X-Git-Url: http://plrg.eecs.uci.edu/git/?a=blobdiff_plain;f=lib%2FTarget%2FARM%2FARMConstantIslandPass.cpp;h=8fa3c04b6c4deb95163ff557d9dd88f6f8d9d021;hb=518bb53485df640d7b7e3f6b0544099020c42aa7;hp=ea64bab79d1ec5b583f0cb1553b62dada32af900;hpb=a1efbbdbf3217598f334a6f39dab84ca06f5de41;p=oota-llvm.git diff --git a/lib/Target/ARM/ARMConstantIslandPass.cpp b/lib/Target/ARM/ARMConstantIslandPass.cpp index ea64bab79d1..8fa3c04b6c4 100644 --- a/lib/Target/ARM/ARMConstantIslandPass.cpp +++ b/lib/Target/ARM/ARMConstantIslandPass.cpp @@ -24,12 +24,15 @@ #include "llvm/CodeGen/MachineJumpTableInfo.h" #include "llvm/Target/TargetData.h" #include "llvm/Target/TargetMachine.h" -#include "llvm/Support/Compiler.h" #include "llvm/Support/Debug.h" #include "llvm/Support/ErrorHandling.h" +#include "llvm/Support/raw_ostream.h" +#include "llvm/ADT/SmallSet.h" #include "llvm/ADT/SmallVector.h" #include "llvm/ADT/STLExtras.h" #include "llvm/ADT/Statistic.h" +#include "llvm/Support/CommandLine.h" +#include using namespace llvm; STATISTIC(NumCPEs, "Number of constpool entries"); @@ -38,6 +41,15 @@ STATISTIC(NumCBrFixed, "Number of cond branches fixed"); STATISTIC(NumUBrFixed, "Number of uncond branches fixed"); STATISTIC(NumTBs, "Number of table branches generated"); STATISTIC(NumT2CPShrunk, "Number of Thumb2 constantpool instructions shrunk"); +STATISTIC(NumT2BrShrunk, "Number of Thumb2 immediate branches shrunk"); +STATISTIC(NumCBZ, "Number of CBZ / CBNZ formed"); +STATISTIC(NumJTMoved, "Number of jump table destination blocks moved"); +STATISTIC(NumJTInserted, "Number of jump table intermediate blocks inserted"); + + +static cl::opt +AdjustJumpTableBlocks("arm-adjust-jump-tables", cl::Hidden, cl::init(true), + cl::desc("Adjust basic block layout to better use TB[BH]")); namespace { /// ARMConstantIslands - Due to limited PC-relative displacements, ARM @@ -51,7 +63,7 @@ namespace { /// Water - Potential places where an island could be formed. /// CPE - A constant pool entry that has been placed somewhere, which /// tracks a list of users. - class VISIBILITY_HIDDEN ARMConstantIslands : public MachineFunctionPass { + class ARMConstantIslands : public MachineFunctionPass { /// BBSizes - The size of each MachineBasicBlock in bytes of code, indexed /// by MBB Number. The two-byte pads required for Thumb alignment are /// counted as part of the following block (i.e., the offset and size for @@ -68,18 +80,36 @@ namespace { /// to a return, unreachable, or unconditional branch). std::vector WaterList; + /// NewWaterList - The subset of WaterList that was created since the + /// previous iteration by inserting unconditional branches. + SmallSet NewWaterList; + + typedef std::vector::iterator water_iterator; + /// CPUser - One user of a constant pool, keeping the machine instruction /// pointer, the constant pool being referenced, and the max displacement - /// allowed from the instruction to the CP. + /// allowed from the instruction to the CP. The HighWaterMark records the + /// highest basic block where a new CPEntry can be placed. To ensure this + /// pass terminates, the CP entries are initially placed at the end of the + /// function and then move monotonically to lower addresses. The + /// exception to this rule is when the current CP entry for a particular + /// CPUser is out of range, but there is another CP entry for the same + /// constant value in range. We want to use the existing in-range CP + /// entry, but if it later moves out of range, the search for new water + /// should resume where it left off. The HighWaterMark is used to record + /// that point. struct CPUser { MachineInstr *MI; MachineInstr *CPEMI; + MachineBasicBlock *HighWaterMark; unsigned MaxDisp; bool NegOk; bool IsSoImm; CPUser(MachineInstr *mi, MachineInstr *cpemi, unsigned maxdisp, bool neg, bool soimm) - : MI(mi), CPEMI(cpemi), MaxDisp(maxdisp), NegOk(neg), IsSoImm(soimm) {} + : MI(mi), CPEMI(cpemi), MaxDisp(maxdisp), NegOk(neg), IsSoImm(soimm) { + HighWaterMark = CPEMI->getParent(); + } }; /// CPUsers - Keep track of all of the machine instructions that use various @@ -132,6 +162,9 @@ namespace { /// the branch fix up pass. bool HasFarJump; + /// HasInlineAsm - True if the function contains inline assembly. + bool HasInlineAsm; + const TargetInstrInfo *TII; const ARMSubtarget *STI; ARMFunctionInfo *AFI; @@ -152,6 +185,7 @@ namespace { void DoInitialPlacement(MachineFunction &MF, std::vector &CPEMIs); CPEntry *findConstPoolEntry(unsigned CPI, const MachineInstr *CPEMI); + void JumpTableFunctionScan(MachineFunction &MF); void InitialFunctionScan(MachineFunction &MF, const std::vector &CPEMIs); MachineBasicBlock *SplitBlockBeforeInstr(MachineInstr *MI); @@ -159,12 +193,9 @@ namespace { void AdjustBBOffsetsAfter(MachineBasicBlock *BB, int delta); bool DecrementOldEntry(unsigned CPI, MachineInstr* CPEMI); int LookForExistingCPEntry(CPUser& U, unsigned UserOffset); - bool LookForWater(CPUser&U, unsigned UserOffset, - MachineBasicBlock** NewMBB); - MachineBasicBlock* AcceptWater(MachineBasicBlock *WaterBB, - std::vector::iterator IP); + bool LookForWater(CPUser&U, unsigned UserOffset, water_iterator &WaterIter); void CreateNewWater(unsigned