Add a public qsimd.h header

This header only covers a part of what qsimd_p.h does, namely
the compile time detection of simd extensions.

Change-Id: I05f1d987f194a5bec335f2405cc2846fbaa88b66
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>

5 files changed, 161 insertions, 22 deletions

diff --git a/src/corelib/.prev_CMakeLists.txt b/src/corelib/.prev_CMakeLists.txt
index 73fc757c73..15b76decd5 100644
--- a/src/corelib/.prev_CMakeLists.txt
+++ b/src/corelib/.prev_CMakeLists.txt
@@ -29,7 +29,7 @@ qt_add_module(Core
         global/qoperatingsystemversion.cpp global/qoperatingsystemversion.h global/qoperatingsystemversion_p.h
         global/qprocessordetection.h
         global/qrandom.cpp global/qrandom.h global/qrandom_p.h
-        global/qsimd.cpp global/qsimd_p.h
+        global/qsimd.cpp global/qsimd.h global/qsimd_p.h
         global/qsysinfo.h
         global/qsystemdetection.h
         global/qtypeinfo.h
diff --git a/src/corelib/CMakeLists.txt b/src/corelib/CMakeLists.txt
index 53d8de6668..e71c8c8c2d 100644
--- a/src/corelib/CMakeLists.txt
+++ b/src/corelib/CMakeLists.txt
@@ -45,7 +45,7 @@ qt_add_module(Core
         global/qoperatingsystemversion.cpp global/qoperatingsystemversion.h global/qoperatingsystemversion_p.h
         global/qprocessordetection.h
         global/qrandom.cpp global/qrandom.h global/qrandom_p.h
-        global/qsimd.cpp global/qsimd_p.h
+        global/qsimd.cpp global/qsimd.h global/qsimd_p.h
         global/qsysinfo.h
         global/qsystemdetection.h
         global/qtypeinfo.h
diff --git a/src/corelib/global/global.pri b/src/corelib/global/global.pri
index 389e866987..6ba39d41bd 100644
--- a/src/corelib/global/global.pri
+++ b/src/corelib/global/global.pri
@@ -20,6 +20,7 @@ HEADERS +=  \
         global/qtypeinfo.h \
         global/qsysinfo.h \
         global/qisenum.h \
+        global/qsimd.h \
         global/qsimd_p.h \
         global/qtypetraits.h \
         global/qflags.h \
diff --git a/src/corelib/global/qsimd.h b/src/corelib/global/qsimd.h
new file mode 100644
index 0000000000..325faf123a
--- /dev/null
+++ b/src/corelib/global/qsimd.h
@@ -0,0 +1,157 @@
+/****************************************************************************
+**
+** Copyright (C) 2020 The Qt Company Ltd.
+** Copyright (C) 2018 Intel Corporation.
+** Contact: https://www.qt.io/licensing/
+**
+** This file is part of the QtCore module of the Qt Toolkit.
+**
+** $QT_BEGIN_LICENSE:LGPL$
+** Commercial License Usage
+** Licensees holding valid commercial Qt licenses may use this file in
+** accordance with the commercial license agreement provided with the
+** Software or, alternatively, in accordance with the terms contained in
+** a written agreement between you and The Qt Company. For licensing terms
+** and conditions see https://www.qt.io/terms-conditions. For further
+** information use the contact form at https://www.qt.io/contact-us.
+**
+** GNU Lesser General Public License Usage
+** Alternatively, this file may be used under the terms of the GNU Lesser
+** General Public License version 3 as published by the Free Software
+** Foundation and appearing in the file LICENSE.LGPL3 included in the
+** packaging of this file. Please review the following information to
+** ensure the GNU Lesser General Public License version 3 requirements
+** will be met: https://www.gnu.org/licenses/lgpl-3.0.html.
+**
+** GNU General Public License Usage
+** Alternatively, this file may be used under the terms of the GNU
+** General Public License version 2.0 or (at your option) the GNU General
+** Public license version 3 or any later version approved by the KDE Free
+** Qt Foundation. The licenses are as published by the Free Software
+** Foundation and appearing in the file LICENSE.GPL2 and LICENSE.GPL3
+** included in the packaging of this file. Please review the following
+** information to ensure the GNU General Public License requirements will
