Restore Neon "detection" in Qt

We don't actually detect whether the compiler can create Neon code or
provides Neon intrinsics. Most of them do, so that test would be mostly
moot. We removed the detection previously because we couldn't
automatically enable Neon due to leakage of instructions outside the
areas protected at runtime.

Instead, we rely on the mkspec properly passing the necessary flags that
enable Neon support.

This commit does not change that. All it does is verify whether the arch
detection found "neon" as part of the target CPU features. In other
words, it moves the test that was in simd.prf to configure.

It does fix the Neon detection in configure.exe, which was always
failing for trying to run a test that didn't exist
(config.tests/unix/neon).

Change-Id: Id561dfb2db7d3dca7b8c29afef63181693bdc0aa
Reviewed-by: Oswald Buddenhagen <oswald.buddenhagen@digia.com>

configure

@@ -4127,6 +4127,16 @@ if [ "$CFG_IWMMXT" = "yes" ]; then
     fi
 fi
 
+# check Neon support
+if [ "$CFG_NEON" = "auto" ]; then
+    # no compile test, just check what the compiler has
+    case "$CFG_CPUFEATURES" in
+        *neon*)
+            CFG_NEON=yes
+            ;;
+    esac
+fi
+
 # detect mips_dsp support
 if [ "$CFG_ARCH" = "mips" ] && [ "${CFG_MIPS_DSP}" = "auto" ]; then
     if "$unixtests/compile.test" "$XQMAKESPEC" "$QMAKE_CONFIG" $OPT_VERBOSE "$relpath" "$outpath" config.tests/unix/mips_dsp "mips_dsp" $L_FLAGS $I_FLAGS $D_FLAGS $l_FLAGS; then
@@ -5634,6 +5644,7 @@ fi
 [ "$CFG_AVX" = "yes" ] && QMAKE_CONFIG="$QMAKE_CONFIG avx"
 [ "$CFG_AVX2" = "yes" ] && QMAKE_CONFIG="$QMAKE_CONFIG avx2"
 [ "$CFG_IWMMXT" = "yes" ] && QMAKE_CONFIG="$QMAKE_CONFIG iwmmxt"
+[ "$CFG_NEON" = "yes" ] && QMAKE_CONFIG="$QMAKE_CONFIG neon"
 if [ "$CFG_ARCH" = "mips" ]; then
     [ "$CFG_MIPS_DSP" = "yes" ] && QMAKE_CONFIG="$QMAKE_CONFIG mips_dsp"
     [ "$CFG_MIPS_DSPR2" = "yes" ] && QMAKE_CONFIG="$QMAKE_CONFIG mips_dspr2"

mkspecs/features/simd.prf

@@ -117,7 +117,7 @@ gcc {       # includes intel_icc and clang variants
         silent:avx2_compiler.commands = @echo compiling[avx2] ${QMAKE_FILE_IN} && $$avx2_compiler.commands
         QMAKE_EXTRA_COMPILERS += avx2_compiler
     }
-    contains(QT_CPU_FEATURES.$$QT_ARCH, neon) {
+    neon {
         HEADERS += $$NEON_HEADERS
 
         neon_compiler.commands = $$QMAKE_CXX -c $(CXXFLAGS)

src/gui/image/image.pri

@@ -78,12 +78,10 @@ contains(QT_CONFIG, jpeg):include($$PWD/qjpeghandler.pri)
 contains(QT_CONFIG, gif):include($$PWD/qgifhandler.pri)
 
 # SIMD
-contains(QT_CPU_FEATURES.$$QT_ARCH, neon) {
-    SOURCES += image/qimage_neon.cpp
-}
 contains(QT_CPU_FEATURES.$$QT_ARCH, sse2) {
     SOURCES += image/qimage_sse2.cpp
     SSSE3_SOURCES += image/qimage_ssse3.cpp
 }
+NEON_SOURCES += image/qimage_neon.cpp
 MIPS_DSPR2_SOURCES += image/qimage_mips_dspr2.cpp
 MIPS_DSPR2_ASM += image/qimage_mips_dspr2_asm.S

src/gui/painting/painting.pri

@@ -97,10 +97,10 @@ contains(QT_CPU_FEATURES.$$QT_ARCH, sse2) {
 }
 IWMMXT_SOURCES += painting/qdrawhelper_iwmmxt.cpp
 
-!ios:contains(QT_CPU_FEATURES.$$QT_ARCH, neon) {
+!ios:neon {
     CONFIG += no_clang_integrated_as
-    SOURCES += painting/qdrawhelper_neon.cpp
-    HEADERS += painting/qdrawhelper_neon_p.h
+    NEON_SOURCES += painting/qdrawhelper_neon.cpp
+    NEON_HEADERS += painting/qdrawhelper_neon_p.h
     NEON_ASM += ../3rdparty/pixman/pixman-arm-neon-asm.S painting/qdrawhelper_neon_asm.S
 }
 

tools/configure/configureapp.cpp

@@ -2280,7 +2280,7 @@ bool Configure::checkAvailability(const QString &part)
         available = (platform() == QNX || platform() == BLACKBERRY)
                     && tryCompileProject("unix/lgmon");
     } else if (part == "NEON") {
-        available = (dictionary["QT_ARCH"] == "arm") && tryCompileProject("unix/neon");
+        available = dictionary["QT_CPU_FEATURES"].contains("neon");
     } else if (part == "FONT_CONFIG") {
         available = tryCompileProject("unix/fontconfig");
     }