[llvm-commits] [llvm] r84774 - in /llvm/trunk/lib/Target/MSP430: MSP430InstrInfo.cpp MSP430InstrInfo.h README.txt
Anton Korobeynikov
asl at math.spbu.ru
Wed Oct 21 12:17:18 PDT 2009
Author: asl
Date: Wed Oct 21 14:17:18 2009
New Revision: 84774
URL: http://llvm.org/viewvc/llvm-project?rev=84774&view=rev
Log:
Implement branch folding
Modified:
llvm/trunk/lib/Target/MSP430/MSP430InstrInfo.cpp
llvm/trunk/lib/Target/MSP430/MSP430InstrInfo.h
llvm/trunk/lib/Target/MSP430/README.txt
Modified: llvm/trunk/lib/Target/MSP430/MSP430InstrInfo.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Target/MSP430/MSP430InstrInfo.cpp?rev=84774&r1=84773&r2=84774&view=diff
==============================================================================
--- llvm/trunk/lib/Target/MSP430/MSP430InstrInfo.cpp (original)
+++ llvm/trunk/lib/Target/MSP430/MSP430InstrInfo.cpp Wed Oct 21 14:17:18 2009
@@ -151,6 +151,164 @@
return true;
}
+unsigned MSP430InstrInfo::RemoveBranch(MachineBasicBlock &MBB) const {
+ MachineBasicBlock::iterator I = MBB.end();
+ unsigned Count = 0;
+
+ while (I != MBB.begin()) {
+ --I;
+ if (I->getOpcode() != MSP430::JMP &&
+ I->getOpcode() != MSP430::JCC)
+ break;
+ // Remove the branch.
+ I->eraseFromParent();
+ I = MBB.end();
+ ++Count;
+ }
+
+ return Count;
+}
+
+
+bool MSP430InstrInfo::
+ReverseBranchCondition(SmallVectorImpl<MachineOperand> &Cond) const {
+ assert(Cond.size() == 1 && "Invalid Xbranch condition!");
+
+ MSP430CC::CondCodes CC = static_cast<MSP430CC::CondCodes>(Cond[0].getImm());
+
+ switch (CC) {
+ default:
+ assert(0 && "Invalid branch condition!");
+ break;
+ case MSP430CC::COND_E:
+ CC = MSP430CC::COND_NE;
+ break;
+ case MSP430CC::COND_NE:
+ CC = MSP430CC::COND_E;
+ break;
+ case MSP430CC::COND_L:
+ CC = MSP430CC::COND_GE;
+ break;
+ case MSP430CC::COND_GE:
+ CC = MSP430CC::COND_L;
+ break;
+ case MSP430CC::COND_HS:
+ CC = MSP430CC::COND_LO;
+ break;
+ case MSP430CC::COND_LO:
+ CC = MSP430CC::COND_HS;
+ break;
+ }
+
+ Cond[0].setImm(CC);
+ return false;
+}
+
+bool MSP430InstrInfo::BlockHasNoFallThrough(const MachineBasicBlock &MBB)const{
+ if (MBB.empty()) return false;
+
+ switch (MBB.back().getOpcode()) {
+ case MSP430::RET: // Return.
+ case MSP430::JMP: // Uncond branch.
+ return true;
+ default: return false;
+ }
+}
+
+bool MSP430InstrInfo::isUnpredicatedTerminator(const MachineInstr *MI) const {
+ const TargetInstrDesc &TID = MI->getDesc();
+ if (!TID.isTerminator()) return false;
+
+ // Conditional branch is a special case.
+ if (TID.isBranch() && !TID.isBarrier())
+ return true;
+ if (!TID.isPredicable())
+ return true;
+ return !isPredicated(MI);
+}
+
+bool MSP430InstrInfo::AnalyzeBranch(MachineBasicBlock &MBB,
+ MachineBasicBlock *&TBB,
+ MachineBasicBlock *&FBB,
+ SmallVectorImpl<MachineOperand> &Cond,
+ bool AllowModify) const {
+ // Start from the bottom of the block and work up, examining the
+ // terminator instructions.
+ MachineBasicBlock::iterator I = MBB.end();
+ while (I != MBB.begin()) {
+ --I;
+ // Working from the bottom, when we see a non-terminator
+ // instruction, we're done.
+ if (!isUnpredicatedTerminator(I))
+ break;
+
+ // A terminator that isn't a branch can't easily be handled
+ // by this analysis.
+ if (!I->getDesc().isBranch())
+ return true;
+
+ // Handle unconditional branches.
+ if (I->getOpcode() == MSP430::JMP) {
+ if (!AllowModify) {
+ TBB = I->getOperand(0).getMBB();
+ continue;
+ }
+
+ // If the block has any instructions after a JMP, delete them.
