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llvm-6502/lib/CodeGen/PrologEpilogInserter.cpp
Manman Ren 519127f758 PEI: Support for non-zero SPAdj at beginning of a basic block. 
We can have a FrameSetup in one basic block and the matching FrameDestroy
in a different basic block when we have struct byval. In that case, SPAdj
is not zero at beginning of the basic block.

Modify PEI to correctly set SPAdj at beginning of each basic block using
DFS traversal. We used to assume SPAdj is 0 at beginning of each basic block.

PEI had an assert SPAdjCount || SPAdj == 0.
If we have a Destroy <n> followed by a Setup <m>, PEI will assert failure.
We can add an extra condition to make sure the pairs are matched:
  The pairs start with a FrameSetup.
But since we are doing a much better job in the verifier, this patch removes
the check in PEI.

PR16393


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@186364 91177308-0d34-0410-b5e6-96231b3b80d8
2013-07-15 23:47:29 +00:00

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//===-- PrologEpilogInserter.cpp - Insert Prolog/Epilog code in function --===//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This pass is responsible for finalizing the functions frame layout, saving
// callee saved registers, and for emitting prolog & epilog code for the
// function.
//
// This pass must be run after register allocation. After this pass is
// executed, it is illegal to construct MO_FrameIndex operands.
//
// This pass provides an optional shrink wrapping variant of prolog/epilog
// insertion, enabled via --shrink-wrap. See ShrinkWrapping.cpp.
//
//===----------------------------------------------------------------------===//
#define DEBUG_TYPE "pei"
#include "PrologEpilogInserter.h"
#include "llvm/ADT/IndexedMap.h"
#include "llvm/ADT/STLExtras.h"
#include "llvm/ADT/SmallSet.h"
#include "llvm/ADT/Statistic.h"
#include "llvm/CodeGen/MachineDominators.h"
#include "llvm/CodeGen/MachineFrameInfo.h"
#include "llvm/CodeGen/MachineInstr.h"
#include "llvm/CodeGen/MachineLoopInfo.h"
#include "llvm/CodeGen/MachineModuleInfo.h"
#include "llvm/CodeGen/MachineRegisterInfo.h"
#include "llvm/CodeGen/RegisterScavenging.h"
#include "llvm/IR/InlineAsm.h"
#include "llvm/Support/CommandLine.h"
#include "llvm/Support/Compiler.h"
#include "llvm/Support/Debug.h"
#include "llvm/Support/raw_ostream.h"
#include "llvm/Target/TargetFrameLowering.h"
#include "llvm/Target/TargetInstrInfo.h"
#include "llvm/Target/TargetMachine.h"
#include "llvm/Target/TargetRegisterInfo.h"
#include <climits>
using namespace llvm;
char PEI::ID = 0;
char &llvm::PrologEpilogCodeInserterID = PEI::ID;
static cl::opt<unsigned>
WarnStackSize("warn-stack-size", cl::Hidden, cl::init((unsigned)-1),
cl::desc("Warn for stack size bigger than the given"
" number"));
INITIALIZE_PASS_BEGIN(PEI, "prologepilog",
"Prologue/Epilogue Insertion", false, false)
INITIALIZE_PASS_DEPENDENCY(MachineLoopInfo)
INITIALIZE_PASS_DEPENDENCY(MachineDominatorTree)
INITIALIZE_PASS_DEPENDENCY(TargetPassConfig)
INITIALIZE_PASS_END(PEI, "prologepilog",
"Prologue/Epilogue Insertion & Frame Finalization",
false, false)
STATISTIC(NumScavengedRegs, "Number of frame index regs scavenged");
STATISTIC(NumBytesStackSpace,
"Number of bytes used for stack in all functions");
/// runOnMachineFunction - Insert prolog/epilog code and replace abstract
/// frame indexes with appropriate references.
///
bool PEI::runOnMachineFunction(MachineFunction &Fn) {
const Function* F = Fn.getFunction();
const TargetRegisterInfo *TRI = Fn.getTarget().getRegisterInfo();
const TargetFrameLowering *TFI = Fn.getTarget().getFrameLowering();
assert(!Fn.getRegInfo().getNumVirtRegs() && "Regalloc must assign all vregs");
RS = TRI->requiresRegisterScavenging(Fn) ? new RegScavenger() : NULL;
FrameIndexVirtualScavenging = TRI->requiresFrameIndexScavenging(Fn);
// Calculate the MaxCallFrameSize and AdjustsStack variables for the
// function's frame information. Also eliminates call frame pseudo
// instructions.
calculateCallsInformation(Fn);
// Allow the target machine to make some adjustments to the function
// e.g. UsedPhysRegs before calculateCalleeSavedRegisters.
