1 //===-- PrologEpilogInserter.cpp - Insert Prolog/Epilog code in function --===//
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 pass is responsible for finalizing the functions frame layout, saving
11 // callee saved registers, and for emitting prolog & epilog code for the
14 // This pass must be run after register allocation. After this pass is
15 // executed, it is illegal to construct MO_FrameIndex operands.
17 // This pass provides an optional shrink wrapping variant of prolog/epilog
18 // insertion, enabled via --shrink-wrap. See ShrinkWrapping.cpp.
20 //===----------------------------------------------------------------------===//
22 #include "PrologEpilogInserter.h"
23 #include "llvm/CodeGen/MachineDominators.h"
24 #include "llvm/CodeGen/MachineLoopInfo.h"
25 #include "llvm/CodeGen/MachineInstr.h"
26 #include "llvm/CodeGen/MachineFrameInfo.h"
27 #include "llvm/CodeGen/MachineRegisterInfo.h"
28 #include "llvm/CodeGen/RegisterScavenging.h"
29 #include "llvm/Target/TargetMachine.h"
30 #include "llvm/Target/TargetRegisterInfo.h"
31 #include "llvm/Target/TargetFrameInfo.h"
32 #include "llvm/Target/TargetInstrInfo.h"
33 #include "llvm/Support/CommandLine.h"
34 #include "llvm/Support/Compiler.h"
35 #include "llvm/ADT/IndexedMap.h"
36 #include "llvm/ADT/STLExtras.h"
43 static RegisterPass<PEI>
44 X("prologepilog", "Prologue/Epilogue Insertion");
46 /// createPrologEpilogCodeInserter - This function returns a pass that inserts
47 /// prolog and epilog code, and eliminates abstract frame references.
49 FunctionPass *llvm::createPrologEpilogCodeInserter() { return new PEI(); }
51 /// runOnMachineFunction - Insert prolog/epilog code and replace abstract
52 /// frame indexes with appropriate references.
54 bool PEI::runOnMachineFunction(MachineFunction &Fn) {
55 const Function* F = Fn.getFunction();
56 const TargetRegisterInfo *TRI = Fn.getTarget().getRegisterInfo();
57 RS = TRI->requiresRegisterScavenging(Fn) ? new RegScavenger() : NULL;
58 FrameIndexVirtualScavenging = TRI->requiresFrameIndexScavenging(Fn);
59 FrameConstantRegMap.clear();
61 // Calculate the MaxCallFrameSize and AdjustsStack variables for the
62 // function's frame information. Also eliminates call frame pseudo
64 calculateCallsInformation(Fn);
66 // Allow the target machine to make some adjustments to the function
67 // e.g. UsedPhysRegs before calculateCalleeSavedRegisters.
68 TRI->processFunctionBeforeCalleeSavedScan(Fn, RS);
70 // Scan the function for modified callee saved registers and insert spill code
71 // for any callee saved registers that are modified.
72 calculateCalleeSavedRegisters(Fn);
74 // Determine placement of CSR spill/restore code:
75 // - with shrink wrapping, place spills and restores to tightly
76 // enclose regions in the Machine CFG of the function where
77 // they are used. Without shrink wrapping
78 // - default (no shrink wrapping), place all spills in the
79 // entry block, all restores in return blocks.
80 placeCSRSpillsAndRestores(Fn);
82 // Add the code to save and restore the callee saved registers
83 if (!F->hasFnAttr(Attribute::Naked))
84 insertCSRSpillsAndRestores(Fn);
86 // Allow the target machine to make final modifications to the function
87 // before the frame layout is finalized.
88 TRI->processFunctionBeforeFrameFinalized(Fn);
90 // Calculate actual frame offsets for all abstract stack objects...
91 calculateFrameObjectOffsets(Fn);
93 // Add prolog and epilog code to the function. This function is required
94 // to align the stack frame as necessary for any stack variables or
95 // called functions. Because of this, calculateCalleeSavedRegisters()
96 // must be called before this function in order to set the AdjustsStack
97 // and MaxCallFrameSize variables.
98 if (!F->hasFnAttr(Attribute::Naked))
99 insertPrologEpilogCode(Fn);
101 // Replace all MO_FrameIndex operands with physical register references
102 // and actual offsets.
