From: Duncan Sands <baldrick@free.fr>
Date: Wed, 6 May 2009 08:42:00 +0000 (+0000)
Subject: Fix PR3754: don't mark functions that wrap MallocInst with
X-Git-Url: http://demsky.eecs.uci.edu/git/?a=commitdiff_plain;h=cfd0ebea276521a48370c197e651064b032a381e;p=oota-llvm.git

Fix PR3754: don't mark functions that wrap MallocInst with
the readnone.  Since MallocInst is scheduled for deletion
it doesn't seem worth doing anything more subtle, such as
having mayWriteToMemory return true for MallocInst.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@71077 91177308-0d34-0410-b5e6-96231b3b80d8
---

diff --git a/lib/Transforms/IPO/FunctionAttrs.cpp b/lib/Transforms/IPO/FunctionAttrs.cpp
index 65faef32e5e..e8315247b23 100644
--- a/lib/Transforms/IPO/FunctionAttrs.cpp
+++ b/lib/Transforms/IPO/FunctionAttrs.cpp
@@ -152,6 +152,11 @@ bool FunctionAttrs::AddReadAttrs(const std::vector<CallGraphNode *> &SCC) {
       if (I->mayWriteToMemory())
         // Writes memory.  Just give up.
         return false;
+
+      if (isa<MallocInst>(I))
+        // MallocInst claims not to write memory!  PR3754.
+        return false;
+
       // If this instruction may read memory, remember that.
       ReadsMemory |= I->mayReadFromMemory();
     }
diff --git a/test/Transforms/FunctionAttrs/2009-05-06-Malloc.ll b/test/Transforms/FunctionAttrs/2009-05-06-Malloc.ll
new file mode 100644
index 00000000000..4022033c3b0
--- /dev/null
+++ b/test/Transforms/FunctionAttrs/2009-05-06-Malloc.ll
@@ -0,0 +1,7 @@
+; RUN: llvm-as < %s | opt -functionattrs | llvm-dis | not grep read
+; PR3754
+
+define i8* @m(i32 %size) {
+	%tmp = malloc i8, i32 %size		; <i8*> [#uses=1]
+	ret i8* %tmp
+}