TFI->processFunctionBeforeCalleeSavedScan(Fn, RS);
// Scan the function for modified callee saved registers and insert spill code
// for any callee saved registers that are modified.
calculateCalleeSavedRegisters(Fn);
// Determine placement of CSR spill/restore code:
// - With shrink wrapping, place spills and restores to tightly
// enclose regions in the Machine CFG of the function where
// they are used.
// - Without shink wrapping (default), place all spills in the
// entry block, all restores in return blocks.
placeCSRSpillsAndRestores(Fn);
// Add the code to save and restore the callee saved registers
if (!F->getAttributes().hasAttribute(AttributeSet::FunctionIndex,
Attribute::Naked))
insertCSRSpillsAndRestores(Fn);
// Allow the target machine to make final modifications to the function
// before the frame layout is finalized.
TFI->processFunctionBeforeFrameFinalized(Fn, RS);
// Calculate actual frame offsets for all abstract stack objects...
calculateFrameObjectOffsets(Fn);
// Add prolog and epilog code to the function. This function is required
// to align the stack frame as necessary for any stack variables or
// called functions. Because of this, calculateCalleeSavedRegisters()
// must be called before this function in order to set the AdjustsStack
// and MaxCallFrameSize variables.
if (!F->getAttributes().hasAttribute(AttributeSet::FunctionIndex,
Attribute::Naked))
insertPrologEpilogCode(Fn);
// Replace all MO_FrameIndex operands with physical register references
// and actual offsets.
//
replaceFrameIndices(Fn);
// If register scavenging is needed, as we've enabled doing it as a
// post-pass, scavenge the virtual registers that frame index elimiation
// inserted.
if (TRI->requiresRegisterScavenging(Fn) && FrameIndexVirtualScavenging)
scavengeFrameVirtualRegs(Fn);
// Clear any vregs created by virtual scavenging.
Fn.getRegInfo().clearVirtRegs();
// Warn on stack size when we exceeds the given limit.
MachineFrameInfo *MFI = Fn.getFrameInfo();
if (WarnStackSize.getNumOccurrences() > 0 &&
WarnStackSize < MFI->getStackSize())
errs() << "warning: Stack size limit exceeded (" << MFI->getStackSize()
<< ") in " << Fn.getName() << ".\n";
delete RS;
clearAllSets();
return true;
}
/// calculateCallsInformation - Calculate the MaxCallFrameSize and AdjustsStack
/// variables for the function's frame information and eliminate call frame
/// pseudo instructions.
void PEI::calculateCallsInformation(MachineFunction &Fn) {
const TargetInstrInfo &TII = *Fn.getTarget().getInstrInfo();
const TargetFrameLowering *TFI = Fn.getTarget().getFrameLowering();
MachineFrameInfo *MFI = Fn.getFrameInfo();
unsigned MaxCallFrameSize = 0;
bool AdjustsStack = MFI->adjustsStack();
// Get the function call frame set-up and tear-down instruction opcode
int FrameSetupOpcode = TII.getCallFrameSetupOpcode();
int FrameDestroyOpcode = TII.getCallFrameDestroyOpcode();
// Early exit for targets which have no call frame setup/destroy pseudo
// instructions.
if (FrameSetupOpcode == -1 && FrameDestroyOpcode == -1)
return;
std::vector<MachineBasicBlock::iterator> FrameSDOps;
for (MachineFunction::iterator BB = Fn.begin(), E = Fn.end(); BB != E; ++BB)
for (MachineBasicBlock::iterator I = BB->begin(); I != BB->end(); ++I)
if (I->getOpcode() == FrameSetupOpcode ||
I->getOpcode() == FrameDestroyOpcode) {
assert(I->getNumOperands() >= 1 && "Call Frame Setup/Destroy Pseudo"
" instructions should have a single immediate argument!");
unsigned Size = I->getOperand(0).getImm();
if (Size > MaxCallFrameSize) MaxCallFrameSize = Size;
AdjustsStack = true;
FrameSDOps.push_back(I);
} else if (I->isInlineAsm()) {
// Some inline asm's need a stack frame, as indicated by operand 1.
unsigned ExtraInfo = I->getOperand(InlineAsm::MIOp_ExtraInfo).getImm();
if (ExtraInfo & InlineAsm::Extra_IsAlignStack)
AdjustsStack = true;
}
MFI->setAdjustsStack(AdjustsStack);
MFI->setMaxCallFrameSize(MaxCallFrameSize);
for (std::vector<MachineBasicBlock::iterator>::iterator
i = FrameSDOps.begin(), e = FrameSDOps.end(); i != e; ++i) {
MachineBasicBlock::iterator I = *i;
// If call frames are not being included as part of the stack frame, and
// the target doesn't indicate otherwise, remove the call frame pseudos
// here. The sub/add sp instruction pairs are still inserted, but we don't
// need to track the SP adjustment for frame index elimination.
if (TFI->canSimplifyCallFramePseudos(Fn))
TFI->eliminateCallFramePseudoInstr(Fn, *I->getParent(), I);
}
}
/// calculateCalleeSavedRegisters - Scan the function for modified callee saved
/// registers.
void PEI::calculateCalleeSavedRegisters(MachineFunction &F) {
const TargetRegisterInfo *RegInfo = F.getTarget().getRegisterInfo();
const TargetFrameLowering *TFI = F.getTarget().getFrameLowering();
MachineFrameInfo *MFI = F.getFrameInfo();
// Get the callee saved register list...
const uint16_t *CSRegs = RegInfo->getCalleeSavedRegs(&F);
// These are used to keep track the callee-save area. Initialize them.
