From 358dec51804ee52e47ea3a47c9248086e458ad7c Mon Sep 17 00:00:00 2001 From: Evan Cheng Date: Mon, 15 Jun 2009 08:28:29 +0000 Subject: Part 1. - Change register allocation hint to a pair of unsigned integers. The hint type is zero (which means prefer the register specified as second part of the pair) or entirely target dependent. - Allow targets to specify alternative register allocation orders based on allocation hint. Part 2. - Use the register allocation hint system to implement more aggressive load / store multiple formation. - Aggressively form LDRD / STRD. These are formed *before* register allocation. It has to be done this way to shorten live interval of base and offset registers. e.g. v1025 = LDR v1024, 0 v1026 = LDR v1024, 0 => v1025,v1026 = LDRD v1024, 0 If this transformation isn't done before allocation, v1024 will overlap v1025 which means it more difficult to allocate a register pair. - Even with the register allocation hint, it may not be possible to get the desired allocation. In that case, the post-allocation load / store multiple pass must fix the ldrd / strd instructions. They can either become ldm / stm instructions or back to a pair of ldr / str instructions. This is work in progress, not yet enabled. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@73381 91177308-0d34-0410-b5e6-96231b3b80d8 --- lib/CodeGen/RegAllocLinearScan.cpp | 25 +++++++++++++------------ 1 file changed, 13 insertions(+), 12 deletions(-) (limited to 'lib/CodeGen/RegAllocLinearScan.cpp') diff --git a/lib/CodeGen/RegAllocLinearScan.cpp b/lib/CodeGen/RegAllocLinearScan.cpp index 3c445e7942..ec956c2c17 100644 --- a/lib/CodeGen/RegAllocLinearScan.cpp +++ b/lib/CodeGen/RegAllocLinearScan.cpp @@ -281,7 +281,8 @@ namespace { /// getFreePhysReg - return a free physical register for this virtual /// register interval if we have one, otherwise return 0. unsigned getFreePhysReg(LiveInterval* cur); - unsigned getFreePhysReg(const TargetRegisterClass *RC, + unsigned getFreePhysReg(LiveInterval* cur, + const TargetRegisterClass *RC, unsigned MaxInactiveCount, SmallVector &inactiveCounts, bool SkipDGRegs); @@ -936,8 +937,7 @@ void RALinScan::assignRegOrStackSlotAtInterval(LiveInterval* cur) if (DstSubReg) Reg = tri_->getMatchingSuperReg(Reg, DstSubReg, RC); if (Reg && allocatableRegs_[Reg] && RC->contains(Reg)) - mri_->setRegAllocationHint(cur->reg, - MachineRegisterInfo::RA_Preference, Reg); + mri_->setRegAllocationHint(cur->reg, 0, Reg); } } } @@ -1046,8 +1046,7 @@ void RALinScan::assignRegOrStackSlotAtInterval(LiveInterval* cur) if (LiveInterval *NextReloadLI = hasNextReloadInterval(cur)) { // "Downgrade" physReg to try to keep physReg from being allocated until // the next reload from the same SS is allocated. - mri_->setRegAllocationHint(NextReloadLI->reg, - MachineRegisterInfo::RA_Preference, physReg); + mri_->setRegAllocationHint(NextReloadLI->reg, 0, physReg); DowngradeRegister(cur, physReg); } return; @@ -1293,7 +1292,7 @@ void RALinScan::assignRegOrStackSlotAtInterval(LiveInterval* cur) // It interval has a preference, it must be defined by a copy. Clear the // preference now since the source interval allocation may have been // undone as well. - mri_->setRegAllocationHint(i->reg, MachineRegisterInfo::RA_None, 0); + mri_->setRegAllocationHint(i->reg, 0, 0); else { UpgradeRegister(ii->second); } @@ -1349,15 +1348,17 @@ void RALinScan::assignRegOrStackSlotAtInterval(LiveInterval* cur) } } -unsigned RALinScan::getFreePhysReg(const TargetRegisterClass *RC, +unsigned RALinScan::getFreePhysReg(LiveInterval* cur, + const TargetRegisterClass *RC, unsigned MaxInactiveCount, SmallVector &inactiveCounts, bool SkipDGRegs) { unsigned FreeReg = 0; unsigned FreeRegInactiveCount = 0; - TargetRegisterClass::iterator I = RC->allocation_order_begin(*mf_); - TargetRegisterClass::iterator E = RC->allocation_order_end(*mf_); + TargetRegisterClass::iterator I, E; + tie(I, E) = tri_->getAllocationOrder(RC, + mri_->getRegAllocationHint(cur->reg), *mf_); assert(I != E && "No allocatable register in this register class!"); // Scan for the first available register. @@ -1380,7 +1381,7 @@ unsigned RALinScan::getFreePhysReg(const TargetRegisterClass *RC, // return this register. if (FreeReg == 0 || FreeRegInactiveCount == MaxInactiveCount) return FreeReg; - + // Continue scanning the registers, looking for the one with the highest // inactive count. Alkis found that this reduced register pressure very // slightly on X86 (in rev 1.94 of this file), though this should probably be @@ -1440,12 +1441,12 @@ unsigned RALinScan::getFreePhysReg(LiveInterval *cur) { } if (!DowngradedRegs.empty()) { - unsigned FreeReg = getFreePhysReg(RC, MaxInactiveCount, inactiveCounts, + unsigned FreeReg = getFreePhysReg(cur, RC, MaxInactiveCount, inactiveCounts, true); if (FreeReg) return FreeReg; } - return getFreePhysReg(RC, MaxInactiveCount, inactiveCounts, false); + return getFreePhysReg(cur, RC, MaxInactiveCount, inactiveCounts, false); } FunctionPass* llvm::createLinearScanRegisterAllocator() { -- cgit v1.2.3-18-g5258