104 replaceFrameIndices(Fn);
106 // If register scavenging is needed, as we've enabled doing it as a
107 // post-pass, scavenge the virtual registers that frame index elimiation
109 if (TRI->requiresRegisterScavenging(Fn) && FrameIndexVirtualScavenging)
110 scavengeFrameVirtualRegs(Fn);
118 void PEI::getAnalysisUsage(AnalysisUsage &AU) const {
119 AU.setPreservesCFG();
120 if (ShrinkWrapping || ShrinkWrapFunc != "") {
121 AU.addRequired<MachineLoopInfo>();
122 AU.addRequired<MachineDominatorTree>();
124 AU.addPreserved<MachineLoopInfo>();
125 AU.addPreserved<MachineDominatorTree>();
126 MachineFunctionPass::getAnalysisUsage(AU);
130 /// calculateCallsInformation - Calculate the MaxCallFrameSize and AdjustsStack
131 /// variables for the function's frame information and eliminate call frame
132 /// pseudo instructions.
133 void PEI::calculateCallsInformation(MachineFunction &Fn) {
134 const TargetRegisterInfo *RegInfo = Fn.getTarget().getRegisterInfo();
135 MachineFrameInfo *MFI = Fn.getFrameInfo();
137 unsigned MaxCallFrameSize = 0;
138 bool AdjustsStack = MFI->adjustsStack();
140 // Get the function call frame set-up and tear-down instruction opcode
141 int FrameSetupOpcode = RegInfo->getCallFrameSetupOpcode();
142 int FrameDestroyOpcode = RegInfo->getCallFrameDestroyOpcode();
144 // Early exit for targets which have no call frame setup/destroy pseudo
146 if (FrameSetupOpcode == -1 && FrameDestroyOpcode == -1)
149 std::vector<MachineBasicBlock::iterator> FrameSDOps;
150 for (MachineFunction::iterator BB = Fn.begin(), E = Fn.end(); BB != E; ++BB)
151 for (MachineBasicBlock::iterator I = BB->begin(); I != BB->end(); ++I)
152 if (I->getOpcode() == FrameSetupOpcode ||
153 I->getOpcode() == FrameDestroyOpcode) {
154 assert(I->getNumOperands() >= 1 && "Call Frame Setup/Destroy Pseudo"
155 " instructions should have a single immediate argument!");
156 unsigned Size = I->getOperand(0).getImm();
157 if (Size > MaxCallFrameSize) MaxCallFrameSize = Size;
159 FrameSDOps.push_back(I);
160 } else if (I->isInlineAsm()) {
161 // An InlineAsm might be a call; assume it is to get the stack frame
162 // aligned correctly for calls.
166 MFI->setAdjustsStack(AdjustsStack);
167 MFI->setMaxCallFrameSize(MaxCallFrameSize);
169 for (std::vector<MachineBasicBlock::iterator>::iterator
170 i = FrameSDOps.begin(), e = FrameSDOps.end(); i != e; ++i) {
171 MachineBasicBlock::iterator I = *i;
173 // If call frames are not being included as part of the stack frame, and
174 // the target doesn't indicate otherwise, remove the call frame pseudos
175 // here. The sub/add sp instruction pairs are still inserted, but we don't
176 // need to track the SP adjustment for frame index elimination.
177 if (RegInfo->canSimplifyCallFramePseudos(Fn))
178 RegInfo->eliminateCallFramePseudoInstr(Fn, *I->getParent(), I);
183 /// calculateCalleeSavedRegisters - Scan the function for modified callee saved
185 void PEI::calculateCalleeSavedRegisters(MachineFunction &Fn) {
186 const TargetRegisterInfo *RegInfo = Fn.getTarget().getRegisterInfo();
187 const TargetFrameInfo *TFI = Fn.getTarget().getFrameInfo();
188 MachineFrameInfo *MFI = Fn.getFrameInfo();
190 // Get the callee saved register list...
191 const unsigned *CSRegs = RegInfo->getCalleeSavedRegs(&Fn);
193 // These are used to keep track the callee-save area. Initialize them.
194 MinCSFrameIndex = INT_MAX;
197 // Early exit for targets which have no callee saved registers.
198 if (CSRegs == 0 || CSRegs[0] == 0)
201 // In Naked functions we aren't going to save any registers.
