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Add reference counting to constantpool entries. Delete the unused ones.
llvm-svn: 34105
This commit is contained in:
Evan Cheng
parent
b1e839a4d3
commit
5e8eb0c198
@ -24,11 +24,12 @@
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#include "llvm/Target/TargetMachine.h"
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#include "llvm/Support/Compiler.h"
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#include "llvm/Support/Debug.h"
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#include "llvm/ADT/SmallVector.h"
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#include "llvm/ADT/STLExtras.h"
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#include "llvm/ADT/Statistic.h"
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#include <iostream>
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using namespace llvm;
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STATISTIC(NumCPEs, "Number of constpool entries");
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STATISTIC(NumSplit, "Number of uncond branches inserted");
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STATISTIC(NumCBrFixed, "Number of cond branches fixed");
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STATISTIC(NumUBrFixed, "Number of uncond branches fixed");
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@ -51,13 +52,13 @@ namespace {
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/// BBSizes - The size of each MachineBasicBlock in bytes of code, indexed
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/// by MBB Number.
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std::vector<unsigned> BBSizes;
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SmallVector<unsigned, 8> BBSizes;
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/// WaterList - A sorted list of basic blocks where islands could be placed
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/// (i.e. blocks that don't fall through to the following block, due
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/// to a return, unreachable, or unconditional branch).
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std::vector<MachineBasicBlock*> WaterList;
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SmallVector<MachineBasicBlock*, 8> WaterList;
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/// CPUser - One user of a constant pool, keeping the machine instruction
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/// pointer, the constant pool being referenced, and the max displacement
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/// allowed from the instruction to the CP.
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@ -71,7 +72,22 @@ namespace {
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/// CPUsers - Keep track of all of the machine instructions that use various
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/// constant pools and their max displacement.
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std::vector<CPUser> CPUsers;
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SmallVector<CPUser, 16> CPUsers;
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/// CPEntry - One per constant pool entry, keeping the machine instruction
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/// pointer, the constpool index, and the number of CPUser's which
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/// reference this entry.
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struct CPEntry {
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MachineInstr *CPEMI;
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unsigned CPI;
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unsigned RefCount;
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CPEntry(MachineInstr *cpemi, unsigned cpi, unsigned rc = 0)
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: CPEMI(cpemi), CPI(cpi), RefCount(rc) {}
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};
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/// CPEntries - Keep track of all of the constant pool entry machine
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/// instructions. For each constpool index, it keeps a vector of entries.
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std::vector<std::vector<CPEntry> > CPEntries;
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/// ImmBranch - One per immediate branch, keeping the machine instruction
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/// pointer, conditional or unconditional, the max displacement,
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@ -88,11 +104,11 @@ namespace {
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/// Branches - Keep track of all the immediate branch instructions.
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///
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std::vector<ImmBranch> ImmBranches;
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SmallVector<ImmBranch, 32> ImmBranches;
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/// PushPopMIs - Keep track of all the Thumb push / pop instructions.
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///
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std::vector<MachineInstr*> PushPopMIs;
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SmallVector<MachineInstr*, 4> PushPopMIs;
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/// HasFarJump - True if any far jump instruction has been emitted during
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/// the branch fix up pass.
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@ -109,9 +125,10 @@ namespace {
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private:
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void DoInitialPlacement(MachineFunction &Fn,
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std::vector<MachineInstr*> &CPEMIs);
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SmallVector<MachineInstr*, 16> &CPEMIs);
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CPEntry *findConstPoolEntry(unsigned CPI, const MachineInstr *CPEMI);
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void InitialFunctionScan(MachineFunction &Fn,
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const std::vector<MachineInstr*> &CPEMIs);
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const SmallVector<MachineInstr*, 16> &CPEMIs);
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MachineBasicBlock *SplitBlockBeforeInstr(MachineInstr *MI);
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void UpdateForInsertedWaterBlock(MachineBasicBlock *NewBB);
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bool HandleConstantPoolUser(MachineFunction &Fn, CPUser &U);
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@ -147,7 +164,7 @@ bool ARMConstantIslands::runOnMachineFunction(MachineFunction &Fn) {
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// Perform the initial placement of the constant pool entries. To start with,
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// we put them all at the end of the function.
