[PATCH] D40645: [SCEV][NFC] Check NoWrap flags before lexicographical comparison of SCEVs

[Max Kazantsev via Phabricator via llvm-commits]

mkazantsev created this revision.

Lexicographical comparison of SCEV trees is potentially expensive for big
expression trees. We can define ordering between them for AddRecs and
N-ary operations by SCEV NoWrap flags to make non-equality check
cheaper.

This change does not prevent grouping eqiovalent SCEVs together and is
not supposed to have any meaningful impact on behavior of any transforms.


https://reviews.llvm.org/D40645

Files:
  lib/Analysis/ScalarEvolution.cpp


Index: lib/Analysis/ScalarEvolution.cpp
===================================================================
--- lib/Analysis/ScalarEvolution.cpp
+++ lib/Analysis/ScalarEvolution.cpp
@@ -694,6 +694,10 @@
     if (LNumOps != RNumOps)
       return (int)LNumOps - (int)RNumOps;
 
+    // Compare NoWrap flags.
+    if (LA->getNoWrapFlags() != RA->getNoWrapFlags())
+      return (int)LA->getNoWrapFlags() - (int)RA->getNoWrapFlags();
+
     // Lexicographically compare.
     for (unsigned i = 0; i != LNumOps; ++i) {
       int X = CompareSCEVComplexity(EqCacheSCEV, LI, LA->getOperand(i),
@@ -717,6 +721,10 @@
     if (LNumOps != RNumOps)
       return (int)LNumOps - (int)RNumOps;
 
+    // Compare NoWrap flags.
+    if (LC->getNoWrapFlags() != RC->getNoWrapFlags())
+      return (int)LC->getNoWrapFlags() - (int)RC->getNoWrapFlags();
+
     for (unsigned i = 0; i != LNumOps; ++i) {
       int X = CompareSCEVComplexity(EqCacheSCEV, LI, LC->getOperand(i),
                                     RC->getOperand(i), DT, Depth + 1);


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