//
// 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 the are likely to be out of range of stack pointer and frame
+// estimates they are likely to be out of range of stack pointer and frame
// pointer relative addressing.
//
//===----------------------------------------------------------------------===//
#include "llvm/Pass.h"
#include "llvm/ADT/SmallSet.h"
#include "llvm/ADT/Statistic.h"
+#include "llvm/ADT/STLExtras.h"
#include "llvm/CodeGen/MachineFrameInfo.h"
#include "llvm/CodeGen/MachineFunction.h"
#include "llvm/CodeGen/MachineFunctionPass.h"
#include "llvm/Support/ErrorHandling.h"
#include "llvm/Support/raw_ostream.h"
#include "llvm/Target/TargetRegisterInfo.h"
-#include "llvm/Target/TargetFrameInfo.h"
+#include "llvm/Target/TargetFrameLowering.h"
using namespace llvm;
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
+ public:
+ FrameRef(MachineBasicBlock::iterator I, int64_t Offset) :
+ MI(I), LocalOffset(Offset) {}
+ bool operator<(const FrameRef &RHS) const {
+ return LocalOffset < RHS.LocalOffset;
+ }
+ MachineBasicBlock::iterator getMachineInstr() { return MI; }
+ };
+
class LocalStackSlotPass: public MachineFunctionPass {
SmallVector<int64_t,16> LocalOffsets;
void AdjustStackOffset(MachineFrameInfo *MFI, int FrameIdx, int64_t &Offset,
- unsigned &MaxAlign);
+ bool StackGrowsDown, unsigned &MaxAlign);
void calculateFrameObjectOffsets(MachineFunction &Fn);
bool insertFrameReferenceRegisters(MachineFunction &Fn);
public:
bool LocalStackSlotPass::runOnMachineFunction(MachineFunction &MF) {
MachineFrameInfo *MFI = MF.getFrameInfo();
+ const TargetRegisterInfo *TRI = MF.getTarget().getRegisterInfo();
unsigned LocalObjectCount = MFI->getObjectIndexEnd();
- // Early exit if there are no locals to consider
- if (!LocalObjectCount)
+ // 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.
/// 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
// Adjust to alignment boundary.
Offset = (Offset + Align - 1) / Align * Align;
+ int64_t LocalOffset = StackGrowsDown ? -Offset : Offset;
DEBUG(dbgs() << "Allocate FI(" << FrameIdx << ") to local offset "
- << Offset << "\n");
+ << LocalOffset << "\n");
// Keep the offset available for base register allocation
- LocalOffsets[FrameIdx] = Offset;
+ LocalOffsets[FrameIdx] = LocalOffset;
// And tell MFI about it for PEI to use later
- MFI->mapLocalFrameObject(FrameIdx, Offset);
- Offset += MFI->getObjectSize(FrameIdx);
+ MFI->mapLocalFrameObject(FrameIdx, LocalOffset);
+
+ if (!StackGrowsDown)
+ Offset += MFI->getObjectSize(FrameIdx);
++NumAllocations;
}
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;
// stack.
SmallSet<int, 16> LargeStackObjs;
if (MFI->getStackProtectorIndex() >= 0) {
- AdjustStackOffset(MFI, MFI->getStackProtectorIndex(), Offset, MaxAlign);
+ AdjustStackOffset(MFI, MFI->getStackProtectorIndex(), Offset,
+ StackGrowsDown, MaxAlign);
// Assign large stack objects first.
for (unsigned i = 0, e = MFI->getObjectIndexEnd(); i != e; ++i) {
if (!MFI->MayNeedStackProtector(i))
continue;
- AdjustStackOffset(MFI, i, Offset, MaxAlign);
+ AdjustStackOffset(MFI, i, Offset, StackGrowsDown, MaxAlign);
LargeStackObjs.insert(i);
}
}
if (LargeStackObjs.count(i))
continue;
- AdjustStackOffset(MFI, i, Offset, MaxAlign);
+ AdjustStackOffset(MFI, i, Offset, StackGrowsDown, MaxAlign);
}
// Remember how big this blob of stack space is
static inline bool
lookupCandidateBaseReg(const SmallVector<std::pair<unsigned, int64_t>, 8> &Regs,
std::pair<unsigned, int64_t> &RegOffset,
+ int64_t FrameSizeAdjust,
int64_t LocalFrameOffset,
const MachineInstr *MI,
const TargetRegisterInfo *TRI) {
RegOffset = Regs[i];
// 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 = LocalFrameOffset - RegOffset.second;
+ int64_t Offset = FrameSizeAdjust + LocalFrameOffset - RegOffset.second;
if (TRI->isFrameOffsetLegal(MI, Offset))
return true;
}
MachineFrameInfo *MFI = Fn.getFrameInfo();
const TargetRegisterInfo *TRI = Fn.getTarget().getRegisterInfo();
+ const TargetFrameLowering &TFI = *Fn.getTarget().getFrameLowering();
+ bool StackGrowsDown =
+ TFI.getStackGrowthDirection() == TargetFrameLowering::StackGrowsDown;
- for (MachineFunction::iterator BB = Fn.begin(),
- E = Fn.end(); BB != E; ++BB) {
- // A base register definition is a register+offset pair.
