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llvm-6502/lib/CodeGen/LocalStackSlotAllocation.cpp
Chandler Carruth 8677f2ff9a [Modules] Remove potential ODR violations by sinking the DEBUG_TYPE 
define below all header includes in the lib/CodeGen/... tree. While the
current modules implementation doesn't check for this kind of ODR
violation yet, it is likely to grow support for it in the future. It
also removes one layer of macro pollution across all the included
headers.

Other sub-trees will follow.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@206837 91177308-0d34-0410-b5e6-96231b3b80d8
2014-04-22 02:02:50 +00:00

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//===- LocalStackSlotAllocation.cpp - Pre-allocate locals to stack slots --===//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This pass assigns local frame indices to stack slots relative to one another
// and allocates additional base registers to access them when the target
// estimates they are likely to be out of range of stack pointer and frame
// pointer relative addressing.
//
//===----------------------------------------------------------------------===//
#include "llvm/CodeGen/Passes.h"
#include "llvm/ADT/STLExtras.h"
#include "llvm/ADT/SetVector.h"
#include "llvm/ADT/SmallSet.h"
#include "llvm/ADT/Statistic.h"
#include "llvm/CodeGen/MachineFrameInfo.h"
#include "llvm/CodeGen/MachineFunction.h"
#include "llvm/CodeGen/MachineFunctionPass.h"
#include "llvm/CodeGen/MachineRegisterInfo.h"
#include "llvm/CodeGen/StackProtector.h"
#include "llvm/IR/Constants.h"
#include "llvm/IR/DerivedTypes.h"
#include "llvm/IR/Instructions.h"
#include "llvm/IR/Intrinsics.h"
#include "llvm/IR/LLVMContext.h"
#include "llvm/IR/Module.h"
#include "llvm/Pass.h"
#include "llvm/Support/Debug.h"
#include "llvm/Support/ErrorHandling.h"
#include "llvm/Support/raw_ostream.h"
#include "llvm/Target/TargetFrameLowering.h"
#include "llvm/Target/TargetRegisterInfo.h"
using namespace llvm;
#define DEBUG_TYPE "localstackalloc"
STATISTIC(NumAllocations, "Number of frame indices allocated into local block");
STATISTIC(NumBaseRegisters, "Number of virtual frame base registers allocated");
STATISTIC(NumReplacements, "Number of frame indices references replaced");
namespace {
class FrameRef {
MachineBasicBlock::iterator MI; // Instr referencing the frame
int64_t LocalOffset; // Local offset of the frame idx referenced
int FrameIdx; // The frame index
public:
FrameRef(MachineBasicBlock::iterator I, int64_t Offset, int Idx) :
MI(I), LocalOffset(Offset), FrameIdx(Idx) {}
bool operator<(const FrameRef &RHS) const {
return LocalOffset < RHS.LocalOffset;
}
MachineBasicBlock::iterator getMachineInstr() const { return MI; }
int64_t getLocalOffset() const { return LocalOffset; }
int getFrameIndex() const { return FrameIdx; }
};
class LocalStackSlotPass: public MachineFunctionPass {
SmallVector<int64_t,16> LocalOffsets;
/// StackObjSet - A set of stack object indexes
typedef SmallSetVector<int, 8> StackObjSet;
void AdjustStackOffset(MachineFrameInfo *MFI, int FrameIdx, int64_t &Offset,
bool StackGrowsDown, unsigned &MaxAlign);
void AssignProtectedObjSet(const StackObjSet &UnassignedObjs,
SmallSet<int, 16> &ProtectedObjs,
MachineFrameInfo *MFI, bool StackGrowsDown,
int64_t &Offset, unsigned &MaxAlign);
void calculateFrameObjectOffsets(MachineFunction &Fn);
bool insertFrameReferenceRegisters(MachineFunction &Fn);
public:
static char ID; // Pass identification, replacement for typeid
explicit LocalStackSlotPass() : MachineFunctionPass(ID) {
initializeLocalStackSlotPassPass(*PassRegistry::getPassRegistry());
}
bool runOnMachineFunction(MachineFunction &MF) override;
void getAnalysisUsage(AnalysisUsage &AU) const override {
AU.setPreservesCFG();
AU.addRequired<StackProtector>();
MachineFunctionPass::getAnalysisUsage(AU);
}
private:
};
} // end anonymous namespace
char LocalStackSlotPass::ID = 0;
char &llvm::LocalStackSlotAllocationID = LocalStackSlotPass::ID;
INITIALIZE_PASS_BEGIN(LocalStackSlotPass, "localstackalloc",
"Local Stack Slot Allocation", false, false)
INITIALIZE_PASS_DEPENDENCY(StackProtector)
INITIALIZE_PASS_END(LocalStackSlotPass, "localstackalloc",
"Local Stack Slot Allocation", false, false)
bool LocalStackSlotPass::runOnMachineFunction(MachineFunction &MF) {
MachineFrameInfo *MFI = MF.getFrameInfo();
const TargetRegisterInfo *TRI = MF.getTarget().getRegisterInfo();
unsigned LocalObjectCount = MFI->getObjectIndexEnd();
// If the target doesn't want/need this pass, or if there are no locals
// to consider, early exit.
