From 213e4e231d7db4aabc375324ba1e6ce1913d7ab6 Mon Sep 17 00:00:00 2001
From: Nathan Froyd <froydnj@mozilla.com>
Date: Mon, 26 Nov 2018 18:51:35 -0500
Subject: [PATCH] Bug 1509927 - use a little more KnownNotNull placement new in
 MFBT; r=njn

This change avoids some useless null checks.
---
 mfbt/HashTable.h       | 5 +++--
 mfbt/SegmentedVector.h | 5 +++--
 2 files changed, 6 insertions(+), 4 deletions(-)

diff --git a/mfbt/HashTable.h b/mfbt/HashTable.h
index dd4890dc4e07b..6cecb3e1d9408 100644
--- a/mfbt/HashTable.h
+++ b/mfbt/HashTable.h
@@ -84,6 +84,7 @@
 #include "mozilla/MemoryReporting.h"
 #include "mozilla/Move.h"
 #include "mozilla/Opaque.h"
+#include "mozilla/OperatorNewExtensions.h"
 #include "mozilla/PodOperations.h"
 #include "mozilla/ReentrancyGuard.h"
 #include "mozilla/TypeTraits.h"
@@ -1168,7 +1169,7 @@ class HashTableEntry
   {
     MOZ_ASSERT(!isLive());
     mKeyHash = aHashNumber;
-    new (valuePtr()) T(std::forward<Args>(aArgs)...);
+    new (KnownNotNull, valuePtr()) T(std::forward<Args>(aArgs)...);
     MOZ_ASSERT(isLive());
   }
 };
@@ -1655,7 +1656,7 @@ class HashTable : private AllocPolicy
                      : aAllocPolicy.template maybe_pod_malloc<Entry>(aCapacity);
     if (table) {
       for (uint32_t i = 0; i < aCapacity; i++) {
-        new (&table[i]) Entry();
+        new (KnownNotNull, &table[i]) Entry();
       }
     }
     return table;
diff --git a/mfbt/SegmentedVector.h b/mfbt/SegmentedVector.h
index 87289b5d2c771..e2adebfa850c4 100644
--- a/mfbt/SegmentedVector.h
+++ b/mfbt/SegmentedVector.h
@@ -26,6 +26,7 @@
 #include "mozilla/LinkedList.h"
 #include "mozilla/MemoryReporting.h"
 #include "mozilla/Move.h"
+#include "mozilla/OperatorNewExtensions.h"
 #include "mozilla/TypeTraits.h"
 
 #include <new>  // for placement new
@@ -100,7 +101,7 @@ class SegmentedVector : private AllocPolicy
       // Pre-increment mLength so that the bounds-check in operator[] passes.
       mLength++;
       T* elem = &(*this)[mLength - 1];
-      new (elem) T(std::forward<U>(aU));
+      new (KnownNotNull, elem) T(std::forward<U>(aU));
     }
 
     void PopLast()
@@ -171,7 +172,7 @@ class SegmentedVector : private AllocPolicy
       if (!last) {
         return false;
       }
-      new (last) Segment();
+      new (KnownNotNull, last) Segment();
       mSegments.insertBack(last);
     }
     last->Append(std::forward<U>(aU));