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Enable ARM base register reuse to local stack slot allocation. Whenever a new

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frame index reference to an object in the local block is seen, check if
it's near enough to any previously allocaated base register to re-use.

rdar://8277890



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@111443 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Jim Grosbach
2010-08-18 22:44:49 +00:00
parent e0b313d599
commit 2b1e202e1c
2 changed files with 102 additions and 10 deletions
Download Patch File Download Diff File Expand all files Collapse all files
lib/CodeGen/LocalStackSlotAllocation.cpp
+33 -10
View File
@@ -43,8 +43,11 @@ STATISTIC(NumReplacements, "Number of frame indices references replaced");
namespace {
class LocalStackSlotPass: public MachineFunctionPass {
void calculateFrameObjectOffsets(MachineFunction &Fn);
SmallVector<int64_t,16> LocalOffsets;
void AdjustStackOffset(MachineFrameInfo *MFI, int FrameIdx, int64_t &Offset,
unsigned &MaxAlign);
void calculateFrameObjectOffsets(MachineFunction &Fn);
void insertFrameReferenceRegisters(MachineFunction &Fn);
public:
static char ID; // Pass identification, replacement for typeid
@@ -70,18 +73,29 @@ FunctionPass *llvm::createLocalStackSlotAllocationPass() {
}
bool LocalStackSlotPass::runOnMachineFunction(MachineFunction &MF) {
MachineFrameInfo *MFI = MF.getFrameInfo();
unsigned LocalObjectCount = MFI->getObjectIndexEnd();
// Early exit if there are no locals to consider
if (!LocalObjectCount)
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.
insertFrameReferenceRegisters(MF);
return true;
}
/// AdjustStackOffset - Helper function used to adjust the stack frame offset.
static inline void
AdjustStackOffset(MachineFrameInfo *MFI, int FrameIdx, int64_t &Offset,
unsigned &MaxAlign) {
void LocalStackSlotPass::AdjustStackOffset(MachineFrameInfo *MFI,
int FrameIdx, int64_t &Offset,
unsigned &MaxAlign) {
unsigned Align = MFI->getObjectAlignment(FrameIdx);
// If the alignment of this object is greater than that of the stack, then
@@ -93,6 +107,9 @@ AdjustStackOffset(MachineFrameInfo *MFI, int FrameIdx, int64_t &Offset,
DEBUG(dbgs() << "Allocate FI(" << FrameIdx << ") to local offset "
<< Offset << "\n");
// Keep the offset available for base register allocation
LocalOffsets[FrameIdx] = Offset;
// And tell MFI about it for PEI to use later
MFI->mapLocalFrameObject(FrameIdx, Offset);
Offset += MFI->getObjectSize(FrameIdx);
@@ -149,12 +166,16 @@ void LocalStackSlotPass::calculateFrameObjectOffsets(MachineFunction &Fn) {
static inline bool
lookupCandidateBaseReg(const SmallVector<std::pair<unsigned, int64_t>, 8> &Regs,
std::pair<unsigned, int64_t> &RegOffset,
int64_t LocalFrameOffset,
const MachineInstr *MI,
const TargetRegisterInfo *TRI) {
unsigned e = Regs.size();
for (unsigned i = 0; i < e; ++i) {
RegOffset = Regs[i];
if (TRI->isBaseRegInRange(MI, RegOffset.first, RegOffset.second))
// 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;
if (TRI->isBaseRegInRange(MI, RegOffset.first, Offset))
return true;
}
return false;
@@ -173,6 +194,9 @@ void LocalStackSlotPass::insertFrameReferenceRegisters(MachineFunction &Fn) {
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;
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
@@ -183,9 +207,6 @@ void LocalStackSlotPass::insertFrameReferenceRegisters(MachineFunction &Fn) {
if (MI->isDebugValue())
continue;
// A base register definition is a register+offset pair.
SmallVector<std::pair<unsigned, int64_t>, 8> BaseRegisters;
// 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
@@ -212,10 +233,12 @@ void LocalStackSlotPass::insertFrameReferenceRegisters(MachineFunction &Fn) {
// create a new one.
std::pair<unsigned, int64_t> RegOffset;
if (lookupCandidateBaseReg(BaseRegisters, RegOffset, MI, TRI)) {
if (lookupCandidateBaseReg(BaseRegisters, RegOffset,
LocalOffsets[FrameIdx], MI, TRI)) {
DEBUG(dbgs() << " Reusing base register " << RegOffset.first);
// We found a register to reuse.
BaseReg = RegOffset.first;
Offset = RegOffset.second;
Offset = LocalOffsets[FrameIdx] - RegOffset.second;
} else {
// No previously defined register was in range, so create a
// new one.