CPUserIndex, unsigned UserOffset, - MachineBasicBlock** NewMBB); + MachineBasicBlock *&NewMBB); bool HandleConstantPoolUser(MachineFunction &MF, unsigned CPUserIndex); void RemoveDeadCPEMI(MachineInstr *CPEMI); bool RemoveUnusedCPEntries(); @@ -182,7 +213,10 @@ namespace { bool UndoLRSpillRestore(); bool OptimizeThumb2Instructions(MachineFunction &MF); bool OptimizeThumb2Branches(MachineFunction &MF); + bool ReorderThumb2JumpTables(MachineFunction &MF); bool OptimizeThumb2JumpTables(MachineFunction &MF); + MachineBasicBlock *AdjustJTTargetBlockForward(MachineBasicBlock *BB, + MachineBasicBlock *JTBB); unsigned GetOffsetOf(MachineInstr *MI) const; void dumpBBs(); @@ -205,18 +239,27 @@ void ARMConstantIslands::verify(MachineFunction &MF) { if (!MBB->empty() && MBB->begin()->getOpcode() == ARM::CONSTPOOL_ENTRY) { unsigned MBBId = MBB->getNumber(); - assert((BBOffsets[MBBId]%4 == 0 && BBSizes[MBBId]%4 == 0) || + assert(HasInlineAsm || + (BBOffsets[MBBId]%4 == 0 && BBSizes[MBBId]%4 == 0) || (BBOffsets[MBBId]%4 != 0 && BBSizes[MBBId]%4 != 0)); } } + for (unsigned i = 0, e = CPUsers.size(); i != e; ++i) { + CPUser &U = CPUsers[i]; + unsigned UserOffset = GetOffsetOf(U.MI) + (isThumb ? 4 : 8); + unsigned CPEOffset = GetOffsetOf(U.CPEMI); + unsigned Disp = UserOffset < CPEOffset ? CPEOffset - UserOffset : + UserOffset - CPEOffset; + assert(Disp <= U.MaxDisp || "Constant pool entry out of range!"); + } #endif } /// print block size and offset information - debugging void ARMConstantIslands::dumpBBs() { for (unsigned J = 0, E = BBOffsets.size(); J !=E; ++J) { - DOUT << "block " << J << " offset " << BBOffsets[J] << - " size " << BBSizes[J] << "\n"; + DEBUG(errs() << "block " << J << " offset " << BBOffsets[J] + << " size " << BBSizes[J] << "\n"); } } @@ -238,17 +281,30 @@ bool ARMConstantIslands::runOnMachineFunction(MachineFunction &MF) { isThumb2 = AFI->isThumb2Function(); HasFarJump = false; + HasInlineAsm = false; // Renumber all of the machine basic blocks in the function, guaranteeing that // the numbers agree with the position of the block in the function. MF.RenumberBlocks(); + // Try to reorder and otherwise adjust the block layout to make good use + // of the TB[BH] instructions. + bool MadeChange = false; + if (isThumb2 && AdjustJumpTableBlocks) { + JumpTableFunctionScan(MF); + MadeChange |= ReorderThumb2JumpTables(MF); + // Data is out of date, so clear it. It'll be re-computed later. + T2JumpTables.clear(); + // Blocks may have shifted around. Keep the numbering up to date. + MF.RenumberBlocks(); + } + // Thumb1 functions containing constant pools get 4-byte alignment. // This is so we can keep exact track of where the alignment padding goes. - // Set default. Thumb1 function is 2-byte aligned, ARM and Thumb2 are 4-byte - // aligned. - AFI->setAlign(isThumb1 ? 1U : 2U); + // ARM and Thumb2 functions need to be 4-byte aligned. + if (!isThumb1) + MF.EnsureAlignment(2); // 2 = log2(4) // Perform the initial placement of the constant pool entries. To start with, // we put them all at the end of the function. @@ -256,7 +312,7 @@ bool ARMConstantIslands::runOnMachineFunction(MachineFunction &MF) { if (!MCP.isEmpty()) { DoInitialPlacement(MF, CPEMIs); if (isThumb1) - AFI->setAlign(2U); + MF.EnsureAlignment(2); // 2 = log2(4) } /// The next UID to take is the first unused one. @@ -273,7 +329,6 @@ bool ARMConstantIslands::runOnMachineFunction(MachineFunction &MF) { // Iteratively place constant pool entries and fix up branches until there // is no change. - bool MadeChange = false; unsigned NoCPIters = 0, NoBRIters = 0; while (true) { bool CPChange = false; @@ -282,6 +337,10 @@ bool ARMConstantIslands::runOnMachineFunction(MachineFunction &MF) { if (CPChange && ++NoCPIters > 30) llvm_unreachable("Constant Island pass failed to converge!"); DEBUG(dumpBBs()); + + // Clear NewWaterList now. If we split a block for branches, it should + // appear as "new water" for the next iteration of constant pool placement. + NewWaterList.clear(); bool BRChange = false; for (unsigned i = 0, e = ImmBranches.size(); i != e; ++i) @@ -349,7 +408,8 @@ void ARMConstantIslands::DoInitialPlacement(MachineFunction &MF, CPEs.push_back(CPEntry(CPEMI, i)); CPEntries.push_back(CPEs); NumCPEs++; - DOUT << "Moved CPI#" << i << " to end of function as #" << i << "\n"; + DEBUG(errs() << "Moved CPI#" << i << " to end of function as #" << i + << "\n"); } } @@ -358,10 +418,10 @@ void ARMConstantIslands::DoInitialPlacement(MachineFunction &MF, static bool BBHasFallthrough(MachineBasicBlock *MBB) { // Get the next machine basic block in the function. MachineFunction::iterator MBBI = MBB; - if (next(MBBI) == MBB->getParent()->end()) // Can't fall off end of function. + if (llvm::next(MBBI) == MBB->getParent()->end()) // Can't fall off end of function. return false; - MachineBasicBlock *NextBB = next(MBBI); + MachineBasicBlock *NextBB = llvm::next(MBBI); for (MachineBasicBlock::succ_iterator I = MBB->succ_begin(), E = MBB->succ_end(); I != E; ++I) if (*I == NextBB) @@ -385,11 +445,39 @@ ARMConstantIslands::CPEntry return NULL; } +/// JumpTableFunctionScan - Do a scan of the function, building up +/// information about the sizes of each block