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various fixes to the lattice transfer functions.

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git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@86952 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Chris Lattner 2009-11-12 04:57:13 +00:00
parent 0e0ff29271
commit f496e79f44
2 changed files with 33 additions and 6 deletions
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33
lib/Analysis/LazyValueInfo.cpp
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@ -141,19 +141,40 @@ public:
if (RHS.isNotConstant()) {
if (isNotConstant()) {
if (getNotConstant() != RHS.getNotConstant())
if (getNotConstant() != RHS.getNotConstant() ||
isa<ConstantExpr>(getNotConstant()) ||
isa<ConstantExpr>(RHS.getNotConstant()))
return markOverdefined();
return false;
}
if (isConstant() && getConstant() != RHS.getNotConstant())
return markOverdefined();
if (isConstant()) {
if (getConstant() == RHS.getNotConstant() ||
isa<ConstantExpr>(RHS.getNotConstant()) ||
isa<ConstantExpr>(getConstant()))
return markOverdefined();
return markNotConstant(RHS.getNotConstant());
}
assert(isUndefined() && "Unexpected lattice");
return markNotConstant(RHS.getNotConstant());
}
// RHS must be a constant, we must be undef or constant.
if (isConstant() && getConstant() != RHS.getConstant())
// RHS must be a constant, we must be undef, constant, or notconstant.
if (isUndefined())
return markConstant(RHS.getConstant());
if (isConstant()) {
if (getConstant() != RHS.getConstant())
return markOverdefined();
return false;
}
// If we are known "!=4" and RHS is "==5", stay at "!=4".
if (getNotConstant() == RHS.getConstant() ||
isa<ConstantExpr>(getNotConstant()) ||
isa<ConstantExpr>(RHS.getConstant()))
return markOverdefined();
return markConstant(RHS.getConstant());
return false;
}
};

6
lib/Transforms/Scalar/JumpThreading.cpp
View File

@ -275,6 +275,12 @@ ComputeValueKnownInPredecessors(Value *V, BasicBlock *BB,PredValueInfo &Result){
/// predecessor based on its terminator.
//
if (LVI) {
// FIXME: change this to use the more-rich 'getPredicateOnEdge' method if
// "I" is a non-local compare-with-a-constant instruction. This would be
// able to handle value inequalities better, for example if the compare is
// "X < 4" and "X < 3" is known true but "X < 4" itself is not available.
// Perhaps getConstantOnEdge should be smart enough to do this?
for (pred_iterator PI = pred_begin(BB), E = pred_end(BB); PI != E; ++PI) {
// If the value is known by LazyValueInfo to be a constant in a
// predecessor, use that information to try to thread this block.