MinCSFrameIndex = INT_MAX;
MaxCSFrameIndex = 0;
// Early exit for targets which have no callee saved registers.
if (CSRegs == 0 || CSRegs[0] == 0)
return;
// In Naked functions we aren't going to save any registers.
if (F.getFunction()->getAttributes().hasAttribute(AttributeSet::FunctionIndex,
Attribute::Naked))
return;
std::vector<CalleeSavedInfo> CSI;
for (unsigned i = 0; CSRegs[i]; ++i) {
unsigned Reg = CSRegs[i];
// Functions which call __builtin_unwind_init get all their registers saved.
if (F.getRegInfo().isPhysRegUsed(Reg) || F.getMMI().callsUnwindInit()) {
// If the reg is modified, save it!
CSI.push_back(CalleeSavedInfo(Reg));
}
}
if (CSI.empty())
return; // Early exit if no callee saved registers are modified!
unsigned NumFixedSpillSlots;
const TargetFrameLowering::SpillSlot *FixedSpillSlots =
TFI->getCalleeSavedSpillSlots(NumFixedSpillSlots);
// Now that we know which registers need to be saved and restored, allocate
// stack slots for them.
for (std::vector<CalleeSavedInfo>::iterator
I = CSI.begin(), E = CSI.end(); I != E; ++I) {
unsigned Reg = I->getReg();
const TargetRegisterClass *RC = RegInfo->getMinimalPhysRegClass(Reg);
int FrameIdx;
if (RegInfo->hasReservedSpillSlot(F, Reg, FrameIdx)) {
I->setFrameIdx(FrameIdx);
continue;
}
// Check to see if this physreg must be spilled to a particular stack slot
// on this target.
const TargetFrameLowering::SpillSlot *FixedSlot = FixedSpillSlots;
while (FixedSlot != FixedSpillSlots+NumFixedSpillSlots &&
FixedSlot->Reg != Reg)
++FixedSlot;
if (FixedSlot == FixedSpillSlots + NumFixedSpillSlots) {
// Nope, just spill it anywhere convenient.
unsigned Align = RC->getAlignment();
unsigned StackAlign = TFI->getStackAlignment();
// We may not be able to satisfy the desired alignment specification of
// the TargetRegisterClass if the stack alignment is smaller. Use the
// min.
Align = std::min(Align, StackAlign);
FrameIdx = MFI->CreateStackObject(RC->getSize(), Align, true);
if ((unsigned)FrameIdx < MinCSFrameIndex) MinCSFrameIndex = FrameIdx;
if ((unsigned)FrameIdx > MaxCSFrameIndex) MaxCSFrameIndex = FrameIdx;
} else {
// Spill it to the stack where we must.
FrameIdx = MFI->CreateFixedObject(RC->getSize(), FixedSlot->Offset, true);
}
I->setFrameIdx(FrameIdx);
}
MFI->setCalleeSavedInfo(CSI);
}
/// insertCSRSpillsAndRestores - Insert spill and restore code for
/// callee saved registers used in the function, handling shrink wrapping.
///
void PEI::insertCSRSpillsAndRestores(MachineFunction &Fn) {
// Get callee saved register information.
MachineFrameInfo *MFI = Fn.getFrameInfo();
const std::vector<CalleeSavedInfo> &CSI = MFI->getCalleeSavedInfo();
MFI->setCalleeSavedInfoValid(true);
// Early exit if no callee saved registers are modified!
if (CSI.empty())
return;
const TargetInstrInfo &TII = *Fn.getTarget().getInstrInfo();
const TargetFrameLowering *TFI = Fn.getTarget().getFrameLowering();
const TargetRegisterInfo *TRI = Fn.getTarget().getRegisterInfo();
MachineBasicBlock::iterator I;
if (!ShrinkWrapThisFunction) {
// Spill using target interface.
I = EntryBlock->begin();
if (!TFI->spillCalleeSavedRegisters(*EntryBlock, I, CSI, TRI)) {
for (unsigned i = 0, e = CSI.size(); i != e; ++i) {
// Add the callee-saved register as live-in.
// It's killed at the spill.
