Implement branch analysis in the MBlaze backend.

llvm-svn: 119951

lib/Target/MBlaze/MBlazeInstrInfo.cpp

@@ -107,17 +107,134 @@ loadRegFromStackSlot(MachineBasicBlock &MBB, MachineBasicBlock::iterator I,
 //===----------------------------------------------------------------------===//
 // Branch Analysis
 //===----------------------------------------------------------------------===//
+bool MBlazeInstrInfo::AnalyzeBranch(MachineBasicBlock &MBB,
+                                    MachineBasicBlock *&TBB,
+                                    MachineBasicBlock *&FBB,
+                                    SmallVectorImpl<MachineOperand> &Cond,
+                                    bool AllowModify) const {
+  // If the block has no terminators, it just falls into the block after it.
+  MachineBasicBlock::iterator I = MBB.end();
+  if (I == MBB.begin())
+    return false;
+  --I;
+  while (I->isDebugValue()) {
+    if (I == MBB.begin())
+      return false;
+    --I;
+  }
+  if (!isUnpredicatedTerminator(I))
+    return false;
+
+  // Get the last instruction in the block.
+  MachineInstr *LastInst = I;
+
+  // If there is only one terminator instruction, process it.
+  unsigned LastOpc = LastInst->getOpcode();
+  if (I == MBB.begin() || !isUnpredicatedTerminator(--I)) {
+    if (MBlaze::isUncondBranchOpcode(LastOpc)) {
+      TBB = LastInst->getOperand(0).getMBB();
+      return false;
+    }
+    if (MBlaze::isCondBranchOpcode(LastOpc)) {
+      // Block ends with fall-through condbranch.
+      TBB = LastInst->getOperand(1).getMBB();
+      Cond.push_back(MachineOperand::CreateImm(LastInst->getOpcode()));
+      Cond.push_back(LastInst->getOperand(0));
+      return false;
+    }
+    // Otherwise, don't know what this is.
+    return true;
+  }
+
+  // Get the instruction before it if it's a terminator.
+  MachineInstr *SecondLastInst = I;
+
+  // If there are three terminators, we don't know what sort of block this is.
+  if (SecondLastInst && I != MBB.begin() && isUnpredicatedTerminator(--I))
+    return true;
+
+  // If the block ends with something like BEQID then BRID, handle it.
+  if (MBlaze::isCondBranchOpcode(SecondLastInst->getOpcode()) &&
+      MBlaze::isUncondBranchOpcode(LastInst->getOpcode())) {
+    TBB = SecondLastInst->getOperand(1).getMBB();
+    Cond.push_back(MachineOperand::CreateImm(SecondLastInst->getOpcode()));
+    Cond.push_back(SecondLastInst->getOperand(0));
+    FBB = LastInst->getOperand(0).getMBB();
+    return false;
+  }
+
+  // If the block ends with two unconditional branches, handle it.
+  // The second one is not executed, so remove it.
+  if (MBlaze::isUncondBranchOpcode(SecondLastInst->getOpcode()) &&
+      MBlaze::isUncondBranchOpcode(LastInst->getOpcode())) {
+    TBB = SecondLastInst->getOperand(0).getMBB();
+    I = LastInst;
+    if (AllowModify)
+      I->eraseFromParent();
+    return false;
+  }
+
+  // Otherwise, can't handle this.
+  return true;
+}
+
 unsigned MBlazeInstrInfo::
 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(MBlaze::BRI)).addMBB(TBB);
-  return 1;
+  // Shouldn't be a fall through.
+  assert(TBB && "InsertBranch must not be told to insert a fallthrough");
+  assert((Cond.size() == 2 || Cond.size() == 0) &&
+         "MBlaze branch conditions have two components!");
+
+  unsigned Opc = MBlaze::BRID;
+  if (!Cond.empty())
+    Opc = (unsigned)Cond[0].getImm();
+
+  if (FBB == 0) {
+    if (Cond.empty()) // Unconditional branch
+      BuildMI(&MBB, DL, get(Opc)).addMBB(TBB);
+    else              // Conditional branch
+      BuildMI(&MBB, DL, get(Opc)).addReg(Cond[1].getReg()).addMBB(TBB);
+    return 1;
+  }
+
+  BuildMI(&MBB, DL, get(Opc)).addReg(Cond[1].getReg()).addMBB(TBB);
+  BuildMI(&MBB, DL, get(MBlaze::BRID)).addMBB(FBB);
+  return 2;
 }
 