+** be met: https://www.gnu.org/licenses/gpl-2.0.html and
+** https://www.gnu.org/licenses/gpl-3.0.html.
+**
+** $QT_END_LICENSE$
+**
+****************************************************************************/
+
+#ifndef QSIMD_H
+#define QSIMD_H
+
+#include <QtCore/qglobal.h>
+
+/*
+ * qconfig.h defines the QT_COMPILER_SUPPORTS_XXX macros.
+ * They mean the compiler supports the necessary flags and the headers
+ * for the x86 and ARM intrinsics.
+ *
+ * Supported instruction set extensions are:
+ *   Flag      | Arch
+ *  neon       | ARM
+ *  mips_dsp   | mips
+ *  mips_dspr2 | mips
+ *  sse2       | x86
+ *  sse4_1     | x86
+ *  sse4_2     | x86
+ *  avx        | x86
+ *
+ * Code can use the following constructs to determine compiler support & status:
+ * - #if QT_COMPILER_USES(XXX) (e.g: #if QT_COMPILER_USES(neon) or QT_COMPILER_USES(sse4_1)
+ *   If this test passes, then the compiler is already generating code using the
+ *   given instruction set. The intrinsics for those instructions are
+ *   #included and can be used without restriction or runtime check.
+ *
+ * Code that requires runtime detection and different code paths at runtime is
+ * currently not supported here, have a look at qsimd_p.h for support.
+ */
+
+#define QT_COMPILER_USES(feature) (1/QT_COMPILER_USES_##feature == 1)
+
+#if defined(Q_PROCESSOR_ARM) && defined(__ARM_NEON) || defined(__ARM_NEON__)
+#  include <arm_neon.h>
+#  define QT_COMPILER_USES_neon 1
+#else
+#  define QT_COMPILER_USES_neon -1
+#endif
+
+#if defined(Q_PROCESSOR_MIPS) && (defined(__MIPS_DSP__) || (defined(__mips_dsp) && defined(Q_PROCESSOR_MIPS_32)))
+#  define QT_COMPILER_USES_mips_dsp 1
+#else
+#  define QT_COMPILER_USES_mips_dsp -1
+#endif
+
+#if defined(Q_PROCESSOR_MIPS) && (defined(__MIPS_DSPR2__) || (defined(__mips_dspr2) && defined(Q_PROCESSOR_MIPS_32)))
+#  define QT_COMPILER_USES_mips_dspr2 1
+#else
+#  define QT_COMPILER_USES_mips_dspr2 -1
+#endif
+
+#if defined(Q_PROCESSOR_X86)
+#if defined(Q_CC_MSVC)
+// MSVC doesn't define __SSE2__, so do it ourselves
+#  if (defined(_M_X64) || _M_IX86_FP >= 2)
+#    define __SSE__ 1
+#    define __SSE2__ 1
+#  endif
+#if (defined(_M_AVX) || defined(__AVX__))
+// Visual Studio defines __AVX__ when /arch:AVX is passed, but not the earlier macros
+// See: https://msdn.microsoft.com/en-us/library/b0084kay.aspx
+#    define __SSE3__                        1
+#    define __SSSE3__                       1
+#    define __SSE4_1__                      1
+#    define __SSE4_2__                      1
+#    ifndef __AVX__
+#      define __AVX__                       1
+#    endif
+#  endif
+#  ifdef __SSE2__
+#    define QT_VECTORCALL __vectorcall
+#  endif
+#endif
+#endif
+
+#if defined(Q_PROCESSOR_X86) && defined(__SSE2__)
+#  include <immintrin.h>
+#  define QT_COMPILER_USES_sse2 1
+#else
+#  define QT_COMPILER_USES_sse2 -1
+#endif
+
+#if defined(Q_PROCESSOR_X86) && defined(__SSE3__)
+#  define QT_COMPILER_USES_sse3 1
+#else
+#  define QT_COMPILER_USES_sse3 -1
+#endif
+
+#if defined(Q_PROCESSOR_X86) && defined(__SSSE3__)
+#  define QT_COMPILER_USES_ssse3 1
+#else
+#  define QT_COMPILER_USES_ssse3 -1
+#endif
+
+#if defined(Q_PROCESSOR_X86) && defined(__SSE4_1__)
+#  define QT_COMPILER_USES_sse4_1 1
+#else
+#  define QT_COMPILER_USES_sse4_1 -1
+#endif
+
+#if defined(Q_PROCESSOR_X86) && defined(__SSE4_2__)
+#  define QT_COMPILER_USES_sse4_2 1
+#else
+#  define QT_COMPILER_USES_sse4_2 -1
+#endif
+
+#if defined(Q_PROCESSOR_X86) && defined(__AVX__)
+#  define QT_COMPILER_USES_avx 1
+#else
+#  define QT_COMPILER_USES_avx -1
+#endif
+
+#ifndef QT_VECTORCALL
+#define QT_VECTORCALL
+#endif
+
+#endif // QSIMD_H
diff --git a/src/corelib/global/qsimd_p.h b/src/corelib/global/qsimd_p.h
index 26e98c4542..2f2d49348f 100644
--- a/src/corelib/global/qsimd_p.h
+++ b/src/corelib/global/qsimd_p.h
@@ -53,6 +53,7 @@
 //
 
