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Remove some wrong code which fortunately was never executed (as explained in

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the comment I added): an extern weak global may have a null address.

llvm-svn: 123373
This commit is contained in:
Duncan Sands 2011-01-13 10:43:08 +00:00
parent 36b007d63b
commit 69fbfa2b0e
1 changed files with 9 additions and 6 deletions
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15
lib/Analysis/InstructionSimplify.cpp
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@ -1024,12 +1024,15 @@ static Value *SimplifyICmpInst(unsigned Predicate, Value *LHS, Value *RHS,
} }
} }
// icmp <global/alloca*/null>, <global/alloca*/null> - Global/Stack value // icmp <alloca*>, <global/alloca*/null> - Different stack variables have
// addresses never equal each other! We already know that Op0 != Op1. // different addresses, and what's more the address of a stack variable is
if ((isa<GlobalValue>(LHS) || isa<AllocaInst>(LHS) || // never null or equal to the address of a global. Note that generalizing
isa<ConstantPointerNull>(LHS)) && // to the case where LHS is a global variable address or null is pointless,
(isa<GlobalValue>(RHS) || isa<AllocaInst>(RHS) || // since if both LHS and RHS are constants then we already constant folded
isa<ConstantPointerNull>(RHS))) // the compare, and if only one of them is then we moved it to RHS already.
if (isa<AllocaInst>(LHS) && (isa<GlobalValue>(RHS) || isa<AllocaInst>(RHS) ||
isa<ConstantPointerNull>(RHS)))
// We already know that LHS != LHS.
return ConstantInt::get(ITy, CmpInst::isFalseWhenEqual(Pred)); return ConstantInt::get(ITy, CmpInst::isFalseWhenEqual(Pred));
// If the comparison is with the result of a select instruction, check whether // If the comparison is with the result of a select instruction, check whether