[llvm-commits] [llvm] r89530 - in /llvm/trunk: include/llvm/CodeGen/LiveVariables.h lib/CodeGen/LiveVariables.cpp lib/CodeGen/PHIElimination.cpp lib/CodeGen/PHIElimination.h
Jakob Stoklund Olesen
stoklund at 2pi.dk
Fri Nov 20 18:05:22 PST 2009
Author: stoklund
Date: Fri Nov 20 20:05:21 2009
New Revision: 89530
URL: http://llvm.org/viewvc/llvm-project?rev=89530&view=rev
Log:
Be more clever about calculating live variables through new basic blocks.
When splitting a critical edge, the registers live through the edge are:
- Used in a PHI instruction, or
- Live out from the predecessor, and
- Live in to the successor.
This allows the coalescer to eliminate even more phi joins.
Modified:
llvm/trunk/include/llvm/CodeGen/LiveVariables.h
llvm/trunk/lib/CodeGen/LiveVariables.cpp
llvm/trunk/lib/CodeGen/PHIElimination.cpp
llvm/trunk/lib/CodeGen/PHIElimination.h
Modified: llvm/trunk/include/llvm/CodeGen/LiveVariables.h
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/include/llvm/CodeGen/LiveVariables.h?rev=89530&r1=89529&r2=89530&view=diff
==============================================================================
--- llvm/trunk/include/llvm/CodeGen/LiveVariables.h (original)
+++ llvm/trunk/include/llvm/CodeGen/LiveVariables.h Fri Nov 20 20:05:21 2009
@@ -107,6 +107,13 @@
/// findKill - Find a kill instruction in MBB. Return NULL if none is found.
MachineInstr *findKill(const MachineBasicBlock *MBB) const;
+ /// isLiveIn - Is Reg live in to MBB? This means that Reg is live through
+ /// MBB, or it is killed in MBB. If Reg is only used by PHI instructions in
+ /// MBB, it is not considered live in.
+ bool isLiveIn(const MachineBasicBlock &MBB,
+ unsigned Reg,
+ MachineRegisterInfo &MRI);
+
void dump() const;
};
@@ -267,11 +274,17 @@
void HandleVirtRegUse(unsigned reg, MachineBasicBlock *MBB,
MachineInstr *MI);
- /// addNewBlock - Add a new basic block BB as an empty succcessor to
- /// DomBB. All variables that are live out of DomBB will be marked as passing
- /// live through BB. This method assumes that the machine code is still in SSA
- /// form.
- void addNewBlock(MachineBasicBlock *BB, MachineBasicBlock *DomBB);
+ bool isLiveIn(unsigned Reg, const MachineBasicBlock &MBB) {
+ return getVarInfo(Reg).isLiveIn(MBB, Reg, *MRI);
+ }
+
+ /// addNewBlock - Add a new basic block BB between DomBB and SuccBB. All
+ /// variables that are live out of DomBB and live into SuccBB will be marked
+ /// as passing live through BB. This method assumes that the machine code is
+ /// still in SSA form.
+ void addNewBlock(MachineBasicBlock *BB,
+ MachineBasicBlock *DomBB,
+ MachineBasicBlock *SuccBB);
};
} // End llvm namespace
Modified: llvm/trunk/lib/CodeGen/LiveVariables.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/CodeGen/LiveVariables.cpp?rev=89530&r1=89529&r2=89530&view=diff
==============================================================================
--- llvm/trunk/lib/CodeGen/LiveVariables.cpp (original)
+++ llvm/trunk/lib/CodeGen/LiveVariables.cpp Fri Nov 20 20:05:21 2009
@@ -656,35 +656,45 @@
.push_back(BBI->getOperand(i).getReg());
}
+bool LiveVariables::VarInfo::isLiveIn(const MachineBasicBlock &MBB,
+ unsigned Reg,
+ MachineRegisterInfo &MRI) {
+ unsigned Num = MBB.getNumber();
+
+ // Reg is live-through.
+ if (AliveBlocks.test(Num))
+ return true;
+
+ // Registers defined in MBB cannot be live in.
+ const MachineInstr *Def = MRI.getVRegDef(Reg);
+ if (Def && Def->getParent() == &MBB)
+ return false;
+
+ // Reg was not defined in MBB, was it killed here?
+ return findKill(&MBB);
+}
+
/// addNewBlock - Add a new basic block BB as an empty succcessor to DomBB. All
/// variables that are live out of DomBB will be marked as passing live through
/// BB.
void LiveVariables::addNewBlock(MachineBasicBlock *BB,
- MachineBasicBlock *DomBB) {
+ MachineBasicBlock *DomBB,
+ MachineBasicBlock *SuccBB) {
const unsigned NumNew = BB->getNumber();
- const unsigned NumDom = DomBB->getNumber();
+
+ // All registers used by PHI nodes in SuccBB must be live through BB.