EntryBlock->addLiveIn(CSI[i].getReg());
// Insert the spill to the stack frame.
unsigned Reg = CSI[i].getReg();
const TargetRegisterClass *RC = TRI->getMinimalPhysRegClass(Reg);
TII.storeRegToStackSlot(*EntryBlock, I, Reg, true,
CSI[i].getFrameIdx(), RC, TRI);
}
}
// Restore using target interface.
for (unsigned ri = 0, re = ReturnBlocks.size(); ri != re; ++ri) {
MachineBasicBlock* MBB = ReturnBlocks[ri];
I = MBB->end(); --I;
// Skip over all terminator instructions, which are part of the return
// sequence.
MachineBasicBlock::iterator I2 = I;
while (I2 != MBB->begin() && (--I2)->isTerminator())
I = I2;
bool AtStart = I == MBB->begin();
MachineBasicBlock::iterator BeforeI = I;
if (!AtStart)
--BeforeI;
// Restore all registers immediately before the return and any
// terminators that precede it.
if (!TFI->restoreCalleeSavedRegisters(*MBB, I, CSI, TRI)) {
for (unsigned i = 0, e = CSI.size(); i != e; ++i) {
unsigned Reg = CSI[i].getReg();
const TargetRegisterClass *RC = TRI->getMinimalPhysRegClass(Reg);
TII.loadRegFromStackSlot(*MBB, I, Reg,
CSI[i].getFrameIdx(),
RC, TRI);
assert(I != MBB->begin() &&
"loadRegFromStackSlot didn't insert any code!");
// Insert in reverse order. loadRegFromStackSlot can insert
// multiple instructions.
if (AtStart)
I = MBB->begin();
else {
I = BeforeI;
++I;
}
}
}
}
return;
}
// Insert spills.
std::vector<CalleeSavedInfo> blockCSI;
for (CSRegBlockMap::iterator BI = CSRSave.begin(),
BE = CSRSave.end(); BI != BE; ++BI) {
MachineBasicBlock* MBB = BI->first;
CSRegSet save = BI->second;
if (save.empty())
continue;
blockCSI.clear();
for (CSRegSet::iterator RI = save.begin(),
RE = save.end(); RI != RE; ++RI) {
blockCSI.push_back(CSI[*RI]);
}
assert(blockCSI.size() > 0 &&
"Could not collect callee saved register info");
I = MBB->begin();
// When shrink wrapping, use stack slot stores/loads.
for (unsigned i = 0, e = blockCSI.size(); i != e; ++i) {
// Add the callee-saved register as live-in.
// It's killed at the spill.
MBB->addLiveIn(blockCSI[i].getReg());
// Insert the spill to the stack frame.
unsigned Reg = blockCSI[i].getReg();
const TargetRegisterClass *RC = TRI->getMinimalPhysRegClass(Reg);
TII.storeRegToStackSlot(*MBB, I, Reg,
true,
blockCSI[i].getFrameIdx(),
RC, TRI);
}
}
for (CSRegBlockMap::iterator BI = CSRRestore.begin(),
BE = CSRRestore.end(); BI != BE; ++BI) {
MachineBasicBlock* MBB = BI->first;
CSRegSet restore = BI->second;
if (restore.empty())
continue;
blockCSI.clear();
for (CSRegSet::iterator RI = restore.begin(),
RE = restore.end(); RI != RE; ++RI) {
blockCSI.push_back(CSI[*RI]);
}
assert(blockCSI.size() > 0 &&
"Could not find callee saved register info");
// If MBB is empty and needs restores, insert at the _beginning_.
if (MBB->empty()) {
I = MBB->begin();
} else {
I = MBB->end();
--I;
// Skip over all terminator instructions, which are part of the
// return sequence.
if (! I->isTerminator()) {
++I;
} else {
MachineBasicBlock::iterator I2 = I;
while (I2 != MBB->begin() && (--I2)->isTerminator())
I = I2;
}
}
bool AtStart = I == MBB->begin();
MachineBasicBlock::iterator BeforeI = I;
if (!AtStart)
--BeforeI;
// Restore all registers immediately before the return and any
// terminators that precede it.
for (unsigned i = 0, e = blockCSI.size(); i != e; ++i) {
unsigned Reg = blockCSI[i].getReg();
const TargetRegisterClass *RC = TRI->getMinimalPhysRegClass(Reg);
TII.loadRegFromStackSlot(*MBB, I, Reg,
blockCSI[i].getFrameIdx(),
RC, TRI);
assert(I != MBB->begin() &&
"loadRegFromStackSlot didn't insert any code!");
// Insert in reverse order. loadRegFromStackSlot can insert
// multiple instructions.
if (AtStart)
I = MBB->begin();
else {
I = BeforeI;
++I;
}
}
}
}
/// AdjustStackOffset - Helper function used to adjust the stack frame offset.
static inline void
AdjustStackOffset(MachineFrameInfo *MFI, int FrameIdx,
bool StackGrowsDown, int64_t &Offset,
unsigned &MaxAlign) {
// If the stack grows down, add the object size to find the lowest address.
if (StackGrowsDown)
Offset += MFI->getObjectSize(FrameIdx);
unsigned Align = MFI->getObjectAlignment(FrameIdx);
// If the alignment of this object is greater than that of the stack, then
// increase the stack alignment to match.
