i965: Build the driver into a shared mesa_dri_drivers.so .

Previously, we've split things such that mesa core is in libdricore,
exposing the whole Mesa core interface in the global namespace, and the
i965_dri.so code all links against that.  Along with polluting application
namespace terribly, it requires extra PLT indirections and prevents LTO.

Instead, we can build all of the driver contents into the same .so with
just a few symbols exposed to be referenced from the actual driver .so
file, allowing LTO and reducing our exposed symbol count massively.

FPS improvement on GLB2.7 with INTEL_NO_HW=1: 2.61061% +/- 1.16957% (n=50)
(without LTO, just the PLT reductions from this commit)

Note that the X Server requires commit
7ecfab47eb221dbb996ea6c033348b8eceaeb893 to successfully load this driver!

v2: Set a global driverAPI variable so loaders don't have to update to
    createNewScreen2() (though they may want to for thread safety).
v3: Drop AM_CPPFLAGS addition (Emil pointed out I'd missed some cflags
    that would be necessary, though only if we actually relied on them).
v4: Fix install with DESTDIR set.

Reviewed-by: Matt Turner <mattst88@gmail.com> (v1)
Reviewed-by: Emil Velikov <emil.l.velikov@gmail.com> (v2)

configure.ac

@@ -711,8 +711,6 @@ fi
 AM_CONDITIONAL(HAVE_DRI_GLX, test "x$enable_glx" = xyes -a \
                                   "x$enable_dri" = xyes)
 AM_CONDITIONAL(HAVE_DRI, test "x$enable_dri" = xyes)
-AM_CONDITIONAL(NEED_LIBMESA, test "x$enable_xlib_glx" = xyes -o \
-                                  "x$enable_osmesa" = xyes)
 
 AC_ARG_ENABLE([shared-glapi],
     [AS_HELP_STRING([--enable-shared-glapi],
@@ -864,8 +862,6 @@ AC_SUBST([GLESv1_CM_PC_LIB_PRIV])
 AC_SUBST([GLESv2_LIB_DEPS])
 AC_SUBST([GLESv2_PC_LIB_PRIV])
 
-DRI_LIB_DEPS="\$(top_builddir)/src/mesa/libdricore/libdricore${VERSION}.la"
-
 AC_SUBST([HAVE_XF86VIDMODE])
 
 dnl
@@ -1039,10 +1035,32 @@ if test "x$enable_dri" = xyes; then
 
     DRI_DRIVER_LDFLAGS="-module -avoid-version -shared -Wl,-Bsymbolic"
 fi
-AM_CONDITIONAL(NEED_LIBDRICORE, test -n "$DRI_DIRS")
+
+enable_dricore=no
+enable_megadriver=no
+for driver in $DRI_DIRS; do
+    if test $driver != "i965"; then
+        enable_dricore=yes
+    else
+        enable_megadriver=yes
+    fi
+done
+
+# megadriver wants to use libmesa.la, while non-megadrivers want to
+# automatically get libdricore.  Some day hopefully we'll transition
+# everything to megadriver.
+MEGADRIVER_DRI_LIB_DEPS=$DRI_LIB_DEPS
+DRI_LIB_DEPS="\$(top_builddir)/src/mesa/libdricore/libdricore${VERSION}.la $DRI_LIB_DEPS"
+
+AM_CONDITIONAL(NEED_LIBDRICORE, test "x$enable_dricore" = xyes)
+AM_CONDITIONAL(NEED_MEGADRIVER, test "x$enable_megadriver" = xyes)
+AM_CONDITIONAL(NEED_LIBMESA, test "x$enable_xlib_glx" = xyes -o \
+                                  "x$enable_osmesa" = xyes -o \
+                                  "x$enable_megadriver" = xyes)
 AC_SUBST([EXPAT_INCLUDES])
 AC_SUBST([DRI_LIB_DEPS])
 AC_SUBST([DRI_DRIVER_LDFLAGS])
+AC_SUBST([MEGADRIVER_DRI_LIB_DEPS])
 AC_SUBST([GALLIUM_DRI_LIB_DEPS])
 
 case $DRI_DIRS in
@@ -1946,6 +1964,7 @@ AC_SUBST([ELF_LIB])
 AM_CONDITIONAL(NEED_LIBPROGRAM, test "x$with_gallium_drivers" != x -o \
                                      "x$enable_xlib_glx" = xyes -o \
                                      "x$enable_osmesa" = xyes -o \
+                                     "x$enable_megadriver" = xyes -o \
                                      "x$enable_gallium_osmesa" = xyes)
 AM_CONDITIONAL(HAVE_X11_DRIVER, test "x$enable_xlib_glx" = xyes)
 AM_CONDITIONAL(HAVE_OSMESA, test "x$enable_osmesa" = xyes)