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std::vector<MachineInstr*> CPEMIs;
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SmallVector<MachineInstr*, 16> CPEMIs;
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if (!MCP.isEmpty())
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DoInitialPlacement(Fn, CPEMIs);
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@ -182,7 +199,9 @@ bool ARMConstantIslands::runOnMachineFunction(MachineFunction &Fn) {
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BBSizes.clear();
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WaterList.clear();
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CPUsers.clear();
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CPEntries.clear();
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ImmBranches.clear();
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PushPopMIs.clear();
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return MadeChange;
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}
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@ -190,7 +209,7 @@ bool ARMConstantIslands::runOnMachineFunction(MachineFunction &Fn) {
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/// DoInitialPlacement - Perform the initial placement of the constant pool
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/// entries. To start with, we put them all at the end of the function.
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void ARMConstantIslands::DoInitialPlacement(MachineFunction &Fn,
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std::vector<MachineInstr*> &CPEMIs){
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SmallVector<MachineInstr*, 16> &CPEMIs){
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// Create the basic block to hold the CPE's.
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MachineBasicBlock *BB = new MachineBasicBlock();
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Fn.getBasicBlockList().push_back(BB);
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@ -211,8 +230,13 @@ void ARMConstantIslands::DoInitialPlacement(MachineFunction &Fn,
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BuildMI(BB, TII->get(ARM::CONSTPOOL_ENTRY))
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.addImm(i).addConstantPoolIndex(i).addImm(Size);
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CPEMIs.push_back(CPEMI);
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DEBUG(std::cerr << "Moved CPI#" << i << " to end of function as #"
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<< i << "\n");
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// Add a new CPEntry, but no corresponding CPUser yet.
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std::vector<CPEntry> CPEs;
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CPEs.push_back(CPEntry(CPEMI, i));
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CPEntries.push_back(CPEs);
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NumCPEs++;
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DOUT << "Moved CPI#" << i << " to end of function as #" << i << "\n";
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}
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}
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@ -233,11 +257,26 @@ static bool BBHasFallthrough(MachineBasicBlock *MBB) {
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return false;
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}
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/// findConstPoolEntry - Given the constpool index and CONSTPOOL_ENTRY MI,
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/// look up the corresponding CPEntry.
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ARMConstantIslands::CPEntry
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*ARMConstantIslands::findConstPoolEntry(unsigned CPI,
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const MachineInstr *CPEMI) {
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std::vector<CPEntry> &CPEs = CPEntries[CPI];
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// Number of entries per constpool index should be small, just do a
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// linear search.
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for (unsigned i = 0, e = CPEs.size(); i != e; ++i) {
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if (CPEs[i].CPEMI == CPEMI)
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return &CPEs[i];
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}
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return NULL;
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}
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/// InitialFunctionScan - Do the initial scan of the function, building up
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/// information about the sizes of each block, the location of all the water,
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/// and finding all of the constant pool users.
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void ARMConstantIslands::InitialFunctionScan(MachineFunction &Fn,
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const std::vector<MachineInstr*> &CPEMIs) {
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const SmallVector<MachineInstr*, 16> &CPEMIs) {
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for (MachineFunction::iterator MBBI = Fn.begin(), E = Fn.end();
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MBBI != E; ++MBBI) {
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MachineBasicBlock &MBB = *MBBI;
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@ -339,9 +378,15 @@ void ARMConstantIslands::InitialFunctionScan(MachineFunction &Fn,
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}
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// Remember that this is a user of a CP entry.
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MachineInstr *CPEMI =CPEMIs[I->getOperand(op).getConstantPoolIndex()];
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unsigned CPI = I->getOperand(op).getConstantPoolIndex();
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MachineInstr *CPEMI = CPEMIs[CPI];
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unsigned MaxOffs = ((1 << Bits)-1) * Scale;
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CPUsers.push_back(CPUser(I, CPEMI, MaxOffs));
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// Increment corresponding CPEntry reference count.