+ for (MachineBasicBlock::const_iterator BBI = SuccBB->begin(),
+ BBE = SuccBB->end();
+ BBI != BBE && BBI->getOpcode() == TargetInstrInfo::PHI; ++BBI)
+ for (unsigned i = 1, e = BBI->getNumOperands(); i != e; i += 2)
+ if (BBI->getOperand(i+1).getMBB() == BB)
+ getVarInfo(BBI->getOperand(i).getReg()).AliveBlocks.set(NumNew);
// Update info for all live variables
for (unsigned Reg = TargetRegisterInfo::FirstVirtualRegister,
E = MRI->getLastVirtReg()+1; Reg != E; ++Reg) {
VarInfo &VI = getVarInfo(Reg);
-
- // Anything live through DomBB is also live through BB.
- if (VI.AliveBlocks.test(NumDom)) {
+ if (!VI.AliveBlocks.test(NumNew) && VI.isLiveIn(*SuccBB, Reg, *MRI))
VI.AliveBlocks.set(NumNew);
- continue;
- }
-
- // Variables not defined in DomBB cannot be live out.
- const MachineInstr *Def = MRI->getVRegDef(Reg);
- if (!Def || Def->getParent() != DomBB)
- continue;
-
- // Killed by DomBB?
- if (VI.findKill(DomBB))
- continue;
-
- // This register is defined in DomBB and live out
- VI.AliveBlocks.set(NumNew);
}
}
Modified: llvm/trunk/lib/CodeGen/PHIElimination.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/CodeGen/PHIElimination.cpp?rev=89530&r1=89529&r2=89530&view=diff
==============================================================================
--- llvm/trunk/lib/CodeGen/PHIElimination.cpp (original)
+++ llvm/trunk/lib/CodeGen/PHIElimination.cpp Fri Nov 20 20:05:21 2009
@@ -353,7 +353,7 @@
// We break edges when registers are live out from the predecessor block
// (not considering PHI nodes). If the register is live in to this block
// anyway, we would gain nothing from splitting.
- if (isLiveOut(Reg, *PreMBB, LV) && !isLiveIn(Reg, MBB, LV))
+ if (!LV.isLiveIn(Reg, MBB) && isLiveOut(Reg, *PreMBB, LV))
SplitCriticalEdge(PreMBB, &MBB);
}
}
@@ -406,22 +406,6 @@
return false;
}
-bool llvm::PHIElimination::isLiveIn(unsigned Reg, const MachineBasicBlock &MBB,
- LiveVariables &LV) {
- LiveVariables::VarInfo &VI = LV.getVarInfo(Reg);
-
- if (VI.AliveBlocks.test(MBB.getNumber()))
- return true;
-
- // defined in MBB?
- const MachineInstr *Def = MRI->getVRegDef(Reg);
- if (Def && Def->getParent() == &MBB)
- return false;
-
- // killed in MBB?
- return VI.findKill(&MBB);
-}
-
MachineBasicBlock *PHIElimination::SplitCriticalEdge(MachineBasicBlock *A,
MachineBasicBlock *B) {
assert(A && B && "Missing MBB end point");
@@ -463,7 +447,7 @@
i->getOperand(ni+1).setMBB(NMBB);
if (LiveVariables *LV=getAnalysisIfAvailable<LiveVariables>())
- LV->addNewBlock(NMBB, A);
+ LV->addNewBlock(NMBB, A, B);
if (MachineDominatorTree *MDT=getAnalysisIfAvailable<MachineDominatorTree>())
MDT->addNewBlock(NMBB, A);
Modified: llvm/trunk/lib/CodeGen/PHIElimination.h
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/CodeGen/PHIElimination.h?rev=89530&r1=89529&r2=89530&view=diff
==============================================================================
--- llvm/trunk/lib/CodeGen/PHIElimination.h (original)
+++ llvm/trunk/lib/CodeGen/PHIElimination.h Fri Nov 20 20:05:21 2009
@@ -99,12 +99,6 @@
bool isLiveOut(unsigned Reg, const MachineBasicBlock &MBB,
LiveVariables &LV);
- /// isLiveIn - Determine if Reg is live in to MBB, not considering PHI
- /// source registers. This means that Reg is either killed by MBB or passes
- /// through it.
- bool isLiveIn(unsigned Reg, const MachineBasicBlock &MBB,
- LiveVariables &LV);
-
/// SplitCriticalEdge - Split a critical edge from A to B by
/// inserting a new MBB. Update branches in A and PHI instructions
/// in B. Return the new block.
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