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Fix r141744. 

1. The speculation check may not have been performed if the BB hasn't had a load
   LICM candidate.
2. If the candidate would be CSE'ed, then go ahead and speculatively LICM the
   instruction even if it's in high register pressure situation.

llvm-svn: 141747
This commit is contained in:
Evan Cheng 2011-10-12 00:09:14 +00:00
parent 39c31a77b8
commit af1389546e
1 changed files with 19 additions and 1 deletions
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20
llvm/lib/CodeGen/MachineLICM.cpp
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@ -251,6 +251,10 @@ namespace {
bool EliminateCSE(MachineInstr *MI,
DenseMap<unsigned, std::vector<const MachineInstr*> >::iterator &CI);
/// MayCSE - Return true if the given instruction will be CSE'd if it's
/// hoisted out of the loop.
bool MayCSE(MachineInstr *MI);
/// Hoist - When an instruction is found to only use loop invariant operands
/// that is safe to hoist, this instruction is called to do the dirty work.
/// It returns true if the instruction is hoisted.
@ -1047,7 +1051,7 @@ bool MachineLICM::IsProfitableToHoist(MachineInstr &MI) {
// Also, do not "speculate" in high register pressure situation. If an
// instruction is not guaranteed to be executed in the loop, it's best to be
// conservative.
if (SpeculationState == SpeculateTrue ||
if ((!IsGuaranteedToExecute(MI.getParent()) && !MayCSE(&MI)) ||
(!TII->isTriviallyReMaterializable(&MI, AA) &&
!MI.isInvariantLoad(AA)))
return false;
@ -1183,6 +1187,20 @@ bool MachineLICM::EliminateCSE(MachineInstr *MI,
return false;
}
/// MayCSE - Return true if the given instruction will be CSE'd if it's
/// hoisted out of the loop.
bool MachineLICM::MayCSE(MachineInstr *MI) {
unsigned Opcode = MI->getOpcode();
DenseMap<unsigned, std::vector<const MachineInstr*> >::iterator
CI = CSEMap.find(Opcode);
// Do not CSE implicit_def so ProcessImplicitDefs can properly propagate
// the undef property onto uses.
if (CI == CSEMap.end() || MI->isImplicitDef())
return false;
return LookForDuplicate(MI, CI->second) != 0;
}
/// Hoist - When an instruction is found to use only loop invariant operands
/// that are safe to hoist, this instruction is called to do the dirty work.
///