Add support for single-file multi-target intrinsics in Qt

GCC 4.9 now allows us to #include any and all intrinsics headers, not
just the one for which we're compiling code, a behavior that ICC and
MSVC have had for some time. With that, we're able to have the functions
for different targets in the same source file. See the GCC manual:
  http://gcc.gnu.org/onlinedocs/gcc/Function-Multiversioning.html

This functionality is notified by the QT_COMPILER_SUPPORTS_HERE(XXX)
macro, which indicates that all the intrinsics from
QT_COMPILER_SUPPORTS_xxx are available and enabled. To complement, a
QT_COMPILER_SUPPORTS(XXX) macro is also added.

Unlike ICC and MSVC, GCC requires a special function attribute, which
will also cause code optimization. That's the QT_FUNCTION_TARGET macro.

Note: because of the absence of the target attribute, ICC and MSVC will
not generate instructions with the VEX prefix unless they only exist
with the VEX prefix or if -mavx / -arch:AVX are enabled.

Change-Id: I0c1880c20324bd8e0fc68a863e36d1fa7755dff0
Reviewed-by: Allan Sandfeld Jensen <allan.jensen@digia.com>

1 files changed, 1 insertions, 1 deletions

diff --git a/configure b/configure
index bb52464e52..9bb09bc36d 100755
--- a/configure
+++ b/configure
@@ -6035,7 +6035,7 @@ for SUBARCH in SSE2 SSE3 SSSE3 SSE4_1 SSE4_2 AVX AVX2 \
     eval "VAL=\$CFG_$SUBARCH"
     case "$VAL" in
         yes)
-            echo "#define QT_COMPILER_SUPPORTS_$SUBARCH" \
+            echo "#define QT_COMPILER_SUPPORTS_$SUBARCH 1" \
                 >>"$outpath/src/corelib/global/qconfig.h.new"
             ;;
     esac