mirror of
https://github.com/c64scene-ar/llvm-6502.git
synced 2024-08-30 21:29:28 +00:00
VISIBILITY_HIDDEN removal. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@85043 91177308-0d34-0410-b5e6-96231b3b80d8
281 lines
10 KiB
C++
281 lines
10 KiB
C++
//===-- MachineSink.cpp - Sinking for machine instructions ----------------===//
|
|
//
|
|
// The LLVM Compiler Infrastructure
|
|
//
|
|
// This file is distributed under the University of Illinois Open Source
|
|
// License. See LICENSE.TXT for details.
|
|
//
|
|
//===----------------------------------------------------------------------===//
|
|
//
|
|
// This pass moves instructions into successor blocks, when possible, so that
|
|
// they aren't executed on paths where their results aren't needed.
|
|
//
|
|
// This pass is not intended to be a replacement or a complete alternative
|
|
// for an LLVM-IR-level sinking pass. It is only designed to sink simple
|
|
// constructs that are not exposed before lowering and instruction selection.
|
|
//
|
|
//===----------------------------------------------------------------------===//
|
|
|
|
#define DEBUG_TYPE "machine-sink"
|
|
#include "llvm/CodeGen/Passes.h"
|
|
#include "llvm/CodeGen/MachineRegisterInfo.h"
|
|
#include "llvm/CodeGen/MachineDominators.h"
|
|
#include "llvm/Analysis/AliasAnalysis.h"
|
|
#include "llvm/Target/TargetRegisterInfo.h"
|
|
#include "llvm/Target/TargetInstrInfo.h"
|
|
#include "llvm/Target/TargetMachine.h"
|
|
#include "llvm/ADT/Statistic.h"
|
|
#include "llvm/Support/Debug.h"
|
|
#include "llvm/Support/raw_ostream.h"
|
|
using namespace llvm;
|
|
|
|
STATISTIC(NumSunk, "Number of machine instructions sunk");
|
|
|
|
namespace {
|
|
class MachineSinking : public MachineFunctionPass {
|
|
const TargetInstrInfo *TII;
|
|
const TargetRegisterInfo *TRI;
|
|
MachineRegisterInfo *RegInfo; // Machine register information
|
|
MachineDominatorTree *DT; // Machine dominator tree
|
|
AliasAnalysis *AA;
|
|
BitVector AllocatableSet; // Which physregs are allocatable?
|
|
|
|
public:
|
|
static char ID; // Pass identification
|
|
MachineSinking() : MachineFunctionPass(&ID) {}
|
|
|
|
virtual bool runOnMachineFunction(MachineFunction &MF);
|
|
|
|
virtual void getAnalysisUsage(AnalysisUsage &AU) const {
|
|
AU.setPreservesCFG();
|
|
MachineFunctionPass::getAnalysisUsage(AU);
|
|
AU.addRequired<AliasAnalysis>();
|
|
AU.addRequired<MachineDominatorTree>();
|
|
AU.addPreserved<MachineDominatorTree>();
|
|
}
|
|
private:
|
|
bool ProcessBlock(MachineBasicBlock &MBB);
|
|
bool SinkInstruction(MachineInstr *MI, bool &SawStore);
|
|
bool AllUsesDominatedByBlock(unsigned Reg, MachineBasicBlock *MBB) const;
|
|
};
|
|
} // end anonymous namespace
|
|
|
|
char MachineSinking::ID = 0;
|
|
static RegisterPass<MachineSinking>
|
|
X("machine-sink", "Machine code sinking");
|
|
|
|
FunctionPass *llvm::createMachineSinkingPass() { return new MachineSinking(); }
|
|
|
|
/// AllUsesDominatedByBlock - Return true if all uses of the specified register
|
|
/// occur in blocks dominated by the specified block.
|
|
bool MachineSinking::AllUsesDominatedByBlock(unsigned Reg,
|
|
MachineBasicBlock *MBB) const {
|
|
assert(TargetRegisterInfo::isVirtualRegister(Reg) &&
|
|
"Only makes sense for vregs");
|
|
for (MachineRegisterInfo::use_iterator I = RegInfo->use_begin(Reg),
|
|
E = RegInfo->use_end(); I != E; ++I) {
|
|
// Determine the block of the use.
|
|
MachineInstr *UseInst = &*I;
|
|
MachineBasicBlock *UseBlock = UseInst->getParent();
|
|
if (UseInst->getOpcode() == TargetInstrInfo::PHI) {
|
|
// PHI nodes use the operand in the predecessor block, not the block with
|
|
// the PHI.