src/mesa/drivers/dri/Makefile.am

@@ -1,4 +1,8 @@
+dridir = $(DRI_DRIVER_INSTALL_DIR)
+
 SUBDIRS =
+MEGADRIVERS =
+MEGADRIVERS_DEPS =
 
 SUBDIRS+=common
 
@@ -7,7 +11,9 @@ SUBDIRS+=i915
 endif
 
 if HAVE_I965_DRI
-SUBDIRS+=i965
+SUBDIRS += i965
+MEGADRIVERS_DEPS += i965/libi965_dri.la
+MEGADRIVERS += i965_dri.so
 endif
 
 if HAVE_NOUVEAU_DRI
@@ -31,3 +37,42 @@ pkgconfig_DATA = dri.pc
 
 driincludedir = $(includedir)/GL/internal
 driinclude_HEADERS = $(top_srcdir)/include/GL/internal/dri_interface.h
+
+nodist_EXTRA_mesa_dri_drivers_la_SOURCES = dummy.cpp
+mesa_dri_drivers_la_SOURCES =
+mesa_dri_drivers_la_LDFLAGS = \
+        -module -avoid-version -shared \
+        -Wl,-Bsymbolic \
+        $()
+mesa_dri_drivers_la_LIBADD = \
+        ../../libmesa.la \
+        common/libmegadriver_stub.la \
+        common/libdricommon.la \
+        $(MEGADRIVERS_DEPS) \
+        $(MEGADRIVER_DRI_LIB_DEPS) \
+        $()
+
+if NEED_MEGADRIVER
+dri_LTLIBRARIES = mesa_dri_drivers.la
+
+# Add a link to allow setting LD_LIBRARY_PATH/LIBGL_DRIVERS_PATH to /lib of the build tree.
+all-local: mesa_dri_drivers.la
+	$(MKDIR_P) $(top_builddir)/$(LIB_DIR);
+	$(AM_V_GEN)ln -f .libs/mesa_dri_drivers.so \
+			 $(top_builddir)/$(LIB_DIR)/mesa_dri_drivers.so;
+	$(AM_V_GEN)for i in $(MEGADRIVERS); do \
+		ln -f $(top_builddir)/$(LIB_DIR)/mesa_dri_drivers.so \
+		      $(top_builddir)/$(LIB_DIR)/$$i; \
+	done;
+
+# hardlink each megadriver instance, but don't actually have
+# mesa_dri_drivers.so in the set of final installed files.
+install-data-hook:
+	for i in $(MEGADRIVERS); do \
+		ln -f $(DESTDIR)$(dridir)/mesa_dri_drivers.so \
+		      $(DESTDIR)$(dridir)/$$i; \
+	done;
+	$(RM) -f $(DESTDIR)$(dridir)/mesa_dri_drivers.so
+	$(RM) -f $(DESTDIR)$(dridir)/mesa_dri_drivers.la
+
+endif

src/mesa/drivers/dri/common/Makefile.am

@@ -32,6 +32,7 @@ AM_CFLAGS = \
 
 noinst_LTLIBRARIES = \
 	libdricommon.la \
+	libmegadriver_stub.la \
 	libdri_test_stubs.la
 
 libdricommon_la_SOURCES = \
@@ -43,4 +44,6 @@ libdri_test_stubs_la_SOURCES = \
 	dri_test.c
 libdri_test_stubs_la_CFLAGS = $(AM_CFLAGS) -DNO_MAIN
 
+libmegadriver_stub_la_SOURCES = megadriver_stub.c
+
 sysconf_DATA = drirc

src/mesa/drivers/dri/common/dri_util.c

@@ -81,6 +81,23 @@ setupLoaderExtensions(__DRIscreen *psp,
     }
 }
 
+/**
+ * This pointer determines which driver API we'll use in the case of the
+ * loader not passing us an explicit driver extensions list (that would,
+ * itself, contain a pointer to a driver API.)
+ *
+ * A driver's driDriverGetExtensions_drivername() can update this pointer to
+ * what it's returning, and a loader that is ignorant of createNewScreen2()
+ * will get the correct driver screen created, as long as no other
+ * driDriverGetExtensions() happened in between the first one and the
+ * createNewScreen().
+ *
+ * This allows the X Server to not require the significant dri_interface.h
+ * updates for doing createNewScreen2(), which would discourage backporting of
+ * the X Server patches to support the new loader interface.
+ */
+const struct __DriverAPIRec *globalDriverAPI = &driDriverAPI;
+
 /**
  * This is the first entrypoint in the driver called by the DRI driver loader
  * after dlopen()ing it.
@@ -102,7 +119,7 @@ dri2CreateNewScreen2(int scrn, int fd,
 	return NULL;
 
     /* By default, use the global driDriverAPI symbol (non-megadrivers). */
-    psp->driver = &driDriverAPI;
+    psp->driver = globalDriverAPI;
 