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CPEntry *CPE = findConstPoolEntry(CPI, CPEMI);
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assert(CPE && "Cannot find a corresponding CPEntry!");
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CPE->RefCount++;
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// Instructions can only use one CP entry, don't bother scanning the
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// rest of the operands.
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@ -415,7 +460,7 @@ void ARMConstantIslands::UpdateForInsertedWaterBlock(MachineBasicBlock *NewBB) {
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// Next, update WaterList. Specifically, we need to add NewMBB as having
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// available water after it.
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std::vector<MachineBasicBlock*>::iterator IP =
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SmallVector<MachineBasicBlock*, 8>::iterator IP =
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std::lower_bound(WaterList.begin(), WaterList.end(), NewBB,
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CompareMBBNumbers);
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WaterList.insert(IP, NewBB);
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@ -487,10 +532,9 @@ bool ARMConstantIslands::CPEIsInRange(MachineInstr *MI, MachineInstr *CPEMI,
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unsigned AlignAdj = AFI->isThumbFunction() ? 2 : 0;
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unsigned CPEOffset = GetOffsetOf(CPEMI) + AlignAdj;
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DEBUG(std::cerr << "User of CPE#" << CPEMI->getOperand(0).getImm()
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<< " max delta=" << MaxDisp
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<< " at offset " << int(CPEOffset-UserOffset) << "\t"
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<< *MI);
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DOUT << "User of CPE#" << CPEMI->getOperand(0).getImm()
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<< " max delta=" << MaxDisp
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<< " at offset " << int(CPEOffset-UserOffset) << "\t" << *MI;
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if (UserOffset <= CPEOffset) {
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// User before the CPE.
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@ -504,6 +548,20 @@ bool ARMConstantIslands::CPEIsInRange(MachineInstr *MI, MachineInstr *CPEMI,
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return false;
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}
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/// BBIsJumpedOver - Return true of the specified basic block's only predecessor
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/// unconditionally branches to its only successor.
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static bool BBIsJumpedOver(MachineBasicBlock *MBB) {
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if (MBB->pred_size() != 1 || MBB->succ_size() != 1)
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return false;
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MachineBasicBlock *Succ = *MBB->succ_begin();
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MachineBasicBlock *Pred = *MBB->pred_begin();
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MachineInstr *PredMI = &Pred->back();
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if (PredMI->getOpcode() == ARM::B || PredMI->getOpcode() == ARM::tB)
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return PredMI->getOperand(0).getMBB() == Succ;
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return false;
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}
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/// HandleConstantPoolUser - Analyze the specified user, checking to see if it
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/// is out-of-range. If so, pick it up the constant pool value and move it some
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/// place in-range.
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@ -550,10 +608,33 @@ bool ARMConstantIslands::HandleConstantPoolUser(MachineFunction &Fn, CPUser &U){
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unsigned CPI = CPEMI->getOperand(1).getConstantPoolIndex();
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unsigned Size = CPEMI->getOperand(2).getImm();
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// Find the old entry. Eliminate it if it is no longer used.
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CPEntry *OldCPE = findConstPoolEntry(CPI, CPEMI);
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assert(OldCPE && "Unexpected!");
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if (--OldCPE->RefCount == 0) {
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MachineBasicBlock *OldCPEBB = OldCPE->CPEMI->getParent();
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if (OldCPEBB->empty()) {
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// In thumb mode, the size of island is padded by two to compensate for
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// the alignment requirement.
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BBSizes[OldCPEBB->getNumber()] = 0;
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// An island has only one predecessor BB and one successor BB. Check if
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// this BB's predecessor jumps directly to this BB's successor. This
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// shouldn't happen currently.
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assert(!BBIsJumpedOver(OldCPEBB) && "How did this happen?");
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// FIXME: remove the empty blocks after all the work is done?
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} else
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BBSizes[OldCPEBB->getNumber()] -= Size;
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OldCPE->CPEMI->eraseFromParent();
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OldCPE->CPEMI = NULL;
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NumCPEs--;
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}
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// Build a new CPE for this user.