 #include <QtCore/private/qglobal_p.h>
+#include <QtCore/qsimd.h>
 
 /*
  * qt_module_config.prf defines the QT_COMPILER_SUPPORTS_XXX macros.
@@ -183,12 +184,6 @@
 #  if defined(Q_CC_MSVC) && (defined(_M_X64) || _M_IX86_FP >= 2)
 // MSVC doesn't define __SSE2__, so do it ourselves
 #    define __SSE__                         1
-#    define __SSE2__                        1
-#  endif
-
-#  ifdef __SSE2__
-// #include the intrinsics
-#    include <immintrin.h>
 #  endif
 
 #  if defined(Q_CC_GNU) && !defined(Q_CC_INTEL)
@@ -196,19 +191,6 @@
 #    include <x86intrin.h>
 #  endif
 
-#  if defined(Q_CC_MSVC) && (defined(_M_AVX) || defined(__AVX__))
-// Visual Studio defines __AVX__ when /arch:AVX is passed, but not the earlier macros
-// See: https://msdn.microsoft.com/en-us/library/b0084kay.aspx
-#    define __SSE3__                        1
-#    define __SSSE3__                       1
-// no Intel CPU supports SSE4a, so don't define it
-#    define __SSE4_1__                      1
-#    define __SSE4_2__                      1
-#    ifndef __AVX__
-#      define __AVX__                       1
-#    endif
-#  endif
-
 #  if defined(__SSE4_2__) && defined(QT_COMPILER_SUPPORTS_SIMD_ALWAYS) && (defined(Q_CC_INTEL) || defined(Q_CC_MSVC))
 // POPCNT instructions:
 // All processors that support SSE4.2 support POPCNT
@@ -287,7 +269,6 @@ QT_END_NAMESPACE
 // NEON intrinsics
 // note: as of GCC 4.9, does not support function targets for ARM
 #if defined(__ARM_NEON) || defined(__ARM_NEON__)
-#include <arm_neon.h>
 #define QT_FUNCTION_TARGET_STRING_NEON      "+neon" // unused: gcc doesn't support function targets on non-aarch64, and on Aarch64 NEON is always available.
 #ifndef __ARM_NEON__
 // __ARM_NEON__ is not defined on AArch64, but we need it in our NEON detection.