202 if (Fn.getFunction()->hasFnAttr(Attribute::Naked))
205 std::vector<CalleeSavedInfo> CSI;
206 for (unsigned i = 0; CSRegs[i]; ++i) {
207 unsigned Reg = CSRegs[i];
208 const TargetRegisterClass *RC = RegInfo->getMinimalPhysRegClass(Reg);
209 if (Fn.getRegInfo().isPhysRegUsed(Reg)) {
210 // If the reg is modified, save it!
211 CSI.push_back(CalleeSavedInfo(Reg, RC));
213 for (const unsigned *AliasSet = RegInfo->getAliasSet(Reg);
214 *AliasSet; ++AliasSet) { // Check alias registers too.
215 if (Fn.getRegInfo().isPhysRegUsed(*AliasSet)) {
216 CSI.push_back(CalleeSavedInfo(Reg, RC));
224 return; // Early exit if no callee saved registers are modified!
226 unsigned NumFixedSpillSlots;
227 const TargetFrameInfo::SpillSlot *FixedSpillSlots =
228 TFI->getCalleeSavedSpillSlots(NumFixedSpillSlots);
230 // Now that we know which registers need to be saved and restored, allocate
231 // stack slots for them.
232 for (std::vector<CalleeSavedInfo>::iterator
233 I = CSI.begin(), E = CSI.end(); I != E; ++I) {
234 unsigned Reg = I->getReg();
235 const TargetRegisterClass *RC = I->getRegClass();
238 if (RegInfo->hasReservedSpillSlot(Fn, Reg, FrameIdx)) {
239 I->setFrameIdx(FrameIdx);
243 // Check to see if this physreg must be spilled to a particular stack slot
245 const TargetFrameInfo::SpillSlot *FixedSlot = FixedSpillSlots;
246 while (FixedSlot != FixedSpillSlots+NumFixedSpillSlots &&
247 FixedSlot->Reg != Reg)
250 if (FixedSlot == FixedSpillSlots + NumFixedSpillSlots) {
251 // Nope, just spill it anywhere convenient.
252 unsigned Align = RC->getAlignment();
253 unsigned StackAlign = TFI->getStackAlignment();
255 // We may not be able to satisfy the desired alignment specification of
256 // the TargetRegisterClass if the stack alignment is smaller. Use the
258 Align = std::min(Align, StackAlign);
259 FrameIdx = MFI->CreateStackObject(RC->getSize(), Align, true);
260 if ((unsigned)FrameIdx < MinCSFrameIndex) MinCSFrameIndex = FrameIdx;
261 if ((unsigned)FrameIdx > MaxCSFrameIndex) MaxCSFrameIndex = FrameIdx;
263 // Spill it to the stack where we must.
264 FrameIdx = MFI->CreateFixedObject(RC->getSize(), FixedSlot->Offset,
268 I->setFrameIdx(FrameIdx);
271 MFI->setCalleeSavedInfo(CSI);
274 /// insertCSRSpillsAndRestores - Insert spill and restore code for
275 /// callee saved registers used in the function, handling shrink wrapping.
277 void PEI::insertCSRSpillsAndRestores(MachineFunction &Fn) {
278 // Get callee saved register information.
279 MachineFrameInfo *MFI = Fn.getFrameInfo();
280 const std::vector<CalleeSavedInfo> &CSI = MFI->getCalleeSavedInfo();
282 MFI->setCalleeSavedInfoValid(true);
284 // Early exit if no callee saved registers are modified!
288 const TargetInstrInfo &TII = *Fn.getTarget().getInstrInfo();
289 const TargetRegisterInfo *TRI = Fn.getTarget().getRegisterInfo();
290 MachineBasicBlock::iterator I;
292 if (! ShrinkWrapThisFunction) {
293 // Spill using target interface.
294 I = EntryBlock->begin();
295 if (!TII.spillCalleeSavedRegisters(*EntryBlock, I, CSI, TRI)) {
296 for (unsigned i = 0, e = CSI.size(); i != e; ++i) {
297 // Add the callee-saved register as live-in.
298 // It's killed at the spill.
299 EntryBlock->addLiveIn(CSI[i].getReg());
301 // Insert the spill to the stack frame.
302 TII.storeRegToStackSlot(*EntryBlock, I, CSI[i].getReg(), true,
303 CSI[i].getFrameIdx(), CSI[i].getRegClass(),TRI);
307 // Restore using target interface.
