From: Dan Gohman <gohman@apple.com>
Date: Thu, 18 Jun 2009 20:21:07 +0000 (+0000)
Subject: Recognize n != 0 ? n : 1 as umax(n, 1). Previously only ULT/UGT/ULE/UGE
X-Git-Url: http://plrg.eecs.uci.edu/git/?a=commitdiff_plain;h=30fb512e95f6a01f0c9c3426c2263ee0458de8e8;p=oota-llvm.git

Recognize n != 0 ? n : 1 as umax(n, 1). Previously only ULT/UGT/ULE/UGE
comparisons were recognized for umax, but instcombine canonicalizes
unsigned comparisons with zero to this simpler form.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@73717 91177308-0d34-0410-b5e6-96231b3b80d8
---

diff --git a/lib/Analysis/ScalarEvolution.cpp b/lib/Analysis/ScalarEvolution.cpp
index 9c6941f0d31..18c136fc0a6 100644
--- a/lib/Analysis/ScalarEvolution.cpp
+++ b/lib/Analysis/ScalarEvolution.cpp
@@ -2580,6 +2580,24 @@ SCEVHandle ScalarEvolution::createSCEV(Value *V) {
           return getNotSCEV(getUMaxExpr(getNotSCEV(getSCEV(LHS)),
                                         getNotSCEV(getSCEV(RHS))));
         break;
+      case ICmpInst::ICMP_NE:
+        // n != 0 ? n : 1  ->  umax(n, 1)
+        if (LHS == U->getOperand(1) &&
+            isa<ConstantInt>(U->getOperand(2)) &&
+            cast<ConstantInt>(U->getOperand(2))->isOne() &&
+            isa<ConstantInt>(RHS) &&
+            cast<ConstantInt>(RHS)->isZero())
+          return getUMaxExpr(getSCEV(LHS), getSCEV(U->getOperand(2)));
+        break;
+      case ICmpInst::ICMP_EQ:
+        // n == 0 ? 1 : n  ->  umax(n, 1)
+        if (LHS == U->getOperand(2) &&
+            isa<ConstantInt>(U->getOperand(1)) &&
+            cast<ConstantInt>(U->getOperand(1))->isOne() &&
+            isa<ConstantInt>(RHS) &&
+            cast<ConstantInt>(RHS)->isZero())
+          return getUMaxExpr(getSCEV(LHS), getSCEV(U->getOperand(1)));
+        break;
       default:
         break;
       }