1 //===-- ARMConstantIslandPass.cpp - ARM constant islands --------*- C++ -*-===//
3 // The LLVM Compiler Infrastructure
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
8 //===----------------------------------------------------------------------===//
10 // This file contains a pass that splits the constant pool up into 'islands'
11 // which are scattered through-out the function. This is required due to the
12 // limited pc-relative displacements that ARM has.
14 //===----------------------------------------------------------------------===//
16 #define DEBUG_TYPE "arm-cp-islands"
18 #include "ARMAddressingModes.h"
19 #include "ARMMachineFunctionInfo.h"
20 #include "ARMInstrInfo.h"
21 #include "llvm/CodeGen/MachineConstantPool.h"
22 #include "llvm/CodeGen/MachineFunctionPass.h"
23 #include "llvm/CodeGen/MachineInstrBuilder.h"
24 #include "llvm/CodeGen/MachineJumpTableInfo.h"
25 #include "llvm/Target/TargetData.h"
26 #include "llvm/Target/TargetMachine.h"
27 #include "llvm/Support/Debug.h"
28 #include "llvm/Support/ErrorHandling.h"
29 #include "llvm/Support/raw_ostream.h"
30 #include "llvm/ADT/SmallSet.h"
31 #include "llvm/ADT/SmallVector.h"
32 #include "llvm/ADT/STLExtras.h"
33 #include "llvm/ADT/Statistic.h"
34 #include "llvm/Support/CommandLine.h"
38 STATISTIC(NumCPEs, "Number of constpool entries");
39 STATISTIC(NumSplit, "Number of uncond branches inserted");
40 STATISTIC(NumCBrFixed, "Number of cond branches fixed");
41 STATISTIC(NumUBrFixed, "Number of uncond branches fixed");
42 STATISTIC(NumTBs, "Number of table branches generated");
43 STATISTIC(NumT2CPShrunk, "Number of Thumb2 constantpool instructions shrunk");
44 STATISTIC(NumT2BrShrunk, "Number of Thumb2 immediate branches shrunk");
45 STATISTIC(NumCBZ, "Number of CBZ / CBNZ formed");
46 STATISTIC(NumJTMoved, "Number of jump table destination blocks moved");
47 STATISTIC(NumJTInserted, "Number of jump table intermediate blocks inserted");
51 AdjustJumpTableBlocks("arm-adjust-jump-tables", cl::Hidden, cl::init(true),
52 cl::desc("Adjust basic block layout to better use TB[BH]"));
55 /// ARMConstantIslands - Due to limited PC-relative displacements, ARM
56 /// requires constant pool entries to be scattered among the instructions
57 /// inside a function. To do this, it completely ignores the normal LLVM
58 /// constant pool; instead, it places constants wherever it feels like with
59 /// special instructions.
61 /// The terminology used in this pass includes:
62 /// Islands - Clumps of constants placed in the function.
63 /// Water - Potential places where an island could be formed.
64 /// CPE - A constant pool entry that has been placed somewhere, which
65 /// tracks a list of users.
66 class ARMConstantIslands : public MachineFunctionPass {
67 /// BBSizes - The size of each MachineBasicBlock in bytes of code, indexed
68 /// by MBB Number. The two-byte pads required for Thumb alignment are
69 /// counted as part of the following block (i.e., the offset and size for
70 /// a padded block will both be ==2 mod 4).
71 std::vector<unsigned> BBSizes;
73 /// BBOffsets - the offset of each MBB in bytes, starting from 0.
74 /// The two-byte pads required for Thumb alignment are counted as part of
75 /// the following block.
76 std::vector<unsigned> BBOffsets;
78 /// WaterList - A sorted list of basic blocks where islands could be placed
79 /// (i.e. blocks that don't fall through to the following block, due
80 /// to a return, unreachable, or unconditional branch).
81 std::vector<MachineBasicBlock*> WaterList;
83 /// NewWaterList - The subset of WaterList that was created since the
84 /// previous iteration by inserting unconditional branches.
85 SmallSet<MachineBasicBlock*, 4> NewWaterList;
87 typedef std::vector<MachineBasicBlock*>::iterator water_iterator;
89 /// CPUser - One user of a constant pool, keeping the machine instruction
90 /// pointer, the constant pool being referenced, and the max displacement
91 /// allowed from the instruction to the CP. The HighWaterMark records the
92 /// highest basic block where a new CPEntry can be placed. To ensure this
93 /// pass terminates, the CP entries are initially placed at the end of the
94 /// function and then move monotonically to lower addresses. The
95 /// exception to this rule is when the current CP entry for a particular
96 /// CPUser is out of range, but there is another CP entry for the same
97 /// constant value in range. We want to use the existing in-range CP
98 /// entry, but if it later moves out of range, the search for new water
99 /// should resume where it left off. The HighWaterMark is used to record
104 MachineBasicBlock *HighWaterMark;
108 CPUser(MachineInstr *mi, MachineInstr *cpemi, unsigned maxdisp,
109 bool neg, bool soimm)
110 : MI(mi), CPEMI(cpemi), MaxDisp(maxdisp), NegOk(neg), IsSoImm(soimm) {
111 HighWaterMark = CPEMI->getParent();
115 /// CPUsers - Keep track of all of the machine instructions that use various
116 /// constant pools and their max displacement.
117 std::vector<CPUser> CPUsers;
119 /// CPEntry - One per constant pool entry, keeping the machine instruction
120 /// pointer, the constpool index, and the number of CPUser's which
121 /// reference this entry.
126 CPEntry(MachineInstr *cpemi, unsigned cpi, unsigned rc = 0)
127 : CPEMI(cpemi), CPI(cpi), RefCount(rc) {}
130 /// CPEntries - Keep track of all of the constant pool entry machine
131 /// instructions. For each original constpool index (i.e. those that
132 /// existed upon entry to this pass), it keeps a vector of entries.
133 /// Original elements are cloned as we go along; the clones are
134 /// put in the vector of the original element, but have distinct CPIs.
135 std::vector<std::vector<CPEntry> > CPEntries;
137 /// ImmBranch - One per immediate branch, keeping the machine instruction
138 /// pointer, conditional or unconditional, the max displacement,
139 /// and (if isCond is true) the corresponding unconditional branch
143 unsigned MaxDisp : 31;
146 ImmBranch(MachineInstr *mi, unsigned maxdisp, bool cond, int ubr)
147 : MI(mi), MaxDisp(maxdisp), isCond(cond), UncondBr(ubr) {}
150 /// ImmBranches - Keep track of all the immediate branch instructions.
152 std::vector<ImmBranch> ImmBranches;
154 /// PushPopMIs - Keep track of all the Thumb push / pop instructions.
156 SmallVector<MachineInstr*, 4> PushPopMIs;
158 /// T2JumpTables - Keep track of all the Thumb2 jumptable instructions.
159 SmallVector<MachineInstr*, 4> T2JumpTables;
161 /// HasFarJump - True if any far jump instruction has been emitted during
162 /// the branch fix up pass.
165 /// HasInlineAsm - True if the function contains inline assembly.
