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typed arrays: swizzle with compiler intrinsics

Implement swizzling with compiler intrinsics and be aware of the native
endianness to correctly swap on big endian machines.

This introduces a template function to swap the bytes of a value,
and macros for the low level swap (taking advantage of gcc and msvc
intrinsics). This produces code like the following (comments are mine):

gcc version 4.2.1 (Based on Apple Inc. build 5658) (LLVM build 2336.11.00)

setValue<double>:
  movd  %xmm0, %rax         ; fp reg -> gen reg
  bswapq  %rax              ; 64-bit byte swap
  movd  %rax, %xmm0         ; gen reg -> fp reg
  movq  %xmm0, (%r15,%r12)  ; store
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1 parent 7d66a9d commit 46a489be73fd87fa3e17dd929c53d9e90860f80a @deanm deanm committed with bnoordhuis Jan 5, 2013
Showing with 188 additions and 20 deletions.
  1. +18 −20 src/v8_typed_array.cc
  2. +170 −0 src/v8_typed_array_bswap.h
View
@@ -23,6 +23,7 @@
#include <string.h> // memmove
#include "v8_typed_array.h"
+#include "v8_typed_array_bswap.h"
#include "node_buffer.h"
#include "node.h"
#include "v8.h"
@@ -665,33 +666,20 @@ class DataView {
return args.This();
}
- // TODO(deanm): This isn't beautiful or optimal.
- static void swizzle(char* buf, size_t len) {
- for (size_t i = 0; i < len / 2; ++i) {
- char t = buf[i];
- buf[i] = buf[len - i - 1];
- buf[len - i - 1] = t;
- }
- }
-
template <typename T>
static T getValue(void* ptr, unsigned int index, bool swiz) {
- char buf[sizeof(T)];
- memcpy(buf, reinterpret_cast<char*>(ptr) + index, sizeof(T));
- if (swiz)
- swizzle(buf, sizeof(T));
T val;
- memcpy(&val, buf, sizeof(T));
+ memcpy(&val, reinterpret_cast<char*>(ptr) + index, sizeof(T));
+ if (swiz)
+ val = v8_typed_array::SwapBytes(val);
return val;
}
template <typename T>
static void setValue(void* ptr, unsigned int index, T val, bool swiz) {
- char buf[sizeof(T)];
- memcpy(buf, &val, sizeof(T));
if (swiz)
- swizzle(buf, sizeof(T));
- memcpy(reinterpret_cast<char*>(ptr) + index, buf, sizeof(T));
+ val = v8_typed_array::SwapBytes(val);
+ memcpy(reinterpret_cast<char*>(ptr) + index, &val, sizeof(T));
}
template <typename T>
@@ -711,7 +699,12 @@ class DataView {
return ThrowError("Index out of range.");
void* ptr = args.This()->GetIndexedPropertiesExternalArrayData();
- return cTypeToValue<T>(getValue<T>(ptr, index, !little_endian));
+#if V8_TYPED_ARRAY_LITTLE_ENDIAN
+ bool swiz = !little_endian;
+#else
+ bool swiz = little_endian;
+#endif
+ return cTypeToValue<T>(getValue<T>(ptr, index, swiz));
}
template <typename T>
@@ -731,7 +724,12 @@ class DataView {
return ThrowError("Index out of range.");
void* ptr = args.This()->GetIndexedPropertiesExternalArrayData();
- setValue<T>(ptr, index, valueToCType<T>(args[1]), !little_endian);
+#if V8_TYPED_ARRAY_LITTLE_ENDIAN
+ bool swiz = !little_endian;
+#else
+ bool swiz = little_endian;
+#endif
+ setValue<T>(ptr, index, valueToCType<T>(args[1]), swiz);
return v8::Undefined();
}
View
@@ -0,0 +1,170 @@
+// V8 Typed Array implementation.
+// (c) Dean McNamee <dean@gmail.com>, 2012.
+//
+// Permission is hereby granted, free of charge, to any person obtaining a copy
+// of this software and associated documentation files (the "Software"), to
+// deal in the Software without restriction, including without limitation the
+// rights to use, copy, modify, merge, publish, distribute, sublicense, and/or
+// sell copies of the Software, and to permit persons to whom the Software is
+// furnished to do so, subject to the following conditions:
+//
+// The above copyright notice and this permission notice shall be included in
+// all copies or substantial portions of the Software.
+//
+// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
+// FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
+// IN THE SOFTWARE.
+
+#ifndef V8_TYPED_ARRAY_BSWAP_H_
+#define V8_TYPED_ARRAY_BSWAP_H_
+
+// Windows will always be little endian (including ARM), so we just need to
+// worry about gcc.
+#if defined (__ppc__) || defined (__ppc64__) || defined(__ARMEB__)
+#define V8_TYPED_ARRAY_BIG_ENDIAN 1
+#else
+#define V8_TYPED_ARRAY_LITTLE_ENDIAN 1
+#endif
+
+#if defined (_MSC_VER) && (_MSC_VER < 1600)
+ typedef unsigned char uint8_t;
+ typedef signed char int8_t;
+ typedef unsigned __int16 uint16_t;
+ typedef signed __int16 int16_t;
+ typedef unsigned __int32 uint32_t;
+ typedef signed __int32 int32_t;
+ typedef unsigned __int64 uint64_t;
+ typedef signed __int64 int64_t;
+ // Definitions to avoid ICU redefinition issue
+ #define U_HAVE_INT8_T 1
+ #define U_HAVE_UINT8_T 1
+ #define U_HAVE_INT16_T 1
+ #define U_HAVE_UINT16_T 1
+ #define U_HAVE_INT32_T 1
+ #define U_HAVE_UINT32_T 1
+ #define U_HAVE_INT64_T 1
+ #define U_HAVE_UINT64_T 1
+#else
+ #include <stdint.h>
+#endif
+
+#if defined (_MSC_VER)
+#define V8_TYPED_ARRAY_BSWAP16 _byteswap_ushort
+#define V8_TYPED_ARRAY_BSWAP32 _byteswap_ulong
+#define V8_TYPED_ARRAY_BSWAP64 _byteswap_uint64
+#else
+// On LLVM based compilers we can feature test, but for GCC we unfortunately
+// have to rely on the version. Additionally __builtin_bswap32/64 were added
+// in GCC 4.3, but __builtin_bswap16 was not added until GCC 4.8.
+// We should be able to assume GCC/LLVM here (and can use ULL constants, etc).
+// Fallback swap macros taken from QEMU bswap.h
+#ifdef __has_builtin
+#define V8_TYPED_ARRAY_BSWAP_HAS_BUILTIN(x) __has_builtin(x)
+#define V8_TYPED_ARRAY_BSWAP_HAS_BUILTIN16(x) __has_builtin(x)
+#else
+#define V8_TYPED_ARRAY_BSWAP_HAS_BUILTIN(x) (defined(__GNUC__) && \
+ (__GNUC__ > 4 || (__GNUC__ == 4 && __GNUC_MINOR__ >= 3)))
+#define V8_TYPED_ARRAY_BSWAP_HAS_BUILTIN16(x) (defined(__GNUC__) && \
+ (__GNUC__ > 4 || (__GNUC__ == 4 && __GNUC_MINOR__ >= 8)))
+#endif
+
+#if V8_TYPED_ARRAY_BSWAP_HAS_BUILTIN(__builtin_bswap64)
+#define V8_TYPED_ARRAY_BSWAP64 __builtin_bswap64
+#else
+#define V8_TYPED_ARRAY_BSWAP64(x) \
+({ \
+ uint64_t __x = (x); \
+ ((uint64_t)( \
+ (uint64_t)(((uint64_t)(__x) & (uint64_t)0x00000000000000ffULL) << 56) | \
+ (uint64_t)(((uint64_t)(__x) & (uint64_t)0x000000000000ff00ULL) << 40) | \
+ (uint64_t)(((uint64_t)(__x) & (uint64_t)0x0000000000ff0000ULL) << 24) | \
+ (uint64_t)(((uint64_t)(__x) & (uint64_t)0x00000000ff000000ULL) << 8) | \
+ (uint64_t)(((uint64_t)(__x) & (uint64_t)0x000000ff00000000ULL) >> 8) | \
+ (uint64_t)(((uint64_t)(__x) & (uint64_t)0x0000ff0000000000ULL) >> 24) | \
+ (uint64_t)(((uint64_t)(__x) & (uint64_t)0x00ff000000000000ULL) >> 40) | \
+ (uint64_t)(((uint64_t)(__x) & (uint64_t)0xff00000000000000ULL) >> 56) )); \
+})
+#endif
+
+#if V8_TYPED_ARRAY_BSWAP_HAS_BUILTIN(__builtin_bswap32)
+#define V8_TYPED_ARRAY_BSWAP32 __builtin_bswap32
+#else
+#define V8_TYPED_ARRAY_BSWAP32(x) \
+({ \
+ uint32_t __x = (x); \
+ ((uint32_t)( \
+ (((uint32_t)(__x) & (uint32_t)0x000000ffUL) << 24) | \
+ (((uint32_t)(__x) & (uint32_t)0x0000ff00UL) << 8) | \
+ (((uint32_t)(__x) & (uint32_t)0x00ff0000UL) >> 8) | \
+ (((uint32_t)(__x) & (uint32_t)0xff000000UL) >> 24) )); \
+})
+#endif
+
+#if V8_TYPED_ARRAY_BSWAP_HAS_BUILTIN16(__builtin_bswap16)
+#define V8_TYPED_ARRAY_BSWAP16 __builtin_bswap16
+#else
+#define V8_TYPED_ARRAY_BSWAP16(x) \
+({ \
+ uint16_t __x = (x); \
+ ((uint16_t)( \
+ (((uint16_t)(__x) & (uint16_t)0x00ffU) << 8) | \
+ (((uint16_t)(__x) & (uint16_t)0xff00U) >> 8) )); \
+})
+#endif
+#endif
+
+
+namespace v8_typed_array {
+
+template <typename T>
+inline T SwapBytes(T x) {
+ typedef char NoSwapBytesForType[sizeof(T) == 0 ? 1 : -1];
@indutny

