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Add reference counting to constantpool entries. Delete the unused ones. 

llvm-svn: 34105
This commit is contained in:
Evan Cheng 2007-02-09 20:54:44 +00:00
parent 5808739fac
commit 8b7700f146
1 changed files with 113 additions and 36 deletions
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149
llvm/lib/Target/ARM/ARMConstantIslandPass.cpp
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@ -24,11 +24,12 @@
#include "llvm/Target/TargetMachine.h"
#include "llvm/Support/Compiler.h"
#include "llvm/Support/Debug.h"
#include "llvm/ADT/SmallVector.h"
#include "llvm/ADT/STLExtras.h"
#include "llvm/ADT/Statistic.h"
#include <iostream>
using namespace llvm;
STATISTIC(NumCPEs, "Number of constpool entries");
STATISTIC(NumSplit, "Number of uncond branches inserted");
STATISTIC(NumCBrFixed, "Number of cond branches fixed");
STATISTIC(NumUBrFixed, "Number of uncond branches fixed");
@ -51,13 +52,13 @@ namespace {
/// BBSizes - The size of each MachineBasicBlock in bytes of code, indexed
/// by MBB Number.
std::vector<unsigned> BBSizes;
SmallVector<unsigned, 8> BBSizes;
/// WaterList - A sorted list of basic blocks where islands could be placed
/// (i.e. blocks that don't fall through to the following block, due
/// to a return, unreachable, or unconditional branch).
std::vector<MachineBasicBlock*> WaterList;
SmallVector<MachineBasicBlock*, 8> WaterList;
/// CPUser - One user of a constant pool, keeping the machine instruction
/// pointer, the constant pool being referenced, and the max displacement
/// allowed from the instruction to the CP.
@ -71,7 +72,22 @@ namespace {
/// CPUsers - Keep track of all of the machine instructions that use various
/// constant pools and their max displacement.
std::vector<CPUser> CPUsers;
SmallVector<CPUser, 16> CPUsers;
/// CPEntry - One per constant pool entry, keeping the machine instruction
/// pointer, the constpool index, and the number of CPUser's which
/// reference this entry.
struct CPEntry {
MachineInstr *CPEMI;
unsigned CPI;
unsigned RefCount;
CPEntry(MachineInstr *cpemi, unsigned cpi, unsigned rc = 0)
: CPEMI(cpemi), CPI(cpi), RefCount(rc) {}
};
/// CPEntries - Keep track of all of the constant pool entry machine
/// instructions. For each constpool index, it keeps a vector of entries.
std::vector<std::vector<CPEntry> > CPEntries;
/// ImmBranch - One per immediate branch, keeping the machine instruction
/// pointer, conditional or unconditional, the max displacement,
@ -88,11 +104,11 @@ namespace {
/// Branches - Keep track of all the immediate branch instructions.
///
std::vector<ImmBranch> ImmBranches;
SmallVector<ImmBranch, 32> ImmBranches;
/// PushPopMIs - Keep track of all the Thumb push / pop instructions.
///
std::vector<MachineInstr*> PushPopMIs;
SmallVector<MachineInstr*, 4> PushPopMIs;
/// HasFarJump - True if any far jump instruction has been emitted during
/// the branch fix up pass.
@ -109,9 +125,10 @@ namespace {
private:
void DoInitialPlacement(MachineFunction &Fn,
std::vector<MachineInstr*> &CPEMIs);
SmallVector<MachineInstr*, 16> &CPEMIs);
CPEntry *findConstPoolEntry(unsigned CPI, const MachineInstr *CPEMI);
void InitialFunctionScan(MachineFunction &Fn,
const std::vector<MachineInstr*> &CPEMIs);
const SmallVector<MachineInstr*, 16> &CPEMIs);
MachineBasicBlock *SplitBlockBeforeInstr(MachineInstr *MI);
void UpdateForInsertedWaterBlock(MachineBasicBlock *NewBB);
bool HandleConstantPoolUser(MachineFunction &Fn, CPUser &U);
@ -147,7 +164,7 @@ bool ARMConstantIslands::runOnMachineFunction(MachineFunction &Fn) {
// Perform the initial placement of the constant pool entries. To start with,
// we put them all at the end of the function.