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U.CPEMI = BuildMI(NewIsland, TII->get(ARM::CONSTPOOL_ENTRY))
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.addImm(ID).addConstantPoolIndex(CPI).addImm(Size);
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CPEntries[CPI].push_back(CPEntry(U.CPEMI, CPI, 1));
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NumCPEs++;
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// Compensate for .align 2 in thumb mode.
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if (isThumb) Size += 2;
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// Increase the size of the island block to account for the new entry.
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@ -566,8 +647,7 @@ bool ARMConstantIslands::HandleConstantPoolUser(MachineFunction &Fn, CPUser &U){
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break;
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}
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DEBUG(std::cerr << " Moved CPE to #" << ID << " CPI=" << CPI << "\t"
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<< *UserMI);
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DOUT << " Moved CPE to #" << ID << " CPI=" << CPI << "\t" << *UserMI;
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return true;
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}
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@ -580,11 +660,10 @@ bool ARMConstantIslands::BBIsInRange(MachineInstr *MI,MachineBasicBlock *DestBB,
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unsigned BrOffset = GetOffsetOf(MI) + PCAdj;
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unsigned DestOffset = GetOffsetOf(DestBB);
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DEBUG(std::cerr << "Branch of destination BB#" << DestBB->getNumber()
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<< " from BB#" << MI->getParent()->getNumber()
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<< " max delta=" << MaxDisp
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<< " at offset " << int(DestOffset-BrOffset) << "\t"
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<< *MI);
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DOUT << "Branch of destination BB#" << DestBB->getNumber()
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<< " from BB#" << MI->getParent()->getNumber()
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<< " max delta=" << MaxDisp
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<< " at offset " << int(DestOffset-BrOffset) << "\t" << *MI;
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if (BrOffset <= DestOffset) {
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if (DestOffset - BrOffset <= MaxDisp)
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@ -612,7 +691,7 @@ bool ARMConstantIslands::FixUpImmediateBr(MachineFunction &Fn, ImmBranch &Br) {
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}
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/// FixUpUnconditionalBr - Fix up an unconditional branches whose destination is
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/// too far away to fit in its displacement field. If LR register has been
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/// too far away to fit in its displacement field. If LR register ha been
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/// spilled in the epilogue, then we can use BL to implement a far jump.
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/// Otherwise, add a intermediate branch instruction to to a branch.
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bool
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@ -628,7 +707,7 @@ ARMConstantIslands::FixUpUnconditionalBr(MachineFunction &Fn, ImmBranch &Br) {
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HasFarJump = true;
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NumUBrFixed++;
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DEBUG(std::cerr << " Changed B to long jump " << *MI);
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DOUT << " Changed B to long jump " << *MI;
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return true;
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}
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@ -677,9 +756,7 @@ ARMConstantIslands::FixUpConditionalBr(MachineFunction &Fn, ImmBranch &Br) {
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// b L1
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MachineBasicBlock *NewDest = BMI->getOperand(0).getMachineBasicBlock();
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if (BBIsInRange(MI, NewDest, Br.MaxDisp)) {
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DEBUG(std::cerr << " Invert Bcc condition and swap its destination"
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<< " with " << *BMI);
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DOUT << " Invert Bcc condition and swap its destination with " << *BMI;
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BMI->getOperand(0).setMachineBasicBlock(DestBB);
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MI->getOperand(0).setMachineBasicBlock(NewDest);
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MI->getOperand(1).setImm(CC);
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@ -696,9 +773,9 @@ ARMConstantIslands::FixUpConditionalBr(MachineFunction &Fn, ImmBranch &Br) {
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}
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MachineBasicBlock *NextBB = next(MachineFunction::iterator(MBB));
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DEBUG(std::cerr << " Insert B to BB#" << DestBB->getNumber()
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<< " also invert condition and change dest. to BB#"
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<< NextBB->getNumber() << "\n");
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DOUT << " Insert B to BB#" << DestBB->getNumber()
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<< " also invert condition and change dest. to BB#"
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<< NextBB->getNumber() << "\n";
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// Insert a unconditional branch and replace the conditional branch.
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// Also update the ImmBranch as well as adding a new entry for the new branch.
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