indutny Jan 11, 2013

Owner

this line ^

+ return 0;
+}
+
+template <>
+inline uint8_t SwapBytes(uint8_t x) { return x; }
+template <>
+inline int8_t SwapBytes(int8_t x) { return x; }
+template <>
+inline uint16_t SwapBytes(uint16_t x) { return V8_TYPED_ARRAY_BSWAP16(x); }
+template <>
+inline int16_t SwapBytes(int16_t x) { return V8_TYPED_ARRAY_BSWAP16(x); }
+template <>
+inline uint32_t SwapBytes(uint32_t x) { return V8_TYPED_ARRAY_BSWAP32(x); }
+template <>
+inline int32_t SwapBytes(int32_t x) { return V8_TYPED_ARRAY_BSWAP32(x); }
+template <>
+inline uint64_t SwapBytes(uint64_t x) { return V8_TYPED_ARRAY_BSWAP64(x); }
+template <>
+inline int64_t SwapBytes(int64_t x) { return V8_TYPED_ARRAY_BSWAP64(x); }
+
+template <>
+inline float SwapBytes(float x) {
+ typedef char VerifySizesAreEqual[sizeof(uint32_t) == sizeof(float) ? 1 : -1];
@indutny

indutny Jan 11, 2013

Owner

@bnoordhuis negative array index broke the build on solaris... it seems to be pretty unobvious for me what this typedef is here for, can you please shed some light on it?

@indutny

indutny Jan 11, 2013

Owner

Correction: negative array size.

@indutny

indutny Jan 11, 2013

Owner

Is it some sort of clever pattern matching?

+ uint32_t swappable;
+ float result;
+ memcpy(&swappable, &x, sizeof(x));
+ swappable = SwapBytes(swappable);
+ memcpy(&result, &swappable, sizeof(x));
+ return result;
+}
+
+template <>
+inline double SwapBytes(double x) {
+ typedef char VerifySizesAreEqual[sizeof(uint64_t) == sizeof(double) ? 1 : -1];
+ uint64_t swappable;
+ double result;
+ memcpy(&swappable, &x, sizeof(x));
+ swappable = SwapBytes(swappable);
+ memcpy(&result, &swappable, sizeof(x));
+ return result;
+}
+
+} // namespace v8_typed_array
+
+#endif // V8_TYPED_ARRAY_BSWAP_H_

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