From 46df4eb46e784036cf895db271fe29e1cf2a975a Mon Sep 17 00:00:00 2001 From: Evan Cheng Date: Wed, 16 Jun 2010 07:35:02 +0000 Subject: Make post-ra scheduling, anti-dep breaking, and register scavenger (conservatively) aware of predicated instructions. This enables ARM to move if-conversion before post-ra scheduler. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@106091 91177308-0d34-0410-b5e6-96231b3b80d8 --- lib/CodeGen/CriticalAntiDepBreaker.cpp | 137 ++++++++++++++++++++------------- 1 file changed, 84 insertions(+), 53 deletions(-) (limited to 'lib/CodeGen/CriticalAntiDepBreaker.cpp') diff --git a/lib/CodeGen/CriticalAntiDepBreaker.cpp b/lib/CodeGen/CriticalAntiDepBreaker.cpp index 42cc44812d..e3746a9856 100644 --- a/lib/CodeGen/CriticalAntiDepBreaker.cpp +++ b/lib/CodeGen/CriticalAntiDepBreaker.cpp @@ -18,6 +18,7 @@ #include "llvm/CodeGen/MachineBasicBlock.h" #include "llvm/CodeGen/MachineFrameInfo.h" #include "llvm/Target/TargetMachine.h" +#include "llvm/Target/TargetInstrInfo.h" #include "llvm/Target/TargetRegisterInfo.h" #include "llvm/Support/Debug.h" #include "llvm/Support/ErrorHandling.h" @@ -29,6 +30,7 @@ CriticalAntiDepBreaker:: CriticalAntiDepBreaker(MachineFunction& MFi) : AntiDepBreaker(), MF(MFi), MRI(MF.getRegInfo()), + TII(MF.getTarget().getInstrInfo()), TRI(MF.getTarget().getRegisterInfo()), AllocatableSet(TRI->getAllocatableSet(MF)) { @@ -71,25 +73,27 @@ void CriticalAntiDepBreaker::StartBlock(MachineBasicBlock *BB) { DefIndices[AliasReg] = ~0u; } } - } else { - // In a non-return block, examine the live-in regs of all successors. - for (MachineBasicBlock::succ_iterator SI = BB->succ_begin(), + } + + // In a non-return block, examine the live-in regs of all successors. + // Note a return block can have successors if the return instruction is + // predicated. + for (MachineBasicBlock::succ_iterator SI = BB->succ_begin(), SE = BB->succ_end(); SI != SE; ++SI) - for (MachineBasicBlock::livein_iterator I = (*SI)->livein_begin(), + for (MachineBasicBlock::livein_iterator I = (*SI)->livein_begin(), E = (*SI)->livein_end(); I != E; ++I) { - unsigned Reg = *I; - Classes[Reg] = reinterpret_cast(-1); - KillIndices[Reg] = BB->size(); - DefIndices[Reg] = ~0u; - // Repeat, for all aliases. - for (const unsigned *Alias = TRI->getAliasSet(Reg); *Alias; ++Alias) { - unsigned AliasReg = *Alias; - Classes[AliasReg] = reinterpret_cast(-1); - KillIndices[AliasReg] = BB->size(); - DefIndices[AliasReg] = ~0u; - } + unsigned Reg = *I; + Classes[Reg] = reinterpret_cast(-1); + KillIndices[Reg] = BB->size(); + DefIndices[Reg] = ~0u; + // Repeat, for all aliases. + for (const unsigned *Alias = TRI->getAliasSet(Reg); *Alias; ++Alias) { + unsigned AliasReg = *Alias; + Classes[AliasReg] = reinterpret_cast(-1); + KillIndices[AliasReg] = BB->size(); + DefIndices[AliasReg] = ~0u; } - } + } // Mark live-out callee-saved registers. In a return block this is // all callee-saved registers. In non-return this is any @@ -164,6 +168,26 @@ static const SDep *CriticalPathStep(const SUnit *SU) { } void CriticalAntiDepBreaker::PrescanInstruction(MachineInstr *MI) { + // It's not safe to change register allocation for source operands of + // that have special allocation requirements. Also assume all registers + // used in a call must not be changed (ABI). + // FIXME: The issue with predicated instruction is more complex. We are being + // conservatively here because the kill markers cannot be trusted after + // if-conversion: + // %R6 = LDR %SP, %reg0, 92, pred:14, pred:%reg0; mem:LD4[FixedStack14] + // ... + // STR %R0, %R6, %reg0, 0, pred:0, pred:%CPSR; mem:ST4[%395] + // %R6 = LDR %SP, %reg0, 100, pred:0, pred:%CPSR; mem:LD4[FixedStack12] + // STR %R0, %R6, %reg0, 0, pred:14, pred:%reg0; mem:ST4[%396](align=8) + // + // The first R6 kill is not really a kill since it's killed by a predicated + // instruction which may not be executed. The second R6 def may or may not + // re-define R6 so it's not safe to change it since the last R6 use cannot be + // changed. + bool Special = MI->getDesc().isCall() || + MI->getDesc().hasExtraSrcRegAllocReq() || + TII->isPredicated(MI); + // Scan the register operands for this instruction and update // Classes and RegRefs. for (unsigned i = 0, e = MI->getNumOperands(); i != e; ++i) { @@ -199,9 +223,7 @@ void CriticalAntiDepBreaker::PrescanInstruction(MachineInstr *MI) { if (Classes[Reg] != reinterpret_cast(-1)) RegRefs.insert(std::make_pair(Reg, &MO)); - // It's not safe to change register allocation for source operands of - // that have special allocation requirements. - if (MO.isUse() && MI->getDesc().hasExtraSrcRegAllocReq()) { + if (MO.isUse() && Special) { if (KeepRegs.insert(Reg)) { for (const unsigned *Subreg = TRI->getSubRegisters(Reg); *Subreg; ++Subreg) @@ -216,38 +238,43 @@ void CriticalAntiDepBreaker::ScanInstruction(MachineInstr *MI, // Update liveness. // Proceding upwards, registers that are defed but not used in this // instruction are now dead. - for (unsigned i = 0, e = MI->getNumOperands(); i != e; ++i) { - MachineOperand &MO = MI->getOperand(i); - if (!MO.isReg()) continue; - unsigned Reg = MO.getReg(); - if (Reg == 0) continue; - if (!MO.isDef()) continue; - // Ignore two-addr defs. - if (MI->isRegTiedToUseOperand(i)) continue; - - DefIndices[Reg] = Count; - KillIndices[Reg] = ~0u; - assert(((KillIndices[Reg] == ~0u) != - (DefIndices[Reg] == ~0u)) && - "Kill and Def maps aren't consistent for Reg!"); - KeepRegs.erase(Reg); - Classes[Reg] = 0; - RegRefs.erase(Reg); - // Repeat, for all subregs. - for (const unsigned *Subreg = TRI->getSubRegisters(Reg); - *Subreg; ++Subreg) { - unsigned SubregReg = *Subreg; - DefIndices[SubregReg] = Count; - KillIndices[SubregReg] = ~0u; - KeepRegs.erase(SubregReg); - Classes[SubregReg] = 0; - RegRefs.erase(SubregReg); - } - // Conservatively mark super-registers as unusable. - for (const unsigned *Super = TRI->getSuperRegisters(Reg); - *Super; ++Super) { - unsigned SuperReg = *Super; - Classes[SuperReg] = reinterpret_cast(-1); + + if (!TII->isPredicated(MI)) { + // Predicated defs are modeled as read + write, i.e. similar to two + // address updates. + for (unsigned i = 0, e = MI->getNumOperands(); i != e; ++i) { + MachineOperand &MO = MI->getOperand(i); + if (!MO.isReg()) continue; + unsigned Reg = MO.getReg(); + if (Reg == 0) continue; + if (!MO.isDef()) continue; + // Ignore two-addr defs. + if (MI->isRegTiedToUseOperand(i)) continue; + + DefIndices[Reg] = Count; + KillIndices[Reg] = ~0u; + assert(((KillIndices[Reg] == ~0u) != + (DefIndices[Reg] == ~0u)) && + "Kill and Def maps aren't consistent for Reg!"); + KeepRegs.erase(Reg); + Classes[Reg] = 0; + RegRefs.erase(Reg); + // Repeat, for all subregs. + for (const unsigned *Subreg = TRI->getSubRegisters(Reg); + *Subreg; ++Subreg) { + unsigned SubregReg = *Subreg; + DefIndices[SubregReg] = Count; + KillIndices[SubregReg] = ~0u; + KeepRegs.erase(SubregReg); + Classes[SubregReg] = 0; + RegRefs.erase(SubregReg); + } + // Conservatively mark super-registers as unusable. + for (const unsigned *Super = TRI->getSuperRegisters(Reg); + *Super; ++Super) { + unsigned SuperReg = *Super; + Classes[SuperReg] = reinterpret_cast(-1); + } } } for (unsigned i = 0, e = MI->getNumOperands(); i != e; ++i) { @@ -478,7 +505,11 @@ BreakAntiDependencies(const std::vector& SUnits, PrescanInstruction(MI); - if (MI->getDesc().hasExtraDefRegAllocReq()) + // If MI's defs have a special allocation requirement, don't allow + // any def registers to be changed. Also assume all registers + // defined in a call must not be changed (ABI). + if (MI->getDesc().isCall() || MI->getDesc().hasExtraDefRegAllocReq() || + TII->isPredicated(MI)) // If this instruction's defs have special allocation requirement, don't // break this anti-dependency. AntiDepReg = 0; @@ -490,7 +521,7 @@ BreakAntiDependencies(const std::vector& SUnits, if (!MO.isReg()) continue; unsigned Reg = MO.getReg(); if (Reg == 0) continue; - if (MO.isUse() && AntiDepReg == Reg) { + if (MO.isUse() && TRI->regsOverlap(AntiDepReg, Reg)) { AntiDepReg = 0; break; } -- cgit v1.2.3