diff options
Diffstat (limited to 'lib/CodeGen/InlineSpiller.cpp')
| -rw-r--r-- | lib/CodeGen/InlineSpiller.cpp | 31 |
1 files changed, 28 insertions, 3 deletions
diff --git a/lib/CodeGen/InlineSpiller.cpp b/lib/CodeGen/InlineSpiller.cpp index 4bd35c3812..44e87ae972 100644 --- a/lib/CodeGen/InlineSpiller.cpp +++ b/lib/CodeGen/InlineSpiller.cpp @@ -303,7 +303,8 @@ MachineInstr *InlineSpiller::traceSiblingValue(unsigned UseReg, VNInfo *UseVNI, // Best spill candidate seen so far. This must dominate UseVNI. SibValueInfo SVI(UseReg, UseVNI); MachineBasicBlock *UseMBB = LIS.getMBBFromIndex(UseVNI->def); - unsigned SpillDepth = Loops.getLoopDepth(UseMBB); + MachineBasicBlock *SpillMBB = UseMBB; + unsigned SpillDepth = Loops.getLoopDepth(SpillMBB); bool SeenOrigPHI = false; // Original PHI met. do { @@ -316,15 +317,39 @@ MachineInstr *InlineSpiller::traceSiblingValue(unsigned UseReg, VNInfo *UseVNI, // Is this value a better spill candidate? if (!isRegToSpill(Reg)) { MachineBasicBlock *MBB = LIS.getMBBFromIndex(VNI->def); - if (MBB != UseMBB && MDT.dominates(MBB, UseMBB)) { + if (MBB == SpillMBB) { + // This is an alternative def earlier in the same MBB. + // Hoist the spill as far as possible in SpillMBB. This can ease + // register pressure: + // + // x = def + // y = use x + // s = copy x + // + // Hoisting the spill of s to immediately after the def removes the + // interference between x and y: + // + // x = def + // spill x + // y = use x<kill> + // + if (VNI->def < SVI.SpillVNI->def) { + DEBUG(dbgs() << " hoist in BB#" << MBB->getNumber() << ": " + << PrintReg(Reg) << ':' << VNI->id << '@' << VNI->def + << '\n'); + SVI.SpillReg = Reg; + SVI.SpillVNI = VNI; + } + } else if (MBB != UseMBB && MDT.dominates(MBB, UseMBB)) { // This is a valid spill location dominating UseVNI. // Prefer to spill at a smaller loop depth. unsigned Depth = Loops.getLoopDepth(MBB); - if (Depth < SpillDepth) { + if (Depth <= SpillDepth) { DEBUG(dbgs() << " spill depth " << Depth << ": " << PrintReg(Reg) << ':' << VNI->id << '@' << VNI->def << '\n'); SVI.SpillReg = Reg; SVI.SpillVNI = VNI; + SpillMBB = MBB; SpillDepth = Depth; } } |