and the locations of all +/// the jump tables. +void ARMConstantIslands::JumpTableFunctionScan(MachineFunction &MF) { + for (MachineFunction::iterator MBBI = MF.begin(), E = MF.end(); + MBBI != E; ++MBBI) { + MachineBasicBlock &MBB = *MBBI; + + for (MachineBasicBlock::iterator I = MBB.begin(), E = MBB.end(); + I != E; ++I) + if (I->getDesc().isBranch() && I->getOpcode() == ARM::t2BR_JT) + T2JumpTables.push_back(I); + } +} + /// InitialFunctionScan - Do the initial scan of the function, building up /// information about the sizes of each block, the location of all the water, /// and finding all of the constant pool users. void ARMConstantIslands::InitialFunctionScan(MachineFunction &MF, const std::vector &CPEMIs) { + // First thing, see if the function has any inline assembly in it. If so, + // we have to be conservative about alignment assumptions, as we don't + // know for sure the size of any instructions in the inline assembly. + for (MachineFunction::iterator MBBI = MF.begin(), E = MF.end(); + MBBI != E; ++MBBI) { + MachineBasicBlock &MBB = *MBBI; + for (MachineBasicBlock::iterator I = MBB.begin(), E = MBB.end(); + I != E; ++I) + if (I->getOpcode() == ARM::INLINEASM) + HasInlineAsm = true; + } + + // Now go back through the instructions and build up our data structures unsigned Offset = 0; for (MachineFunction::iterator MBBI = MF.begin(), E = MF.end(); MBBI != E; ++MBBI) { @@ -418,8 +506,8 @@ void ARMConstantIslands::InitialFunctionScan(MachineFunction &MF, case ARM::tBR_JTr: // A Thumb1 table jump may involve padding; for the offsets to // be right, functions containing these must be 4-byte aligned. - AFI->setAlign(2U); - if ((Offset+MBBSize)%4 != 0) + MF.EnsureAlignment(2U); + if ((Offset+MBBSize)%4 != 0 || HasInlineAsm) // FIXME: Add a pseudo ALIGN instruction instead. MBBSize += 2; // padding continue; // Does not get an entry in ImmBranches @@ -479,8 +567,6 @@ void ARMConstantIslands::InitialFunctionScan(MachineFunction &MF, bool NegOk = false; bool IsSoImm = false; - // FIXME: Temporary workaround until I can figure out what's going on. - unsigned Slack = T2JumpTables.empty() ? 0 : 4; switch (Opc) { default: llvm_unreachable("Unknown addressing mode for CP reference!"); @@ -490,7 +576,7 @@ void ARMConstantIslands::InitialFunctionScan(MachineFunction &MF, case ARM::LEApcrel: // This takes a SoImm, which is 8 bit immediate rotated. We'll // pretend the maximum offset is 255 * 4. Since each instruction - // 4 byte wide, this is always correct. We'llc heck for other + // 4 byte wide, this is always correct. We'll check for other // displacements that fits in a SoImm as well. Bits = 8; Scale = 4; @@ -519,8 +605,8 @@ void ARMConstantIslands::InitialFunctionScan(MachineFunction &MF, Scale = 4; // +(offset_8*4) break; - case ARM::FLDD: - case ARM::FLDS: + case ARM::VLDRD: + case ARM::VLDRS: Bits = 8; Scale = 4; // +-(offset_8*4) NegOk = true; @@ -530,7 +616,7 @@ void ARMConstantIslands::InitialFunctionScan(MachineFunction &MF, // Remember that this is a user of a CP entry. unsigned CPI = I->getOperand(op).getIndex(); MachineInstr *CPEMI = CPEMIs[CPI]; - unsigned MaxOffs = ((1 << Bits)-1) * Scale - Slack; + unsigned MaxOffs = ((1 << Bits)-1) * Scale; CPUsers.push_back(CPUser(I, CPEMI, MaxOffs, NegOk, IsSoImm)); // Increment corresponding CPEntry reference count. @@ -549,7 +635,7 @@ void ARMConstantIslands::InitialFunctionScan(MachineFunction &MF, if (isThumb && !MBB.empty() && MBB.begin()->getOpcode() == ARM::CONSTPOOL_ENTRY && - (Offset%4) != 0) + ((Offset%4) != 0 || HasInlineAsm)) MBBSize += 2; BBSizes.push_back(MBBSize); @@ -573,7 +659,7 @@ unsigned ARMConstantIslands::GetOffsetOf(MachineInstr *MI) const { // alignment padding, and compensate if so. if (isThumb && MI->getOpcode() == ARM::CONSTPOOL_ENTRY && - Offset%4 != 0) + (Offset%4 != 0 || HasInlineAsm)) Offset += 2; // Sum instructions before MI in MBB. @@ -607,7 +693,7 @@ void ARMConstantIslands::UpdateForInsertedWaterBlock(MachineBasicBlock *NewBB) { // Next, update WaterList. Specifically, we need to add NewMBB as having // available water after it. - std::vector::iterator IP = + water_iterator IP = std::lower_bound(WaterList.begin(), WaterList.end(), NewBB, CompareMBBNumbers); WaterList.insert(IP, NewBB); @@ -615,7 +701,7 @@ void ARMConstantIslands::UpdateForInsertedWaterBlock(MachineBasicBlock *NewBB) { /// Split the basic block containing MI into two blocks, which are joined by -/// an unconditional branch. Update datastructures and renumber blocks to +/// an unconditional branch. Update data structures and renumber blocks to /// account for this change and returns the newly created block. MachineBasicBlock *ARMConstantIslands::SplitBlockBeforeInstr(MachineInstr *MI) { MachineBasicBlock *OrigBB = MI->getParent(); @@ -646,7 +732,7 @@ MachineBasicBlock *ARMConstantIslands::SplitBlockBeforeInstr(MachineInstr *MI) { // This pass should be run after register allocation, so there should be no // PHI nodes to update. - assert((Succ->empty() || Succ->begin()->getOpcode() != TargetInstrInfo::PHI) + assert((Succ->empty() || !Succ->begin()->isPHI()) && "PHI nodes should be eliminated by now!"); } @@ -669,14 +755,15 @@ MachineBasicBlock *ARMConstantIslands::SplitBlockBeforeInstr(MachineInstr *MI) { // available water after it (but not if it's already there, which happens // when splitting before a conditional branch that is followed by an // unconditional branch - in that case we want to insert NewBB). - std::vector::iterator IP = + water_iterator IP = std::lower_bound(WaterList.begin(), WaterList.end(), OrigBB, CompareMBBNumbers); MachineBasicBlock* WaterBB = *IP; if (WaterBB == OrigBB) - WaterList.insert(next(IP), NewBB); + WaterList.insert(llvm::next(IP), NewBB); else WaterList.insert(IP, OrigBB); + NewWaterList.insert(OrigBB); // Figure out how large the first NewMBB is. (It cannot // contain a constpool_entry or tablejump.) @@ -714,11 +801,23 @@ bool ARMConstantIslands::OffsetIsInRange(unsigned UserOffset, // purposes of the displacement computation; compensate for that here. // Effectively, the valid range of displacements is 2 bytes smaller for such // references. - if (isThumb && UserOffset%4 !=0) + unsigned TotalAdj = 0; + if (isThumb && UserOffset%4 !=0) { UserOffset -= 2; + TotalAdj = 2; + } // CPEs will be rounded up to a multiple of 4. - if (isThumb && TrialOffset%4 != 0) + if (isThumb && TrialOffset%4 != 0) { TrialOffset += 2; + TotalAdj += 2; + } + + // In Thumb2 mode, later branch adjustments can shift instructions up and + // cause alignment change. In the worst case scenario this can cause the + // user's effective address to be subtracted by 2 and the CPE's address to + // be plus 2. + if (isThumb2 && TotalAdj != 4) + MaxDisp -= (4 - TotalAdj); if (UserOffset <= TrialOffset) { // User before the Trial. @@ -743,8 +842,7 @@ bool ARMConstantIslands::WaterIsInRange(unsigned UserOffset, BBSizes[Water->getNumber()]; // If the CPE is to be inserted before the instruction, that will raise - // the offset of the instruction. (Currently applies only to ARM, so - // no alignment compensation attempted here.) + // the offset of the instruction. if (CPEOffset < UserOffset) UserOffset += U.CPEMI->getOperand(2).getImm(); @@ -757,14 +855,14 @@ bool ARMConstantIslands::CPEIsInRange(MachineInstr *MI, unsigned UserOffset, MachineInstr *CPEMI, unsigned MaxDisp, bool NegOk, bool DoDump) { unsigned CPEOffset = GetOffsetOf(CPEMI); - assert(CPEOffset%4 == 0 && "Misaligned CPE"); + assert((CPEOffset%4 == 0 || HasInlineAsm) && "Misaligned CPE"); if (DoDump) { - DOUT << "User of CPE#" << CPEMI->getOperand(0).getImm() - << " max delta=" << MaxDisp - << " insn address=" << UserOffset - << " CPE address=" << CPEOffset - << " offset=" << int(CPEOffset-UserOffset) << "\t" << *MI; + DEBUG(errs() << "User of CPE#" << CPEMI->getOperand(0).getImm() + << " max delta=" << MaxDisp + << " insn address=" << UserOffset + << " CPE address=" << CPEOffset + << " offset=" << int(CPEOffset-UserOffset) << "\t" << *MI); } return OffsetIsInRange(UserOffset, CPEOffset, MaxDisp, NegOk); @@ -789,7 +887,7 @@ static bool BBIsJumpedOver(MachineBasicBlock *MBB) { void ARMConstantIslands::AdjustBBOffsetsAfter(MachineBasicBlock *BB, int delta) { - MachineFunction::iterator MBBI = BB; MBBI = next(MBBI); + MachineFunction::iterator MBBI = BB; MBBI = llvm::next(MBBI); for(unsigned i = BB->getNumber()+1, e = BB->getParent()->getNumBlockIDs(); i < e; ++i) { BBOffsets[i] += delta; @@ -798,7 +896,7 @@ void ARMConstantIslands::AdjustBBOffsetsAfter(MachineBasicBlock *BB, if (!isThumb) continue; MachineBasicBlock *MBB = MBBI; - if (!MBB->empty()) { + if (!MBB->empty() && !HasInlineAsm) { // Constant pool entries require padding. if (MBB->begin()->getOpcode() == ARM::CONSTPOOL_ENTRY) { unsigned OldOffset = BBOffsets[i] - delta; @@ -831,7 +929,7 @@ void ARMConstantIslands::AdjustBBOffsetsAfter(MachineBasicBlock *BB, if (delta==0) return; } - MBBI = next(MBBI); + MBBI = llvm::next(MBBI); } } @@ -866,7 +964,7 @@ int ARMConstantIslands::LookForExistingCPEntry(CPUser& U, unsigned UserOffset) // Check to see if the CPE is already in-range. if (CPEIsInRange(UserMI, UserOffset, CPEMI, U.MaxDisp, U.NegOk, true)) { - DOUT << "In range\n"; + DEBUG(errs() << "In range\n"); return 1; } @@ -881,7 +979,8 @@ int ARMConstantIslands::LookForExistingCPEntry(CPUser& U, unsigned UserOffset) if (CPEs[i].CPEMI == NULL) continue; if (CPEIsInRange(UserMI, UserOffset, CPEs[i].CPEMI, U.MaxDisp, U.NegOk)) { - DOUT << "Replacing CPE#" << CPI << " with CPE#" << CPEs[i].CPI << "\n"; + DEBUG(errs() << "Replacing CPE#" << CPI << " with CPE#" + << CPEs[i].CPI << "\n"); // Point the CPUser node to the replacement U.CPEMI = CPEs[i].CPEMI; // Change the CPI in the instruction operand to refer to the clone. @@ -915,56 +1014,54 @@ static inline unsigned getUnconditionalBrDisp(int Opc) { return ((1<<23)-1)*4; } -/// AcceptWater - Small amount of common code factored out of the following. - -MachineBasicBlock* ARMConstantIslands::AcceptWater(MachineBasicBlock *WaterBB, - std::vector::iterator IP) { - DOUT << "found water in range\n"; - // Remove the original WaterList entry; we want subsequent - // insertions in this vicinity to go after the one we're - // about to insert. This considerably reduces the number - // of times we have to move the same CPE more than once. - WaterList.erase(IP); - // CPE goes