[llvm] r249654 - [SCEV] Check `Pred` first in isKnownPredicateViaSplitting

[Sanjoy Das via llvm-commits]

Author: sanjoy
Date: Wed Oct  7 22:46:00 2015
New Revision: 249654

URL: http://llvm.org/viewvc/llvm-project?rev=249654&view=rev
Log:
[SCEV] Check `Pred` first in isKnownPredicateViaSplitting

Comparing `Pred` with `ICmpInst::ICMP_ULT` is cheaper that memory access
-- do that check before loading / storing `ProvingSplitPredicate`.

Modified:
    llvm/trunk/lib/Analysis/ScalarEvolution.cpp

Modified: llvm/trunk/lib/Analysis/ScalarEvolution.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Analysis/ScalarEvolution.cpp?rev=249654&r1=249653&r2=249654&view=diff
==============================================================================
--- llvm/trunk/lib/Analysis/ScalarEvolution.cpp (original)
+++ llvm/trunk/lib/Analysis/ScalarEvolution.cpp Wed Oct  7 22:46:00 2015
@@ -7132,7 +7132,7 @@ ScalarEvolution::isKnownPredicateWithRan
 bool ScalarEvolution::isKnownPredicateViaSplitting(ICmpInst::Predicate Pred,
                                                    const SCEV *LHS,
                                                    const SCEV *RHS) {
-  if (ProvingSplitPredicate)
+  if (Pred != ICmpInst::ICMP_ULT || ProvingSplitPredicate)
     return false;
 
   // Allowing arbitrary number of activations of isKnownPredicateViaSplitting on
@@ -7146,7 +7146,7 @@ bool ScalarEvolution::isKnownPredicateVi
   // expensive; and using isKnownNonNegative(RHS) is sufficient for most of the
   // interesting cases seen in practice.  We can consider "upgrading" L >= 0 to
   // use isKnownPredicate later if needed.
-  if (Pred == ICmpInst::ICMP_ULT && isKnownNonNegative(RHS) &&
+  if (isKnownNonNegative(RHS) &&
       isKnownPredicate(CmpInst::ICMP_SGE, LHS, getZero(LHS->getType())) &&
       isKnownPredicate(CmpInst::ICMP_SLT, LHS, RHS))
     return true;