diff options
| -rw-r--r-- | lib/CodeGen/RegAllocLocal.cpp | 30 |
1 files changed, 26 insertions, 4 deletions
diff --git a/lib/CodeGen/RegAllocLocal.cpp b/lib/CodeGen/RegAllocLocal.cpp index c25c24a..04303cf 100644 --- a/lib/CodeGen/RegAllocLocal.cpp +++ b/lib/CodeGen/RegAllocLocal.cpp @@ -490,10 +490,12 @@ MachineInstr *RALocal::reloadVirtReg(MachineBasicBlock &MBB, MachineInstr *MI, // If the virtual register is already available, just update the instruction // and return. if (unsigned PR = getVirt2PhysRegMapSlot(VirtReg)) { - MarkPhysRegRecentlyUsed(PR); // Already have this value available! MI->getOperand(OpNum).setReg(PR); // Assign the input register - if (!MI->isDebugValue()) + if (!MI->isDebugValue()) { + // Do not do these for DBG_VALUE as they can affect codegen. + MarkPhysRegRecentlyUsed(PR); // Already have this value available! getVirtRegLastUse(VirtReg) = std::make_pair(MI, OpNum); + } return MI; } @@ -694,7 +696,13 @@ void RALocal::ComputeLocalLiveness(MachineBasicBlock& MBB) { bool usedOutsideBlock = isPhysReg ? false : UsedInMultipleBlocks.test(MO.getReg() - TargetRegisterInfo::FirstVirtualRegister); - if (!isPhysReg && !usedOutsideBlock) + if (!isPhysReg && !usedOutsideBlock) { + // DBG_VALUE complicates this: if the only refs of a register outside + // this block are DBG_VALUE, we can't keep the reg live just for that, + // as it will cause the reg to be spilled at the end of this block when + // it wouldn't have been otherwise. Nullify the DBG_VALUEs when that + // happens. + bool UsedByDebugValueOnly = false; for (MachineRegisterInfo::reg_iterator UI = MRI.reg_begin(MO.getReg()), UE = MRI.reg_end(); UI != UE; ++UI) // Two cases: @@ -702,12 +710,26 @@ void RALocal::ComputeLocalLiveness(MachineBasicBlock& MBB) { // - used in the same block before it is defined (loop) if (UI->getParent() != &MBB || (MO.isDef() && UI.getOperand().isUse() && precedes(&*UI, MI))) { + if (UI->isDebugValue()) { + UsedByDebugValueOnly = true; + continue; + } + // A non-DBG_VALUE use means we can leave DBG_VALUE uses alone. UsedInMultipleBlocks.set(MO.getReg() - TargetRegisterInfo::FirstVirtualRegister); usedOutsideBlock = true; + UsedByDebugValueOnly = false; break; } - + if (UsedByDebugValueOnly) + for (MachineRegisterInfo::reg_iterator UI = MRI.reg_begin(MO.getReg()), + UE = MRI.reg_end(); UI != UE; ++UI) + if (UI->isDebugValue() && + (UI->getParent() != &MBB || + (MO.isDef() && precedes(&*UI, MI)))) + UI.getOperand().setReg(0U); + } + // Physical registers and those that are not live-out of the block // are killed/dead at their last use/def within this block. if (isPhysReg || !usedOutsideBlock) { |