if (!TRI->requiresVirtualBaseRegisters(MF) || LocalObjectCount == 0)
return true;
// Make sure we have enough space to store the local offsets.
LocalOffsets.resize(MFI->getObjectIndexEnd());
// Lay out the local blob.
calculateFrameObjectOffsets(MF);
// Insert virtual base registers to resolve frame index references.
bool UsedBaseRegs = insertFrameReferenceRegisters(MF);
// Tell MFI whether any base registers were allocated. PEI will only
// want to use the local block allocations from this pass if there were any.
// Otherwise, PEI can do a bit better job of getting the alignment right
// without a hole at the start since it knows the alignment of the stack
// at the start of local allocation, and this pass doesn't.
MFI->setUseLocalStackAllocationBlock(UsedBaseRegs);
return true;
}
/// AdjustStackOffset - Helper function used to adjust the stack frame offset.
void LocalStackSlotPass::AdjustStackOffset(MachineFrameInfo *MFI,
int FrameIdx, int64_t &Offset,
bool StackGrowsDown,
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;
int64_t LocalOffset = StackGrowsDown ? -Offset : Offset;
DEBUG(dbgs() << "Allocate FI(" << FrameIdx << ") to local offset "
<< LocalOffset << "\n");
// Keep the offset available for base register allocation
LocalOffsets[FrameIdx] = LocalOffset;
// And tell MFI about it for PEI to use later
MFI->mapLocalFrameObject(FrameIdx, LocalOffset);
if (!StackGrowsDown)
Offset += MFI->getObjectSize(FrameIdx);
++NumAllocations;
}
/// AssignProtectedObjSet - Helper function to assign large stack objects (i.e.,
/// those required to be close to the Stack Protector) to stack offsets.
void LocalStackSlotPass::AssignProtectedObjSet(const StackObjSet &UnassignedObjs,
SmallSet<int, 16> &ProtectedObjs,
MachineFrameInfo *MFI,
bool StackGrowsDown, int64_t &Offset,
unsigned &MaxAlign) {
for (StackObjSet::const_iterator I = UnassignedObjs.begin(),
E = UnassignedObjs.end(); I != E; ++I) {
int i = *I;
AdjustStackOffset(MFI, i, Offset, StackGrowsDown, MaxAlign);
ProtectedObjs.insert(i);
}
}
/// calculateFrameObjectOffsets - Calculate actual frame offsets for all of the
/// abstract stack objects.
///
void LocalStackSlotPass::calculateFrameObjectOffsets(MachineFunction &Fn) {
// Loop over all of the stack objects, assigning sequential addresses...
MachineFrameInfo *MFI = Fn.getFrameInfo();
const TargetFrameLowering &TFI = *Fn.getTarget().getFrameLowering();
bool StackGrowsDown =
TFI.getStackGrowthDirection() == TargetFrameLowering::StackGrowsDown;
int64_t Offset = 0;
unsigned MaxAlign = 0;
StackProtector *SP = &getAnalysis<StackProtector>();
// Make sure that the stack protector comes before the local variables on the
// stack.