168 const TargetInstrInfo *TII;
169 const ARMSubtarget *STI;
170 ARMFunctionInfo *AFI;
176 ARMConstantIslands() : MachineFunctionPass(&ID) {}
178 virtual bool runOnMachineFunction(MachineFunction &MF);
180 virtual const char *getPassName() const {
181 return "ARM constant island placement and branch shortening pass";
185 void DoInitialPlacement(MachineFunction &MF,
186 std::vector<MachineInstr*> &CPEMIs);
187 CPEntry *findConstPoolEntry(unsigned CPI, const MachineInstr *CPEMI);
188 void JumpTableFunctionScan(MachineFunction &MF);
189 void InitialFunctionScan(MachineFunction &MF,
190 const std::vector<MachineInstr*> &CPEMIs);
191 MachineBasicBlock *SplitBlockBeforeInstr(MachineInstr *MI);
192 void UpdateForInsertedWaterBlock(MachineBasicBlock *NewBB);
193 void AdjustBBOffsetsAfter(MachineBasicBlock *BB, int delta);
194 bool DecrementOldEntry(unsigned CPI, MachineInstr* CPEMI);
195 int LookForExistingCPEntry(CPUser& U, unsigned UserOffset);
196 bool LookForWater(CPUser&U, unsigned UserOffset, water_iterator &WaterIter);
197 void CreateNewWater(unsigned CPUserIndex, unsigned UserOffset,
198 MachineBasicBlock *&NewMBB);
199 bool HandleConstantPoolUser(MachineFunction &MF, unsigned CPUserIndex);
200 void RemoveDeadCPEMI(MachineInstr *CPEMI);
201 bool RemoveUnusedCPEntries();
202 bool CPEIsInRange(MachineInstr *MI, unsigned UserOffset,
203 MachineInstr *CPEMI, unsigned Disp, bool NegOk,
204 bool DoDump = false);
205 bool WaterIsInRange(unsigned UserOffset, MachineBasicBlock *Water,
207 bool OffsetIsInRange(unsigned UserOffset, unsigned TrialOffset,
208 unsigned Disp, bool NegativeOK, bool IsSoImm = false);
209 bool BBIsInRange(MachineInstr *MI, MachineBasicBlock *BB, unsigned Disp);
210 bool FixUpImmediateBr(MachineFunction &MF, ImmBranch &Br);
211 bool FixUpConditionalBr(MachineFunction &MF, ImmBranch &Br);
212 bool FixUpUnconditionalBr(MachineFunction &MF, ImmBranch &Br);
213 bool UndoLRSpillRestore();
214 bool OptimizeThumb2Instructions(MachineFunction &MF);
215 bool OptimizeThumb2Branches(MachineFunction &MF);
216 bool ReorderThumb2JumpTables(MachineFunction &MF);
217 bool OptimizeThumb2JumpTables(MachineFunction &MF);
218 MachineBasicBlock *AdjustJTTargetBlockForward(MachineBasicBlock *BB,
219 MachineBasicBlock *JTBB);
221 unsigned GetOffsetOf(MachineInstr *MI) const;
223 void verify(MachineFunction &MF);
225 char ARMConstantIslands::ID = 0;
228 /// verify - check BBOffsets, BBSizes, alignment of islands
229 void ARMConstantIslands::verify(MachineFunction &MF) {
230 assert(BBOffsets.size() == BBSizes.size());
231 for (unsigned i = 1, e = BBOffsets.size(); i != e; ++i)
232 assert(BBOffsets[i-1]+BBSizes[i-1] == BBOffsets[i]);
236 for (MachineFunction::iterator MBBI = MF.begin(), E = MF.end();
238 MachineBasicBlock *MBB = MBBI;
240 MBB->begin()->getOpcode() == ARM::CONSTPOOL_ENTRY) {
241 unsigned MBBId = MBB->getNumber();
242 assert(HasInlineAsm ||
243 (BBOffsets[MBBId]%4 == 0 && BBSizes[MBBId]%4 == 0) ||
244 (BBOffsets[MBBId]%4 != 0 && BBSizes[MBBId]%4 != 0));
247 for (unsigned i = 0, e = CPUsers.size(); i != e; ++i) {
248 CPUser &U = CPUsers[i];
249 unsigned UserOffset = GetOffsetOf(U.MI) + (isThumb ? 4 : 8);
250 unsigned CPEOffset = GetOffsetOf(U.CPEMI);
251 unsigned Disp = UserOffset < CPEOffset ? CPEOffset - UserOffset :
252 UserOffset - CPEOffset;
253 assert(Disp <= U.MaxDisp || "Constant pool entry out of range!");
258 /// print block size and offset information - debugging
259 void ARMConstantIslands::dumpBBs() {
260 for (unsigned J = 0, E = BBOffsets.size(); J !=E; ++J) {
261 DEBUG(errs() << "block " << J << " offset " << BBOffsets[J]
262 << " size " << BBSizes[J] << "\n");
266 /// createARMConstantIslandPass - returns an instance of the constpool
268 FunctionPass *llvm::createARMConstantIslandPass() {
269 return new ARMConstantIslands();
272 bool ARMConstantIslands::runOnMachineFunction(MachineFunction &MF) {
273 MachineConstantPool &MCP = *MF.getConstantPool();
275 TII = MF.getTarget().getInstrInfo();
276 AFI = MF.getInfo<ARMFunctionInfo>();
277 STI = &MF.getTarget().getSubtarget<ARMSubtarget>();
279 isThumb = AFI->isThumbFunction();
280 isThumb1 = AFI->isThumb1OnlyFunction();
281 isThumb2 = AFI->isThumb2Function();
284 HasInlineAsm = false;
286 // Renumber all of the machine basic blocks in the function, guaranteeing that
287 // the numbers agree with the position of the block in the function.
290 // Try to reorder and otherwise adjust the block layout to make good use
291 // of the TB[BH] instructions.
292 bool MadeChange = false;
293 if (isThumb2 && AdjustJumpTableBlocks) {
294 JumpTableFunctionScan(MF);
295 MadeChange |= ReorderThumb2JumpTables(MF);
296 // Data is out of date, so clear it. It'll be re-computed later.
297 T2JumpTables.clear();
298 // Blocks may have shifted around. Keep the numbering up to date.
302 // Thumb1 functions containing constant pools get 4-byte alignment.
303 // This is so we can keep exact track of where the alignment padding goes.
305 // ARM and Thumb2 functions need to be 4-byte aligned.
307 MF.EnsureAlignment(2); // 2 = log2(4)
309 // Perform the initial placement of the constant pool entries. To start with,
310 // we put them all at the end of the function.
311 std::vector<MachineInstr*> CPEMIs;
312 if (!MCP.isEmpty()) {
313 DoInitialPlacement(MF, CPEMIs);
315 MF.EnsureAlignment(2); // 2 = log2(4)
318 /// The next UID to take is the first unused one.
319 AFI->initConstPoolEntryUId(CPEMIs.size());
321 // Do the initial scan of the function, building up information about the
322 // sizes of each block, the location of all the water, and finding all of the
323 // constant pool users.
324 InitialFunctionScan(MF, CPEMIs);
327 /// Remove dead constant pool entries.
328 RemoveUnusedCPEntries();
330 // Iteratively place constant pool entries and fix up branches until there
332 unsigned NoCPIters = 0, NoBRIters = 0;
334 bool CPChange = false;
335 for (unsigned i = 0, e = CPUsers.size(); i != e; ++i)
336 CPChange |= HandleConstantPoolUser(MF, i);
337 if (CPChange && ++NoCPIters > 30)
338 llvm_unreachable("Constant Island pass failed to converge!");
341 // Clear NewWaterList now. If we split a block for branches, it should
342 // appear as "new water" for the next iteration of constant pool placement.
343 NewWaterList.clear();
345 bool BRChange = false;
346 for (unsigned i = 0, e = ImmBranches.size(); i != e; ++i)
347 BRChange |= FixUpImmediateBr(MF, ImmBranches[i]);
348 if (BRChange && ++NoBRIters > 30)
349 llvm_unreachable("Branch Fix Up pass failed to converge!");
352 if (!CPChange && !BRChange)
357 // Shrink 32-bit Thumb2 branch, load, and store instructions.
359 MadeChange |= OptimizeThumb2Instructions(MF);
361 // After a while, this might be made debug-only, but it is not expensive.
364 // If LR has been forced spilled and no far jumps (i.e. BL) has been issued.
365 // Undo the spill / restore of LR if possible.
366 if (isThumb && !HasFarJump && AFI->isLRSpilledForFarJump())
367 MadeChange |= UndoLRSpillRestore();
376 T2JumpTables.clear();
381 /// DoInitialPlacement - Perform the initial placement of the constant pool
382 /// entries. To start with, we put them all at the end of the function.
383 void ARMConstantIslands::DoInitialPlacement(MachineFunction &MF,
384 std::vector<MachineInstr*> &CPEMIs) {
385 // Create the basic block to hold the CPE's.
386 MachineBasicBlock *BB = MF.CreateMachineBasicBlock();
389 // Add all of the constants from the constant pool to the end block, use an
390 // identity mapping of CPI's to CPE's.
391 const std::vector<MachineConstantPoolEntry> &CPs =
392 MF.getConstantPool()->getConstants();
394 const TargetData &TD = *MF.getTarget().getTargetData();
395 for (unsigned i = 0, e = CPs.size(); i != e; ++i) {
396 unsigned Size = TD.getTypeAllocSize(CPs[i].getType());
397 // Verify that all constant pool entries are a multiple of 4 bytes. If not,
398 // we would have to pad them out or something so that instructions stay
400 assert((Size & 3) == 0 && "CP Entry not multiple of 4 bytes!");
401 MachineInstr *CPEMI =
402 BuildMI(BB, DebugLoc::getUnknownLoc(), TII->get(ARM::CONSTPOOL_ENTRY))
403 .addImm(i).addConstantPoolIndex(i).addImm(Size);
404 CPEMIs.push_back(CPEMI);
406 // Add a new CPEntry, but no corresponding CPUser yet.
407 std::vector<CPEntry> CPEs;
408 CPEs.push_back(CPEntry(CPEMI, i));
409 CPEntries.push_back(CPEs);
411 DEBUG(errs() << "Moved CPI#" << i << " to end of function as #" << i
416 /// BBHasFallthrough - Return true if the specified basic block can fallthrough
417 /// into the block immediately after it.
418 static bool BBHasFallthrough(MachineBasicBlock *MBB) {
419 // Get the next machine basic block in the function.
420 MachineFunction::iterator MBBI = MBB;
421 if (llvm::next(MBBI) == MBB->getParent()->end()) // Can't fall off end of function.
424 MachineBasicBlock *NextBB = llvm::next(MBBI);
425 for (MachineBasicBlock::succ_iterator I = MBB->succ_begin(),
426 E = MBB->succ_end(); I != E; ++I)
433 /// findConstPoolEntry - Given the constpool index and CONSTPOOL_ENTRY MI,
434 /// look up the corresponding CPEntry.
