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 65faef32e5e2b5df4d149102649886af7e7825f7..e8315247b23cbf2567c2d94b2c9cef9c71b5463a 100644 (file)
--- 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 (file)
index 0000000..4022033
--- /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
+}