SmallSet<int, 16> ProtectedObjs;
if (MFI->getStackProtectorIndex() >= 0) {
StackObjSet LargeArrayObjs;
StackObjSet SmallArrayObjs;
StackObjSet AddrOfObjs;
AdjustStackOffset(MFI, MFI->getStackProtectorIndex(), Offset,
StackGrowsDown, MaxAlign);
// Assign large stack objects first.
for (unsigned i = 0, e = MFI->getObjectIndexEnd(); i != e; ++i) {
if (MFI->isDeadObjectIndex(i))
continue;
if (MFI->getStackProtectorIndex() == (int)i)
continue;
switch (SP->getSSPLayout(MFI->getObjectAllocation(i))) {
case StackProtector::SSPLK_None:
continue;
case StackProtector::SSPLK_SmallArray:
SmallArrayObjs.insert(i);
continue;
case StackProtector::SSPLK_AddrOf:
AddrOfObjs.insert(i);
continue;
case StackProtector::SSPLK_LargeArray:
LargeArrayObjs.insert(i);
continue;
}
llvm_unreachable("Unexpected SSPLayoutKind.");
}
AssignProtectedObjSet(LargeArrayObjs, ProtectedObjs, MFI, StackGrowsDown,
Offset, MaxAlign);
AssignProtectedObjSet(SmallArrayObjs, ProtectedObjs, MFI, StackGrowsDown,
Offset, MaxAlign);
AssignProtectedObjSet(AddrOfObjs, ProtectedObjs, MFI, StackGrowsDown,
Offset, MaxAlign);
}
// 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->isDeadObjectIndex(i))
continue;
if (MFI->getStackProtectorIndex() == (int)i)
continue;
if (ProtectedObjs.count(i))
continue;
AdjustStackOffset(MFI, i, Offset, StackGrowsDown, MaxAlign);
}
// Remember how big this blob of stack space is
MFI->setLocalFrameSize(Offset);
MFI->setLocalFrameMaxAlign(MaxAlign);
}
static inline bool
lookupCandidateBaseReg(int64_t BaseOffset,
int64_t FrameSizeAdjust,
int64_t LocalFrameOffset,
const MachineInstr *MI,
const TargetRegisterInfo *TRI) {
// Check if the relative offset from the where the base register references
// to the target address is in range for the instruction.
int64_t Offset = FrameSizeAdjust + LocalFrameOffset - BaseOffset;
return TRI->isFrameOffsetLegal(MI, Offset);
}
bool LocalStackSlotPass::insertFrameReferenceRegisters(MachineFunction &Fn) {
// Scan the function's instructions looking for frame index references.
// For each, ask the target if it wants a virtual base register for it
// based on what we can tell it about where the local will end up in the
// stack frame. If it wants one, re-use a suitable one we've previously
// allocated, or if there isn't one that fits the bill, allocate a new one
// and ask the target to create a defining instruction for it.
bool UsedBaseReg = false;
MachineFrameInfo *MFI = Fn.getFrameInfo();
const TargetRegisterInfo *TRI = Fn.getTarget().getRegisterInfo();
const TargetFrameLowering &TFI = *Fn.getTarget().getFrameLowering();
bool StackGrowsDown =
TFI.getStackGrowthDirection() == TargetFrameLowering::StackGrowsDown;
// Collect all of the instructions in the block that reference
// a frame index. Also store the frame index referenced to ease later
// lookup. (For any insn that has more than one FI reference, we arbitrarily
// choose the first one).
SmallVector<FrameRef, 64> FrameReferenceInsns;
for (MachineFunction::iterator BB = Fn.begin(), E = Fn.end(); BB != E; ++BB) {
for (MachineBasicBlock::iterator I = BB->begin(); I != BB->end(); ++I) {
MachineInstr *MI = I;
// Debug value, stackmap and patchpoint instructions can't be out of
// range, so they don't need any updates.
if (MI->isDebugValue() ||
MI->getOpcode() == TargetOpcode::STACKMAP ||
MI->getOpcode() == TargetOpcode::PATCHPOINT)
continue;
// For now, allocate the base register(s) within the basic block
// where they're used, and don't try to keep them around outside
// of that. It may be beneficial to try sharing them more broadly
// than that, but the increased register pressure makes that a
// tricky thing to balance. Investigate if re-materializing these
// becomes an issue.
for (unsigned i = 0, e = MI->getNumOperands(); i != e; ++i) {
// Consider replacing all frame index operands that reference
// an object allocated in the local block.
if (MI->getOperand(i).isFI()) {
// Don't try this with values not in the local block.