std::vector<MachineInstr*> CPEMIs;
SmallVector<MachineInstr*, 16> CPEMIs;
if (!MCP.isEmpty())
DoInitialPlacement(Fn, CPEMIs);
@ -182,7 +199,9 @@ bool ARMConstantIslands::runOnMachineFunction(MachineFunction &Fn) {
BBSizes.clear();
WaterList.clear();
CPUsers.clear();
CPEntries.clear();
ImmBranches.clear();
PushPopMIs.clear();
return MadeChange;
}
@ -190,7 +209,7 @@ bool ARMConstantIslands::runOnMachineFunction(MachineFunction &Fn) {
/// DoInitialPlacement - Perform the initial placement of the constant pool
/// entries. To start with, we put them all at the end of the function.
void ARMConstantIslands::DoInitialPlacement(MachineFunction &Fn,
std::vector<MachineInstr*> &CPEMIs){
SmallVector<MachineInstr*, 16> &CPEMIs){
// Create the basic block to hold the CPE's.
MachineBasicBlock *BB = new MachineBasicBlock();
Fn.getBasicBlockList().push_back(BB);
@ -211,8 +230,13 @@ void ARMConstantIslands::DoInitialPlacement(MachineFunction &Fn,
BuildMI(BB, TII->get(ARM::CONSTPOOL_ENTRY))
.addImm(i).addConstantPoolIndex(i).addImm(Size);
CPEMIs.push_back(CPEMI);
DEBUG(std::cerr << "Moved CPI#" << i << " to end of function as #"
<< i << "\n");
// Add a new CPEntry, but no corresponding CPUser yet.
std::vector<CPEntry> CPEs;
CPEs.push_back(CPEntry(CPEMI, i));
CPEntries.push_back(CPEs);
NumCPEs++;
DOUT << "Moved CPI#" << i << " to end of function as #" << i << "\n";
}
}
@ -233,11 +257,26 @@ static bool BBHasFallthrough(MachineBasicBlock *MBB) {
return false;
}
/// findConstPoolEntry - Given the constpool index and CONSTPOOL_ENTRY MI,
/// look up the corresponding CPEntry.
ARMConstantIslands::CPEntry
*ARMConstantIslands::findConstPoolEntry(unsigned CPI,
const MachineInstr *CPEMI) {
std::vector<CPEntry> &CPEs = CPEntries[CPI];
// Number of entries per constpool index should be small, just do a
// linear search.
for (unsigned i = 0, e = CPEs.size(); i != e; ++i) {
if (CPEs[i].CPEMI == CPEMI)
return &CPEs[i];
}
return NULL;
}
/// InitialFunctionScan - Do the initial scan of the function, building up
/// information about the sizes of each block, the location of all the water,
/// and finding all of the constant pool users.
void ARMConstantIslands::InitialFunctionScan(MachineFunction &Fn,
const std::vector<MachineInstr*> &CPEMIs) {
const SmallVector<MachineInstr*, 16> &CPEMIs) {
for (MachineFunction::iterator MBBI = Fn.begin(), E = Fn.end();
MBBI != E; ++MBBI) {
MachineBasicBlock &MBB = *MBBI;
@ -339,9 +378,15 @@ void ARMConstantIslands::InitialFunctionScan(MachineFunction &Fn,
}
// Remember that this is a user of a CP entry.
MachineInstr *CPEMI =CPEMIs[I->getOperand(op).getConstantPoolIndex()];
unsigned CPI = I->getOperand(op).getConstantPoolIndex();
MachineInstr *CPEMI = CPEMIs[CPI];
unsigned MaxOffs = ((1 << Bits)-1) * Scale;
CPUsers.push_back(CPUser(I, CPEMI, MaxOffs));
// Increment corresponding CPEntry reference count.
