[PATCH] D139818: [IndVars][NFCI] Remove supposedly dead code to save some CT

[Max Kazantsev via Phabricator via llvm-commits]

mkazantsev created this revision.
mkazantsev added reviewers: nikic, lebedev.ri, fhahn, reames.
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I ran a big corps of Fuzz tests and could not find a case when predicate
evaluated to 'false' would fire here, seems that they all get optimized away
by other means. I am not 100% sure this is an NFC, but if it really causes
any troubles, we should add a test demonstrating it's useful. Otherwise,
we save some CT by reducing number of SCEV queries.


https://reviews.llvm.org/D139818

Files:
  llvm/lib/Transforms/Scalar/IndVarSimplify.cpp


Index: llvm/lib/Transforms/Scalar/IndVarSimplify.cpp
===================================================================
--- llvm/lib/Transforms/Scalar/IndVarSimplify.cpp
+++ llvm/lib/Transforms/Scalar/IndVarSimplify.cpp
@@ -1384,8 +1384,8 @@
   const SCEV *LHSS = SE->getSCEVAtScope(LHS, L);
   const SCEV *RHSS = SE->getSCEVAtScope(RHS, L);
   // Can we prove it to be trivially true or false?
-  if (auto EV = SE->evaluatePredicateAt(Pred, LHSS, RHSS, BI)) {
-    foldExit(L, ExitingBB, /*IsTaken*/ !*EV, DeadInsts);
+  if (SE->isKnownPredicate(Pred, LHSS, RHSS, BI)) {
+    foldExit(L, ExitingBB, /*IsTaken*/ false, DeadInsts);
     return true;
   }
 


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