if (!MFI->isObjectPreAllocated(MI->getOperand(i).getIndex()))
break;
int Idx = MI->getOperand(i).getIndex();
int64_t LocalOffset = LocalOffsets[Idx];
if (!TRI->needsFrameBaseReg(MI, LocalOffset))
break;
FrameReferenceInsns.
push_back(FrameRef(MI, LocalOffset, Idx));
break;
}
}
}
}
// Sort the frame references by local offset
array_pod_sort(FrameReferenceInsns.begin(), FrameReferenceInsns.end());
MachineBasicBlock *Entry = Fn.begin();
unsigned BaseReg = 0;
int64_t BaseOffset = 0;
// Loop through the frame references and allocate for them as necessary.
for (int ref = 0, e = FrameReferenceInsns.size(); ref < e ; ++ref) {
FrameRef &FR = FrameReferenceInsns[ref];
MachineBasicBlock::iterator I = FR.getMachineInstr();
MachineInstr *MI = I;
int64_t LocalOffset = FR.getLocalOffset();
int FrameIdx = FR.getFrameIndex();
assert(MFI->isObjectPreAllocated(FrameIdx) &&
"Only pre-allocated locals expected!");
DEBUG(dbgs() << "Considering: " << *MI);
unsigned idx = 0;
for (unsigned f = MI->getNumOperands(); idx != f; ++idx) {
if (!MI->getOperand(idx).isFI())
continue;
if (FrameIdx == I->getOperand(idx).getIndex())
break;
}
assert(idx < MI->getNumOperands() && "Cannot find FI operand");
int64_t Offset = 0;
int64_t FrameSizeAdjust = StackGrowsDown ? MFI->getLocalFrameSize() : 0;
DEBUG(dbgs() << " Replacing FI in: " << *MI);
// If we have a suitable base register available, use it; otherwise
// create a new one. Note that any offset encoded in the
// instruction itself will be taken into account by the target,
// so we don't have to adjust for it here when reusing a base
// register.
if (UsedBaseReg && lookupCandidateBaseReg(BaseOffset, FrameSizeAdjust,
LocalOffset, MI, TRI)) {
DEBUG(dbgs() << " Reusing base register " << BaseReg << "\n");
// We found a register to reuse.
Offset = FrameSizeAdjust + LocalOffset - BaseOffset;
} else {
// No previously defined register was in range, so create a // new one.
int64_t InstrOffset = TRI->getFrameIndexInstrOffset(MI, idx);
int64_t PrevBaseOffset = BaseOffset;
BaseOffset = FrameSizeAdjust + LocalOffset + InstrOffset;
// We'd like to avoid creating single-use virtual base registers.
// Because the FrameRefs are in sorted order, and we've already
// processed all FrameRefs before this one, just check whether or not
// the next FrameRef will be able to reuse this new register. If not,
// then don't bother creating it.
if (ref + 1 >= e ||
!lookupCandidateBaseReg(
BaseOffset, FrameSizeAdjust,
FrameReferenceInsns[ref + 1].getLocalOffset(),
FrameReferenceInsns[ref + 1].getMachineInstr(), TRI)) {
BaseOffset = PrevBaseOffset;
continue;
}
const MachineFunction *MF = MI->getParent()->getParent();
const TargetRegisterClass *RC = TRI->getPointerRegClass(*MF);
BaseReg = Fn.getRegInfo().createVirtualRegister(RC);
DEBUG(dbgs() << " Materializing base register " << BaseReg <<
" at frame local offset " << LocalOffset + InstrOffset << "\n");
// Tell the target to insert the instruction to initialize
// the base register.
// MachineBasicBlock::iterator InsertionPt = Entry->begin();
TRI->materializeFrameBaseRegister(Entry, BaseReg, FrameIdx,
InstrOffset);
// The base register already includes any offset specified
// by the instruction, so account for that so it doesn't get
// applied twice.
Offset = -InstrOffset;
++NumBaseRegisters;
UsedBaseReg = true;
}
assert(BaseReg != 0 && "Unable to allocate virtual base register!");
// Modify the instruction to use the new base register rather
// than the frame index operand.
TRI->resolveFrameIndex(*I, BaseReg, Offset);
DEBUG(dbgs() << "Resolved: " << *MI);
++NumReplacements;
}
return UsedBaseReg;
}
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