CPEntry *CPE = findConstPoolEntry(CPI, CPEMI);
assert(CPE && "Cannot find a corresponding CPEntry!");
CPE->RefCount++;
// Instructions can only use one CP entry, don't bother scanning the
// rest of the operands.
@ -415,7 +460,7 @@ void ARMConstantIslands::UpdateForInsertedWaterBlock(MachineBasicBlock *NewBB) {
// Next, update WaterList. Specifically, we need to add NewMBB as having
// available water after it.
std::vector<MachineBasicBlock*>::iterator IP =
SmallVector<MachineBasicBlock*, 8>::iterator IP =
std::lower_bound(WaterList.begin(), WaterList.end(), NewBB,
CompareMBBNumbers);
WaterList.insert(IP, NewBB);
@ -487,10 +532,9 @@ bool ARMConstantIslands::CPEIsInRange(MachineInstr *MI, MachineInstr *CPEMI,
unsigned AlignAdj = AFI->isThumbFunction() ? 2 : 0;
unsigned CPEOffset = GetOffsetOf(CPEMI) + AlignAdj;
DEBUG(std::cerr << "User of CPE#" << CPEMI->getOperand(0).getImm()
<< " max delta=" << MaxDisp
<< " at offset " << int(CPEOffset-UserOffset) << "\t"
<< *MI);
DOUT << "User of CPE#" << CPEMI->getOperand(0).getImm()
<< " max delta=" << MaxDisp
<< " at offset " << int(CPEOffset-UserOffset) << "\t" << *MI;
if (UserOffset <= CPEOffset) {
// User before the CPE.
@ -504,6 +548,20 @@ bool ARMConstantIslands::CPEIsInRange(MachineInstr *MI, MachineInstr *CPEMI,
return false;
}
/// BBIsJumpedOver - Return true of the specified basic block's only predecessor
/// unconditionally branches to its only successor.
static bool BBIsJumpedOver(MachineBasicBlock *MBB) {
if (MBB->pred_size() != 1 || MBB->succ_size() != 1)
return false;
MachineBasicBlock *Succ = *MBB->succ_begin();
MachineBasicBlock *Pred = *MBB->pred_begin();
MachineInstr *PredMI = &Pred->back();
if (PredMI->getOpcode() == ARM::B || PredMI->getOpcode() == ARM::tB)
return PredMI->getOperand(0).getMBB() == Succ;
return false;
}
/// HandleConstantPoolUser - Analyze the specified user, checking to see if it
/// is out-of-range. If so, pick it up the constant pool value and move it some
/// place in-range.
@ -550,10 +608,33 @@ bool ARMConstantIslands::HandleConstantPoolUser(MachineFunction &Fn, CPUser &U){
unsigned CPI = CPEMI->getOperand(1).getConstantPoolIndex();
unsigned Size = CPEMI->getOperand(2).getImm();
// Find the old entry. Eliminate it if it is no longer used.
CPEntry *OldCPE = findConstPoolEntry(CPI, CPEMI);
assert(OldCPE && "Unexpected!");
if (--OldCPE->RefCount == 0) {
MachineBasicBlock *OldCPEBB = OldCPE->CPEMI->getParent();
if (OldCPEBB->empty()) {
// In thumb mode, the size of island is padded by two to compensate for
// the alignment requirement.
BBSizes[OldCPEBB->getNumber()] = 0;
// An island has only one predecessor BB and one successor BB. Check if
// this BB's predecessor jumps directly to this BB's successor. This
// shouldn't happen currently.
assert(!BBIsJumpedOver(OldCPEBB) && "How did this happen?");
// FIXME: remove the empty blocks after all the work is done?
} else
BBSizes[OldCPEBB->getNumber()] -= Size;
OldCPE->CPEMI->eraseFromParent();
OldCPE->CPEMI = NULL;
NumCPEs--;
}
// Build a new CPE for this user.