435 ARMConstantIslands::CPEntry
436 *ARMConstantIslands::findConstPoolEntry(unsigned CPI,
437 const MachineInstr *CPEMI) {
438 std::vector<CPEntry> &CPEs = CPEntries[CPI];
439 // Number of entries per constpool index should be small, just do a
441 for (unsigned i = 0, e = CPEs.size(); i != e; ++i) {
442 if (CPEs[i].CPEMI == CPEMI)
448 /// JumpTableFunctionScan - Do a scan of the function, building up
449 /// information about the sizes of each block and the locations of all
451 void ARMConstantIslands::JumpTableFunctionScan(MachineFunction &MF) {
452 for (MachineFunction::iterator MBBI = MF.begin(), E = MF.end();
454 MachineBasicBlock &MBB = *MBBI;
456 for (MachineBasicBlock::iterator I = MBB.begin(), E = MBB.end();
458 if (I->getDesc().isBranch() && I->getOpcode() == ARM::t2BR_JT)
459 T2JumpTables.push_back(I);
463 /// InitialFunctionScan - Do the initial scan of the function, building up
464 /// information about the sizes of each block, the location of all the water,
465 /// and finding all of the constant pool users.
466 void ARMConstantIslands::InitialFunctionScan(MachineFunction &MF,
467 const std::vector<MachineInstr*> &CPEMIs) {
468 // First thing, see if the function has any inline assembly in it. If so,
469 // we have to be conservative about alignment assumptions, as we don't
470 // know for sure the size of any instructions in the inline assembly.
471 for (MachineFunction::iterator MBBI = MF.begin(), E = MF.end();
473 MachineBasicBlock &MBB = *MBBI;
474 for (MachineBasicBlock::iterator I = MBB.begin(), E = MBB.end();
476 if (I->getOpcode() == ARM::INLINEASM)
480 // Now go back through the instructions and build up our data structures
482 for (MachineFunction::iterator MBBI = MF.begin(), E = MF.end();
484 MachineBasicBlock &MBB = *MBBI;
486 // If this block doesn't fall through into the next MBB, then this is
487 // 'water' that a constant pool island could be placed.
488 if (!BBHasFallthrough(&MBB))
489 WaterList.push_back(&MBB);
491 unsigned MBBSize = 0;
492 for (MachineBasicBlock::iterator I = MBB.begin(), E = MBB.end();
494 // Add instruction size to MBBSize.
495 MBBSize += TII->GetInstSizeInBytes(I);
497 int Opc = I->getOpcode();
498 if (I->getDesc().isBranch()) {
505 continue; // Ignore other JT branches
507 // A Thumb1 table jump may involve padding; for the offsets to
508 // be right, functions containing these must be 4-byte aligned.
509 MF.EnsureAlignment(2U);
510 if ((Offset+MBBSize)%4 != 0 || HasInlineAsm)
511 // FIXME: Add a pseudo ALIGN instruction instead.
512 MBBSize += 2; // padding
513 continue; // Does not get an entry in ImmBranches
515 T2JumpTables.push_back(I);
516 continue; // Does not get an entry in ImmBranches
547 // Record this immediate branch.
548 unsigned MaxOffs = ((1 << (Bits-1))-1) * Scale;
549 ImmBranches.push_back(ImmBranch(I, MaxOffs, isCond, UOpc));
552 if (Opc == ARM::tPUSH || Opc == ARM::tPOP_RET)
553 PushPopMIs.push_back(I);
555 if (Opc == ARM::CONSTPOOL_ENTRY)
558 // Scan the instructions for constant pool operands.
559 for (unsigned op = 0, e = I->getNumOperands(); op != e; ++op)
560 if (I->getOperand(op).isCPI()) {
561 // We found one. The addressing mode tells us the max displacement
562 // from the PC that this instruction permits.
564 // Basic size info comes from the TSFlags field.
568 bool IsSoImm = false;
572 llvm_unreachable("Unknown addressing mode for CP reference!");
575 // Taking the address of a CP entry.
577 // This takes a SoImm, which is 8 bit immediate rotated. We'll
578 // pretend the maximum offset is 255 * 4. Since each instruction
579 // 4 byte wide, this is always correct. We'll check for other
580 // displacements that fits in a SoImm as well.
586 case ARM::t2LEApcrel:
598 Bits = 12; // +-offset_12
605 Scale = 4; // +(offset_8*4)
611 Scale = 4; // +-(offset_8*4)
616 // Remember that this is a user of a CP entry.
617 unsigned CPI = I->getOperand(op).getIndex();
618 MachineInstr *CPEMI = CPEMIs[CPI];
619 unsigned MaxOffs = ((1 << Bits)-1) * Scale;
620 CPUsers.push_back(CPUser(I, CPEMI, MaxOffs, NegOk, IsSoImm));
622 // Increment corresponding CPEntry reference count.
623 CPEntry *CPE = findConstPoolEntry(CPI, CPEMI);
624 assert(CPE && "Cannot find a corresponding CPEntry!");
627 // Instructions can only use one CP entry, don't bother scanning the
628 // rest of the operands.
633 // In thumb mode, if this block is a constpool island, we may need padding
634 // so it's aligned on 4 byte boundary.
637 MBB.begin()->getOpcode() == ARM::CONSTPOOL_ENTRY &&
638 ((Offset%4) != 0 || HasInlineAsm))
641 BBSizes.push_back(MBBSize);
642 BBOffsets.push_back(Offset);
647 /// GetOffsetOf - Return the current offset of the specified machine instruction
648 /// from the start of the function. This offset changes as stuff is moved
649 /// around inside the function.
650 unsigned ARMConstantIslands::GetOffsetOf(MachineInstr *MI) const {
651 MachineBasicBlock *MBB = MI->getParent();
653 // The offset is composed of two things: the sum of the sizes of all MBB's
654 // before this instruction's block, and the offset from the start of the block
656 unsigned Offset = BBOffsets[MBB->getNumber()];
658 // If we're looking for a CONSTPOOL_ENTRY in Thumb, see if this block has
659 // alignment padding, and compensate if so.
661 MI->getOpcode() == ARM::CONSTPOOL_ENTRY &&
662 (Offset%4 != 0 || HasInlineAsm))
665 // Sum instructions before MI in MBB.
666 for (MachineBasicBlock::iterator I = MBB->begin(); ; ++I) {
667 assert(I != MBB->end() && "Didn't find MI in its own basic block?");
668 if (&*I == MI) return Offset;
669 Offset += TII->GetInstSizeInBytes(I);
673 /// CompareMBBNumbers - Little predicate function to sort the WaterList by MBB
675 static bool CompareMBBNumbers(const MachineBasicBlock *LHS,
676 const MachineBasicBlock *RHS) {
677 return LHS->getNumber() < RHS->getNumber();
680 /// UpdateForInsertedWaterBlock - When a block is newly inserted into the
681 /// machine function, it upsets all of the block numbers. Renumber the blocks
682 /// and update the arrays that parallel this numbering.
683 void ARMConstantIslands::UpdateForInsertedWaterBlock(MachineBasicBlock *NewBB) {
684 // Renumber the MBB's to keep them consequtive.
685 NewBB->getParent()->RenumberBlocks(NewBB);
687 // Insert a size into BBSizes to align it properly with the (newly
688 // renumbered) block numbers.
689 BBSizes.insert(BBSizes.begin()+NewBB->getNumber(), 0);
691 // Likewise for BBOffsets.
692 BBOffsets.insert(BBOffsets.begin()+NewBB->getNumber(), 0);
694 // Next, update WaterList. Specifically, we need to add NewMBB as having
695 // available water after it.
697 std::lower_bound(WaterList.begin(), WaterList.end(), NewBB,
699 WaterList.insert(IP, NewBB);
703 /// Split the basic block containing MI into two blocks, which are joined by
704 /// an unconditional branch. Update data structures and renumber blocks to
705 /// account for this change and returns the newly created block.
706 MachineBasicBlock *ARMConstantIslands::SplitBlockBeforeInstr(MachineInstr *MI) {
707 MachineBasicBlock *OrigBB = MI->getParent();
708 MachineFunction &MF = *OrigBB->getParent();
710 // Create a new MBB for the code after the OrigBB.
711 MachineBasicBlock *NewBB =
712 MF.CreateMachineBasicBlock(OrigBB->getBasicBlock());
713 MachineFunction::iterator MBBI = OrigBB; ++MBBI;
714 MF.insert(MBBI, NewBB);
716 // Splice the instructions starting with MI over to NewBB.
717 NewBB->splice(NewBB->end(), OrigBB, MI, OrigBB->end());
719 // Add an unconditional branch from OrigBB to NewBB.
720 // Note the new unconditional branch is not being recorded.
721 // There doesn't seem to be meaningful DebugInfo available; this doesn't
722 // correspond to anything in the source.
723 unsigned Opc = isThumb ? (isThumb2 ? ARM::t2B : ARM::tB) : ARM::B;
724 BuildMI(OrigBB, DebugLoc::getUnknownLoc(), TII->get(Opc)).addMBB(NewBB);
727 // Update the CFG. All succs of OrigBB are now succs of NewBB.
728 while (!OrigBB->succ_empty()) {
729 MachineBasicBlock *Succ = *OrigBB->succ_begin();
730 OrigBB->removeSuccessor(Succ);
731 NewBB->addSuccessor(Succ);
733 // This pass should be run after register allocation, so there should be no
734 // PHI nodes to update.
735 assert((Succ->empty() || !Succ->begin()->isPHI())
736 && "PHI nodes should be eliminated by now!");
739 // OrigBB branches to NewBB.
740 OrigBB->addSuccessor(NewBB);
742 // Update internal data structures to account for the newly inserted MBB.
743 // This is almost the same as UpdateForInsertedWaterBlock, except that
744 // the Water goes after OrigBB, not NewBB.
745 MF.RenumberBlocks(NewBB);
747 // Insert a size into BBSizes to align it properly with the (newly
748 // renumbered) block numbers.
