configurable alignment for Arena

[folly.git] / folly / Range.cpp

diff --git a/folly/Range.cpp b/folly/Range.cpp
index c1e58eda0120c4b4b6d50cbf73a29da86ed820c7..8a73e805831f6337496de4d308ef628eb1b0d213 100644 (file)
--- a/folly/Range.cpp
+++ b/folly/Range.cpp
@@ -1,5 +1,5 @@
 /*
- * Copyright 2013 Facebook, Inc.
+ * Copyright 2014 Facebook, Inc.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -19,9 +19,10 @@
 
 #include "folly/Range.h"
 
+#if FOLLY_HAVE_EMMINTRIN_H
 #include <emmintrin.h>  // __v16qi
+#endif
 #include <iostream>
-#include "folly/Likely.h"
 
 namespace folly {
 
@@ -66,18 +67,22 @@ static_assert(kMinPageSize >= 16,
 #define PAGE_FOR(addr) \
   (reinterpret_cast<uintptr_t>(addr) / kMinPageSize)
 
+
+// Earlier versions of GCC (for example, Clang on Mac OS X, which is based on
+// GCC 4.2) do not have a full compliment of SSE builtins.
+#if FOLLY_HAVE_EMMINTRIN_H && __GNUC_PREREQ(4, 6)
 inline size_t nextAlignedIndex(const char* arr) {
-  auto firstPossible = reinterpret_cast<uintptr_t>(arr) + 1;
-  return 1 +                       // add 1 because the index starts at 'arr'
-    ((firstPossible + 15) & ~0xF)  // round up to next multiple of 16
-    - firstPossible;
+   auto firstPossible = reinterpret_cast<uintptr_t>(arr) + 1;
+   return 1 +                       // add 1 because the index starts at 'arr'
+     ((firstPossible + 15) & ~0xF)  // round up to next multiple of 16
+     - firstPossible;
 }
 
-#if FOLLY_HAVE_EMMINTRIN_H
 // build sse4.2-optimized version even if -msse4.2 is not passed to GCC
 size_t qfind_first_byte_of_needles16(const StringPiece& haystack,
                                      const StringPiece& needles)
-  __attribute__ ((__target__("sse4.2"), noinline));
+  __attribute__ ((__target__("sse4.2"), noinline))
+  FOLLY_DISABLE_ADDRESS_SANITIZER;
 
 // helper method for case where needles.size() <= 16
 size_t qfind_first_byte_of_needles16(const StringPiece& haystack,
@@ -118,7 +123,7 @@ size_t qfind_first_byte_of_needles16(const StringPiece& haystack,
   }
   return StringPiece::npos;
 }
-#endif // FOLLY_HAVE_EMMINTRIN_H
+#endif // FOLLY_HAVE_EMMINTRIN_H && GCC 4.6+
 
 // Aho, Hopcroft, and Ullman refer to this trick in "The Design and Analysis
 // of Computer Algorithms" (1974), but the best description is here:
@@ -164,23 +169,28 @@ size_t qfind_first_byte_of_byteset(const StringPiece& haystack,
   return StringPiece::npos;
 }
 
-#if FOLLY_HAVE_EMMINTRIN_H
+#if FOLLY_HAVE_EMMINTRIN_H && __GNUC_PREREQ(4, 6)
 
 template <bool HAYSTACK_ALIGNED>
-inline size_t scanHaystackBlock(const StringPiece& haystack,
-                                const StringPiece& needles,
-                                int64_t idx)
+size_t scanHaystackBlock(const StringPiece& haystack,
+                         const StringPiece& needles,
+                         int64_t idx)
 // inline is okay because it's only called from other sse4.2 functions
-  __attribute__ ((__target__("sse4.2")));
+  __attribute__ ((__target__("sse4.2")))
+// Turn off ASAN because the "arr2 = ..." assignment in the loop below reads
+// up to 15 bytes beyond end of the buffer in #needles#.  That is ok because
+// ptr2 is always 16-byte aligned, so the read can never span a page boundary.
+// Also, the extra data that may be read is never actually used.
+  FOLLY_DISABLE_ADDRESS_SANITIZER;
 
 // Scans a 16-byte block of haystack (starting at blockStartIdx) to find first
 // needle. If HAYSTACK_ALIGNED, then haystack must be 16byte aligned.
 // If !HAYSTACK_ALIGNED, then caller must ensure that it is safe to load the
 // block.
 template <bool HAYSTACK_ALIGNED>
-inline size_t scanHaystackBlock(const StringPiece& haystack,
-                                const StringPiece& needles,
-                                int64_t blockStartIdx) {
+size_t scanHaystackBlock(const StringPiece& haystack,
+                         const StringPiece& needles,
+                         int64_t blockStartIdx) {
   DCHECK_GT(needles.size(), 16);  // should handled by *needles16() method
   DCHECK(blockStartIdx + 16 <= haystack.size() ||
          (PAGE_FOR(haystack.data() + blockStartIdx) ==
@@ -253,7 +263,7 @@ size_t qfind_first_byte_of_sse42(const StringPiece& haystack,
 
   return StringPiece::npos;
 }
-#endif // FOLLY_HAVE_EMMINTRIN_H
+#endif // FOLLY_HAVE_EMMINTRIN_H && GCC 4.6+
 
 size_t qfind_first_byte_of_nosse(const StringPiece& haystack,
                                  const StringPiece& needles) {