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It is safe to speculate load from GOT. This fixes performance regression caused by r141689. 

Radar 10281206.

llvm-svn: 142202
This commit is contained in:
Devang Patel 2011-10-17 17:35:01 +00:00
parent d4bde54da5
commit 69a4565e65
1 changed files with 17 additions and 1 deletions
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18
llvm/lib/CodeGen/MachineLICM.cpp
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@ -762,6 +762,21 @@ void MachineLICM::UpdateRegPressure(const MachineInstr *MI) {
}
}
/// isLoadFromGOT - Return true if this machine instruction loads from
/// global offset table.
static bool isLoadFromGOT(MachineInstr &MI) {
assert (MI.getDesc().mayLoad() && "Expected MI that loads!");
for (MachineInstr::mmo_iterator I = MI.memoperands_begin(),
E = MI.memoperands_end(); I != E; ++I) {
if (const Value *V = (*I)->getValue()) {
if (const PseudoSourceValue *PSV = dyn_cast<PseudoSourceValue>(V))
if (PSV == PSV->getGOT())
return true;
}
}
return false;
}
/// IsLICMCandidate - Returns true if the instruction may be a suitable
/// candidate for LICM. e.g. If the instruction is a call, then it's obviously
/// not safe to hoist it.
@ -775,7 +790,8 @@ bool MachineLICM::IsLICMCandidate(MachineInstr &I) {
// it dominates all exiting blocks. If it doesn't, then there is a path out of
// the loop which does not execute this load, so we can't hoist it.
// Stores and side effects are already checked by isSafeToMove.
if (I.getDesc().mayLoad() && !IsGuaranteedToExecute(I.getParent()))
if (I.getDesc().mayLoad() && !isLoadFromGOT(I) &&
!IsGuaranteedToExecute(I.getParent()))
return false;
return true;