+unsigned MBlazeInstrInfo::RemoveBranch(MachineBasicBlock &MBB) const {
+  MachineBasicBlock::iterator I = MBB.end();
+  if (I == MBB.begin()) return 0;
+  --I;
+  while (I->isDebugValue()) {
+    if (I == MBB.begin())
+      return 0;
+    --I;
+  }
+
+  if (!MBlaze::isUncondBranchOpcode(I->getOpcode()) &&
+      !MBlaze::isCondBranchOpcode(I->getOpcode()))
+    return 0;
+
+  // Remove the branch.
+  I->eraseFromParent();
+
+  I = MBB.end();
+
+  if (I == MBB.begin()) return 1;
+  --I;
+  if (!MBlaze::isCondBranchOpcode(I->getOpcode()))
+    return 1;
+
+  // Remove the branch.
+  I->eraseFromParent();
+  return 2;
+}
+
+
 /// getGlobalBaseReg - Return a virtual register initialized with the
 /// the global base register value. Output instructions required to
 /// initialize the register in the function entry block, if necessary.

lib/Target/MBlaze/MBlazeInstrInfo.h

@@ -73,59 +73,92 @@ namespace MBlaze {
     FCOND_GT,
 
     // Only integer conditions
-    COND_E,
-    COND_GZ,
-    COND_GEZ,
-    COND_LZ,
-    COND_LEZ,
+    COND_EQ,
+    COND_GT,
+    COND_GE,
+    COND_LT,
+    COND_LE,
     COND_NE,
     COND_INVALID
   };
 
   // Turn condition code into conditional branch opcode.
-  unsigned GetCondBranchFromCond(CondCode CC);
+  inline static unsigned GetCondBranchFromCond(CondCode CC) {
+    switch (CC) {
+    default: llvm_unreachable("Unknown condition code");
+    case COND_EQ: return MBlaze::BEQID;
+    case COND_NE: return MBlaze::BNEID;
+    case COND_GT: return MBlaze::BGTID;
+    case COND_GE: return MBlaze::BGEID;
+    case COND_LT: return MBlaze::BLTID;
+    case COND_LE: return MBlaze::BLEID;
+    }
+  }
 
   /// GetOppositeBranchCondition - Return the inverse of the specified cond,
   /// e.g. turning COND_E to COND_NE.
-  CondCode GetOppositeBranchCondition(MBlaze::CondCode CC);
+  // CondCode GetOppositeBranchCondition(MBlaze::CondCode CC);
 
