Don't set -mfpu=neon globally if the compiler supports neon.

By default only drawhelpers and image loaders will now use neon.
If -mfpu=neon has been explicitly enabled in the mkspec,
QT_ALWAYS_HAVE_NEON will be defined, allowing the use of neon
intrinsics elsewhere.

Task-number: QTBUG-15163
Reviewed-by: Benjamin Poulain <benjamin.poulain@nokia.com>

6 files changed, 7 insertions, 15 deletions

diff --git a/configure b/configure
index a2383005ca..5aab180f32 100755
--- a/configure
+++ b/configure
@@ -3526,7 +3526,7 @@ Usage:  $relconf [-h] [-prefix <dir>] [-prefix-install] [-bindir <dir>] [-libdir
         [-verbose] [-v] [-silent] [-no-nis] [-nis] [-no-cups] [-cups] [-no-iconv]
         [-iconv] [-no-pch] [-pch] [-no-dbus] [-dbus] [-dbus-linked] [-no-gui]
         [-no-separate-debug-info] [-no-mmx] [-no-3dnow] [-no-sse] [-no-sse2]
-        [-no-sse3] [-no-ssse3] [-no-sse4.1] [-no-sse4.2] [-no-avx]
+        [-no-sse3] [-no-ssse3] [-no-sse4.1] [-no-sse4.2] [-no-avx] [-no-neon]
         [-qtnamespace <namespace>] [-qtlibinfix <infix>] [-separate-debug-info] [-armfpa]
         [-no-optimized-qmake] [-optimized-qmake] [-no-xmlpatterns] [-xmlpatterns]
         [-no-multimedia] [-multimedia] [-no-phonon] [-phonon] [-no-phonon-backend] [-phonon-backend]
@@ -3730,6 +3730,7 @@ cat << EOF
     -no-sse4.1.......... Do not compile with use of SSE4.1 instructions.
     -no-sse4.2.......... Do not compile with use of SSE4.2 instructions.
     -no-avx ............ Do not compile with use of AVX instructions.
+    -no-neon ........... Do not compile with use of NEON instructions.
 
     -qtnamespace <name>  Wraps all Qt library code in 'namespace <name> {...}'.
     -qtlibinfix <infix>  Renames all libQt*.so to libQt*<infix>.so.
@@ -4161,8 +4162,6 @@ Qt for Embedded Linux only:
 
     -iwmmxt ............ Compile using the iWMMXt instruction set
                          (available on some XScale CPUs).
-
-    -no-neon ........... Do not compile with use of NEON instructions.
 EOF
 fi
 
diff --git a/src/corelib/corelib.pro b/src/corelib/corelib.pro
index b7d6034609..a0019407b5 100644
--- a/src/corelib/corelib.pro
+++ b/src/corelib/corelib.pro
@@ -37,10 +37,3 @@ symbian: {
     MMP_RULES -= PAGED
     MMP_RULES *= UNPAGED
 }
-
-neon {
-    DEFINES += QT_HAVE_NEON
-    QMAKE_CXXFLAGS *= -mfpu=neon
-}
-
-
diff --git a/src/corelib/tools/qsimd.cpp b/src/corelib/tools/qsimd.cpp
index b2fe2dabad..63ebafbde2 100644
--- a/src/corelib/tools/qsimd.cpp
+++ b/src/corelib/tools/qsimd.cpp
@@ -135,7 +135,7 @@ static inline uint detectProcessorFeatures()
 #if defined(QT_HAVE_IWMMXT)
     // runtime detection only available when running as a previlegied process
     features = IWMMXT;
-#elif defined(QT_HAVE_NEON)
+#elif defined(QT_ALWAYS_HAVE_NEON)
     features = NEON;
 #endif
 
diff --git a/src/corelib/tools/qsimd_p.h b/src/corelib/tools/qsimd_p.h
index 664543b136..87fa7700eb 100644
--- a/src/corelib/tools/qsimd_p.h
+++ b/src/corelib/tools/qsimd_p.h
@@ -105,7 +105,8 @@ QT_BEGIN_HEADER
 #endif // defined(QT_HAVE_SSE2) && (defined(__SSE2__) || defined(Q_CC_MSVC))
 
 // NEON intrinsics
-#if defined(QT_HAVE_NEON)
+#if defined __ARM_NEON__
+#define QT_ALWAYS_HAVE_NEON
 #include <arm_neon.h>
 #endif
 
diff --git a/src/corelib/tools/qstring.cpp b/src/corelib/tools/qstring.cpp
index bfbdb733aa..d4a1248d32 100644
--- a/src/corelib/tools/qstring.cpp
+++ b/src/corelib/tools/qstring.cpp
@@ -3572,7 +3572,7 @@ static QByteArray toLatin1_helper(const QChar *data, int length)
             }
             length = length % 16;
         }
-#elif QT_HAVE_NEON
+#elif QT_ALWAYS_HAVE_NEON
         // Refer to the documentation of the SSE2 implementation
         // this use eactly the same method as for SSE except:
         // 1) neon has unsigned comparison
diff --git a/src/gui/gui.pro b/src/gui/gui.pro
index 90b5de5971..4d51fa8ce3 100644
--- a/src/gui/gui.pro
+++ b/src/gui/gui.pro
@@ -64,13 +64,12 @@ symbian {
 
 neon:*-g++* {
     DEFINES += QT_HAVE_NEON
-    QMAKE_CXXFLAGS *= -mfpu=neon
     HEADERS += $$NEON_HEADERS
     SOURCES += $$NEON_SOURCES
 
     DRAWHELPER_NEON_ASM_FILES = $$NEON_ASM
 
-    neon_compiler.commands = $$QMAKE_CXX -c
+    neon_compiler.commands = $$QMAKE_CXX -c -mfpu=neon
     neon_compiler.commands += $(CXXFLAGS) $(INCPATH) ${QMAKE_FILE_IN} -o ${QMAKE_FILE_OUT}
     neon_compiler.dependency_type = TYPE_C
     neon_compiler.output = ${QMAKE_VAR_OBJECTS_DIR}${QMAKE_FILE_BASE}$${first(QMAKE_EXT_OBJ)}