MaxAlign = std::max(MaxAlign, Align);
// Adjust to alignment boundary.
Offset = (Offset + Align - 1) / Align * Align;
if (StackGrowsDown) {
DEBUG(dbgs() << "alloc FI(" << FrameIdx << ") at SP[" << -Offset << "]\n");
MFI->setObjectOffset(FrameIdx, -Offset); // Set the computed offset
} else {
DEBUG(dbgs() << "alloc FI(" << FrameIdx << ") at SP[" << Offset << "]\n");
MFI->setObjectOffset(FrameIdx, Offset);
Offset += MFI->getObjectSize(FrameIdx);
}
}
/// calculateFrameObjectOffsets - Calculate actual frame offsets for all of the
/// abstract stack objects.
///
void PEI::calculateFrameObjectOffsets(MachineFunction &Fn) {
const TargetFrameLowering &TFI = *Fn.getTarget().getFrameLowering();
bool StackGrowsDown =
TFI.getStackGrowthDirection() == TargetFrameLowering::StackGrowsDown;
// Loop over all of the stack objects, assigning sequential addresses...
MachineFrameInfo *MFI = Fn.getFrameInfo();
// Start at the beginning of the local area.
// The Offset is the distance from the stack top in the direction
// of stack growth -- so it's always nonnegative.
int LocalAreaOffset = TFI.getOffsetOfLocalArea();
if (StackGrowsDown)
LocalAreaOffset = -LocalAreaOffset;
assert(LocalAreaOffset >= 0
&& "Local area offset should be in direction of stack growth");
int64_t Offset = LocalAreaOffset;
// If there are fixed sized objects that are preallocated in the local area,
// non-fixed objects can't be allocated right at the start of local area.
// We currently don't support filling in holes in between fixed sized
// objects, so we adjust 'Offset' to point to the end of last fixed sized
// preallocated object.
for (int i = MFI->getObjectIndexBegin(); i != 0; ++i) {
int64_t FixedOff;
if (StackGrowsDown) {
// The maximum distance from the stack pointer is at lower address of
// the object -- which is given by offset. For down growing stack
// the offset is negative, so we negate the offset to get the distance.
FixedOff = -MFI->getObjectOffset(i);
} else {
// The maximum distance from the start pointer is at the upper
// address of the object.
FixedOff = MFI->getObjectOffset(i) + MFI->getObjectSize(i);
}
if (FixedOff > Offset) Offset = FixedOff;
}
// First assign frame offsets to stack objects that are used to spill
// callee saved registers.
if (StackGrowsDown) {
for (unsigned i = MinCSFrameIndex; i <= MaxCSFrameIndex; ++i) {
// If the stack grows down, we need to add the size to find the lowest
// address of the object.
Offset += MFI->getObjectSize(i);
unsigned Align = MFI->getObjectAlignment(i);
// Adjust to alignment boundary
Offset = (Offset+Align-1)/Align*Align;
MFI->setObjectOffset(i, -Offset); // Set the computed offset
}
} else {
int MaxCSFI = MaxCSFrameIndex, MinCSFI = MinCSFrameIndex;
for (int i = MaxCSFI; i >= MinCSFI ; --i) {
unsigned Align = MFI->getObjectAlignment(i);
// Adjust to alignment boundary
Offset = (Offset+Align-1)/Align*Align;
MFI->setObjectOffset(i, Offset);
Offset += MFI->getObjectSize(i);
}
}
unsigned MaxAlign = MFI->getMaxAlignment();
// Make sure the special register scavenging spill slot is closest to the
// incoming stack pointer if a frame pointer is required and is closer
// to the incoming rather than the final stack pointer.
const TargetRegisterInfo *RegInfo = Fn.getTarget().getRegisterInfo();
bool EarlyScavengingSlots = (TFI.hasFP(Fn) &&
TFI.isFPCloseToIncomingSP() &&
RegInfo->useFPForScavengingIndex(Fn) &&
!RegInfo->needsStackRealignment(Fn));
if (RS && EarlyScavengingSlots) {
SmallVector<int, 2> SFIs;
RS->getScavengingFrameIndices(SFIs);
for (SmallVectorImpl<int>::iterator I = SFIs.begin(),
IE = SFIs.end(); I != IE; ++I)
AdjustStackOffset(MFI, *I, StackGrowsDown, Offset, MaxAlign);
}
// FIXME: Once this is working, then enable flag will change to a target
// check for whether the frame is large enough to want to use virtual
// frame index registers. Functions which don't want/need this optimization
// will continue to use the existing code path.
if (MFI->getUseLocalStackAllocationBlock()) {
unsigned Align = MFI->getLocalFrameMaxAlign();
// Adjust to alignment boundary.