U.CPEMI = BuildMI(NewIsland, TII->get(ARM::CONSTPOOL_ENTRY))
.addImm(ID).addConstantPoolIndex(CPI).addImm(Size);
CPEntries[CPI].push_back(CPEntry(U.CPEMI, CPI, 1));
NumCPEs++;
// Compensate for .align 2 in thumb mode.
if (isThumb) Size += 2;
// Increase the size of the island block to account for the new entry.
@ -566,8 +647,7 @@ bool ARMConstantIslands::HandleConstantPoolUser(MachineFunction &Fn, CPUser &U){
break;
}
DEBUG(std::cerr << " Moved CPE to #" << ID << " CPI=" << CPI << "\t"
<< *UserMI);
DOUT << " Moved CPE to #" << ID << " CPI=" << CPI << "\t" << *UserMI;
return true;
}
@ -580,11 +660,10 @@ bool ARMConstantIslands::BBIsInRange(MachineInstr *MI,MachineBasicBlock *DestBB,
unsigned BrOffset = GetOffsetOf(MI) + PCAdj;
unsigned DestOffset = GetOffsetOf(DestBB);
DEBUG(std::cerr << "Branch of destination BB#" << DestBB->getNumber()
<< " from BB#" << MI->getParent()->getNumber()
<< " max delta=" << MaxDisp
<< " at offset " << int(DestOffset-BrOffset) << "\t"
<< *MI);
DOUT << "Branch of destination BB#" << DestBB->getNumber()
<< " from BB#" << MI->getParent()->getNumber()
<< " max delta=" << MaxDisp
<< " at offset " << int(DestOffset-BrOffset) << "\t" << *MI;
if (BrOffset <= DestOffset) {
if (DestOffset - BrOffset <= MaxDisp)
@ -612,7 +691,7 @@ bool ARMConstantIslands::FixUpImmediateBr(MachineFunction &Fn, ImmBranch &Br) {
}
/// FixUpUnconditionalBr - Fix up an unconditional branches whose destination is
/// too far away to fit in its displacement field. If LR register has been
/// too far away to fit in its displacement field. If LR register ha been
/// spilled in the epilogue, then we can use BL to implement a far jump.
/// Otherwise, add a intermediate branch instruction to to a branch.
bool
@ -628,7 +707,7 @@ ARMConstantIslands::FixUpUnconditionalBr(MachineFunction &Fn, ImmBranch &Br) {
HasFarJump = true;
NumUBrFixed++;
DEBUG(std::cerr << " Changed B to long jump " << *MI);
DOUT << " Changed B to long jump " << *MI;
return true;
}
@ -677,9 +756,7 @@ ARMConstantIslands::FixUpConditionalBr(MachineFunction &Fn, ImmBranch &Br) {
// b L1
MachineBasicBlock *NewDest = BMI->getOperand(0).getMachineBasicBlock();
if (BBIsInRange(MI, NewDest, Br.MaxDisp)) {
DEBUG(std::cerr << " Invert Bcc condition and swap its destination"
<< " with " << *BMI);
DOUT << " Invert Bcc condition and swap its destination with " << *BMI;
BMI->getOperand(0).setMachineBasicBlock(DestBB);
MI->getOperand(0).setMachineBasicBlock(NewDest);
MI->getOperand(1).setImm(CC);
@ -696,9 +773,9 @@ ARMConstantIslands::FixUpConditionalBr(MachineFunction &Fn, ImmBranch &Br) {
}
MachineBasicBlock *NextBB = next(MachineFunction::iterator(MBB));
DEBUG(std::cerr << " Insert B to BB#" << DestBB->getNumber()
<< " also invert condition and change dest. to BB#"
<< NextBB->getNumber() << "\n");
DOUT << " Insert B to BB#" << DestBB->getNumber()
<< " also invert condition and change dest. to BB#"
<< NextBB->getNumber() << "\n";
// Insert a unconditional branch and replace the conditional branch.
// Also update the ImmBranch as well as adding a new entry for the new branch.