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Factor out LiveIntervalAnalysis' code to determine whether an instruction

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is trivially rematerializable and integrate it into
TargetInstrInfo::isTriviallyReMaterializable. This way, all places that
need to know whether an instruction is rematerializable will get the
same answer.

This enables the useful parts of the aggressive-remat option by
default -- using AliasAnalysis to determine whether a memory location
is invariant, and removes the questionable parts -- rematting operations
with virtual register inputs that may not be live everywhere.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@83687 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Dan Gohman
2009-10-09 23:27:56 +00:00
parent ac1ceb3dd3
commit a70dca156f
14 changed files with 161 additions and 130 deletions
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12
lib/CodeGen/MachineInstr.cpp
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@ -933,7 +933,8 @@ void MachineInstr::copyPredicates(const MachineInstr *MI) {
/// SawStore is set to true, it means that there is a store (or call) between
/// the instruction's location and its intended destination.
bool MachineInstr::isSafeToMove(const TargetInstrInfo *TII,
bool &SawStore) const {
bool &SawStore,
AliasAnalysis *AA) const {
// Ignore stuff that we obviously can't move.
if (TID->mayStore() || TID->isCall()) {
SawStore = true;
@ -947,7 +948,7 @@ bool MachineInstr::isSafeToMove(const TargetInstrInfo *TII,
// destination. The check for isInvariantLoad gives the targe the chance to
// classify the load as always returning a constant, e.g. a constant pool
// load.
if (TID->mayLoad() && !isInvariantLoad())
if (TID->mayLoad() && !isInvariantLoad(AA))
// Otherwise, this is a real load. If there is a store between the load and
// end of block, or if the load is volatile, we can't move it.
return !SawStore && !hasVolatileMemoryRef();
@ -958,10 +959,11 @@ bool MachineInstr::isSafeToMove(const TargetInstrInfo *TII,
/// isSafeToReMat - Return true if it's safe to rematerialize the specified
/// instruction which defined the specified register instead of copying it.
bool MachineInstr::isSafeToReMat(const TargetInstrInfo *TII,
unsigned DstReg) const {
unsigned DstReg,
AliasAnalysis *AA) const {
bool SawStore = false;
if (!TII->isTriviallyReMaterializable(this) ||
!isSafeToMove(TII, SawStore))
if (!TII->isTriviallyReMaterializable(this, AA) ||
!isSafeToMove(TII, SawStore, AA))
return false;
for (unsigned i = 0, e = getNumOperands(); i != e; ++i) {
const MachineOperand &MO = getOperand(i);