|
|
UseBlock = UseInst->getOperand(I.getOperandNo()+1).getMBB();
|
|
}
|
|
// Check that it dominates.
|
|
if (!DT->dominates(MBB, UseBlock))
|
|
return false;
|
|
}
|
|
return true;
|
|
}
|
|
|
|
bool MachineSinking::runOnMachineFunction(MachineFunction &MF) {
|
|
DEBUG(errs() << "******** Machine Sinking ********\n");
|
|
|
|
const TargetMachine &TM = MF.getTarget();
|
|
TII = TM.getInstrInfo();
|
|
TRI = TM.getRegisterInfo();
|
|
RegInfo = &MF.getRegInfo();
|
|
DT = &getAnalysis<MachineDominatorTree>();
|
|
AA = &getAnalysis<AliasAnalysis>();
|
|
AllocatableSet = TRI->getAllocatableSet(MF);
|
|
|
|
bool EverMadeChange = false;
|
|
|
|
while (1) {
|
|
bool MadeChange = false;
|
|
|
|
// Process all basic blocks.
|
|
for (MachineFunction::iterator I = MF.begin(), E = MF.end();
|
|
I != E; ++I)
|
|
MadeChange |= ProcessBlock(*I);
|
|
|
|
// If this iteration over the code changed anything, keep iterating.
|
|
if (!MadeChange) break;
|
|
EverMadeChange = true;
|
|
}
|
|
return EverMadeChange;
|
|
}
|
|
|
|
bool MachineSinking::ProcessBlock(MachineBasicBlock &MBB) {
|
|
// Can't sink anything out of a block that has less than two successors.
|
|
if (MBB.succ_size() <= 1 || MBB.empty()) return false;
|
|
|
|
bool MadeChange = false;
|
|
|
|
// Walk the basic block bottom-up. Remember if we saw a store.
|
|
MachineBasicBlock::iterator I = MBB.end();
|
|
--I;
|
|
bool ProcessedBegin, SawStore = false;
|
|
do {
|
|
MachineInstr *MI = I; // The instruction to sink.
|
|
|
|
// Predecrement I (if it's not begin) so that it isn't invalidated by
|
|
// sinking.
|
|
ProcessedBegin = I == MBB.begin();
|
|
if (!ProcessedBegin)
|
|
--I;
|
|
|
|
if (SinkInstruction(MI, SawStore))
|
|
++NumSunk, MadeChange = true;
|
|
|
|
// If we just processed the first instruction in the block, we're done.
|
|
} while (!ProcessedBegin);
|
|
|
|
return MadeChange;
|
|
}
|
|
|
|
/// SinkInstruction - Determine whether it is safe to sink the specified machine
|
|
/// instruction out of its current block into a successor.
|
|
bool MachineSinking::SinkInstruction(MachineInstr *MI, bool &SawStore) {
|
|
// Check if it's safe to move the instruction.
|
|
if (!MI->isSafeToMove(TII, SawStore, AA))
|
|
return false;
|
|
|
|
// FIXME: This should include support for sinking instructions within the
|
|
// block they are currently in to shorten the live ranges. We often get
|
|
// instructions sunk into the top of a large block, but it would be better to
|
|
// also sink them down before their first use in the block. This xform has to
|
|
// be careful not to *increase* register pressure though, e.g. sinking
|
|
// "x = y + z" down if it kills y and z would increase the live ranges of y
|
|
// and z and only shrink the live range of x.
|
|
|
|
// Loop over all the operands of the specified instruction. If there is
|
|
// anything we can't handle, bail out.
|
|
MachineBasicBlock *ParentBlock = MI->getParent();
|
|
|
|
// SuccToSinkTo - This is the successor to sink this instruction to, once we
|
|
// decide.
|
|
MachineBasicBlock *SuccToSinkTo = 0;
|
|
|
|
for (unsigned i = 0, e = MI->getNumOperands(); i != e; ++i) {
|
|
const MachineOperand &MO = MI->getOperand(i);
|
|
if (!MO.isReg()) continue; // Ignore non-register operands.
|
|
|
|
unsigned Reg = MO.getReg();
|
|
if (Reg == 0) continue;
|
|
|
|
if (TargetRegisterInfo::isPhysicalRegister(Reg)) {
|
|
if (MO.isUse()) {
|
|
// If the physreg has no defs anywhere, it's just an ambient register
|
|
// and we can freely move its uses. Alternatively, if it's allocatable,
|
|
// it could get allocated to something with a def during allocation.
