dev-qt/qtscript LTO build fix

[pchome]

Based on https://bugs.webkit.org/show_bug.cgi?id=56088

--- a/src/3rdparty/javascriptcore/JavaScriptCore/jit/JITStubs.h 2017-10-09 14:40:55.050363361 +0300
+++ b/src/3rdparty/javascriptcore/JavaScriptCore/jit/JITStubs.h 2017-10-09 14:45:50.271354448 +0300
@@ -316,7 +316,7 @@
     EncodedJSValue JIT_STUB cti_op_to_primitive(STUB_ARGS_DECLARATION);
     EncodedJSValue JIT_STUB cti_op_typeof(STUB_ARGS_DECLARATION);
     EncodedJSValue JIT_STUB cti_op_urshift(STUB_ARGS_DECLARATION);
-    EncodedJSValue JIT_STUB cti_vm_throw(STUB_ARGS_DECLARATION);
+    EncodedJSValue JIT_STUB cti_vm_throw(STUB_ARGS_DECLARATION) __attribute__((used));
     EncodedJSValue JIT_STUB cti_to_object(STUB_ARGS_DECLARATION);
     JSObject* JIT_STUB cti_op_construct_JSConstruct(STUB_ARGS_DECLARATION);
     JSObject* JIT_STUB cti_op_new_array(STUB_ARGS_DECLARATION);

I don't tested it further but at least it builds w/ this patch in /etc/portage/patches/dev-qt/qtscript/

[pchome]

Ok, I played a little with Qt-5.9.2 today and finally it full LTOed for me.

Here the installed packages list:

$ eix -I --only-names dev-qt/*

dev-qt/designer
dev-qt/linguist-tools
dev-qt/qdbus
dev-qt/qtchooser
dev-qt/qtconcurrent
dev-qt/qtcore
dev-qt/qtdbus
dev-qt/qtdeclarative
dev-qt/qtgraphicaleffects
dev-qt/qtgui
dev-qt/qtimageformats
dev-qt/qtlockedfile
dev-qt/qtmultimedia
dev-qt/qtnetwork
dev-qt/qtopengl
dev-qt/qtpaths
dev-qt/qtprintsupport
dev-qt/qtquickcontrols
dev-qt/qtquickcontrols2
dev-qt/qtscript
dev-qt/qtsingleapplication
dev-qt/qtsql
dev-qt/qtsvg
dev-qt/qttest
dev-qt/qtwayland
dev-qt/qtwidgets
dev-qt/qtx11extras
dev-qt/qtxml
dev-qt/qtxmlpatterns

Notes:

• some packages affected by strip problem so I tested STRIP_MASK="*.a" env var on them and this trick fixes build (dev-qt/qtdeclarative used by dev-qt/linguist-tools and dev-qt/qtgui used by dev-qt/qtwayland).
  It's like FEATURES="${FEATURES} nostrip" but only *.a files remain unstripped after installation (checked) + ( https://forums.gentoo.org/viewtopic-p-8124664-highlight-stripmask.html?sid=348bc8f7ccf9d0798f0366ff43423f01#8124664 ).
• dev-qt/qtscript patched
• dev-qt/qtwidgets build problem w/ USE=gtk ( https://archives.gentoo.org/gentoo-user/message/f84142041a4c836698411687db50a053 )
• dev-qt/qtcore *FLAGS ignored while cmake/* directory make process which leads to no-LTO objects linking w/ -flto later. While all *FLAGS redefined there the EXTRA_CXXFLAGS and EXTRA_LFLAGS not used and still available:
  CXXFLAGS = $(EXTRA_CXXFLAGS) $(CONFIG_CXXFLAGS) $(CPPFLAGS)
LFLAGS = $(EXTRA_LFLAGS) $(CONFIG_LFLAGS)
  So adding them to env did the trick:
  EXTRA_CXXFLAGS="${CXXFLAGS}"
EXTRA_LFLAGS="${LDFLAGS}"
• dev-qt/qtcore w/ STRIP_MASK="*.a" as it contains *.a files, but seems still not required by currently installed packages.

FYI

[InBetweenNames]

While I'm not convinced that the lack of a strip plugin is a problem as of yet, I do find this very encouraging. It sounds like a couple more upstream patches would get all of Qt built using LTO. Nicely done! I'll leave this issue open for more discussion on this.

[pchome]

dev-qt/designer is one more package I need to rebuild w/ STRIP_MASK="*.a" for kde-plasma/kwin-5.11.0::kde
So I decided to add STRIP_MASK="*.a" in my make.conf and the only package.env redefinitions left is:

dev-qt/qtcore +extra-flags-var
net-misc/openssh -lto
media-sound/pulseaudio +cv-linker-pipe

done:
$ grep flto /var/db/pkg/*/*/CFLAGS | wc -l
340
todo:
$ grep -v flto /var/db/pkg/*/*/CFLAGS | wc -l
687

[InBetweenNames]

With the info here, I was able to reproduce this. Only two exceptions (not listed here): qtwebkit and qtwebengine.

[InBetweenNames]

qtscript LTO fix works on 5.11.2, it has been re-enabled in master.

[InBetweenNames]

Had to revert the LTO fix again -- it was causing crashes in kwin.