Offset = (Offset + Align - 1) / Align * Align;
DEBUG(dbgs() << "Local frame base offset: " << Offset << "\n");
// Resolve offsets for objects in the local block.
for (unsigned i = 0, e = MFI->getLocalFrameObjectCount(); i != e; ++i) {
std::pair<int, int64_t> Entry = MFI->getLocalFrameObjectMap(i);
int64_t FIOffset = (StackGrowsDown ? -Offset : Offset) + Entry.second;
DEBUG(dbgs() << "alloc FI(" << Entry.first << ") at SP[" <<
FIOffset << "]\n");
MFI->setObjectOffset(Entry.first, FIOffset);
}
// Allocate the local block
Offset += MFI->getLocalFrameSize();
MaxAlign = std::max(Align, MaxAlign);
}
// Make sure that the stack protector comes before the local variables on the
// stack.
SmallSet<int, 16> LargeStackObjs;
if (MFI->getStackProtectorIndex() >= 0) {
AdjustStackOffset(MFI, MFI->getStackProtectorIndex(), StackGrowsDown,
Offset, MaxAlign);
// Assign large stack objects first.
for (unsigned i = 0, e = MFI->getObjectIndexEnd(); i != e; ++i) {
if (MFI->isObjectPreAllocated(i) &&
MFI->getUseLocalStackAllocationBlock())
continue;
if (i >= MinCSFrameIndex && i <= MaxCSFrameIndex)
continue;
if (RS && RS->isScavengingFrameIndex((int)i))
continue;
if (MFI->isDeadObjectIndex(i))
continue;
if (MFI->getStackProtectorIndex() == (int)i)
continue;
if (!MFI->MayNeedStackProtector(i))
continue;
AdjustStackOffset(MFI, i, StackGrowsDown, Offset, MaxAlign);
LargeStackObjs.insert(i);
}
}
// Then assign frame offsets to stack objects that are not used to spill
// callee saved registers.
for (unsigned i = 0, e = MFI->getObjectIndexEnd(); i != e; ++i) {
if (MFI->isObjectPreAllocated(i) &&
MFI->getUseLocalStackAllocationBlock())
continue;
if (i >= MinCSFrameIndex && i <= MaxCSFrameIndex)
continue;
if (RS && RS->isScavengingFrameIndex((int)i))
continue;
if (MFI->isDeadObjectIndex(i))
continue;
if (MFI->getStackProtectorIndex() == (int)i)
continue;
if (LargeStackObjs.count(i))
continue;
AdjustStackOffset(MFI, i, StackGrowsDown, Offset, MaxAlign);
}
// Make sure the special register scavenging spill slot is closest to the
// stack pointer.
if (RS && !EarlyScavengingSlots) {
SmallVector<int, 2> SFIs;
RS->getScavengingFrameIndices(SFIs);
for (SmallVectorImpl<int>::iterator I = SFIs.begin(),
IE = SFIs.end(); I != IE; ++I)
AdjustStackOffset(MFI, *I, StackGrowsDown, Offset, MaxAlign);
}
if (!TFI.targetHandlesStackFrameRounding()) {
// If we have reserved argument space for call sites in the function
// immediately on entry to the current function, count it as part of the
// overall stack size.
if (MFI->adjustsStack() && TFI.hasReservedCallFrame(Fn))
Offset += MFI->getMaxCallFrameSize();
// Round up the size to a multiple of the alignment. If the function has
// any calls or alloca's, align to the target's StackAlignment value to
// ensure that the callee's frame or the alloca data is suitably aligned;
// otherwise, for leaf functions, align to the TransientStackAlignment
// value.
unsigned StackAlign;
if (MFI->adjustsStack() || MFI->hasVarSizedObjects() ||
(RegInfo->needsStackRealignment(Fn) && MFI->getObjectIndexEnd() != 0))
StackAlign = TFI.getStackAlignment();
else
StackAlign = TFI.getTransientStackAlignment();
// If the frame pointer is eliminated, all frame offsets will be relative to
// SP not FP. Align to MaxAlign so this works.
StackAlign = std::max(StackAlign, MaxAlign);
unsigned AlignMask = StackAlign - 1;
Offset = (Offset + AlignMask) & ~uint64_t(AlignMask);
}
// Update frame info to pretend that this is part of the stack...
int64_t StackSize = Offset - LocalAreaOffset;
MFI->setStackSize(StackSize);
NumBytesStackSpace += StackSize;
}
/// insertPrologEpilogCode - Scan the function for modified callee saved
/// registers, insert spill code for these callee saved registers, then add
/// prolog and epilog code to the function.