749 BBSizes.insert(BBSizes.begin()+NewBB->getNumber(), 0);
751 // Likewise for BBOffsets.
752 BBOffsets.insert(BBOffsets.begin()+NewBB->getNumber(), 0);
754 // Next, update WaterList. Specifically, we need to add OrigMBB as having
755 // available water after it (but not if it's already there, which happens
756 // when splitting before a conditional branch that is followed by an
757 // unconditional branch - in that case we want to insert NewBB).
759 std::lower_bound(WaterList.begin(), WaterList.end(), OrigBB,
761 MachineBasicBlock* WaterBB = *IP;
762 if (WaterBB == OrigBB)
763 WaterList.insert(llvm::next(IP), NewBB);
765 WaterList.insert(IP, OrigBB);
766 NewWaterList.insert(OrigBB);
768 // Figure out how large the first NewMBB is. (It cannot
769 // contain a constpool_entry or tablejump.)
770 unsigned NewBBSize = 0;
771 for (MachineBasicBlock::iterator I = NewBB->begin(), E = NewBB->end();
773 NewBBSize += TII->GetInstSizeInBytes(I);
775 unsigned OrigBBI = OrigBB->getNumber();
776 unsigned NewBBI = NewBB->getNumber();
777 // Set the size of NewBB in BBSizes.
778 BBSizes[NewBBI] = NewBBSize;
780 // We removed instructions from UserMBB, subtract that off from its size.
781 // Add 2 or 4 to the block to count the unconditional branch we added to it.
782 int delta = isThumb1 ? 2 : 4;
783 BBSizes[OrigBBI] -= NewBBSize - delta;
785 // ...and adjust BBOffsets for NewBB accordingly.
786 BBOffsets[NewBBI] = BBOffsets[OrigBBI] + BBSizes[OrigBBI];
788 // All BBOffsets following these blocks must be modified.
789 AdjustBBOffsetsAfter(NewBB, delta);
794 /// OffsetIsInRange - Checks whether UserOffset (the location of a constant pool
795 /// reference) is within MaxDisp of TrialOffset (a proposed location of a
796 /// constant pool entry).
797 bool ARMConstantIslands::OffsetIsInRange(unsigned UserOffset,
798 unsigned TrialOffset, unsigned MaxDisp,
799 bool NegativeOK, bool IsSoImm) {
800 // On Thumb offsets==2 mod 4 are rounded down by the hardware for
801 // purposes of the displacement computation; compensate for that here.
802 // Effectively, the valid range of displacements is 2 bytes smaller for such
804 unsigned TotalAdj = 0;
805 if (isThumb && UserOffset%4 !=0) {
809 // CPEs will be rounded up to a multiple of 4.
810 if (isThumb && TrialOffset%4 != 0) {
815 // In Thumb2 mode, later branch adjustments can shift instructions up and
816 // cause alignment change. In the worst case scenario this can cause the
817 // user's effective address to be subtracted by 2 and the CPE's address to
819 if (isThumb2 && TotalAdj != 4)
820 MaxDisp -= (4 - TotalAdj);
822 if (UserOffset <= TrialOffset) {
823 // User before the Trial.
824 if (TrialOffset - UserOffset <= MaxDisp)
826 // FIXME: Make use full range of soimm values.
827 } else if (NegativeOK) {
828 if (UserOffset - TrialOffset <= MaxDisp)
830 // FIXME: Make use full range of soimm values.
835 /// WaterIsInRange - Returns true if a CPE placed after the specified
836 /// Water (a basic block) will be in range for the specific MI.
838 bool ARMConstantIslands::WaterIsInRange(unsigned UserOffset,
839 MachineBasicBlock* Water, CPUser &U) {
840 unsigned MaxDisp = U.MaxDisp;
841 unsigned CPEOffset = BBOffsets[Water->getNumber()] +
842 BBSizes[Water->getNumber()];
844 // If the CPE is to be inserted before the instruction, that will raise
845 // the offset of the instruction.
846 if (CPEOffset < UserOffset)
847 UserOffset += U.CPEMI->getOperand(2).getImm();
849 return OffsetIsInRange(UserOffset, CPEOffset, MaxDisp, U.NegOk, U.IsSoImm);
852 /// CPEIsInRange - Returns true if the distance between specific MI and
853 /// specific ConstPool entry instruction can fit in MI's displacement field.
854 bool ARMConstantIslands::CPEIsInRange(MachineInstr *MI, unsigned UserOffset,
855 MachineInstr *CPEMI, unsigned MaxDisp,
856 bool NegOk, bool DoDump) {
857 unsigned CPEOffset = GetOffsetOf(CPEMI);
858 assert((CPEOffset%4 == 0 || HasInlineAsm) && "Misaligned CPE");
861 DEBUG(errs() << "User of CPE#" << CPEMI->getOperand(0).getImm()
862 << " max delta=" << MaxDisp
863 << " insn address=" << UserOffset
864 << " CPE address=" << CPEOffset
865 << " offset=" << int(CPEOffset-UserOffset) << "\t" << *MI);
868 return OffsetIsInRange(UserOffset, CPEOffset, MaxDisp, NegOk);
872 /// BBIsJumpedOver - Return true of the specified basic block's only predecessor
873 /// unconditionally branches to its only successor.
874 static bool BBIsJumpedOver(MachineBasicBlock *MBB) {
875 if (MBB->pred_size() != 1 || MBB->succ_size() != 1)
878 MachineBasicBlock *Succ = *MBB->succ_begin();
879 MachineBasicBlock *Pred = *MBB->pred_begin();
880 MachineInstr *PredMI = &Pred->back();
881 if (PredMI->getOpcode() == ARM::B || PredMI->getOpcode() == ARM::tB
882 || PredMI->getOpcode() == ARM::t2B)
883 return PredMI->getOperand(0).getMBB() == Succ;
888 void ARMConstantIslands::AdjustBBOffsetsAfter(MachineBasicBlock *BB,
890 MachineFunction::iterator MBBI = BB; MBBI = llvm::next(MBBI);
891 for(unsigned i = BB->getNumber()+1, e = BB->getParent()->getNumBlockIDs();
893 BBOffsets[i] += delta;
894 // If some existing blocks have padding, adjust the padding as needed, a
895 // bit tricky. delta can be negative so don't use % on that.
898 MachineBasicBlock *MBB = MBBI;
899 if (!MBB->empty() && !HasInlineAsm) {
900 // Constant pool entries require padding.
901 if (MBB->begin()->getOpcode() == ARM::CONSTPOOL_ENTRY) {
902 unsigned OldOffset = BBOffsets[i] - delta;
903 if ((OldOffset%4) == 0 && (BBOffsets[i]%4) != 0) {
907 } else if ((OldOffset%4) != 0 && (BBOffsets[i]%4) == 0) {
908 // remove existing padding
913 // Thumb1 jump tables require padding. They should be at the end;
914 // following unconditional branches are removed by AnalyzeBranch.
915 MachineInstr *ThumbJTMI = prior(MBB->end());
916 if (ThumbJTMI->getOpcode() == ARM::tBR_JTr) {
917 unsigned NewMIOffset = GetOffsetOf(ThumbJTMI);
918 unsigned OldMIOffset = NewMIOffset - delta;
919 if ((OldMIOffset%4) == 0 && (NewMIOffset%4) != 0) {
920 // remove existing padding
923 } else if ((OldMIOffset%4) != 0 && (NewMIOffset%4) == 0) {
932 MBBI = llvm::next(MBBI);
936 /// DecrementOldEntry - find the constant pool entry with index CPI
937 /// and instruction CPEMI, and decrement its refcount. If the refcount
938 /// becomes 0 remove the entry and instruction. Returns true if we removed
939 /// the entry, false if we didn't.
941 bool ARMConstantIslands::DecrementOldEntry(unsigned CPI, MachineInstr *CPEMI) {
942 // Find the old entry. Eliminate it if it is no longer used.
943 CPEntry *CPE = findConstPoolEntry(CPI, CPEMI);
944 assert(CPE && "Unexpected!");
945 if (--CPE->RefCount == 0) {
946 RemoveDeadCPEMI(CPEMI);
954 /// LookForCPEntryInRange - see if the currently referenced CPE is in range;
955 /// if not, see if an in-range clone of the CPE is in range, and if so,
956 /// change the data structures so the user references the clone. Returns:
957 /// 0 = no existing entry found
958 /// 1 = entry found, and there were no code insertions or deletions
959 /// 2 = entry found, and there were code insertions or deletions
960 int ARMConstantIslands::LookForExistingCPEntry(CPUser& U, unsigned UserOffset)
962 MachineInstr *UserMI = U.MI;
963 MachineInstr *CPEMI = U.CPEMI;
965 // Check to see if the CPE is already in-range.
966 if (CPEIsInRange(UserMI, UserOffset, CPEMI, U.MaxDisp, U.NegOk, true)) {
967 DEBUG(errs() << "In range\n");
971 // No. Look for previously created clones of the CPE that are in range.