before following block (NewMBB). - return next(MachineFunction::iterator(WaterBB)); -} - -/// LookForWater - look for an existing entry in the WaterList in which +/// LookForWater - Look for an existing entry in the WaterList in which /// we can place the CPE referenced from U so it's within range of U's MI. -/// Returns true if found, false if not. If it returns true, *NewMBB -/// is set to the WaterList entry. -/// For ARM, we prefer the water that's farthest away. For Thumb, prefer -/// water that will not introduce padding to water that will; within each -/// group, prefer the water that's farthest away. +/// Returns true if found, false if not. If it returns true, WaterIter +/// is set to the WaterList entry. For Thumb, prefer water that will not +/// introduce padding to water that will. To ensure that this pass +/// terminates, the CPE location for a particular CPUser is only allowed to +/// move to a lower address, so search backward from the end of the list and +/// prefer the first water that is in range. bool ARMConstantIslands::LookForWater(CPUser &U, unsigned UserOffset, - MachineBasicBlock** NewMBB) { - std::vector::iterator IPThatWouldPad; - MachineBasicBlock* WaterBBThatWouldPad = NULL; - if (!WaterList.empty()) { - for (std::vector::iterator IP = prior(WaterList.end()), - B = WaterList.begin();; --IP) { - MachineBasicBlock* WaterBB = *IP; - if (WaterIsInRange(UserOffset, WaterBB, U)) { - unsigned WBBId = WaterBB->getNumber(); - if (isThumb && - (BBOffsets[WBBId] + BBSizes[WBBId])%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 (!WaterBBThatWouldPad) { - WaterBBThatWouldPad = WaterBB; - IPThatWouldPad = IP; - } - } else { - *NewMBB = AcceptWater(WaterBB, IP); - return true; + water_iterator &WaterIter) { + if (WaterList.empty()) + return false; + + bool FoundWaterThatWouldPad = false; + water_iterator IPThatWouldPad; + 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 + // the previous iteration by inserting an unconditional branch. In the + // latter case, we want to allow resetting the high water mark back to + // this new water since we haven't seen it before. Inserting branches + // 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) && + (WaterBB->getNumber() < U.HighWaterMark->getNumber() || + NewWaterList.count(WaterBB))) { + unsigned WBBId = WaterBB->getNumber(); + if (isThumb && + (BBOffsets[WBBId] + BBSizes[WBBId])%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; + return true; } - if (IP == B) - break; } + if (IP == B) + break; } - if (isThumb && WaterBBThatWouldPad) { - *NewMBB = AcceptWater(WaterBBThatWouldPad, IPThatWouldPad); + if (FoundWaterThatWouldPad) { + WaterIter = IPThatWouldPad; return true; } return false; @@ -974,12 +1071,12 @@ bool ARMConstantIslands::LookForWater(CPUser &U, unsigned UserOffset, /// CPUsers[CPUserIndex], so create a place to put the CPE. The end of the /// block is used if in range, and the conditional branch munged so control /// flow is correct. Otherwise the block is split to create a hole with an -/// unconditional branch around it. In either case *NewMBB is set to a +/// unconditional branch around it. In either case NewMBB is set to a /// block following which the new island can be inserted (the WaterList /// is not adjusted). - void ARMConstantIslands::CreateNewWater(unsigned CPUserIndex, - unsigned UserOffset, MachineBasicBlock** NewMBB) { + unsigned UserOffset, + MachineBasicBlock *&NewMBB) { CPUser &U = CPUsers[CPUserIndex]; MachineInstr *UserMI = U.MI; MachineInstr *CPEMI = U.CPEMI; @@ -988,20 +1085,18 @@ void ARMConstantIslands::CreateNewWater(unsigned CPUserIndex, BBSizes[UserMBB->getNumber()]; assert(OffsetOfNextBlock== BBOffsets[UserMBB->getNumber()+1]); - // If the use is at the end of the block, or the end of the block - // is within range, make new water there. (The addition below is - // for the unconditional branch we will be adding: 4 bytes on ARM + Thumb2, - // 2 on Thumb1. Possible Thumb1 alignment padding is allowed for + // If the block does not end in an unconditional branch already, and if the + // end of the block is within range, make new water there. (The addition + // below is for the unconditional branch we will be adding: 4 bytes on ARM + + // Thumb2, 2 on Thumb1. Possible Thumb1 alignment padding is allowed for // inside OffsetIsInRange. - // If the block ends in an unconditional branch already, it is water, - // and is known to be out of range, so we'll always be adding a branch.) - if (&UserMBB->back() == UserMI || + if (BBHasFallthrough(UserMBB) && OffsetIsInRange(UserOffset, OffsetOfNextBlock + (isThumb1 ? 