  case SPCC::FCC_LE:   return SPCC::FCC_G;
+  case SPCC::FCC_UG:   return SPCC::FCC_ULE;
+  case SPCC::FCC_ULE:  return SPCC::FCC_UG;
+  case SPCC::FCC_L:    return SPCC::FCC_GE;
+  case SPCC::FCC_GE:   return SPCC::FCC_L;
+  case SPCC::FCC_UL:   return SPCC::FCC_UGE;
+  case SPCC::FCC_UGE:  return SPCC::FCC_UL;
+  case SPCC::FCC_LG:   return SPCC::FCC_UE;
+  case SPCC::FCC_UE:   return SPCC::FCC_LG;
+  case SPCC::FCC_NE:   return SPCC::FCC_E;
+  case SPCC::FCC_E:    return SPCC::FCC_NE;
+  }
+}
+
+
+bool SparcInstrInfo::AnalyzeBranch(MachineBasicBlock &MBB,
+                                   MachineBasicBlock *&TBB,
+                                   MachineBasicBlock *&FBB,
+                                   SmallVectorImpl<MachineOperand> &Cond,
+                                   bool AllowModify) const
+{
+
+  MachineBasicBlock::iterator I = MBB.end();
+  MachineBasicBlock::iterator UnCondBrIter = MBB.end();
+  while (I != MBB.begin()) {
+    --I;
+
+    if (I->isDebugValue())
+      continue;
+
+    //When we see a non-terminator, we are done
+    if (!isUnpredicatedTerminator(I))
+      break;
+
+    //Terminator is not a branch
+    if (!I->getDesc().isBranch())
+      return true;
+
+    //Handle Unconditional branches
+    if (I->getOpcode() == SP::BA) {
+      UnCondBrIter = I;
+
+      if (!AllowModify) {
+        TBB = I->getOperand(0).getMBB();
+        continue;
+      }
+
+      while (llvm::next(I) != MBB.end())
+        llvm::next(I)->eraseFromParent();
+
+      Cond.clear();
+      FBB = 0;
+
+      if (MBB.isLayoutSuccessor(I->getOperand(0).getMBB())) {
+        TBB = 0;
+        I->eraseFromParent();
+        I = MBB.end();
+        UnCondBrIter = MBB.end();
+        continue;
+      }
+
+      TBB = I->getOperand(0).getMBB();
+      continue;
+    }
+
+    unsigned Opcode = I->getOpcode();
+    if (Opcode != SP::BCOND && Opcode != SP::FBCOND)
+      return true; //Unknown Opcode
+
+    SPCC::CondCodes BranchCode = (SPCC::CondCodes)I->getOperand(1).getImm();
+
+    if (Cond.empty()) {
+      MachineBasicBlock *TargetBB = I->getOperand(0).getMBB();
+      if (AllowModify && UnCondBrIter != MBB.end() &&
+          MBB.isLayoutSuccessor(TargetBB)) {
+
+        //Transform the code
+        //
+        //    brCC L1
+        //    ba L2
+        // L1:
+        //    ..
+        // L2:
+        //
+        // into
+        //
+        //   brnCC L2
+        // L1:
+        //   ...
+        // L2:
+        //
+        BranchCode = GetOppositeBranchCondition(BranchCode);
+        MachineBasicBlock::iterator OldInst = I;
+        BuildMI(MBB, UnCondBrIter, MBB.findDebugLoc(I), get(Opcode))
+          .addMBB(UnCondBrIter->getOperand(0).getMBB()).addImm(BranchCode);
+        BuildMI(MBB, UnCondBrIter, MBB.findDebugLoc(I), get(SP::BA))
+          .addMBB(TargetBB);
+        MBB.addSuccessor(TargetBB);
+        OldInst->eraseFromParent();
+        UnCondBrIter->eraseFromParent();
+
+        UnCondBrIter = MBB.end();
+        I = MBB.end();
+        continue;
+      }
+      FBB = TBB;
+      TBB = I->getOperand(0).getMBB();
+      Cond.push_back(MachineOperand::CreateImm(BranchCode));
+      continue;
+    }
+    //FIXME: Handle subsequent conditional branches
+    //For now, we can't handle multiple conditional branches
+    return true;
+  }
+  return false;
+}
+
 unsigned
 SparcInstrInfo::InsertBranch(MachineBasicBlock &MBB,MachineBasicBlock *TBB,
                              MachineBasicBlock *FBB,
                              const SmallVectorImpl<MachineOperand> &Cond,
-                             DebugLoc DL)const{
-  // Can only insert uncond branches so far.
-  assert(Cond.empty() && !FBB && TBB && "Can only handle uncond branches!");
-  BuildMI(&MBB, DL, get(SP::BA)).addMBB(TBB);
-  return 1;
+                             DebugLoc DL) const {
+  assert(TBB && "InsertBranch must not be told to insert a fallthrough");
+  assert((Cond.size() == 1 || Cond.size() == 0) &&
+         "Sparc branch conditions should have one component!");
+
+  if (Cond.empty()) {
+    assert(!FBB && "Unconditional branch with multiple successors!");
+    BuildMI(&MBB, DL, get(SP::BA)).addMBB(TBB);
+    return 1;
+  }
+
+  //Conditional branch
+  unsigned CC = Cond[0].getImm();
+
+  if (IsIntegerCC(CC))
+    BuildMI(&MBB, DL, get(SP::BCOND)).addMBB(TBB).addImm(CC);
+  else
+    BuildMI(&MBB, DL, get(SP::FBCOND)).addMBB(TBB).addImm(CC);
+  if (!FBB)
+    return 1;
+
+  BuildMI(&MBB, DL, get(SP::BA)).addMBB(FBB);
+  return 2;
+}
+
+unsigned SparcInstrInfo::RemoveBranch(MachineBasicBlock &MBB) const
+{
+  MachineBasicBlock::iterator I = MBB.end();
+  unsigned Count = 0;
+  while (I != MBB.begin()) {
+    --I;
+
+    if (I->isDebugValue())
+      continue;
+
+    if (I->getOpcode() != SP::BA
+        && I->getOpcode() != SP::BCOND
+        && I->getOpcode() != SP::FBCOND)
+      break; // Not a branch
+
+    I->eraseFromParent();
+    I = MBB.end();
+    ++Count;
+  }
+  return Count;
 }
 
 void SparcInstrInfo::copyPhysReg(MachineBasicBlock &MBB,
diff --git a/lib/Target/Sparc/SparcInstrInfo.h b/lib/Target/Sparc/SparcInstrInfo.h
index c00bd21..b2d24f5 100644
--- a/lib/Target/Sparc/SparcInstrInfo.h
+++ b/lib/Target/Sparc/SparcInstrInfo.h
@@ -58,8 +58,15 @@ public:
   /// any side effects other than storing to the stack slot.
   virtual unsigned isStoreToStackSlot(const MachineInstr *MI,
                                       int &FrameIndex) const;
-  
-  
+
+
+  virtual bool AnalyzeBranch(MachineBasicBlock &MBB, MachineBasicBlock *&TBB,
+                             MachineBasicBlock *&FBB,
+                             SmallVectorImpl<MachineOperand> &Cond,
+                             bool AllowModify = false) const ;
+
+  virtual unsigned RemoveBranch(MachineBasicBlock &MBB) const;
+
   virtual unsigned InsertBranch(MachineBasicBlock &MBB, MachineBasicBlock *TBB,
                                 MachineBasicBlock *FBB,
                                 const SmallVectorImpl<MachineOperand> &Cond,