972 unsigned CPI = CPEMI->getOperand(1).getIndex();
973 std::vector<CPEntry> &CPEs = CPEntries[CPI];
974 for (unsigned i = 0, e = CPEs.size(); i != e; ++i) {
975 // We already tried this one
976 if (CPEs[i].CPEMI == CPEMI)
978 // Removing CPEs can leave empty entries, skip
979 if (CPEs[i].CPEMI == NULL)
981 if (CPEIsInRange(UserMI, UserOffset, CPEs[i].CPEMI, U.MaxDisp, U.NegOk)) {
982 DEBUG(errs() << "Replacing CPE#" << CPI << " with CPE#"
983 << CPEs[i].CPI << "\n");
984 // Point the CPUser node to the replacement
985 U.CPEMI = CPEs[i].CPEMI;
986 // Change the CPI in the instruction operand to refer to the clone.
987 for (unsigned j = 0, e = UserMI->getNumOperands(); j != e; ++j)
988 if (UserMI->getOperand(j).isCPI()) {
989 UserMI->getOperand(j).setIndex(CPEs[i].CPI);
992 // Adjust the refcount of the clone...
994 // ...and the original. If we didn't remove the old entry, none of the
995 // addresses changed, so we don't need another pass.
996 return DecrementOldEntry(CPI, CPEMI) ? 2 : 1;
1002 /// getUnconditionalBrDisp - Returns the maximum displacement that can fit in
1003 /// the specific unconditional branch instruction.
1004 static inline unsigned getUnconditionalBrDisp(int Opc) {
1007 return ((1<<10)-1)*2;
1009 return ((1<<23)-1)*2;
1014 return ((1<<23)-1)*4;
1017 /// LookForWater - Look for an existing entry in the WaterList in which
1018 /// we can place the CPE referenced from U so it's within range of U's MI.
1019 /// Returns true if found, false if not. If it returns true, WaterIter
1020 /// is set to the WaterList entry. For Thumb, prefer water that will not
1021 /// introduce padding to water that will. To ensure that this pass
1022 /// terminates, the CPE location for a particular CPUser is only allowed to
1023 /// move to a lower address, so search backward from the end of the list and
1024 /// prefer the first water that is in range.
1025 bool ARMConstantIslands::LookForWater(CPUser &U, unsigned UserOffset,
1026 water_iterator &WaterIter) {
1027 if (WaterList.empty())
1030 bool FoundWaterThatWouldPad = false;
1031 water_iterator IPThatWouldPad;
1032 for (water_iterator IP = prior(WaterList.end()),
1033 B = WaterList.begin();; --IP) {
1034 MachineBasicBlock* WaterBB = *IP;
1035 // Check if water is in range and is either at a lower address than the
1036 // current "high water mark" or a new water block that was created since
1037 // the previous iteration by inserting an unconditional branch. In the
1038 // latter case, we want to allow resetting the high water mark back to
1039 // this new water since we haven't seen it before. Inserting branches
1040 // should be relatively uncommon and when it does happen, we want to be
1041 // sure to take advantage of it for all the CPEs near that block, so that
1042 // we don't insert more branches than necessary.
1043 if (WaterIsInRange(UserOffset, WaterBB, U) &&
1044 (WaterBB->getNumber() < U.HighWaterMark->getNumber() ||
1045 NewWaterList.count(WaterBB))) {
1046 unsigned WBBId = WaterBB->getNumber();
1048 (BBOffsets[WBBId] + BBSizes[WBBId])%4 != 0) {
1049 // This is valid Water, but would introduce padding. Remember
1050 // it in case we don't find any Water that doesn't do this.
1051 if (!FoundWaterThatWouldPad) {
1052 FoundWaterThatWouldPad = true;
1053 IPThatWouldPad = IP;
1063 if (FoundWaterThatWouldPad) {
1064 WaterIter = IPThatWouldPad;
1070 /// CreateNewWater - No existing WaterList entry will work for
1071 /// CPUsers[CPUserIndex], so create a place to put the CPE. The end of the
1072 /// block is used if in range, and the conditional branch munged so control
1073 /// flow is correct. Otherwise the block is split to create a hole with an
1074 /// unconditional branch around it. In either case NewMBB is set to a
1075 /// block following which the new island can be inserted (the WaterList
1076 /// is not adjusted).
1077 void ARMConstantIslands::CreateNewWater(unsigned CPUserIndex,
1078 unsigned UserOffset,
1079 MachineBasicBlock *&NewMBB) {
1080 CPUser &U = CPUsers[CPUserIndex];
1081 MachineInstr *UserMI = U.MI;
1082 MachineInstr *CPEMI = U.CPEMI;
1083 MachineBasicBlock *UserMBB = UserMI->getParent();
1084 unsigned OffsetOfNextBlock = BBOffsets[UserMBB->getNumber()] +
1085 BBSizes[UserMBB->getNumber()];
1086 assert(OffsetOfNextBlock== BBOffsets[UserMBB->getNumber()+1]);
1088 // If the block does not end in an unconditional branch already, and if the
1089 // end of the block is within range, make new water there. (The addition
1090 // below is for the unconditional branch we will be adding: 4 bytes on ARM +
1091 // Thumb2, 2 on Thumb1. Possible Thumb1 alignment padding is allowed for
1092 // inside OffsetIsInRange.
1093 if (BBHasFallthrough(UserMBB) &&
1094 OffsetIsInRange(UserOffset, OffsetOfNextBlock + (isThumb1 ? 2: 4),
1095 U.MaxDisp, U.NegOk, U.IsSoImm)) {
1096 DEBUG(errs() << "Split at end of block\n");
1097 if (&UserMBB->back() == UserMI)
1098 assert(BBHasFallthrough(UserMBB) && "Expected a fallthrough BB!");
1099 NewMBB = llvm::next(MachineFunction::iterator(UserMBB));
1100 // Add an unconditional branch from UserMBB to fallthrough block.
1101 // Record it for branch lengthening; this new branch will not get out of
1102 // range, but if the preceding conditional branch is out of range, the
1103 // targets will be exchanged, and the altered branch may be out of
1104 // range, so the machinery has to know about it.
1105 int UncondBr = isThumb ? ((isThumb2) ? ARM::t2B : ARM::tB) : ARM::B;
1106 BuildMI(UserMBB, DebugLoc::getUnknownLoc(),
1107 TII->get(UncondBr)).addMBB(NewMBB);
1108 unsigned MaxDisp = getUnconditionalBrDisp(UncondBr);
1109 ImmBranches.push_back(ImmBranch(&UserMBB->back(),
1110 MaxDisp, false, UncondBr));
1111 int delta = isThumb1 ? 2 : 4;
1112 BBSizes[UserMBB->getNumber()] += delta;
1113 AdjustBBOffsetsAfter(UserMBB, delta);
1115 // What a big block. Find a place within the block to split it.
1116 // This is a little tricky on Thumb1 since instructions are 2 bytes
1117 // and constant pool entries are 4 bytes: if instruction I references
1118 // island CPE, and instruction I+1 references CPE', it will
1119 // not work well to put CPE as far forward as possible, since then
1120 // CPE' cannot immediately follow it (that location is 2 bytes
1121 // farther away from I+1 than CPE was from I) and we'd need to create
1122 // a new island. So, we make a first guess, then walk through the
1123 // instructions between the one currently being looked at and the
1124 // possible insertion point, and make sure any other instructions
1125 // that reference CPEs will be able to use the same island area;
1126 // if not, we back up the insertion point.
1128 // The 4 in the following is for the unconditional branch we'll be
1129 // inserting (allows for long branch on Thumb1). Alignment of the
1130 // island is handled inside OffsetIsInRange.
1131 unsigned BaseInsertOffset = UserOffset + U.MaxDisp -4;
1132 // This could point off the end of the block if we've already got
1133 // constant pool entries following this block; only the last one is
1134 // in the water list. Back past any possible branches (allow for a
1135 // conditional and a maximally long unconditional).
1136 if (BaseInsertOffset >= BBOffsets[UserMBB->getNumber()+1])
1137 BaseInsertOffset = BBOffsets[UserMBB->getNumber()+1] -
1139 unsigned EndInsertOffset = BaseInsertOffset +
1140 CPEMI->getOperand(2).getImm();
1141 MachineBasicBlock::iterator MI = UserMI;
1143 unsigned CPUIndex = CPUserIndex+1;
1144 for (unsigned Offset = UserOffset+TII->GetInstSizeInBytes(UserMI);
1145 Offset < BaseInsertOffset;
1146 Offset += TII->GetInstSizeInBytes(MI),
1147 MI = llvm::next(MI)) {
1148 if (CPUIndex < CPUsers.size() && CPUsers[CPUIndex].MI == MI) {
1149 CPUser &U = CPUsers[CPUIndex];
1150 if (!OffsetIsInRange(Offset, EndInsertOffset,
1151 U.MaxDisp, U.NegOk, U.IsSoImm)) {
1152 BaseInsertOffset -= (isThumb1 ? 2 : 4);
1153 EndInsertOffset -= (isThumb1 ? 2 : 4);
1155 // This is overly conservative, as we don't account for CPEMIs
1156 // being reused within the block, but it doesn't matter much.
1157 EndInsertOffset += CPUsers[CPUIndex].CPEMI->getOperand(2).getImm();
1161 DEBUG(errs() << "Split in middle of big block\n");
1162 NewMBB = SplitBlockBeforeInstr(prior(MI));
1166 /// HandleConstantPoolUser - Analyze the specified user, checking to see if it
1167 /// is out-of-range. If so, pick up the constant pool value and move it some
1168 /// place in-range. Return true if we changed any addresses (thus must run
1169 /// another pass of branch lengthening), false otherwise.