2: 4), U.MaxDisp, U.NegOk, U.IsSoImm)) { - DOUT << "Split at end of block\n"; + DEBUG(errs() << "Split at end of block\n"); if (&UserMBB->back() == UserMI) assert(BBHasFallthrough(UserMBB) && "Expected a fallthrough BB!"); - *NewMBB = next(MachineFunction::iterator(UserMBB)); + NewMBB = llvm::next(MachineFunction::iterator(UserMBB)); // Add an unconditional branch from UserMBB to fallthrough block. // Record it for branch lengthening; this new branch will not get out of // range, but if the preceding conditional branch is out of range, the @@ -1009,7 +1104,7 @@ void ARMConstantIslands::CreateNewWater(unsigned CPUserIndex, // range, so the machinery has to know about it. int UncondBr = isThumb ? ((isThumb2) ? ARM::t2B : ARM::tB) : ARM::B; BuildMI(UserMBB, DebugLoc::getUnknownLoc(), - TII->get(UncondBr)).addMBB(*NewMBB); + TII->get(UncondBr)).addMBB(NewMBB); unsigned MaxDisp = getUnconditionalBrDisp(UncondBr); ImmBranches.push_back(ImmBranch(&UserMBB->back(), MaxDisp, false, UncondBr)); @@ -1049,7 +1144,7 @@ void ARMConstantIslands::CreateNewWater(unsigned CPUserIndex, for (unsigned Offset = UserOffset+TII->GetInstSizeInBytes(UserMI); Offset < BaseInsertOffset; Offset += TII->GetInstSizeInBytes(MI), - MI = next(MI)) { + MI = llvm::next(MI)) { if (CPUIndex < CPUsers.size() && CPUsers[CPUIndex].MI == MI) { CPUser &U = CPUsers[CPUIndex]; if (!OffsetIsInRange(Offset, EndInsertOffset, @@ -1063,8 +1158,8 @@ void ARMConstantIslands::CreateNewWater(unsigned CPUserIndex, CPUIndex++; } } - DOUT << "Split in middle of big block\n"; - *NewMBB = SplitBlockBeforeInstr(prior(MI)); + DEBUG(errs() << "Split in middle of big block\n"); + NewMBB = SplitBlockBeforeInstr(prior(MI)); } } @@ -1079,7 +1174,6 @@ bool ARMConstantIslands::HandleConstantPoolUser(MachineFunction &MF, MachineInstr *CPEMI = U.CPEMI; unsigned CPI = CPEMI->getOperand(1).getIndex(); unsigned Size = CPEMI->getOperand(2).getImm(); - MachineBasicBlock *NewMBB; // Compute this only once, it's expensive. The 4 or 8 is the value the // hardware keeps in the PC. unsigned UserOffset = GetOffsetOf(UserMI) + (isThumb ? 4 : 8); @@ -1094,18 +1188,51 @@ bool ARMConstantIslands::HandleConstantPoolUser(MachineFunction &MF, // We will be generating a new clone. Get a UID for it. unsigned ID = AFI->createConstPoolEntryUId(); - // Look for water where we can place this CPE. We look for the farthest one - // away that will work. Forward references only for now (although later - // we might find some that are backwards). + // Look for water where we can place this CPE. + MachineBasicBlock *NewIsland = MF.CreateMachineBasicBlock(); + MachineBasicBlock *NewMBB; + water_iterator IP; + if (LookForWater(U, UserOffset, IP)) { + DEBUG(errs() << "found water in range\n"); + MachineBasicBlock *WaterBB = *IP; + + // If the original WaterList entry was "new water" on this iteration, + // propagate that to the new island. This is just keeping NewWaterList + // updated to match the WaterList, which will be updated below. + if (NewWaterList.count(WaterBB)) { + NewWaterList.erase(WaterBB); + NewWaterList.insert(NewIsland); + } + // The new CPE goes before the following block (NewMBB). + NewMBB = llvm::next(MachineFunction::iterator(WaterBB)); - if (!LookForWater(U, UserOffset, &NewMBB)) { + } else { // No water found. - DOUT << "No water found\n"; - CreateNewWater(CPUserIndex, UserOffset, &NewMBB); + DEBUG(errs() << "No water found\n"); + CreateNewWater(CPUserIndex, UserOffset, NewMBB); + + // SplitBlockBeforeInstr adds to WaterList, which is important when it is + // called while handling branches so that the water will be seen on the + // next iteration for constant pools, but in this context, we don't want + // it. Check for this so it will be removed from the WaterList. + // Also remove any entry from NewWaterList. + MachineBasicBlock *WaterBB = prior(MachineFunction::iterator(NewMBB)); + IP = std::find(WaterList.begin(), WaterList.end(), WaterBB); + if (IP != WaterList.end()) + NewWaterList.erase(WaterBB); + + // We are adding new water. Update NewWaterList. + NewWaterList.insert(NewIsland); } + // Remove the original WaterList entry; we want subsequent insertions in + // this vicinity to go after the one we're about to insert. This + // considerably reduces the number of times we have to move the same CPE + // more than once and is also important to ensure the algorithm terminates. + if (IP != WaterList.end()) + WaterList.erase(IP); + // Okay, we know we can put an island before NewMBB now, do it! - MachineBasicBlock *NewIsland = MF.CreateMachineBasicBlock(); MF.insert(NewMBB, NewIsland); // Update internal data structures to account for the newly inserted MBB. @@ -1116,6 +1243,7 @@ bool ARMConstantIslands::HandleConstantPoolUser(MachineFunction &MF, // Now that we have an island to add the CPE to, clone the original CPE and // add it to the island. + U.HighWaterMark = NewIsland; U.CPEMI = BuildMI(NewIsland, DebugLoc::getUnknownLoc(), TII->get(ARM::CONSTPOOL_ENTRY)) .addImm(ID).addConstantPoolIndex(CPI).addImm(Size); @@ -1124,7 +1252,7 @@ bool ARMConstantIslands::HandleConstantPoolUser(MachineFunction &MF, BBOffsets[NewIsland->getNumber()] = BBOffsets[NewMBB->getNumber()]; // Compensate for .align 2 in thumb mode. - if (isThumb && BBOffsets[NewIsland->getNumber()]%4 != 0) + if (isThumb && (BBOffsets[NewIsland->getNumber()]%4 != 0 || HasInlineAsm)) Size += 2; // Increase the size of the island block to account for the new entry. BBSizes[NewIsland->getNumber()] += Size; @@ -1137,7 +1265,8 @@ bool ARMConstantIslands::HandleConstantPoolUser(MachineFunction &MF, break; } - DOUT << " Moved CPE to #" << ID << " CPI=" << CPI << "\t" << *UserMI; + DEBUG(errs() << " Moved CPE to #" << ID << " CPI=" << CPI + << '\t' << *UserMI); return true; } @@ -1193,11 +1322,11 @@ bool ARMConstantIslands::BBIsInRange(MachineInstr *MI,MachineBasicBlock *DestBB, unsigned BrOffset = GetOffsetOf(MI) + PCAdj; unsigned DestOffset = BBOffsets[DestBB->getNumber()]; - DOUT << "Branch of destination BB#" << DestBB->getNumber() - << " from BB#" << MI->getParent()->getNumber() - << " max delta=" << MaxDisp - << " from " << GetOffsetOf(MI) << " to " << DestOffset - << " offset " << int(DestOffset-BrOffset) << "\t" << *MI; + DEBUG(errs() << "Branch of destination BB#" << DestBB->getNumber() + << " from BB#" << MI->getParent()->getNumber() + << " max delta=" << MaxDisp + << " from " << GetOffsetOf(MI) << " to " << DestOffset + << " offset " << int(DestOffset-BrOffset) << "\t" << *MI); if (BrOffset <= DestOffset) { // Branch before the Dest. @@ -1244,7 +1373,7 @@ ARMConstantIslands::FixUpUnconditionalBr(MachineFunction &MF, ImmBranch &Br) { HasFarJump = true; NumUBrFixed++; - DOUT << " Changed B to long jump " << *MI; + DEBUG(errs() << " Changed B to long jump " << *MI); return true; } @@ -1277,7 +1406,7 @@ ARMConstantIslands::FixUpConditionalBr(MachineFunction &MF, ImmBranch &Br) { NumCBrFixed++; if (BMI != MI) { - if (next(MachineBasicBlock::iterator(MI)) == prior(MBB->end()) && + if (llvm::next(MachineBasicBlock::iterator(MI)) == prior(MBB->end()) && BMI->getOpcode() == Br.UncondBr) { // Last MI in the BB is an unconditional branch. Can we simply invert the // condition and swap destinations: @@ -1288,7 +1417,8 @@ ARMConstantIslands::FixUpConditionalBr(MachineFunction &MF, ImmBranch &Br) { // b L1 MachineBasicBlock *NewDest = BMI->getOperand(0).getMBB(); if (BBIsInRange(MI, NewDest, Br.MaxDisp)) { - DOUT << " Invert Bcc condition and swap its destination with " << *BMI; + DEBUG(errs() << " Invert Bcc condition and swap its destination with " + << *BMI); BMI->getOperand(0).setMBB(DestBB); MI->getOperand(0).setMBB(NewDest); MI->getOperand(1).setImm(CC); @@ -1303,16 +1433,16 @@ ARMConstantIslands::FixUpConditionalBr(MachineFunction &MF, ImmBranch &Br) { // branch to the destination. int delta = TII->GetInstSizeInBytes(&MBB->back()); BBSizes[MBB->getNumber()] -= delta; - MachineBasicBlock* SplitBB = next(MachineFunction::iterator(MBB)); + MachineBasicBlock* SplitBB = llvm::next(MachineFunction::iterator(MBB)); AdjustBBOffsetsAfter(SplitBB, -delta); MBB->back().eraseFromParent(); // BBOffsets[SplitBB] is wrong temporarily, fixed below } - MachineBasicBlock *NextBB = next(MachineFunction::iterator(MBB)); + MachineBasicBlock *NextBB = llvm::next(MachineFunction::iterator(MBB)); - DOUT << " Insert B to BB#" << DestBB->getNumber() - << " also invert condition and change dest. to BB#" - << NextBB->getNumber() << "\n"; + DEBUG(errs() << " Insert B to BB#" << DestBB->getNumber() + << " also invert condition and change dest. to BB#" + << NextBB->getNumber() << "\n"); // Insert a new conditional branch and a new unconditional branch. // Also update the ImmBranch as well as adding a new entry for the new branch. @@ -1343,9 +1473,11 @@ bool ARMConstantIslands::UndoLRSpillRestore() { bool MadeChange = false; for (unsigned i = 0, e = PushPopMIs.size(); i != e; ++i) { MachineInstr *MI = PushPopMIs[i]; + // First two operands are predicates, the third is a zero since there + // is no writeback. if (MI->getOpcode() == ARM::tPOP_RET && - MI->getOperand(2).getReg() == ARM::PC && - MI->getNumExplicitOperands() == 3) { + MI->getOperand(3).getReg() == ARM::PC && + MI->getNumExplicitOperands() == 4) { BuildMI(MI->getParent(), MI->getDebugLoc(), TII->get(ARM::tBX_RET)); MI->eraseFromParent(); MadeChange = true; @@ -1398,15 +1530,91 @@ bool ARMConstantIslands::OptimizeThumb2Instructions(MachineFunction &MF) { } } - MadeChange |= OptimizeThumb2JumpTables(MF); MadeChange |= OptimizeThumb2Branches(MF); + MadeChange |= OptimizeThumb2JumpTables(MF); return MadeChange; } bool ARMConstantIslands::OptimizeThumb2Branches(MachineFunction &MF) { - return false; -} + bool MadeChange = false; + for (unsigned i = 0, e = ImmBranches.size(); i != e; ++i) { + ImmBranch &Br = ImmBranches[i]; + unsigned Opcode = Br.MI->getOpcode(); + unsigned NewOpc = 0; + unsigned Scale = 1; + unsigned Bits = 0; + switch (Opcode) { + default: break; + case ARM::t2B: + NewOpc = ARM::tB; + Bits = 11; + Scale = 2; + break; + case ARM::t2Bcc: { + NewOpc = ARM::tBcc; + Bits = 8; + Scale = 2; + break; + } + } + if (NewOpc) { + unsigned MaxOffs = ((1 << (Bits-1))-1) * Scale; + MachineBasicBlock *DestBB = Br.MI->getOperand(0).getMBB(); + if (BBIsInRange(Br.MI, DestBB, MaxOffs)) { + Br.MI->setDesc(TII->get(NewOpc)); + MachineBasicBlock *MBB = Br.MI->getParent(); + BBSizes[MBB->getNumber()] -= 2; + AdjustBBOffsetsAfter(MBB, -2); + ++NumT2BrShrunk; + MadeChange = true; + } + } + + Opcode = Br.MI->getOpcode(); + if (Opcode != ARM::tBcc) + continue; + + NewOpc = 0; + unsigned PredReg = 0; + ARMCC::CondCodes Pred = llvm::getInstrPredicate(Br.MI, PredReg); + if (Pred == ARMCC::EQ) + NewOpc = ARM::tCBZ; + else if (Pred == ARMCC::NE) + NewOpc = ARM::tCBNZ; + if (!NewOpc) + continue; + MachineBasicBlock *DestBB = Br.MI->getOperand(0).getMBB(); + // Check if the distance is within 126. Subtract starting offset by 2 + // because the cmp will