|
|
if (!RegInfo->def_empty(Reg))
|
|
return false;
|
|
if (AllocatableSet.test(Reg))
|
|
return false;
|
|
// Check for a def among the register's aliases too.
|
|
for (const unsigned *Alias = TRI->getAliasSet(Reg); *Alias; ++Alias) {
|
|
unsigned AliasReg = *Alias;
|
|
if (!RegInfo->def_empty(AliasReg))
|
|
return false;
|
|
if (AllocatableSet.test(AliasReg))
|
|
return false;
|
|
}
|
|
} else if (!MO.isDead()) {
|
|
// A def that isn't dead. We can't move it.
|
|
return false;
|
|
}
|
|
} else {
|
|
// Virtual register uses are always safe to sink.
|
|
if (MO.isUse()) continue;
|
|
|
|
// If it's not safe to move defs of the register class, then abort.
|
|
if (!TII->isSafeToMoveRegClassDefs(RegInfo->getRegClass(Reg)))
|
|
return false;
|
|
|
|
// FIXME: This picks a successor to sink into based on having one
|
|
// successor that dominates all the uses. However, there are cases where
|
|
// sinking can happen but where the sink point isn't a successor. For
|
|
// example:
|
|
// x = computation
|
|
// if () {} else {}
|
|
// use x
|
|
// the instruction could be sunk over the whole diamond for the
|
|
// if/then/else (or loop, etc), allowing it to be sunk into other blocks
|
|
// after that.
|
|
|
|
// Virtual register defs can only be sunk if all their uses are in blocks
|
|
// dominated by one of the successors.
|
|
if (SuccToSinkTo) {
|
|
// If a previous operand picked a block to sink to, then this operand
|
|
// must be sinkable to the same block.
|
|
if (!AllUsesDominatedByBlock(Reg, SuccToSinkTo))
|
|
return false;
|
|
continue;
|
|
}
|
|
|
|
// Otherwise, we should look at all the successors and decide which one
|
|
// we should sink to.
|
|
for (MachineBasicBlock::succ_iterator SI = ParentBlock->succ_begin(),
|
|
E = ParentBlock->succ_end(); SI != E; ++SI) {
|
|
if (AllUsesDominatedByBlock(Reg, *SI)) {
|
|
SuccToSinkTo = *SI;
|
|
break;
|
|
}
|
|
}
|
|
|
|
// If we couldn't find a block to sink to, ignore this instruction.
|
|
if (SuccToSinkTo == 0)
|
|
return false;
|
|
}
|
|
}
|
|
|
|
// If there are no outputs, it must have side-effects.
|
|
if (SuccToSinkTo == 0)
|
|
return false;
|
|
|
|
// It's not safe to sink instructions to EH landing pad. Control flow into
|
|
// landing pad is implicitly defined.
|
|
if (SuccToSinkTo->isLandingPad())
|
|
return false;
|
|
|
|
// It is not possible to sink an instruction into its own block. This can
|
|
// happen with loops.
|
|
if (MI->getParent() == SuccToSinkTo)
|
|
return false;
|
|
|
|
DEBUG(errs() << "Sink instr " << *MI);
|
|
DEBUG(errs() << "to block " << *SuccToSinkTo);
|
|
|
|
// If the block has multiple predecessors, this would introduce computation on
|
|
// a path that it doesn't already exist. We could split the critical edge,
|
|
// but for now we just punt.
|
|
// FIXME: Split critical edges if not backedges.
|
|
if (SuccToSinkTo->pred_size() > 1) {
|
|
DEBUG(errs() << " *** PUNTING: Critical edge found\n");
|
|
return false;
|
|
}
|
|
|
|
// Determine where to insert into. Skip phi nodes.
|
|
MachineBasicBlock::iterator InsertPos = SuccToSinkTo->begin();
|
|
while (InsertPos != SuccToSinkTo->end() &&
|
|
InsertPos->getOpcode() == TargetInstrInfo::PHI)
|
|
++InsertPos;
|
|
|
|
// Move the instruction.
|
|
SuccToSinkTo->splice(InsertPos, ParentBlock, MI,
|
|
++MachineBasicBlock::iterator(MI));
|
|
return true;
|
|
}
|