From: Benjamin Kramer <benny.kra@googlemail.com>
Date: Mon, 2 Mar 2015 22:20:22 +0000 (+0000)
Subject: IndexedMap: Document why SmallVector<T, 0> is preferable here.
X-Git-Tag: llvmorg-3.7.0-rc1~10399
X-Git-Url: http://review.tizen.org/git/?a=commitdiff_plain;h=bb76eaa2c73818c79773fdc8012b92846a1eebbe;p=platform%2Fupstream%2Fllvm.git

IndexedMap: Document why SmallVector<T, 0> is preferable here.

llvm-svn: 231028
---

diff --git a/llvm/include/llvm/ADT/IndexedMap.h b/llvm/include/llvm/ADT/IndexedMap.h
index a830a41..5ba85c0 100644
--- a/llvm/include/llvm/ADT/IndexedMap.h
+++ b/llvm/include/llvm/ADT/IndexedMap.h
@@ -30,6 +30,9 @@ namespace llvm {
 template <typename T, typename ToIndexT = llvm::identity<unsigned> >
   class IndexedMap {
     typedef typename ToIndexT::argument_type IndexT;
+    // Prefer SmallVector with zero inline storage over std::vector. IndexedMaps
+    // can grow very large and SmallVector grows more efficiently as long as T
+    // is trivially copyable.
     typedef SmallVector<T, 0> StorageT;
     StorageT storage_;
     T nullVal_;