[LazyValueInfo] Don't run the more complex predicate handling code for EQ and NE in getPredicateResult

[craig.topper]

Summary

Unless I'm mistaken, the special handling for EQ/NE should cover everything and there is no reason to fallthrough to the more complex code. For that matter I'm not sure there's any reason to special case EQ/NE other than avoiding creating temporary ConstantRanges.

This patch moves the complex code into an else so we only do it when we are handling a predicate other than EQ/NE.

[anna]

This change looks good to me, and I agree with your summary. I think this is where additional tests to the LVI Printer pass (see -print-lazy-value-info) in lvi-after-jumpthreading.ll would help, i.e. did we change existing LVI values being calculated?

[craig.topper]

This function is just calculating a predicate result based on a LVI lattice value. I don't think it affects the calculation of LVI lattice values themselves. So I don't think the printer can see it.

[anna]

In D34000#776491, @craig.topper wrote:

This function is just calculating a predicate result based on a LVI lattice value. I don't think it affects the calculation of LVI lattice values themselves. So I don't think the printer can see it.

agreed, getPredicateAt uses the LVI result within CVP and Jumpthreading.

LGTM.

llvm/trunk/lib/Analysis/LazyValueInfo.cpp

if (Pred == ICmpInst::ICMP_EQ) {
       if (CR.isSingleElement())
         return LazyValueInfo::True;
     } else if (Pred == ICmpInst::ICMP_NE) {
       if (!CR.contains(CI->getValue()))
         return LazyValueInfo::True;
 
       if (CR.isSingleElement())
         return LazyValueInfo::False;
-    }
-
+    } else {
       // Handle more complex predicates.
       ConstantRange TrueValues = ConstantRange::makeExactICmpRegion(
           (ICmpInst::Predicate)Pred, CI->getValue());
       if (TrueValues.contains(CR))
         return LazyValueInfo::True;
       if (TrueValues.inverse().contains(CR))
         return LazyValueInfo::False;
+    }
     return LazyValueInfo::Unknown;
   }
 
   if (Result.isNotConstant()) {
     // If this is an equality comparison, we can try to fold it knowing that
     // "V != C1".
     if (Pred == ICmpInst::ICMP_EQ) {
       // !C1 == C -> false iff C1 == C.