308 for (unsigned ri = 0, re = ReturnBlocks.size(); ri != re; ++ri) {
309 MachineBasicBlock* MBB = ReturnBlocks[ri];
312 // Skip over all terminator instructions, which are part of the return
314 MachineBasicBlock::iterator I2 = I;
315 while (I2 != MBB->begin() && (--I2)->getDesc().isTerminator())
318 bool AtStart = I == MBB->begin();
319 MachineBasicBlock::iterator BeforeI = I;
323 // Restore all registers immediately before the return and any
324 // terminators that preceed it.
325 if (!TII.restoreCalleeSavedRegisters(*MBB, I, CSI, TRI)) {
326 for (unsigned i = 0, e = CSI.size(); i != e; ++i) {
327 TII.loadRegFromStackSlot(*MBB, I, CSI[i].getReg(),
328 CSI[i].getFrameIdx(),
329 CSI[i].getRegClass(), TRI);
330 assert(I != MBB->begin() &&
331 "loadRegFromStackSlot didn't insert any code!");
332 // Insert in reverse order. loadRegFromStackSlot can insert
333 // multiple instructions.
347 std::vector<CalleeSavedInfo> blockCSI;
348 for (CSRegBlockMap::iterator BI = CSRSave.begin(),
349 BE = CSRSave.end(); BI != BE; ++BI) {
350 MachineBasicBlock* MBB = BI->first;
351 CSRegSet save = BI->second;
357 for (CSRegSet::iterator RI = save.begin(),
358 RE = save.end(); RI != RE; ++RI) {
359 blockCSI.push_back(CSI[*RI]);
361 assert(blockCSI.size() > 0 &&
362 "Could not collect callee saved register info");
366 // When shrink wrapping, use stack slot stores/loads.
367 for (unsigned i = 0, e = blockCSI.size(); i != e; ++i) {
368 // Add the callee-saved register as live-in.
369 // It's killed at the spill.
370 MBB->addLiveIn(blockCSI[i].getReg());
372 // Insert the spill to the stack frame.
373 TII.storeRegToStackSlot(*MBB, I, blockCSI[i].getReg(),
375 blockCSI[i].getFrameIdx(),
376 blockCSI[i].getRegClass(), TRI);
380 for (CSRegBlockMap::iterator BI = CSRRestore.begin(),
381 BE = CSRRestore.end(); BI != BE; ++BI) {
382 MachineBasicBlock* MBB = BI->first;
383 CSRegSet restore = BI->second;
389 for (CSRegSet::iterator RI = restore.begin(),
390 RE = restore.end(); RI != RE; ++RI) {
391 blockCSI.push_back(CSI[*RI]);
393 assert(blockCSI.size() > 0 &&
394 "Could not find callee saved register info");
396 // If MBB is empty and needs restores, insert at the _beginning_.
403 // Skip over all terminator instructions, which are part of the
405 if (! I->getDesc().isTerminator()) {
408 MachineBasicBlock::iterator I2 = I;
409 while (I2 != MBB->begin() && (--I2)->getDesc().isTerminator())
414 bool AtStart = I == MBB->begin();
415 MachineBasicBlock::iterator BeforeI = I;
419 // Restore all registers immediately before the return and any
420 // terminators that preceed it.
421 for (unsigned i = 0, e = blockCSI.size(); i != e; ++i) {
422 TII.loadRegFromStackSlot(*MBB, I, blockCSI[i].getReg(),
423 blockCSI[i].getFrameIdx(),
424 blockCSI[i].getRegClass(), TRI);
425 assert(I != MBB->begin() &&
426 "loadRegFromStackSlot didn't insert any code!");
427 // Insert in reverse order. loadRegFromStackSlot can insert
428 // multiple instructions.
439 /// AdjustStackOffset - Helper function used to adjust the stack frame offset.
441 AdjustStackOffset(MachineFrameInfo *MFI, int FrameIdx,
442 bool StackGrowsDown, int64_t &Offset,
443 unsigned &MaxAlign) {
444 // If the stack grows down, add the object size to find the lowest address.
446 Offset += MFI->getObjectSize(FrameIdx);
448 unsigned Align = MFI->getObjectAlignment(FrameIdx);
450 // If the alignment of this object is greater than that of the stack, then
451 // increase the stack alignment to match.
452 MaxAlign = std::max(MaxAlign, Align);
454 // Adjust to alignment boundary.
