From 30fb512e95f6a01f0c9c3426c2263ee0458de8e8 Mon Sep 17 00:00:00 2001
From: Dan Gohman <gohman@apple.com>
Date: Thu, 18 Jun 2009 20:21:07 +0000
Subject: [PATCH] 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
---
 lib/Analysis/ScalarEvolution.cpp | 18 ++++++++++++++++++
 1 file changed, 18 insertions(+)

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;
       }