1berry/qtbase
1
0
Fork 0
Code Issues Pull Requests Actions Packages Projects Releases Wiki Activity

Fix detection of F16C for the Intel compiler (again) and Visual Studio

Browse Source 
Neither the Intel compiler nor Visual C++ have a dedicated switch to
enable F16C support, like GCC and Clang do. So we used the AVX switch
for that in commit 8241d51f7049d48912ce25fbd49ef4d22c58e340, as it was
the closest, lowest denominator. That was incorrect and insufficient.

The Intel compiler silently miscompiles the intrinsics with -xAVX,
making calls to out-of-line functions like _mm_cvtps_ph, which don't
exist. So we actually have to use AVX2 support to generate correct code.
That might be a problem later, since Ivy Bridge supports F16C but not
AVX2.

Visual C++ is able to generate F16C code with just -arch:AVX.

Either way, since there's no dedicated command-line switch, there's also
no dedicated preprocessor macro. We're using __AVX2__ for both
compilers, as that's a sufficient condition to indicate a processor that
supports F16C.

Change-Id: I27b55fdf514247549455fffd14b205b8d8b86da7
Reviewed-by: Allan Sandfeld Jensen <allan.jensen@qt.io>
This commit is contained in:
Thiago Macieira 2017-04-03 16:05:18 -07:00
parent c817b33b45
commit 280e321e52
5 changed files with 7 additions and 5 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

2
mkspecs/common/msvc-version.conf
View File

@ -49,6 +49,8 @@ greaterThan(QMAKE_MSC_VER, 1799) {
QMAKE_CFLAGS += -FS
QMAKE_CXXFLAGS += -FS
QMAKE_CFLAGS_F16C = -arch:AVX
equals(QMAKE_MSC_VER, 1800) {
QMAKE_CFLAGS_RELEASE += -Zc:strictStrings
QMAKE_CFLAGS_RELEASE_WITH_DEBUGINFO += -Zc:strictStrings

2
mkspecs/linux-icc/qmake.conf
View File

@ -42,7 +42,7 @@ QMAKE_CFLAGS_AVX512PF += -xMIC-AVX512
QMAKE_CFLAGS_AVX512DQ += -xCORE-AVX512
QMAKE_CFLAGS_AVX512BW += -xCORE-AVX512
QMAKE_CFLAGS_AVX512VL += -xCORE-AVX512
QMAKE_CFLAGS_F16C += -xAVX
QMAKE_CFLAGS_F16C += $$QMAKE_CFLAGS_AVX2
QMAKE_CXX = icpc
QMAKE_CXXFLAGS = $$QMAKE_CFLAGS

2
mkspecs/macx-icc/qmake.conf
View File

@ -40,7 +40,7 @@ QMAKE_CFLAGS_AVX512PF += -xMIC-AVX512
QMAKE_CFLAGS_AVX512DQ += -xCORE-AVX512
QMAKE_CFLAGS_AVX512BW += -xCORE-AVX512
QMAKE_CFLAGS_AVX512VL += -xCORE-AVX512
QMAKE_CFLAGS_F16C += -xAVX
QMAKE_CFLAGS_F16C += $$QMAKE_CFLAGS_AVX2
QMAKE_CXX = icpc
QMAKE_CXXFLAGS = $$QMAKE_CFLAGS

2
mkspecs/win32-icc/qmake.conf
View File

@ -33,7 +33,7 @@ QMAKE_CFLAGS_AVX512PF += -QxMIC-AVX512
QMAKE_CFLAGS_AVX512DQ += -QxCORE-AVX512
QMAKE_CFLAGS_AVX512BW += -QxCORE-AVX512
QMAKE_CFLAGS_AVX512VL += -QxCORE-AVX512
QMAKE_CFLAGS_F16C = -QxAVX
QMAKE_CFLAGS_F16C = $$QMAKE_CFLAGS_AVX2
QMAKE_CXX = $$QMAKE_CC
QMAKE_CXXFLAGS = $$QMAKE_CFLAGS /Zc:forScope

4
src/corelib/global/qfloat16.h
View File

@ -117,7 +117,7 @@ QT_WARNING_PUSH
QT_WARNING_DISABLE_CLANG("-Wc99-extensions")
inline qfloat16::qfloat16(float f) Q_DECL_NOTHROW
{
#if defined(QT_COMPILER_SUPPORTS_F16C) && defined(__F16C__)
#if defined(QT_COMPILER_SUPPORTS_F16C) && (defined(__F16C__) || defined(__AVX2__))
__m128 packsingle = _mm_set_ss(f);
__m128i packhalf = _mm_cvtps_ph(packsingle, 0);
b16 = _mm_extract_epi16(packhalf, 0);
@ -135,7 +135,7 @@ QT_WARNING_POP
inline qfloat16::operator float() const Q_DECL_NOTHROW
{
#if defined(QT_COMPILER_SUPPORTS_F16C) && defined(__F16C__)
#if defined(QT_COMPILER_SUPPORTS_F16C) && (defined(__F16C__) || defined(__AVX2__))
__m128i packhalf = _mm_cvtsi32_si128(b16);
__m128 packsingle = _mm_cvtph_ps(packhalf);
return _mm_cvtss_f32(packsingle);