455 Offset = (Offset + Align - 1) / Align * Align;
457 if (StackGrowsDown) {
458 MFI->setObjectOffset(FrameIdx, -Offset); // Set the computed offset
460 MFI->setObjectOffset(FrameIdx, Offset);
461 Offset += MFI->getObjectSize(FrameIdx);
465 /// calculateFrameObjectOffsets - Calculate actual frame offsets for all of the
466 /// abstract stack objects.
468 void PEI::calculateFrameObjectOffsets(MachineFunction &Fn) {
469 const TargetFrameInfo &TFI = *Fn.getTarget().getFrameInfo();
471 bool StackGrowsDown =
472 TFI.getStackGrowthDirection() == TargetFrameInfo::StackGrowsDown;
474 // Loop over all of the stack objects, assigning sequential addresses...
475 MachineFrameInfo *MFI = Fn.getFrameInfo();
477 // Start at the beginning of the local area.
478 // The Offset is the distance from the stack top in the direction
479 // of stack growth -- so it's always nonnegative.
480 int LocalAreaOffset = TFI.getOffsetOfLocalArea();
482 LocalAreaOffset = -LocalAreaOffset;
483 assert(LocalAreaOffset >= 0
484 && "Local area offset should be in direction of stack growth");
485 int64_t Offset = LocalAreaOffset;
487 // If there are fixed sized objects that are preallocated in the local area,
488 // non-fixed objects can't be allocated right at the start of local area.
489 // We currently don't support filling in holes in between fixed sized
490 // objects, so we adjust 'Offset' to point to the end of last fixed sized
491 // preallocated object.
492 for (int i = MFI->getObjectIndexBegin(); i != 0; ++i) {
494 if (StackGrowsDown) {
495 // The maximum distance from the stack pointer is at lower address of
496 // the object -- which is given by offset. For down growing stack
497 // the offset is negative, so we negate the offset to get the distance.
498 FixedOff = -MFI->getObjectOffset(i);
500 // The maximum distance from the start pointer is at the upper
501 // address of the object.
502 FixedOff = MFI->getObjectOffset(i) + MFI->getObjectSize(i);
504 if (FixedOff > Offset) Offset = FixedOff;
507 // First assign frame offsets to stack objects that are used to spill
508 // callee saved registers.
509 if (StackGrowsDown) {
510 for (unsigned i = MinCSFrameIndex; i <= MaxCSFrameIndex; ++i) {
511 // If the stack grows down, we need to add the size to find the lowest
512 // address of the object.
513 Offset += MFI->getObjectSize(i);
515 unsigned Align = MFI->getObjectAlignment(i);
516 // Adjust to alignment boundary
517 Offset = (Offset+Align-1)/Align*Align;
519 MFI->setObjectOffset(i, -Offset); // Set the computed offset
522 int MaxCSFI = MaxCSFrameIndex, MinCSFI = MinCSFrameIndex;
523 for (int i = MaxCSFI; i >= MinCSFI ; --i) {
524 unsigned Align = MFI->getObjectAlignment(i);
525 // Adjust to alignment boundary
526 Offset = (Offset+Align-1)/Align*Align;
528 MFI->setObjectOffset(i, Offset);
529 Offset += MFI->getObjectSize(i);
533 unsigned MaxAlign = MFI->getMaxAlignment();
535 // Make sure the special register scavenging spill slot is closest to the
536 // frame pointer if a frame pointer is required.
537 const TargetRegisterInfo *RegInfo = Fn.getTarget().getRegisterInfo();
538 if (RS && RegInfo->hasFP(Fn) && !RegInfo->needsStackRealignment(Fn)) {
539 int SFI = RS->getScavengingFrameIndex();
541 AdjustStackOffset(MFI, SFI, StackGrowsDown, Offset, MaxAlign);
544 // Make sure that the stack protector comes before the local variables on the
546 if (MFI->getStackProtectorIndex() >= 0)
547 AdjustStackOffset(MFI, MFI->getStackProtectorIndex(), StackGrowsDown,
550 // Then assign frame offsets to stack objects that are not used to spill
551 // callee saved registers.