be eliminated. + unsigned BrOffset = GetOffsetOf(Br.MI) + 4 - 2; + unsigned DestOffset = BBOffsets[DestBB->getNumber()]; + if (BrOffset < DestOffset && (DestOffset - BrOffset) <= 126) { + MachineBasicBlock::iterator CmpMI = Br.MI; --CmpMI; + if (CmpMI->getOpcode() == ARM::tCMPzi8) { + unsigned Reg = CmpMI->getOperand(0).getReg(); + Pred = llvm::getInstrPredicate(CmpMI, PredReg); + if (Pred == ARMCC::AL && + CmpMI->getOperand(1).getImm() == 0 && + isARMLowRegister(Reg)) { + MachineBasicBlock *MBB = Br.MI->getParent(); + MachineInstr *NewBR = + BuildMI(*MBB, CmpMI, Br.MI->getDebugLoc(), TII->get(NewOpc)) + .addReg(Reg).addMBB(DestBB, Br.MI->getOperand(0).getTargetFlags()); + CmpMI->eraseFromParent(); + Br.MI->eraseFromParent(); + Br.MI = NewBR; + BBSizes[MBB->getNumber()] -= 2; + AdjustBBOffsetsAfter(MBB, -2); + ++NumCBZ; + MadeChange = true; + } + } + } + } + + return MadeChange; +} /// OptimizeThumb2JumpTables - Use tbb / tbh instructions to generate smaller /// jumptables when it's possible. @@ -1415,7 +1623,9 @@ bool ARMConstantIslands::OptimizeThumb2JumpTables(MachineFunction &MF) { // FIXME: After the tables are shrunk, can we get rid some of the // constantpool tables? - const MachineJumpTableInfo *MJTI = MF.getJumpTableInfo(); + MachineJumpTableInfo *MJTI = MF.getJumpTableInfo(); + if (MJTI == 0) return false; + const std::vector &JT = MJTI->getJumpTables(); for (unsigned i = 0, e = T2JumpTables.size(); i != e; ++i) { MachineInstr *MI = T2JumpTables[i]; @@ -1515,3 +1725,101 @@ bool ARMConstantIslands::OptimizeThumb2JumpTables(MachineFunction &MF) { return MadeChange; } + +/// ReorderThumb2JumpTables - Adjust the function's block layout to ensure that +/// jump tables always branch forwards, since that's what tbb and tbh need. +bool ARMConstantIslands::ReorderThumb2JumpTables(MachineFunction &MF) { + bool MadeChange = false; + + MachineJumpTableInfo *MJTI = MF.getJumpTableInfo(); + if (MJTI == 0) return false; + + const std::vector &JT = MJTI->getJumpTables(); + for (unsigned i = 0, e = T2JumpTables.size(); i != e; ++i) { + MachineInstr *MI = T2JumpTables[i]; + const TargetInstrDesc &TID = MI->getDesc(); + unsigned NumOps = TID.getNumOperands(); + unsigned JTOpIdx = NumOps - (TID.isPredicable() ? 3 : 2); + MachineOperand JTOP = MI->getOperand(JTOpIdx); + unsigned JTI = JTOP.getIndex(); + assert(JTI < JT.size()); + + // We prefer if target blocks for the jump table come after the jump + // instruction so we can use TB[BH]. Loop through the target blocks + // and try to adjust them such that that's true. + int JTNumber = MI->getParent()->getNumber(); + const std::vector &JTBBs = JT[JTI].MBBs; + for (unsigned j = 0, ee = JTBBs.size(); j != ee; ++j) { + MachineBasicBlock *MBB = JTBBs[j]; + int DTNumber = MBB->getNumber(); + + if (DTNumber < JTNumber) { + // The destination precedes the switch. Try to move the block forward + // so we have a positive offset. + MachineBasicBlock *NewBB = + AdjustJTTargetBlockForward(MBB, MI->getParent()); + if (NewBB) + MJTI->ReplaceMBBInJumpTable(JTI, JTBBs[j], NewBB); + MadeChange = true; + } + } + } + + return MadeChange; +} + +MachineBasicBlock *ARMConstantIslands:: +AdjustJTTargetBlockForward(MachineBasicBlock *BB, MachineBasicBlock *JTBB) +{ + MachineFunction &MF = *BB->getParent(); + + // If it's the destination block is terminated by an unconditional branch, + // try to move it; otherwise, create a new block following the jump + // table that branches back to the actual target. This is a very simple + // heuristic. FIXME: We can definitely improve it. + MachineBasicBlock *TBB = 0, *FBB = 0; + SmallVector Cond; + SmallVector CondPrior; + MachineFunction::iterator BBi = BB; + MachineFunction::iterator OldPrior = prior(BBi); + + // If the block terminator isn't analyzable, don't try to move the block + bool B = TII->AnalyzeBranch(*BB, TBB, FBB, Cond); + + // If the block ends in an unconditional branch, move it. The prior block + // has to have an analyzable terminator for us to move this one. Be paranoid + // and make sure we're not trying to move the entry block of the function. + if (!B && Cond.empty() && BB != MF.begin() && + !TII->AnalyzeBranch(*OldPrior, TBB, FBB, CondPrior)) { + BB->moveAfter(JTBB); + OldPrior->updateTerminator(); + BB->updateTerminator(); + // Update numbering to account for the block being moved. + MF.RenumberBlocks(); + ++NumJTMoved; + return NULL; + } + + // Create a new MBB for the code after the jump BB. + MachineBasicBlock *NewBB = + MF.CreateMachineBasicBlock(JTBB->getBasicBlock()); + MachineFunction::iterator MBBI = JTBB; ++MBBI; + MF.insert(MBBI, NewBB); + + // Add an unconditional branch from NewBB to BB. + // There doesn't seem to be meaningful DebugInfo available; this doesn't + // correspond directly to anything in the source. + assert (isThumb2 && "Adjusting for TB[BH] but not in Thumb2?"); + BuildMI(NewBB, DebugLoc::getUnknownLoc(), TII->get(ARM::t2B)).addMBB(BB); + + // Update internal data structures to account for the newly inserted MBB. + MF.RenumberBlocks(NewBB); + + // Update the CFG. + NewBB->addSuccessor(BB); + JTBB->removeSuccessor(BB); + JTBB->addSuccessor(NewBB); + + ++NumJTInserted; + return NewBB; +}