///
void PEI::insertPrologEpilogCode(MachineFunction &Fn) {
const TargetFrameLowering &TFI = *Fn.getTarget().getFrameLowering();
// Add prologue to the function...
TFI.emitPrologue(Fn);
// Add epilogue to restore the callee-save registers in each exiting block
for (MachineFunction::iterator I = Fn.begin(), E = Fn.end(); I != E; ++I) {
// If last instruction is a return instruction, add an epilogue
if (!I->empty() && I->back().isReturn())
TFI.emitEpilogue(Fn, *I);
}
// Emit additional code that is required to support segmented stacks, if
// we've been asked for it. This, when linked with a runtime with support
// for segmented stacks (libgcc is one), will result in allocating stack
// space in small chunks instead of one large contiguous block.
if (Fn.getTarget().Options.EnableSegmentedStacks)
TFI.adjustForSegmentedStacks(Fn);
// Emit additional code that is required to explicitly handle the stack in
// HiPE native code (if needed) when loaded in the Erlang/OTP runtime. The
// approach is rather similar to that of Segmented Stacks, but it uses a
// different conditional check and another BIF for allocating more stack
// space.
if (Fn.getFunction()->getCallingConv() == CallingConv::HiPE)
TFI.adjustForHiPEPrologue(Fn);
}
/// replaceFrameIndices - Replace all MO_FrameIndex operands with physical
/// register references and actual offsets.
///
void PEI::replaceFrameIndices(MachineFunction &Fn) {
if (!Fn.getFrameInfo()->hasStackObjects()) return; // Nothing to do?
// Store SPAdj at exit of a basic block.
SmallVector<int, 8> SPState;
SPState.resize(Fn.getNumBlockIDs());
SmallPtrSet<MachineBasicBlock*, 8> Reachable;
// Iterate over the reachable blocks in DFS order.
for (df_ext_iterator<MachineFunction*, SmallPtrSet<MachineBasicBlock*, 8> >
DFI = df_ext_begin(&Fn, Reachable), DFE = df_ext_end(&Fn, Reachable);
DFI != DFE; ++DFI) {
int SPAdj = 0;
// Check the exit state of the DFS stack predecessor.
if (DFI.getPathLength() >= 2) {
MachineBasicBlock *StackPred = DFI.getPath(DFI.getPathLength() - 2);
assert(Reachable.count(StackPred) &&
"DFS stack predecessor is already visited.\n");
SPAdj = SPState[StackPred->getNumber()];
}
MachineBasicBlock *BB = *DFI;
replaceFrameIndices(BB, Fn, SPAdj);
SPState[BB->getNumber()] = SPAdj;
}
// Handle the unreachable blocks.
for (MachineFunction::iterator BB = Fn.begin(), E = Fn.end(); BB != E; ++BB) {
if (Reachable.count(BB))
// Already handled in DFS traversal.
continue;
int SPAdj = 0;
replaceFrameIndices(BB, Fn, SPAdj);
}
}
void PEI::replaceFrameIndices(MachineBasicBlock *BB, MachineFunction &Fn,
int &SPAdj) {
const TargetMachine &TM = Fn.getTarget();
assert(TM.getRegisterInfo() && "TM::getRegisterInfo() must be implemented!");
const TargetInstrInfo &TII = *Fn.getTarget().getInstrInfo();
const TargetRegisterInfo &TRI = *TM.getRegisterInfo();
const TargetFrameLowering *TFI = TM.getFrameLowering();
bool StackGrowsDown =
TFI->getStackGrowthDirection() == TargetFrameLowering::StackGrowsDown;
int FrameSetupOpcode = TII.getCallFrameSetupOpcode();
int FrameDestroyOpcode = TII.getCallFrameDestroyOpcode();
if (RS && !FrameIndexVirtualScavenging) RS->enterBasicBlock(BB);
for (MachineBasicBlock::iterator I = BB->begin(); I != BB->end(); ) {
if (I->getOpcode() == FrameSetupOpcode ||
I->getOpcode() == FrameDestroyOpcode) {
// Remember how much SP has been adjusted to create the call
// frame.
int Size = I->getOperand(0).getImm();
if ((!StackGrowsDown && I->getOpcode() == FrameSetupOpcode) ||
(StackGrowsDown && I->getOpcode() == FrameDestroyOpcode))
Size = -Size;
SPAdj += Size;
MachineBasicBlock::iterator PrevI = BB->end();
if (I != BB->begin()) PrevI = prior(I);
TFI->eliminateCallFramePseudoInstr(Fn, *BB, I);
// Visit the instructions created by eliminateCallFramePseudoInstr().
if (PrevI == BB->end())
I = BB->begin(); // The replaced instr was the first in the block.