552 for (unsigned i = 0, e = MFI->getObjectIndexEnd(); i != e; ++i) {
553 if (i >= MinCSFrameIndex && i <= MaxCSFrameIndex)
555 if (RS && (int)i == RS->getScavengingFrameIndex())
557 if (MFI->isDeadObjectIndex(i))
559 if (MFI->getStackProtectorIndex() == (int)i)
562 AdjustStackOffset(MFI, i, StackGrowsDown, Offset, MaxAlign);
565 // Make sure the special register scavenging spill slot is closest to the
567 if (RS && (!RegInfo->hasFP(Fn) || RegInfo->needsStackRealignment(Fn))) {
568 int SFI = RS->getScavengingFrameIndex();
570 AdjustStackOffset(MFI, SFI, StackGrowsDown, Offset, MaxAlign);
573 if (!RegInfo->targetHandlesStackFrameRounding()) {
574 // If we have reserved argument space for call sites in the function
575 // immediately on entry to the current function, count it as part of the
576 // overall stack size.
577 if (MFI->adjustsStack() && RegInfo->hasReservedCallFrame(Fn))
578 Offset += MFI->getMaxCallFrameSize();
580 // Round up the size to a multiple of the alignment. If the function has
581 // any calls or alloca's, align to the target's StackAlignment value to
582 // ensure that the callee's frame or the alloca data is suitably aligned;
583 // otherwise, for leaf functions, align to the TransientStackAlignment
586 if (MFI->adjustsStack() || MFI->hasVarSizedObjects() ||
587 (RegInfo->needsStackRealignment(Fn) && MFI->getObjectIndexEnd() != 0))
588 StackAlign = TFI.getStackAlignment();
590 StackAlign = TFI.getTransientStackAlignment();
592 // If the frame pointer is eliminated, all frame offsets will be relative to
593 // SP not FP. Align to MaxAlign so this works.
594 StackAlign = std::max(StackAlign, MaxAlign);
595 unsigned AlignMask = StackAlign - 1;
596 Offset = (Offset + AlignMask) & ~uint64_t(AlignMask);
599 // Update frame info to pretend that this is part of the stack...
600 MFI->setStackSize(Offset - LocalAreaOffset);
603 /// insertPrologEpilogCode - Scan the function for modified callee saved
604 /// registers, insert spill code for these callee saved registers, then add
605 /// prolog and epilog code to the function.
607 void PEI::insertPrologEpilogCode(MachineFunction &Fn) {
608 const TargetRegisterInfo *TRI = Fn.getTarget().getRegisterInfo();
610 // Add prologue to the function...
611 TRI->emitPrologue(Fn);
613 // Add epilogue to restore the callee-save registers in each exiting block
614 for (MachineFunction::iterator I = Fn.begin(), E = Fn.end(); I != E; ++I) {
615 // If last instruction is a return instruction, add an epilogue
616 if (!I->empty() && I->back().getDesc().isReturn())
617 TRI->emitEpilogue(Fn, *I);
621 /// replaceFrameIndices - Replace all MO_FrameIndex operands with physical
622 /// register references and actual offsets.
624 void PEI::replaceFrameIndices(MachineFunction &Fn) {
625 if (!Fn.getFrameInfo()->hasStackObjects()) return; // Nothing to do?
627 const TargetMachine &TM = Fn.getTarget();
628 assert(TM.getRegisterInfo() && "TM::getRegisterInfo() must be implemented!");
629 const TargetRegisterInfo &TRI = *TM.getRegisterInfo();
630 const TargetFrameInfo *TFI = TM.getFrameInfo();
631 bool StackGrowsDown =
632 TFI->getStackGrowthDirection() == TargetFrameInfo::StackGrowsDown;
633 int FrameSetupOpcode = TRI.getCallFrameSetupOpcode();
634 int FrameDestroyOpcode = TRI.getCallFrameDestroyOpcode();
636 for (MachineFunction::iterator BB = Fn.begin(),
637 E = Fn.end(); BB != E; ++BB) {
638 int SPAdj = 0; // SP offset due to call frame setup / destroy.
639 if (RS && !FrameIndexVirtualScavenging) RS->enterBasicBlock(BB);
641 for (MachineBasicBlock::iterator I = BB->begin(); I != BB->end(); ) {
643 if (I->getOpcode() == FrameSetupOpcode ||
644 I->getOpcode() == FrameDestroyOpcode) {
645 // Remember how much SP has been adjusted to create the call
647 int Size = I->getOperand(0).getImm();
649 if ((!StackGrowsDown && I->getOpcode() == FrameSetupOpcode) ||
650 (StackGrowsDown && I->getOpcode() == FrameDestroyOpcode))
655 MachineBasicBlock::iterator PrevI = BB->end();
656 if (I != BB->begin()) PrevI = prior(I);
657 TRI.eliminateCallFramePseudoInstr(Fn, *BB, I);
659 // Visit the instructions created by eliminateCallFramePseudoInstr().