1170 bool ARMConstantIslands::HandleConstantPoolUser(MachineFunction &MF,
1171 unsigned CPUserIndex) {
1172 CPUser &U = CPUsers[CPUserIndex];
1173 MachineInstr *UserMI = U.MI;
1174 MachineInstr *CPEMI = U.CPEMI;
1175 unsigned CPI = CPEMI->getOperand(1).getIndex();
1176 unsigned Size = CPEMI->getOperand(2).getImm();
1177 // Compute this only once, it's expensive. The 4 or 8 is the value the
1178 // hardware keeps in the PC.
1179 unsigned UserOffset = GetOffsetOf(UserMI) + (isThumb ? 4 : 8);
1181 // See if the current entry is within range, or there is a clone of it
1183 int result = LookForExistingCPEntry(U, UserOffset);
1184 if (result==1) return false;
1185 else if (result==2) return true;
1187 // No existing clone of this CPE is within range.
1188 // We will be generating a new clone. Get a UID for it.
1189 unsigned ID = AFI->createConstPoolEntryUId();
1191 // Look for water where we can place this CPE.
1192 MachineBasicBlock *NewIsland = MF.CreateMachineBasicBlock();
1193 MachineBasicBlock *NewMBB;
1195 if (LookForWater(U, UserOffset, IP)) {
1196 DEBUG(errs() << "found water in range\n");
1197 MachineBasicBlock *WaterBB = *IP;
1199 // If the original WaterList entry was "new water" on this iteration,
1200 // propagate that to the new island. This is just keeping NewWaterList
1201 // updated to match the WaterList, which will be updated below.
1202 if (NewWaterList.count(WaterBB)) {
1203 NewWaterList.erase(WaterBB);
1204 NewWaterList.insert(NewIsland);
1206 // The new CPE goes before the following block (NewMBB).
1207 NewMBB = llvm::next(MachineFunction::iterator(WaterBB));
1211 DEBUG(errs() << "No water found\n");
1212 CreateNewWater(CPUserIndex, UserOffset, NewMBB);
1214 // SplitBlockBeforeInstr adds to WaterList, which is important when it is
1215 // called while handling branches so that the water will be seen on the
1216 // next iteration for constant pools, but in this context, we don't want
1217 // it. Check for this so it will be removed from the WaterList.
1218 // Also remove any entry from NewWaterList.
1219 MachineBasicBlock *WaterBB = prior(MachineFunction::iterator(NewMBB));
1220 IP = std::find(WaterList.begin(), WaterList.end(), WaterBB);
1221 if (IP != WaterList.end())
1222 NewWaterList.erase(WaterBB);
1224 // We are adding new water. Update NewWaterList.
1225 NewWaterList.insert(NewIsland);
1228 // Remove the original WaterList entry; we want subsequent insertions in
1229 // this vicinity to go after the one we're about to insert. This
1230 // considerably reduces the number of times we have to move the same CPE
1231 // more than once and is also important to ensure the algorithm terminates.
1232 if (IP != WaterList.end())
1233 WaterList.erase(IP);
1235 // Okay, we know we can put an island before NewMBB now, do it!
1236 MF.insert(NewMBB, NewIsland);
1238 // Update internal data structures to account for the newly inserted MBB.
1239 UpdateForInsertedWaterBlock(NewIsland);
1241 // Decrement the old entry, and remove it if refcount becomes 0.
1242 DecrementOldEntry(CPI, CPEMI);
1244 // Now that we have an island to add the CPE to, clone the original CPE and
1245 // add it to the island.
1246 U.HighWaterMark = NewIsland;
1247 U.CPEMI = BuildMI(NewIsland, DebugLoc::getUnknownLoc(),
1248 TII->get(ARM::CONSTPOOL_ENTRY))
1249 .addImm(ID).addConstantPoolIndex(CPI).addImm(Size);
1250 CPEntries[CPI].push_back(CPEntry(U.CPEMI, ID, 1));
1253 BBOffsets[NewIsland->getNumber()] = BBOffsets[NewMBB->getNumber()];
1254 // Compensate for .align 2 in thumb mode.
1255 if (isThumb && (BBOffsets[NewIsland->getNumber()]%4 != 0 || HasInlineAsm))
1257 // Increase the size of the island block to account for the new entry.
1258 BBSizes[NewIsland->getNumber()] += Size;
1259 AdjustBBOffsetsAfter(NewIsland, Size);
1261 // Finally, change the CPI in the instruction operand to be ID.
1262 for (unsigned i = 0, e = UserMI->getNumOperands(); i != e; ++i)
1263 if (UserMI->getOperand(i).isCPI()) {
1264 UserMI->getOperand(i).setIndex(ID);
1268 DEBUG(errs() << " Moved CPE to #" << ID << " CPI=" << CPI
1269 << '\t' << *UserMI);
1274 /// RemoveDeadCPEMI - Remove a dead constant pool entry instruction. Update
1275 /// sizes and offsets of impacted basic blocks.
1276 void ARMConstantIslands::RemoveDeadCPEMI(MachineInstr *CPEMI) {
1277 MachineBasicBlock *CPEBB = CPEMI->getParent();
1278 unsigned Size = CPEMI->getOperand(2).getImm();
1279 CPEMI->eraseFromParent();
1280 BBSizes[CPEBB->getNumber()] -= Size;
1281 // All succeeding offsets have the current size value added in, fix this.
1282 if (CPEBB->empty()) {
1283 // In thumb1 mode, the size of island may be padded by two to compensate for
1284 // the alignment requirement. Then it will now be 2 when the block is
1285 // empty, so fix this.
1286 // All succeeding offsets have the current size value added in, fix this.
1287 if (BBSizes[CPEBB->getNumber()] != 0) {
1288 Size += BBSizes[CPEBB->getNumber()];
1289 BBSizes[CPEBB->getNumber()] = 0;
1292 AdjustBBOffsetsAfter(CPEBB, -Size);
1293 // An island has only one predecessor BB and one successor BB. Check if
1294 // this BB's predecessor jumps directly to this BB's successor. This
1295 // shouldn't happen currently.
1296 assert(!BBIsJumpedOver(CPEBB) && "How did this happen?");
1297 // FIXME: remove the empty blocks after all the work is done?
1300 /// RemoveUnusedCPEntries - Remove constant pool entries whose refcounts
1302 bool ARMConstantIslands::RemoveUnusedCPEntries() {
1303 unsigned MadeChange = false;
1304 for (unsigned i = 0, e = CPEntries.size(); i != e; ++i) {
1305 std::vector<CPEntry> &CPEs = CPEntries[i];
1306 for (unsigned j = 0, ee = CPEs.size(); j != ee; ++j) {
1307 if (CPEs[j].RefCount == 0 && CPEs[j].CPEMI) {
1308 RemoveDeadCPEMI(CPEs[j].CPEMI);
1309 CPEs[j].CPEMI = NULL;
1317 /// BBIsInRange - Returns true if the distance between specific MI and
1318 /// specific BB can fit in MI's displacement field.
1319 bool ARMConstantIslands::BBIsInRange(MachineInstr *MI,MachineBasicBlock *DestBB,
1321 unsigned PCAdj = isThumb ? 4 : 8;
1322 unsigned BrOffset = GetOffsetOf(MI) + PCAdj;
1323 unsigned DestOffset = BBOffsets[DestBB->getNumber()];
1325 DEBUG(errs() << "Branch of destination BB#" << DestBB->getNumber()
1326 << " from BB#" << MI->getParent()->getNumber()
1327 << " max delta=" << MaxDisp
1328 << " from " << GetOffsetOf(MI) << " to " << DestOffset
1329 << " offset " << int(DestOffset-BrOffset) << "\t" << *MI);
1331 if (BrOffset <= DestOffset) {
1332 // Branch before the Dest.
1333 if (DestOffset-BrOffset <= MaxDisp)
1336 if (BrOffset-DestOffset <= MaxDisp)
1342 /// FixUpImmediateBr - Fix up an immediate branch whose destination is too far
1343 /// away to fit in its displacement field.
1344 bool ARMConstantIslands::FixUpImmediateBr(MachineFunction &MF, ImmBranch &Br) {
1345 MachineInstr *MI = Br.MI;
1346 MachineBasicBlock *DestBB = MI->getOperand(0).getMBB();
1348 // Check to see if the DestBB is already in-range.
1349 if (BBIsInRange(MI, DestBB, Br.MaxDisp))
1353 return FixUpUnconditionalBr(MF, Br);
1354 return FixUpConditionalBr(MF, Br);
1357 /// FixUpUnconditionalBr - Fix up an unconditional branch whose destination is
1358 /// too far away to fit in its displacement field. If the LR register has been
1359 /// spilled in the epilogue, then we can use BL to implement a far jump.
1360 /// Otherwise, add an intermediate branch instruction to a branch.
1362 ARMConstantIslands::FixUpUnconditionalBr(MachineFunction &MF, ImmBranch &Br) {
1363 MachineInstr *MI = Br.MI;
1364 MachineBasicBlock *MBB = MI->getParent();
1366 llvm_unreachable("FixUpUnconditionalBr is Thumb1 only!");
1368 // Use BL to implement far jump.