+ while (next(I) != MBB.end())
+ next(I)->eraseFromParent();
+ Cond.clear();
+ FBB = 0;
+
+ // Delete the JMP if it's equivalent to a fall-through.
+ if (MBB.isLayoutSuccessor(I->getOperand(0).getMBB())) {
+ TBB = 0;
+ I->eraseFromParent();
+ I = MBB.end();
+ continue;
+ }
+
+ // TBB is used to indicate the unconditinal destination.
+ TBB = I->getOperand(0).getMBB();
+ continue;
+ }
+
+ // Handle conditional branches.
+ assert(I->getOpcode() == MSP430::JCC && "Invalid conditional branch");
+ MSP430CC::CondCodes BranchCode =
+ static_cast<MSP430CC::CondCodes>(I->getOperand(1).getImm());
+ if (BranchCode == MSP430CC::COND_INVALID)
+ return true; // Can't handle weird stuff.
+
+ // Working from the bottom, handle the first conditional branch.
+ if (Cond.empty()) {
+ FBB = TBB;
+ TBB = I->getOperand(0).getMBB();
+ Cond.push_back(MachineOperand::CreateImm(BranchCode));
+ continue;
+ }
+
+ // Handle subsequent conditional branches. Only handle the case where all
+ // conditional branches branch to the same destination.
+ assert(Cond.size() == 1);
+ assert(TBB);
+
+ // Only handle the case where all conditional branches branch to
+ // the same destination.
+ if (TBB != I->getOperand(0).getMBB())
+ return true;
+
+ MSP430CC::CondCodes OldBranchCode = (MSP430CC::CondCodes)Cond[0].getImm();
+ // If the conditions are the same, we can leave them alone.
+ if (OldBranchCode == BranchCode)
+ continue;
+
+ return true;
+ }
+
+ return false;
+}
+
unsigned
MSP430InstrInfo::InsertBranch(MachineBasicBlock &MBB, MachineBasicBlock *TBB,
MachineBasicBlock *FBB,
@@ -172,7 +330,13 @@
// Conditional branch.
unsigned Count = 0;
- llvm_unreachable("Implement conditional branches!");
+ BuildMI(&MBB, dl, get(MSP430::JCC)).addMBB(TBB).addImm(Cond[0].getImm());
+ ++Count;
+ if (FBB) {
+ // Two-way Conditional branch. Insert the second branch.
+ BuildMI(&MBB, dl, get(MSP430::JMP)).addMBB(FBB);
+ ++Count;
+ }
return Count;
}
Modified: llvm/trunk/lib/Target/MSP430/MSP430InstrInfo.h
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Target/MSP430/MSP430InstrInfo.h?rev=84774&r1=84773&r2=84774&view=diff
==============================================================================
--- llvm/trunk/lib/Target/MSP430/MSP430InstrInfo.h (original)
+++ llvm/trunk/lib/Target/MSP430/MSP430InstrInfo.h Wed Oct 21 14:17:18 2009
@@ -59,9 +59,19 @@
MachineBasicBlock::iterator MI,
const std::vector<CalleeSavedInfo> &CSI) const;
- virtual unsigned InsertBranch(MachineBasicBlock &MBB, MachineBasicBlock *TBB,
- MachineBasicBlock *FBB,
- const SmallVectorImpl<MachineOperand> &Cond) const;
+ // Branch folding goodness
+ bool ReverseBranchCondition(SmallVectorImpl<MachineOperand> &Cond) const;
+ bool BlockHasNoFallThrough(const MachineBasicBlock &MBB) const;
+ bool isUnpredicatedTerminator(const MachineInstr *MI) const;
+ bool AnalyzeBranch(MachineBasicBlock &MBB,
+ MachineBasicBlock *&TBB, MachineBasicBlock *&FBB,
+ SmallVectorImpl<MachineOperand> &Cond,
+ bool AllowModify) const;
+
+ unsigned RemoveBranch(MachineBasicBlock &MBB) const;
+ unsigned InsertBranch(MachineBasicBlock &MBB, MachineBasicBlock *TBB,
+ MachineBasicBlock *FBB,
+ const SmallVectorImpl<MachineOperand> &Cond) const;
};
Modified: llvm/trunk/lib/Target/MSP430/README.txt
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Target/MSP430/README.txt?rev=84774&r1=84773&r2=84774&view=diff
==============================================================================
--- llvm/trunk/lib/Target/MSP430/README.txt (original)
+++ llvm/trunk/lib/Target/MSP430/README.txt Wed Oct 21 14:17:18 2009
@@ -40,5 +40,3 @@
10. Handle imm in comparisons in better way (see comment in MSP430InstrInfo.td)
11. Implement hooks for better memory op folding, etc.
-
-12. Implement branch folding.
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