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[InstCombine] Simplify the logic from r219067 using ValueTracking

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Joerg suggested on IRC that I look at generalizing the logic from r219067 to
handle more general redundancies (like removing an assume(x > 3) dominated by
an assume(x > 5)). The way to do this would be to ask ValueTracking to
determine the value of the i1 argument. It turns out that ValueTracking is not
very good at this right now (although it does get the trivial redundancy case)
because it does not understand ICmps. Nevertheless, the resulting code in
InstCombine is simpler than r219067, so we might as well do it now.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@219070 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Hal Finkel 2014-10-05 00:53:02 +00:00
parent 3cdf75c5cf
commit bda7a45f8e
1 changed files with 4 additions and 12 deletions
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16
lib/Transforms/InstCombine/InstCombineCalls.cpp
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@ -1020,18 +1020,10 @@ Instruction *InstCombiner::visitCallInst(CallInst &CI) {
// If there is a dominating assume with the same condition as this one,
// then this one is redundant, and should be removed.
if (DT) {
for (User *U : IIOperand->users()) {
Instruction *User = dyn_cast<Instruction>(U);
if (!User || User == II)
continue;
if (match(User,
m_Intrinsic<Intrinsic::assume>(m_Specific(IIOperand))) &&
DT->dominates(User, II))
return EraseInstFromFunction(*II);
}
}
APInt KnownZero(1, 0), KnownOne(1, 0);
computeKnownBits(IIOperand, KnownZero, KnownOne, 0, II);
if (KnownOne.isAllOnesValue())
return EraseInstFromFunction(*II);
break;
}