1369 Br.MaxDisp = (1 << 21) * 2;
1370 MI->setDesc(TII->get(ARM::tBfar));
1371 BBSizes[MBB->getNumber()] += 2;
1372 AdjustBBOffsetsAfter(MBB, 2);
1376 DEBUG(errs() << " Changed B to long jump " << *MI);
1381 /// FixUpConditionalBr - Fix up a conditional branch whose destination is too
1382 /// far away to fit in its displacement field. It is converted to an inverse
1383 /// conditional branch + an unconditional branch to the destination.
1385 ARMConstantIslands::FixUpConditionalBr(MachineFunction &MF, ImmBranch &Br) {
1386 MachineInstr *MI = Br.MI;
1387 MachineBasicBlock *DestBB = MI->getOperand(0).getMBB();
1389 // Add an unconditional branch to the destination and invert the branch
1390 // condition to jump over it:
1396 ARMCC::CondCodes CC = (ARMCC::CondCodes)MI->getOperand(1).getImm();
1397 CC = ARMCC::getOppositeCondition(CC);
1398 unsigned CCReg = MI->getOperand(2).getReg();
1400 // If the branch is at the end of its MBB and that has a fall-through block,
1401 // direct the updated conditional branch to the fall-through block. Otherwise,
1402 // split the MBB before the next instruction.
1403 MachineBasicBlock *MBB = MI->getParent();
1404 MachineInstr *BMI = &MBB->back();
1405 bool NeedSplit = (BMI != MI) || !BBHasFallthrough(MBB);
1409 if (llvm::next(MachineBasicBlock::iterator(MI)) == prior(MBB->end()) &&
1410 BMI->getOpcode() == Br.UncondBr) {
1411 // Last MI in the BB is an unconditional branch. Can we simply invert the
1412 // condition and swap destinations:
1418 MachineBasicBlock *NewDest = BMI->getOperand(0).getMBB();
1419 if (BBIsInRange(MI, NewDest, Br.MaxDisp)) {
1420 DEBUG(errs() << " Invert Bcc condition and swap its destination with "
1422 BMI->getOperand(0).setMBB(DestBB);
1423 MI->getOperand(0).setMBB(NewDest);
1424 MI->getOperand(1).setImm(CC);
1431 SplitBlockBeforeInstr(MI);
1432 // No need for the branch to the next block. We're adding an unconditional
1433 // branch to the destination.
1434 int delta = TII->GetInstSizeInBytes(&MBB->back());
1435 BBSizes[MBB->getNumber()] -= delta;
1436 MachineBasicBlock* SplitBB = llvm::next(MachineFunction::iterator(MBB));
1437 AdjustBBOffsetsAfter(SplitBB, -delta);
1438 MBB->back().eraseFromParent();
1439 // BBOffsets[SplitBB] is wrong temporarily, fixed below
1441 MachineBasicBlock *NextBB = llvm::next(MachineFunction::iterator(MBB));
1443 DEBUG(errs() << " Insert B to BB#" << DestBB->getNumber()
1444 << " also invert condition and change dest. to BB#"
1445 << NextBB->getNumber() << "\n");
1447 // Insert a new conditional branch and a new unconditional branch.
1448 // Also update the ImmBranch as well as adding a new entry for the new branch.
1449 BuildMI(MBB, DebugLoc::getUnknownLoc(),
1450 TII->get(MI->getOpcode()))
1451 .addMBB(NextBB).addImm(CC).addReg(CCReg);
1452 Br.MI = &MBB->back();
1453 BBSizes[MBB->getNumber()] += TII->GetInstSizeInBytes(&MBB->back());
1454 BuildMI(MBB, DebugLoc::getUnknownLoc(), TII->get(Br.UncondBr)).addMBB(DestBB);
1455 BBSizes[MBB->getNumber()] += TII->GetInstSizeInBytes(&MBB->back());
1456 unsigned MaxDisp = getUnconditionalBrDisp(Br.UncondBr);
1457 ImmBranches.push_back(ImmBranch(&MBB->back(), MaxDisp, false, Br.UncondBr));
1459 // Remove the old conditional branch. It may or may not still be in MBB.
1460 BBSizes[MI->getParent()->getNumber()] -= TII->GetInstSizeInBytes(MI);
1461 MI->eraseFromParent();
1463 // The net size change is an addition of one unconditional branch.
1464 int delta = TII->GetInstSizeInBytes(&MBB->back());
1465 AdjustBBOffsetsAfter(MBB, delta);
1469 /// UndoLRSpillRestore - Remove Thumb push / pop instructions that only spills
1470 /// LR / restores LR to pc. FIXME: This is done here because it's only possible
1471 /// to do this if tBfar is not used.
1472 bool ARMConstantIslands::UndoLRSpillRestore() {
1473 bool MadeChange = false;
1474 for (unsigned i = 0, e = PushPopMIs.size(); i != e; ++i) {
1475 MachineInstr *MI = PushPopMIs[i];
1476 // First two operands are predicates, the third is a zero since there
1478 if (MI->getOpcode() == ARM::tPOP_RET &&
1479 MI->getOperand(3).getReg() == ARM::PC &&
1480 MI->getNumExplicitOperands() == 4) {
1481 BuildMI(MI->getParent(), MI->getDebugLoc(), TII->get(ARM::tBX_RET));
1482 MI->eraseFromParent();
1489 bool ARMConstantIslands::OptimizeThumb2Instructions(MachineFunction &MF) {
1490 bool MadeChange = false;
1492 // Shrink ADR and LDR from constantpool.
1493 for (unsigned i = 0, e = CPUsers.size(); i != e; ++i) {
1494 CPUser &U = CPUsers[i];
1495 unsigned Opcode = U.MI->getOpcode();
1496 unsigned NewOpc = 0;
1501 case ARM::t2LEApcrel:
1502 if (isARMLowRegister(U.MI->getOperand(0).getReg())) {
1503 NewOpc = ARM::tLEApcrel;
1509 if (isARMLowRegister(U.MI->getOperand(0).getReg())) {
1510 NewOpc = ARM::tLDRpci;
1520 unsigned UserOffset = GetOffsetOf(U.MI) + 4;
1521 unsigned MaxOffs = ((1 << Bits) - 1) * Scale;
1522 // FIXME: Check if offset is multiple of scale if scale is not 4.
1523 if (CPEIsInRange(U.MI, UserOffset, U.CPEMI, MaxOffs, false, true)) {
1524 U.MI->setDesc(TII->get(NewOpc));
1525 MachineBasicBlock *MBB = U.MI->getParent();
1526 BBSizes[MBB->getNumber()] -= 2;
1527 AdjustBBOffsetsAfter(MBB, -2);
1533 MadeChange |= OptimizeThumb2Branches(MF);
1534 MadeChange |= OptimizeThumb2JumpTables(MF);
1538 bool ARMConstantIslands::OptimizeThumb2Branches(MachineFunction &MF) {
1539 bool MadeChange = false;
1541 for (unsigned i = 0, e = ImmBranches.size(); i != e; ++i) {
1542 ImmBranch &Br = ImmBranches[i];
1543 unsigned Opcode = Br.MI->getOpcode();
1544 unsigned NewOpc = 0;
1562 unsigned MaxOffs = ((1 << (Bits-1))-1) * Scale;
1563 MachineBasicBlock *DestBB = Br.MI->getOperand(0).getMBB();
1564 if (BBIsInRange(Br.MI, DestBB, MaxOffs)) {
1565 Br.MI->setDesc(TII->get(NewOpc));
1566 MachineBasicBlock *MBB = Br.MI->getParent();
1567 BBSizes[MBB->getNumber()] -= 2;
1568 AdjustBBOffsetsAfter(MBB, -2);
1574 Opcode = Br.MI->getOpcode();
1575 if (Opcode != ARM::tBcc)
1579 unsigned PredReg = 0;
1580 ARMCC::CondCodes Pred = llvm::getInstrPredicate(Br.MI, PredReg);
1581 if (Pred == ARMCC::EQ)
1583 else if (Pred == ARMCC::NE)
1584 NewOpc = ARM::tCBNZ;
1587 MachineBasicBlock *DestBB = Br.MI->getOperand(0).getMBB();
1588 // Check if the distance is within 126. Subtract starting offset by 2
1589 // because the cmp will be eliminated.
1590 unsigned BrOffset = GetOffsetOf(Br.MI) + 4 - 2;
1591 unsigned DestOffset = BBOffsets[DestBB->getNumber()];
1592 if (BrOffset < DestOffset && (DestOffset - BrOffset) <= 126) {
1593 MachineBasicBlock::iterator CmpMI = Br.MI; --CmpMI;
1594 if (CmpMI->getOpcode() == ARM::tCMPzi8) {
1595 unsigned Reg = CmpMI->getOperand(0).getReg();
1596 Pred = llvm::getInstrPredicate(CmpMI, PredReg);
1597 if (Pred == ARMCC::AL &&
1598 CmpMI->getOperand(1).getImm() == 0 &&
1599 isARMLowRegister(Reg)) {
1600 MachineBasicBlock *MBB = Br.MI->getParent();
1601 MachineInstr *NewBR =
1602 BuildMI(*MBB, CmpMI, Br.MI->getDebugLoc(), TII->get(NewOpc))
1603 .addReg(Reg).addMBB(DestBB, Br.MI->getOperand(0).getTargetFlags());
1604 CmpMI->eraseFromParent();
1605 Br.MI->eraseFromParent();
1607 BBSizes[MBB->getNumber()] -= 2;
1608 AdjustBBOffsetsAfter(MBB, -2);
1619 /// OptimizeThumb2JumpTables - Use tbb / tbh instructions to generate smaller
1620 /// jumptables when it's possible.
