[llvm] r319889 - [SCEV][NFC] Check NoWrap flags before lexicographical comparison of SCEVs

[Max Kazantsev via llvm-commits]

Author: mkazantsev
Date: Wed Dec  6 04:44:56 2017
New Revision: 319889

URL: http://llvm.org/viewvc/llvm-project?rev=319889&view=rev
Log:
[SCEV][NFC] Check NoWrap flags before lexicographical comparison of SCEVs

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 eqivalent SCEVs together and is
not supposed to have any meaningful impact on behavior of any transforms.


Reviewed By: sanjoy
Differential Revision: https://reviews.llvm.org/D40645

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=319889&r1=319888&r2=319889&view=diff
==============================================================================
--- llvm/trunk/lib/Analysis/ScalarEvolution.cpp (original)
+++ llvm/trunk/lib/Analysis/ScalarEvolution.cpp Wed Dec  6 04:44:56 2017
@@ -694,6 +694,10 @@ static int CompareSCEVComplexity(
     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, EqCacheValue, LI,
@@ -718,6 +722,10 @@ static int CompareSCEVComplexity(
     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, EqCacheValue, LI,
                                     LC->getOperand(i), RC->getOperand(i), DT,