- SmallVector<std::pair<unsigned, int64_t>, 8> BaseRegisters;
+ // 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;
+ // A base register definition is a register + offset pair.
+ SmallVector<std::pair<unsigned, int64_t>, 8> BaseRegisters;
+
+ 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 instructions can't be out of range, so they don't need
// any updates.
- // FIXME: When we extend this stuff to handle functions with both
- // VLAs and dynamic realignment, we should update the debug values
- // to reference the new base pointer when possible.
if (MI->isDebugValue())
continue;
// Consider replacing all frame index operands that reference
// an object allocated in the local block.
if (MI->getOperand(i).isFI()) {
- int FrameIdx = MI->getOperand(i).getIndex();
-
// Don't try this with values not in the local block.
- if (!MFI->isObjectPreAllocated(FrameIdx))
- continue;
-
- DEBUG(dbgs() << "Considering: " << *MI);
- if (TRI->needsFrameBaseReg(MI, i)) {
- unsigned BaseReg = 0;
- int64_t Offset = 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.
- std::pair<unsigned, int64_t> RegOffset;
- if (lookupCandidateBaseReg(BaseRegisters, RegOffset,
- LocalOffsets[FrameIdx], MI, TRI)) {
- DEBUG(dbgs() << " Reusing base register " <<
- RegOffset.first << "\n");
- // We found a register to reuse.
- BaseReg = RegOffset.first;
- Offset = LocalOffsets[FrameIdx] - RegOffset.second;
- } else {
- // No previously defined register was in range, so create a
- // new one.
- int64_t InstrOffset = TRI->getFrameIndexInstrOffset(MI, i);
- const TargetRegisterClass *RC = TRI->getPointerRegClass();
- BaseReg = Fn.getRegInfo().createVirtualRegister(RC);
-
- DEBUG(dbgs() << " Materializing base register " << BaseReg <<
- " at frame local offset " <<
- LocalOffsets[FrameIdx] + InstrOffset << "\n");
- // Tell the target to insert the instruction to initialize
- // the base register.
- TRI->materializeFrameBaseRegister(I, 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;
-
- BaseRegisters.push_back(
- std::pair<unsigned, int64_t>(BaseReg,
- LocalOffsets[FrameIdx] + 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);
-
- ++NumReplacements;
+ if (!MFI->isObjectPreAllocated(MI->getOperand(i).getIndex()))
+ break;
+ FrameReferenceInsns.
+ push_back(FrameRef(MI, LocalOffsets[MI->getOperand(i).getIndex()]));
+ break;
+ }
+ }
+ }
+ }
+
+ // Sort the frame references by local offset
+ array_pod_sort(FrameReferenceInsns.begin(), FrameReferenceInsns.end());
+
+ MachineBasicBlock *Entry = Fn.begin();
+
+ // Loop through the frame references and allocate for them as necessary.
+ for (int ref = 0, e = FrameReferenceInsns.size(); ref < e ; ++ref) {
+ MachineBasicBlock::iterator I =
+ FrameReferenceInsns[ref].getMachineInstr();
+ MachineInstr *MI = I;
+ for (unsigned idx = 0, e = MI->getNumOperands(); idx != e; ++idx) {
+ // Consider replacing all frame index operands that reference
+ // an object allocated in the local block.
+ if (MI->getOperand(idx).isFI()) {
+ int FrameIdx = MI->getOperand(idx).getIndex();
+
+ assert(MFI->isObjectPreAllocated(FrameIdx) &&
+ "Only pre-allocated locals expected!");
+
+ DEBUG(dbgs() << "Considering: " << *MI);
+ if (TRI->needsFrameBaseReg(MI, LocalOffsets[FrameIdx])) {
+ unsigned BaseReg = 0;
+ 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.
+ std::pair<unsigned, int64_t> RegOffset;
+ if (lookupCandidateBaseReg(BaseRegisters, RegOffset,
+ FrameSizeAdjust,
+ LocalOffsets[FrameIdx],
+ MI, TRI)) {
+ DEBUG(dbgs() << " Reusing base register " <<
+ RegOffset.first << "\n");
+ // We found a register to reuse.
+ BaseReg = RegOffset.first;
+ Offset = FrameSizeAdjust + LocalOffsets[FrameIdx] -
+ RegOffset.second;
+ } else {
+ // No previously defined register was in range, so create a
+ // new one.
+ int64_t InstrOffset = TRI->getFrameIndexInstrOffset(MI, idx);
+ const TargetRegisterClass *RC = TRI->getPointerRegClass();
+ BaseReg = Fn.getRegInfo().createVirtualRegister(RC);
+
+ DEBUG(dbgs() << " Materializing base register " << BaseReg <<
+ " at frame local offset " <<
+ LocalOffsets[FrameIdx] + 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;
+
+ int64_t BaseOffset = FrameSizeAdjust + LocalOffsets[FrameIdx] +
+ InstrOffset;
+ BaseRegisters.push_back(
+ std::pair<unsigned, int64_t>(BaseReg, BaseOffset));
+ ++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;
}
}
}
projects / oota-llvm.git / blobdiff