From 201d1e56bb7535802c70d5eb46601afcc325045d Mon Sep 17 00:00:00 2001
From: Chris Lattner <sabre@nondot.org>
Date: Tue, 30 Nov 2010 00:28:45 +0000
Subject: Teach basicaa that memset's modref set is at worst "mod" and never
 contains "ref".

Enhance DSE to use a modref query instead of a store-specific hack
to generalize the "ignore may-alias stores" optimization to handle
memset and memcpy.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@120368 91177308-0d34-0410-b5e6-96231b3b80d8
---
 lib/Analysis/BasicAliasAnalysis.cpp | 2 ++
 1 file changed, 2 insertions(+)

(limited to 'lib/Analysis/BasicAliasAnalysis.cpp')

diff --git a/lib/Analysis/BasicAliasAnalysis.cpp b/lib/Analysis/BasicAliasAnalysis.cpp
index bf1b689587..3e63424090 100644
--- a/lib/Analysis/BasicAliasAnalysis.cpp
+++ b/lib/Analysis/BasicAliasAnalysis.cpp
@@ -703,6 +703,8 @@ BasicAliasAnalysis::getModRefInfo(ImmutableCallSite CS,
         if (isNoAlias(Location(Dest, Len), Loc))
           return NoModRef;
       }
+      // We know that memset doesn't load anything.
+      Min = Mod;
       break;
     case Intrinsic::atomic_cmp_swap:
     case Intrinsic::atomic_swap:
-- 
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