Disable AVX512 for iOS simulator xcode 9 builds.

iOS simulator has the option to build with xcode instead of clang.
GN use_xcode_clang=true enables the xcode build.
As of version Xcode 9.2, the clang version used does not support
AVX512.  The version reported is version 9, but for normal clang,
version 7 is sufficient to AVX512.
When a version of XCode does support AVX512, the version check can
be updated to allow AVX512 for newer versions of XCode.
with XCode 9.2 the following macro is set.
__APPLE_CC__ 6000

Bug: libyuv:789
Test: gn gen out/Release "--args=is_debug=false target_os=\"ios\" ios_enable_code_signing=false target_cpu=\"x86\" use_xcode_clang=true"
Change-Id: I5a9a0b4a2760c7d09a4bcb464b3668979113b07e
Reviewed-on: https://chromium-review.googlesource.com/991595Reviewed-by: richard winterton <rrwinterton@gmail.com>

README.chromium

 Name: libyuv
 URL: http://code.google.com/p/libyuv/
-Version: 1707
+Version: 1708
 License: BSD
 License File: LICENSE
 

docs/getting_started.md

@@ -98,8 +98,8 @@ arm64
 
 ios simulator
 
-    gn gen out/Release "--args=is_debug=false target_os=\"ios\" ios_enable_code_signing=false target_cpu=\"x86\""
-    gn gen out/Debug "--args=is_debug=true target_os=\"ios\" ios_enable_code_signing=false target_cpu=\"x86\""
+    gn gen out/Release "--args=is_debug=false target_os=\"ios\" ios_enable_code_signing=false use_xcode_clang=true target_cpu=\"x86\""
+    gn gen out/Debug "--args=is_debug=true target_os=\"ios\" ios_enable_code_signing=false use_xcode_clang=true target_cpu=\"x86\""
     ninja -v -C out/Debug libyuv_unittest
     ninja -v -C out/Release libyuv_unittest
 

include/libyuv/row.h

@@ -55,11 +55,12 @@ extern "C" {
 #endif  // clang >= 3.4
 #endif  // __clang__
 
-// clang >= 7.0.0 required for AVX512.
+// clang >= 6.0.0 required for AVX512.
+// TODO(fbarchard): fix xcode 9 ios b/789.
 #if defined(__clang__) && (defined(__x86_64__) || defined(__i386__))
-#if (__clang_major__ >= 7)
+#if (__clang_major__ >= 7) && !defined(__APPLE_EMBEDDED_SIMULATOR__)
 #define CLANG_HAS_AVX512 1
-#endif  // clang >= 6
+#endif  // clang >= 7
 #endif  // __clang__
 
 // Visual C 2012 required for AVX2.
@@ -297,6 +298,7 @@ extern "C" {
 
 // The following are available for AVX512 clang x86 platforms:
 // TODO(fbarchard): Port to GCC and Visual C
+// TODO(fbarchard): re-enable HAS_ARGBTORGB24ROW_AVX512VBMI. Issue libyuv:789
 #if !defined(LIBYUV_DISABLE_X86) &&                                       \
     (defined(__x86_64__) || (defined(__i386__) && !defined(_MSC_VER))) && \
     (defined(CLANG_HAS_AVX512))

include/libyuv/version.h

@@ -11,6 +11,6 @@
 #ifndef INCLUDE_LIBYUV_VERSION_H_
 #define INCLUDE_LIBYUV_VERSION_H_
 
-#define LIBYUV_VERSION 1707
+#define LIBYUV_VERSION 1708
 
 #endif  // INCLUDE_LIBYUV_VERSION_H_

source/row_gcc.cc

@@ -569,8 +569,7 @@ static const ulvec8 kPermARGBToRGB24_2 = {
     36u, 37u, 38u, 40u, 41u, 42u, 44u, 45u, 46u, 48u, 49u,
     50u, 52u, 53u, 54u, 56u, 57u, 58u, 60u, 61u, 62u};
 
-void __attribute__ ((__target__ ("avx512vbmi")))
-  ARGBToRGB24Row_AVX512VBMI(const uint8_t* src, uint8_t* dst, int width) {
+void ARGBToRGB24Row_AVX512VBMI(const uint8_t* src, uint8_t* dst, int width) {
   asm volatile(
       "vmovdqa    %3,%%ymm5                      \n"
       "vmovdqa    %4,%%ymm6                      \n"