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Implement some more interesting select sccp cases. This implements:

Browse Source 
test/Regression/Transforms/SCCP/select.ll


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@26049 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Chris Lattner 2006-02-08 02:38:11 +00:00
parent d27460f291
commit fe243ebb64
1 changed files with 35 additions and 15 deletions
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48
lib/Transforms/Scalar/SCCP.cpp
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@ -242,6 +242,11 @@ private:
markOverdefined(IV, V);
}
inline void mergeInValue(Value *V, LatticeVal &MergeWithV) {
return mergeInValue(ValueState[V], V, MergeWithV);
}
// getValueState - Return the LatticeVal object that corresponds to the value.
// This function is necessary because not all values should start out in the
// underdefined state... Argument's should be overdefined, and
@ -589,22 +594,37 @@ void SCCPSolver::visitCastInst(CastInst &I) {
void SCCPSolver::visitSelectInst(SelectInst &I) {
LatticeVal &CondValue = getValueState(I.getCondition());
if (CondValue.isOverdefined())
markOverdefined(&I);
else if (CondValue.isConstant()) {
if (CondValue.isUndefined())
return;
if (CondValue.isConstant()) {
Value *InVal = 0;
if (CondValue.getConstant() == ConstantBool::True) {
LatticeVal &Val = getValueState(I.getTrueValue());
if (Val.isOverdefined())
markOverdefined(&I);
else if (Val.isConstant())
markConstant(&I, Val.getConstant());
mergeInValue(&I, getValueState(I.getTrueValue()));
return;
} else if (CondValue.getConstant() == ConstantBool::False) {
LatticeVal &Val = getValueState(I.getFalseValue());
if (Val.isOverdefined())
markOverdefined(&I);
else if (Val.isConstant())
markConstant(&I, Val.getConstant());
} else
mergeInValue(&I, getValueState(I.getFalseValue()));
return;
}
}
// Otherwise, the condition is overdefined or a constant we can't evaluate.
// See if we can produce something better than overdefined based on the T/F
// value.
LatticeVal &TVal = getValueState(I.getTrueValue());
LatticeVal &FVal = getValueState(I.getFalseValue());
// select ?, C, C -> C.
if (TVal.isConstant() && FVal.isConstant() &&
TVal.getConstant() == FVal.getConstant()) {
markConstant(&I, FVal.getConstant());
return;
}
if (TVal.isUndefined()) { // select ?, undef, X -> X.
mergeInValue(&I, FVal);
} else if (FVal.isUndefined()) { // select ?, X, undef -> X.
mergeInValue(&I, TVal);
} else {
markOverdefined(&I);
}
}