660 if (PrevI == BB->end())
661 I = BB->begin(); // The replaced instr was the first in the block.
663 I = llvm::next(PrevI);
667 MachineInstr *MI = I;
669 for (unsigned i = 0, e = MI->getNumOperands(); i != e; ++i)
670 if (MI->getOperand(i).isFI()) {
671 // Some instructions (e.g. inline asm instructions) can have
672 // multiple frame indices and/or cause eliminateFrameIndex
673 // to insert more than one instruction. We need the register
674 // scavenger to go through all of these instructions so that
675 // it can update its register information. We keep the
676 // iterator at the point before insertion so that we can
677 // revisit them in full.
678 bool AtBeginning = (I == BB->begin());
679 if (!AtBeginning) --I;
681 // If this instruction has a FrameIndex operand, we need to
682 // use that target machine register info object to eliminate
684 TargetRegisterInfo::FrameIndexValue Value;
686 TRI.eliminateFrameIndex(MI, SPAdj, &Value,
687 FrameIndexVirtualScavenging ? NULL : RS);
689 assert (FrameIndexVirtualScavenging &&
690 "Not scavenging, but virtual returned from "
691 "eliminateFrameIndex()!");
692 FrameConstantRegMap[VReg] = FrameConstantEntry(Value, SPAdj);
695 // Reset the iterator if we were at the beginning of the BB.
705 if (DoIncr && I != BB->end()) ++I;
707 // Update register states.
708 if (RS && !FrameIndexVirtualScavenging && MI) RS->forward(MI);
711 assert(SPAdj == 0 && "Unbalanced call frame setup / destroy pairs?");
715 /// findLastUseReg - find the killing use of the specified register within
716 /// the instruciton range. Return the operand number of the kill in Operand.
717 static MachineBasicBlock::iterator
718 findLastUseReg(MachineBasicBlock::iterator I, MachineBasicBlock::iterator ME,
720 // Scan forward to find the last use of this virtual register
721 for (++I; I != ME; ++I) {
722 MachineInstr *MI = I;
723 bool isDefInsn = false;
724 bool isKillInsn = false;
725 for (unsigned i = 0, e = MI->getNumOperands(); i != e; ++i)
726 if (MI->getOperand(i).isReg()) {
727 unsigned OpReg = MI->getOperand(i).getReg();
728 if (OpReg == 0 || !TargetRegisterInfo::isVirtualRegister(OpReg))
731 && "overlapping use of scavenged index register!");
732 // If this is the killing use, we have a candidate.
733 if (MI->getOperand(i).isKill())
735 else if (MI->getOperand(i).isDef())
738 if (isKillInsn && !isDefInsn)
741 // If we hit the end of the basic block, there was no kill of
742 // the virtual register, which is wrong.
743 assert (0 && "scavenged index register never killed!");
747 /// scavengeFrameVirtualRegs - Replace all frame index virtual registers
748 /// with physical registers. Use the register scavenger to find an
749 /// appropriate register to use.
750 void PEI::scavengeFrameVirtualRegs(MachineFunction &Fn) {
751 // Run through the instructions and find any virtual registers.
752 for (MachineFunction::iterator BB = Fn.begin(),
753 E = Fn.end(); BB != E; ++BB) {
754 RS->enterBasicBlock(BB);
756 // FIXME: The logic flow in this function is still too convoluted.
757 // It needs a cleanup refactoring. Do that in preparation for tracking
758 // more than one scratch register value and using ranges to find
759 // available scratch registers.
760 unsigned CurrentVirtReg = 0;
761 unsigned CurrentScratchReg = 0;
762 bool havePrevValue = false;
763 TargetRegisterInfo::FrameIndexValue PrevValue(0,0);
764 TargetRegisterInfo::FrameIndexValue Value(0,0);
765 MachineInstr *PrevLastUseMI = NULL;
766 unsigned PrevLastUseOp = 0;
767 bool trackingCurrentValue = false;
770 // The instruction stream may change in the loop, so check BB->end()
772 for (MachineBasicBlock::iterator I = BB->begin(); I != BB->end(); ) {
773 MachineInstr *MI = I;
774 bool isDefInsn = false;
775 bool isKillInsn = false;
776 bool clobbersScratchReg = false;
778 for (unsigned i = 0, e = MI->getNumOperands(); i != e; ++i) {
779 if (MI->getOperand(i).isReg()) {
780 MachineOperand &MO = MI->getOperand(i);
781 unsigned Reg = MO.getReg();
784 if (!TargetRegisterInfo::isVirtualRegister(Reg)) {
785 // If we have a previous scratch reg, check and see if anything
786 // here kills whatever value is in there.