else
I = llvm::next(PrevI);
continue;
}
MachineInstr *MI = I;
bool DoIncr = true;
for (unsigned i = 0, e = MI->getNumOperands(); i != e; ++i) {
if (!MI->getOperand(i).isFI())
continue;
// Frame indicies in debug values are encoded in a target independent
// way with simply the frame index and offset rather than any
// target-specific addressing mode.
if (MI->isDebugValue()) {
assert(i == 0 && "Frame indicies can only appear as the first "
"operand of a DBG_VALUE machine instruction");
unsigned Reg;
MachineOperand &Offset = MI->getOperand(1);
Offset.setImm(Offset.getImm() +
TFI->getFrameIndexReference(
Fn, MI->getOperand(0).getIndex(), Reg));
MI->getOperand(0).ChangeToRegister(Reg, false /*isDef*/);
continue;
}
// Some instructions (e.g. inline asm instructions) can have
// multiple frame indices and/or cause eliminateFrameIndex
// to insert more than one instruction. We need the register
// scavenger to go through all of these instructions so that
// it can update its register information. We keep the
// iterator at the point before insertion so that we can
// revisit them in full.
bool AtBeginning = (I == BB->begin());
if (!AtBeginning) --I;
// If this instruction has a FrameIndex operand, we need to
// use that target machine register info object to eliminate
// it.
TRI.eliminateFrameIndex(MI, SPAdj, i,
FrameIndexVirtualScavenging ? NULL : RS);
// Reset the iterator if we were at the beginning of the BB.
if (AtBeginning) {
I = BB->begin();
DoIncr = false;
}
MI = 0;
break;
}
if (DoIncr && I != BB->end()) ++I;
// Update register states.
if (RS && !FrameIndexVirtualScavenging && MI) RS->forward(MI);
}
}
/// scavengeFrameVirtualRegs - Replace all frame index virtual registers
/// with physical registers. Use the register scavenger to find an
/// appropriate register to use.
///
/// FIXME: Iterating over the instruction stream is unnecessary. We can simply
/// iterate over the vreg use list, which at this point only contains machine
/// operands for which eliminateFrameIndex need a new scratch reg.
void PEI::scavengeFrameVirtualRegs(MachineFunction &Fn) {
// Run through the instructions and find any virtual registers.
for (MachineFunction::iterator BB = Fn.begin(),
E = Fn.end(); BB != E; ++BB) {
RS->enterBasicBlock(BB);
int SPAdj = 0;
// The instruction stream may change in the loop, so check BB->end()
// directly.
for (MachineBasicBlock::iterator I = BB->begin(); I != BB->end(); ) {
// We might end up here again with a NULL iterator if we scavenged a
// register for which we inserted spill code for definition by what was
// originally the first instruction in BB.
if (I == MachineBasicBlock::iterator(NULL))
I = BB->begin();
MachineInstr *MI = I;
MachineBasicBlock::iterator J = llvm::next(I);
MachineBasicBlock::iterator P = I == BB->begin() ?
MachineBasicBlock::iterator(NULL) : llvm::prior(I);
// RS should process this instruction before we might scavenge at this
// location. This is because we might be replacing a virtual register
// defined by this instruction, and if so, registers killed by this
// instruction are available, and defined registers are not.
RS->forward(I);
for (unsigned i = 0, e = MI->getNumOperands(); i != e; ++i) {
if (MI->getOperand(i).isReg()) {
MachineOperand &MO = MI->getOperand(i);
unsigned Reg = MO.getReg();
if (Reg == 0)
continue;
if (!TargetRegisterInfo::isVirtualRegister(Reg))
continue;
// When we first encounter a new virtual register, it
// must be a definition.
assert(MI->getOperand(i).isDef() &&
"frame index virtual missing def!");
// Scavenge a new scratch register
const TargetRegisterClass *RC = Fn.getRegInfo().getRegClass(Reg);
unsigned ScratchReg = RS->scavengeRegister(RC, J, SPAdj);
++NumScavengedRegs;
// Replace this reference to the virtual register with the
// scratch register.
assert (ScratchReg && "Missing scratch register!");
Fn.getRegInfo().replaceRegWith(Reg, ScratchReg);
// Because this instruction was processed by the RS before this
// register was allocated, make sure that the RS now records the
// register as being used.
RS->setUsed(ScratchReg);
}
}
// If the scavenger needed to use one of its spill slots, the
// spill code will have been inserted in between I and J. This is a
// problem because we need the spill code before I: Move I to just
// prior to J.
if (I != llvm::prior(J)) {
BB->splice(J, BB, I);
// Before we move I, we need to prepare the RS to visit I again.
// Specifically, RS will assert if it sees uses of registers that
// it believes are undefined. Because we have already processed
// register kills in I, when it visits I again, it will believe that
// those registers are undefined. To avoid this situation, unprocess
// the instruction I.
assert(RS->getCurrentPosition() == I &&
"The register scavenger has an unexpected position");
I = P;
RS->unprocess(P);
} else
++I;
}
}
}
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