   /// MBlazeCCToString - Map each FP condition code to its string
-  inline static const char *MBlazeFCCToString(MBlaze::CondCode CC)
-  {
+  inline static const char *MBlazeFCCToString(MBlaze::CondCode CC) {
     switch (CC) {
-      default: llvm_unreachable("Unknown condition code");
-      case FCOND_F:
-      case FCOND_T:   return "f";
-      case FCOND_UN:
-      case FCOND_OR:  return "un";
-      case FCOND_EQ:
-      case FCOND_NEQ: return "eq";
-      case FCOND_UEQ:
-      case FCOND_OGL: return "ueq";
-      case FCOND_OLT:
-      case FCOND_UGE: return "olt";
-      case FCOND_ULT:
-      case FCOND_OGE: return "ult";
-      case FCOND_OLE:
-      case FCOND_UGT: return "ole";
-      case FCOND_ULE:
-      case FCOND_OGT: return "ule";
-      case FCOND_SF:
-      case FCOND_ST:  return "sf";
-      case FCOND_NGLE:
-      case FCOND_GLE: return "ngle";
-      case FCOND_SEQ:
-      case FCOND_SNE: return "seq";
-      case FCOND_NGL:
-      case FCOND_GL:  return "ngl";
-      case FCOND_LT:
-      case FCOND_NLT: return "lt";
-      case FCOND_NGE:
-      case FCOND_GE:  return "ge";
-      case FCOND_LE:
-      case FCOND_NLE: return "nle";
-      case FCOND_NGT:
-      case FCOND_GT:  return "gt";
+    default: llvm_unreachable("Unknown condition code");
+    case FCOND_F:
+    case FCOND_T:   return "f";
+    case FCOND_UN:
+    case FCOND_OR:  return "un";
+    case FCOND_EQ:
+    case FCOND_NEQ: return "eq";
+    case FCOND_UEQ:
+    case FCOND_OGL: return "ueq";
+    case FCOND_OLT:
+    case FCOND_UGE: return "olt";
+    case FCOND_ULT:
+    case FCOND_OGE: return "ult";
+    case FCOND_OLE:
+    case FCOND_UGT: return "ole";
+    case FCOND_ULE:
+    case FCOND_OGT: return "ule";
+    case FCOND_SF:
+    case FCOND_ST:  return "sf";
+    case FCOND_NGLE:
+    case FCOND_GLE: return "ngle";
+    case FCOND_SEQ:
+    case FCOND_SNE: return "seq";
+    case FCOND_NGL:
+    case FCOND_GL:  return "ngl";
+    case FCOND_LT:
+    case FCOND_NLT: return "lt";
+    case FCOND_NGE:
+    case FCOND_GE:  return "ge";
+    case FCOND_LE:
+    case FCOND_NLE: return "nle";
+    case FCOND_NGT:
+    case FCOND_GT:  return "gt";
+    }
+  }
+
+  inline static bool isUncondBranchOpcode(int Opc) {
+    switch (Opc) {
+    default: return false;
+    case MBlaze::BRI:
+    case MBlaze::BRAI:
+    case MBlaze::BRID:
+    case MBlaze::BRAID:
+      return true;
+    }
+  }
+
+  inline static bool isCondBranchOpcode(int Opc) {
+    switch (Opc) {
+    default: return false;
+    case MBlaze::BEQI: case MBlaze::BEQID:
+    case MBlaze::BNEI: case MBlaze::BNEID:
+    case MBlaze::BGTI: case MBlaze::BGTID:
+    case MBlaze::BGEI: case MBlaze::BGEID:
+    case MBlaze::BLTI: case MBlaze::BLTID:
+    case MBlaze::BLEI: case MBlaze::BLEID:
+      return true;
     }
   }
 }
@@ -215,10 +248,15 @@ public:
                                       int &FrameIndex) const;
 
   /// Branch Analysis
+  virtual bool AnalyzeBranch(MachineBasicBlock &MBB, MachineBasicBlock *&TBB,
+                             MachineBasicBlock *&FBB,
+                             SmallVectorImpl<MachineOperand> &Cond,
+                             bool AllowModify) const;
   virtual unsigned InsertBranch(MachineBasicBlock &MBB, MachineBasicBlock *TBB,
                                 MachineBasicBlock *FBB,
                                 const SmallVectorImpl<MachineOperand> &Cond,
                                 DebugLoc DL) const;
+  virtual unsigned RemoveBranch(MachineBasicBlock &MBB) const;
   virtual void copyPhysReg(MachineBasicBlock &MBB,
                            MachineBasicBlock::iterator I, DebugLoc DL,
                            unsigned DestReg, unsigned SrcReg,

test/CodeGen/MBlaze/brind.ll

@@ -68,5 +68,5 @@ finish:
     %tmp.8 = urem i32 %tmp.7, 5
 
     br label %loop
-    ; CHECK:        brid
+    ; CHECK:        brd
 }