787 if (Reg == CurrentScratchReg) {
789 // Two-address operands implicitly kill
790 if (MO.isKill() || MI->isRegTiedToDefOperand(i))
791 clobbersScratchReg = true;
794 clobbersScratchReg = true;
799 // If this is a def, remember that this insn defines the value.
800 // This lets us properly consider insns which re-use the scratch
801 // register, such as r2 = sub r2, #imm, in the middle of the
806 // Have we already allocated a scratch register for this virtual?
807 if (Reg != CurrentVirtReg) {
808 // When we first encounter a new virtual register, it
809 // must be a definition.
810 assert(MI->getOperand(i).isDef() &&
811 "frame index virtual missing def!");
812 // We can't have nested virtual register live ranges because
813 // there's only a guarantee of one scavenged register at a time.
814 assert (CurrentVirtReg == 0 &&
815 "overlapping frame index virtual registers!");
817 // If the target gave us information about what's in the register,
818 // we can use that to re-use scratch regs.
819 DenseMap<unsigned, FrameConstantEntry>::iterator Entry =
820 FrameConstantRegMap.find(Reg);
821 trackingCurrentValue = Entry != FrameConstantRegMap.end();
822 if (trackingCurrentValue) {
823 SPAdj = (*Entry).second.second;
824 Value = (*Entry).second.first;
831 // If the scratch register from the last allocation is still
832 // available, see if the value matches. If it does, just re-use it.
833 if (trackingCurrentValue && havePrevValue && PrevValue == Value) {
834 // FIXME: This assumes that the instructions in the live range
835 // for the virtual register are exclusively for the purpose
836 // of populating the value in the register. That's reasonable
837 // for these frame index registers, but it's still a very, very
838 // strong assumption. rdar://7322732. Better would be to
839 // explicitly check each instruction in the range for references
840 // to the virtual register. Only delete those insns that
841 // touch the virtual register.
843 // Find the last use of the new virtual register. Remove all
844 // instruction between here and there, and update the current
845 // instruction to reference the last use insn instead.
846 MachineBasicBlock::iterator LastUseMI =
847 findLastUseReg(I, BB->end(), Reg);
849 // Remove all instructions up 'til the last use, since they're
850 // just calculating the value we already have.
851 BB->erase(I, LastUseMI);
854 // Extend the live range of the scratch register
855 PrevLastUseMI->getOperand(PrevLastUseOp).setIsKill(false);
856 RS->setUsed(CurrentScratchReg);
857 CurrentVirtReg = Reg;
859 // We deleted the instruction we were scanning the operands of.
860 // Jump back to the instruction iterator loop. Don't increment
861 // past this instruction since we updated the iterator already.
866 // Scavenge a new scratch register
867 CurrentVirtReg = Reg;
868 const TargetRegisterClass *RC = Fn.getRegInfo().getRegClass(Reg);
869 CurrentScratchReg = RS->FindUnusedReg(RC);
870 if (CurrentScratchReg == 0)
871 // No register is "free". Scavenge a register.
872 CurrentScratchReg = RS->scavengeRegister(RC, I, SPAdj);
876 // replace this reference to the virtual register with the
878 assert (CurrentScratchReg && "Missing scratch register!");
879 MI->getOperand(i).setReg(CurrentScratchReg);
881 if (MI->getOperand(i).isKill()) {
888 // If this is the last use of the scratch, stop tracking it. The
889 // last use will be a kill operand in an instruction that does
890 // not also define the scratch register.
891 if (isKillInsn && !isDefInsn) {
893 havePrevValue = trackingCurrentValue;
895 // Similarly, notice if instruction clobbered the value in the
896 // register we're tracking for possible later reuse. This is noted
897 // above, but enforced here since the value is still live while we
898 // process the rest of the operands of the instruction.
899 if (clobbersScratchReg) {
900 havePrevValue = false;
901 CurrentScratchReg = 0;