llvm-6502/lib/CodeGen/LocalStackSlotAllocation.cpp
Chandler Carruth 0b8c9a80f2 Move all of the header files which are involved in modelling the LLVM IR
into their new header subdirectory: include/llvm/IR. This matches the
directory structure of lib, and begins to correct a long standing point
of file layout clutter in LLVM.

There are still more header files to move here, but I wanted to handle
them in separate commits to make tracking what files make sense at each
layer easier.

The only really questionable files here are the target intrinsic
tablegen files. But that's a battle I'd rather not fight today.

I've updated both CMake and Makefile build systems (I think, and my
tests think, but I may have missed something).

I've also re-sorted the includes throughout the project. I'll be
committing updates to Clang, DragonEgg, and Polly momentarily.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@171366 91177308-0d34-0410-b5e6-96231b3b80d8
2013-01-02 11:36:10 +00:00

357 lines
14 KiB
C++

//===- 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.
//
//===----------------------------------------------------------------------===//
#define DEBUG_TYPE "localstackalloc"
#include "llvm/CodeGen/Passes.h"
#include "llvm/ADT/STLExtras.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/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;
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
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,
bool StackGrowsDown, unsigned &MaxAlign);
void calculateFrameObjectOffsets(MachineFunction &Fn);
bool insertFrameReferenceRegisters(MachineFunction &Fn);
public:
static char ID; // Pass identification, replacement for typeid
explicit LocalStackSlotPass() : MachineFunctionPass(ID) { }
bool runOnMachineFunction(MachineFunction &MF);
virtual void getAnalysisUsage(AnalysisUsage &AU) const {
AU.setPreservesCFG();
MachineFunctionPass::getAnalysisUsage(AU);
}
private:
};
} // end anonymous namespace
char LocalStackSlotPass::ID = 0;
char &llvm::LocalStackSlotAllocationID = LocalStackSlotPass::ID;
INITIALIZE_PASS(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;
}
/// 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;
// 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(), 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;
if (!MFI->MayNeedStackProtector(i))
continue;
AdjustStackOffset(MFI, i, Offset, StackGrowsDown, 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->isDeadObjectIndex(i))
continue;
if (MFI->getStackProtectorIndex() == (int)i)
continue;
if (LargeStackObjs.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(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) {
unsigned e = Regs.size();
for (unsigned i = 0; i < e; ++i) {
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 = FrameSizeAdjust + LocalFrameOffset - RegOffset.second;
if (TRI->isFrameOffsetLegal(MI, Offset))
return true;
}
return false;
}
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;
// 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.
if (MI->isDebugValue())
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;
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 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 " <<
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;
}
}
}
}
return UsedBaseReg;
}