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.

llvm-svn: 71077

1 files changed, 5 insertions, 0 deletions

diff --git a/llvm/lib/Transforms/IPO/FunctionAttrs.cpp b/llvm/lib/Transforms/IPO/FunctionAttrs.cpp
index 65faef32e5e..e8315247b23 100644
--- a/llvm/lib/Transforms/IPO/FunctionAttrs.cpp
+++ b/llvm/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();
     }