diff options
| -rw-r--r-- | lib/Target/ARM/ARMConstantIslandPass.cpp | 82 |
1 files changed, 51 insertions, 31 deletions
diff --git a/lib/Target/ARM/ARMConstantIslandPass.cpp b/lib/Target/ARM/ARMConstantIslandPass.cpp index 3bdaa3e3e4..7babb58679 100644 --- a/lib/Target/ARM/ARMConstantIslandPass.cpp +++ b/lib/Target/ARM/ARMConstantIslandPass.cpp @@ -293,7 +293,7 @@ namespace { MachineInstr *CPEMI, unsigned Disp, bool NegOk, bool DoDump = false); bool WaterIsInRange(unsigned UserOffset, MachineBasicBlock *Water, - CPUser &U); + CPUser &U, unsigned &Growth); bool BBIsInRange(MachineInstr *MI, MachineBasicBlock *BB, unsigned Disp); bool FixUpImmediateBr(ImmBranch &Br); bool FixUpConditionalBr(ImmBranch &Br); @@ -967,15 +967,42 @@ bool ARMConstantIslands::OffsetIsInRange(unsigned UserOffset, /// WaterIsInRange - Returns true if a CPE placed after the specified /// Water (a basic block) will be in range for the specific MI. - +/// +/// Compute how much the function will grow by inserting a CPE after Water. bool ARMConstantIslands::WaterIsInRange(unsigned UserOffset, - MachineBasicBlock* Water, CPUser &U) { - unsigned CPEOffset = BBInfo[Water->getNumber()].postOffset(); - - // If the CPE is to be inserted before the instruction, that will raise - // the offset of the instruction. - if (CPEOffset < UserOffset) - UserOffset += U.CPEMI->getOperand(2).getImm(); + MachineBasicBlock* Water, CPUser &U, + unsigned &Growth) { + unsigned CPELogAlign = getCPELogAlign(U.CPEMI); + unsigned CPEOffset = BBInfo[Water->getNumber()].postOffset(CPELogAlign); + unsigned NextBlockOffset, NextBlockAlignment; + MachineFunction::const_iterator NextBlock = Water; + if (++NextBlock == MF->end()) { + NextBlockOffset = BBInfo[Water->getNumber()].postOffset(); + NextBlockAlignment = 0; + } else { + NextBlockOffset = BBInfo[NextBlock->getNumber()].Offset; + NextBlockAlignment = NextBlock->getAlignment(); + } + unsigned Size = U.CPEMI->getOperand(2).getImm(); + unsigned CPEEnd = CPEOffset + Size; + + // The CPE may be able to hide in the alignment padding before the next + // block. It may also cause more padding to be required if it is more aligned + // that the next block. + if (CPEEnd > NextBlockOffset) { + Growth = CPEEnd - NextBlockOffset; + // Compute the padding that would go at the end of the CPE to align the next + // block. + Growth += OffsetToAlignment(CPEEnd, 1u << NextBlockAlignment); + + // If the CPE is to be inserted before the instruction, that will raise + // the offset of the instruction. Also account for unknown alignment padding + // in blocks between CPE and the user. + if (CPEOffset < UserOffset) + UserOffset += Growth + UnknownPadding(MF->getAlignment(), CPELogAlign); + } else + // CPE fits in existing padding. + Growth = 0; return OffsetIsInRange(UserOffset, CPEOffset, U); } @@ -1130,10 +1157,9 @@ bool ARMConstantIslands::LookForWater(CPUser &U, unsigned UserOffset, if (WaterList.empty()) return false; - bool FoundWaterThatWouldPad = false; - water_iterator IPThatWouldPad; - for (water_iterator IP = prior(WaterList.end()), - B = WaterList.begin();; --IP) { + unsigned BestGrowth = ~0u; + for (water_iterator IP = prior(WaterList.end()), B = WaterList.begin();; + --IP) { MachineBasicBlock* WaterBB = *IP; // Check if water is in range and is either at a lower address than the // current "high water mark" or a new water block that was created since @@ -1143,30 +1169,24 @@ bool ARMConstantIslands::LookForWater(CPUser &U, unsigned UserOffset, // should be relatively uncommon and when it does happen, we want to be // sure to take advantage of it for all the CPEs near that block, so that // we don't insert more branches than necessary. - if (WaterIsInRange(UserOffset, WaterBB, U) && + unsigned Growth; + if (WaterIsInRange(UserOffset, WaterBB, U, Growth) && (WaterBB->getNumber() < U.HighWaterMark->getNumber() || - NewWaterList.count(WaterBB))) { - unsigned WBBId = WaterBB->getNumber(); - if (isThumb && BBInfo[WBBId].postOffset()%4 != 0) { - // This is valid Water, but would introduce padding. Remember - // it in case we don't find any Water that doesn't do this. - if (!FoundWaterThatWouldPad) { - FoundWaterThatWouldPad = true; - IPThatWouldPad = IP; - } - } else { - WaterIter = IP; + NewWaterList.count(WaterBB)) && Growth < BestGrowth) { + // This is the least amount of required padding seen so far. + BestGrowth = Growth; + WaterIter = IP; + DEBUG(dbgs() << "Found water after BB#" << WaterBB->getNumber() + << " Growth=" << Growth << '\n'); + + // Keep looking unless it is perfect. + if (BestGrowth == 0) return true; - } } if (IP == B) break; } - if (FoundWaterThatWouldPad) { - WaterIter = IPThatWouldPad; - return true; - } - return false; + return BestGrowth != ~0u; } /// CreateNewWater - No existing WaterList entry will work for |