1621 bool ARMConstantIslands::OptimizeThumb2JumpTables(MachineFunction &MF) {
1622 bool MadeChange = false;
1624 // FIXME: After the tables are shrunk, can we get rid some of the
1625 // constantpool tables?
1626 MachineJumpTableInfo *MJTI = MF.getJumpTableInfo();
1627 if (MJTI == 0) return false;
1629 const std::vector<MachineJumpTableEntry> &JT = MJTI->getJumpTables();
1630 for (unsigned i = 0, e = T2JumpTables.size(); i != e; ++i) {
1631 MachineInstr *MI = T2JumpTables[i];
1632 const TargetInstrDesc &TID = MI->getDesc();
1633 unsigned NumOps = TID.getNumOperands();
1634 unsigned JTOpIdx = NumOps - (TID.isPredicable() ? 3 : 2);
1635 MachineOperand JTOP = MI->getOperand(JTOpIdx);
1636 unsigned JTI = JTOP.getIndex();
1637 assert(JTI < JT.size());
1640 bool HalfWordOk = true;
1641 unsigned JTOffset = GetOffsetOf(MI) + 4;
1642 const std::vector<MachineBasicBlock*> &JTBBs = JT[JTI].MBBs;
1643 for (unsigned j = 0, ee = JTBBs.size(); j != ee; ++j) {
1644 MachineBasicBlock *MBB = JTBBs[j];
1645 unsigned DstOffset = BBOffsets[MBB->getNumber()];
1646 // Negative offset is not ok. FIXME: We should change BB layout to make
1647 // sure all the branches are forward.
1648 if (ByteOk && (DstOffset - JTOffset) > ((1<<8)-1)*2)
1650 unsigned TBHLimit = ((1<<16)-1)*2;
1651 if (HalfWordOk && (DstOffset - JTOffset) > TBHLimit)
1653 if (!ByteOk && !HalfWordOk)
1657 if (ByteOk || HalfWordOk) {
1658 MachineBasicBlock *MBB = MI->getParent();
1659 unsigned BaseReg = MI->getOperand(0).getReg();
1660 bool BaseRegKill = MI->getOperand(0).isKill();
1663 unsigned IdxReg = MI->getOperand(1).getReg();
1664 bool IdxRegKill = MI->getOperand(1).isKill();
1665 MachineBasicBlock::iterator PrevI = MI;
1666 if (PrevI == MBB->begin())
1669 MachineInstr *AddrMI = --PrevI;
1671 // Examine the instruction that calculate the jumptable entry address.
1672 // If it's not the one just before the t2BR_JT, we won't delete it, then
1673 // it's not worth doing the optimization.
1674 for (unsigned k = 0, eee = AddrMI->getNumOperands(); k != eee; ++k) {
1675 const MachineOperand &MO = AddrMI->getOperand(k);
1676 if (!MO.isReg() || !MO.getReg())
1678 if (MO.isDef() && MO.getReg() != BaseReg) {
1682 if (MO.isUse() && !MO.isKill() && MO.getReg() != IdxReg) {
1690 // The previous instruction should be a tLEApcrel or t2LEApcrelJT, we want
1691 // to delete it as well.
1692 MachineInstr *LeaMI = --PrevI;
1693 if ((LeaMI->getOpcode() != ARM::tLEApcrelJT &&
1694 LeaMI->getOpcode() != ARM::t2LEApcrelJT) ||
1695 LeaMI->getOperand(0).getReg() != BaseReg)
1701 unsigned Opc = ByteOk ? ARM::t2TBB : ARM::t2TBH;
1702 MachineInstr *NewJTMI = BuildMI(MBB, MI->getDebugLoc(), TII->get(Opc))
1703 .addReg(IdxReg, getKillRegState(IdxRegKill))
1704 .addJumpTableIndex(JTI, JTOP.getTargetFlags())
1705 .addImm(MI->getOperand(JTOpIdx+1).getImm());
1706 // FIXME: Insert an "ALIGN" instruction to ensure the next instruction
1707 // is 2-byte aligned. For now, asm printer will fix it up.
1708 unsigned NewSize = TII->GetInstSizeInBytes(NewJTMI);
1709 unsigned OrigSize = TII->GetInstSizeInBytes(AddrMI);
1710 OrigSize += TII->GetInstSizeInBytes(LeaMI);
1711 OrigSize += TII->GetInstSizeInBytes(MI);
1713 AddrMI->eraseFromParent();
1714 LeaMI->eraseFromParent();
1715 MI->eraseFromParent();
1717 int delta = OrigSize - NewSize;
1718 BBSizes[MBB->getNumber()] -= delta;
1719 AdjustBBOffsetsAfter(MBB, -delta);
1729 /// ReorderThumb2JumpTables - Adjust the function's block layout to ensure that
1730 /// jump tables always branch forwards, since that's what tbb and tbh need.
1731 bool ARMConstantIslands::ReorderThumb2JumpTables(MachineFunction &MF) {
1732 bool MadeChange = false;
1734 MachineJumpTableInfo *MJTI = MF.getJumpTableInfo();
1735 if (MJTI == 0) return false;
1737 const std::vector<MachineJumpTableEntry> &JT = MJTI->getJumpTables();
1738 for (unsigned i = 0, e = T2JumpTables.size(); i != e; ++i) {
1739 MachineInstr *MI = T2JumpTables[i];
1740 const TargetInstrDesc &TID = MI->getDesc();
1741 unsigned NumOps = TID.getNumOperands();
1742 unsigned JTOpIdx = NumOps - (TID.isPredicable() ? 3 : 2);
1743 MachineOperand JTOP = MI->getOperand(JTOpIdx);
1744 unsigned JTI = JTOP.getIndex();
1745 assert(JTI < JT.size());
1747 // We prefer if target blocks for the jump table come after the jump
1748 // instruction so we can use TB[BH]. Loop through the target blocks
1749 // and try to adjust them such that that's true.
1750 int JTNumber = MI->getParent()->getNumber();
1751 const std::vector<MachineBasicBlock*> &JTBBs = JT[JTI].MBBs;
1752 for (unsigned j = 0, ee = JTBBs.size(); j != ee; ++j) {
1753 MachineBasicBlock *MBB = JTBBs[j];
1754 int DTNumber = MBB->getNumber();
1756 if (DTNumber < JTNumber) {
1757 // The destination precedes the switch. Try to move the block forward
1758 // so we have a positive offset.
1759 MachineBasicBlock *NewBB =
1760 AdjustJTTargetBlockForward(MBB, MI->getParent());
1762 MJTI->ReplaceMBBInJumpTable(JTI, JTBBs[j], NewBB);
1771 MachineBasicBlock *ARMConstantIslands::
1772 AdjustJTTargetBlockForward(MachineBasicBlock *BB, MachineBasicBlock *JTBB)
1774 MachineFunction &MF = *BB->getParent();
1776 // If it's the destination block is terminated by an unconditional branch,
1777 // try to move it; otherwise, create a new block following the jump
1778 // table that branches back to the actual target. This is a very simple
1779 // heuristic. FIXME: We can definitely improve it.
1780 MachineBasicBlock *TBB = 0, *FBB = 0;
1781 SmallVector<MachineOperand, 4> Cond;
1782 SmallVector<MachineOperand, 4> CondPrior;
1783 MachineFunction::iterator BBi = BB;
1784 MachineFunction::iterator OldPrior = prior(BBi);
1786 // If the block terminator isn't analyzable, don't try to move the block
1787 bool B = TII->AnalyzeBranch(*BB, TBB, FBB, Cond);
1789 // If the block ends in an unconditional branch, move it. The prior block
1790 // has to have an analyzable terminator for us to move this one. Be paranoid
1791 // and make sure we're not trying to move the entry block of the function.
1792 if (!B && Cond.empty() && BB != MF.begin() &&
1793 !TII->AnalyzeBranch(*OldPrior, TBB, FBB, CondPrior)) {
1794 BB->moveAfter(JTBB);
1795 OldPrior->updateTerminator();
1796 BB->updateTerminator();
1797 // Update numbering to account for the block being moved.
1798 MF.RenumberBlocks();
1803 // Create a new MBB for the code after the jump BB.
1804 MachineBasicBlock *NewBB =
1805 MF.CreateMachineBasicBlock(JTBB->getBasicBlock());
1806 MachineFunction::iterator MBBI = JTBB; ++MBBI;
1807 MF.insert(MBBI, NewBB);
1809 // Add an unconditional branch from NewBB to BB.
1810 // There doesn't seem to be meaningful DebugInfo available; this doesn't
1811 // correspond directly to anything in the source.
1812 assert (isThumb2 && "Adjusting for TB[BH] but not in Thumb2?");
1813 BuildMI(NewBB, DebugLoc::getUnknownLoc(), TII->get(ARM::t2B)).addMBB(BB);
1815 // Update internal data structures to account for the newly inserted MBB.
1816 MF.RenumberBlocks(NewBB);
1819 NewBB->addSuccessor(BB);
1820 JTBB->removeSuccessor(BB);
1821 JTBB->addSuccessor(NewBB);