Add, and infer, a nofree function attribute

This patch adds a function attribute, nofree, to indicate that a function does
not, directly or indirectly, call a memory-deallocation function (e.g., free,
C++'s operator delete).

Reviewers: jdoerfert

Differential Revision: https://reviews.llvm.org/D49165

llvm-svn: 365336
diff --git a/llvm/test/Transforms/FunctionAttrs/atomic.ll b/llvm/test/Transforms/FunctionAttrs/atomic.ll
index af87a28..35de0ce 100644
--- a/llvm/test/Transforms/FunctionAttrs/atomic.ll
+++ b/llvm/test/Transforms/FunctionAttrs/atomic.ll
@@ -21,4 +21,4 @@
 }
 
 ; CHECK: attributes #0 = { norecurse nounwind readnone ssp uwtable }
-; CHECK: attributes #1 = { norecurse nounwind ssp uwtable }
+; CHECK: attributes #1 = { nofree norecurse nounwind ssp uwtable }