     /* If the driver exposes its vtable through its extensions list
      * (megadrivers), use that instead.

src/mesa/drivers/dri/common/dri_util.h

@@ -116,7 +116,7 @@ struct __DriverAPIRec {
 };
 
 extern const struct __DriverAPIRec driDriverAPI;
-
+extern const struct __DriverAPIRec *globalDriverAPI;
 
 /**
  * Per-screen private driver information.

src/mesa/drivers/dri/common/megadriver_stub.c

@@ -0,0 +1,41 @@
+/*
+ * Copyright © 2013 Intel Corporation
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a
+ * copy of this software and associated documentation files (the "Software"),
+ * to deal in the Software without restriction, including without limitation
+ * the rights to use, copy, modify, merge, publish, distribute, sublicense,
+ * and/or sell copies of the Software, and to permit persons to whom the
+ * Software is furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice (including the next
+ * paragraph) shall be included in all copies or substantial portions of the
+ * Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
+ * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
+ * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
+ * IN THE SOFTWARE.
+ */
+
+#include <stdio.h>
+#include "dri_util.h"
+
+static const
+__DRIconfig **stub_error_init_screen(__DRIscreen *psp)
+{
+   fprintf(stderr, "An updated DRI driver loader (libGL.so or X Server) is "
+           "required for this Mesa driver.\n");
+   return NULL;
+}
+
+/**
+ * This is a stub driDriverAPI that is referenced by dri_util.c but should
+ * never be used.
+ */
+const struct __DriverAPIRec driDriverAPI = {
+   .InitScreen = stub_error_init_screen,
+};

src/mesa/drivers/dri/i965/Makefile.am

@@ -38,30 +38,19 @@ AM_CFLAGS = \
 
 AM_CXXFLAGS = $(AM_CFLAGS)
 
-dridir = $(DRI_DRIVER_INSTALL_DIR)
-
 noinst_LTLIBRARIES = libi965_dri.la
-dri_LTLIBRARIES = i965_dri.la
-
 libi965_dri_la_SOURCES = $(i965_FILES)
-
-# list of libs to be linked against by i965_dri.so and i965 test programs.
-COMMON_LIBS = \
-	libi965_dri.la \
-	../common/libdricommon.la \
-	$(DRI_LIB_DEPS) \
-	$(INTEL_LIBS)
+libi965_dri_la_LIBADD = $(INTEL_LIBS)
 
 TEST_LIBS = \
-	$(COMMON_LIBS) \
+	libi965_dri.la \
+	../common/libdricommon.la \
+	../common/libmegadriver_stub.la \
+	$(MEGADRIVER_DRI_LIB_DEPS) \
+        ../../../libmesa.la \
         -lrt \
 	../common/libdri_test_stubs.la
 
-i965_dri_la_SOURCES =
-nodist_EXTRA_i965_dri_la_SOURCES = dummy2.cpp
-i965_dri_la_LIBADD = $(COMMON_LIBS)
-i965_dri_la_LDFLAGS = $(DRI_DRIVER_LDFLAGS)
-
 TESTS = \
         test_eu_compact \
         test_vec4_register_coalesce
@@ -77,9 +66,3 @@ test_eu_compact_SOURCES = \
 	test_eu_compact.c
 nodist_EXTRA_test_eu_compact_SOURCES = dummy.cpp
 test_eu_compact_LDADD = $(TEST_LIBS)
-
-# Provide compatibility with scripts for the old Mesa build system for
-# a while by putting a link to the driver into /lib of the build tree.
-all-local: i965_dri.la
-	$(MKDIR_P) $(top_builddir)/$(LIB_DIR);
-	ln -f .libs/i965_dri.so $(top_builddir)/$(LIB_DIR)/i965_dri.so;

src/mesa/drivers/dri/i965/intel_screen.c

@@ -1314,7 +1314,7 @@ intelReleaseBuffer(__DRIscreen *screen, __DRIbuffer *buffer)
 }
 
 
-const struct __DriverAPIRec driDriverAPI = {
+static const struct __DriverAPIRec brw_driver_api = {
    .InitScreen		 = intelInitScreen2,
    .DestroyScreen	 = intelDestroyScreen,
    .CreateContext	 = brwCreateContext,
@@ -1327,10 +1327,22 @@ const struct __DriverAPIRec driDriverAPI = {
    .ReleaseBuffer        = intelReleaseBuffer
 };
 
-/* This is the table of extensions that the loader will dlsym() for. */
-PUBLIC const __DRIextension *__driDriverExtensions[] = {
+static const struct __DRIDriverVtableExtensionRec brw_vtable = {
+   .base = { __DRI_DRIVER_VTABLE, 1 },
+   .vtable = &brw_driver_api,
+};
+
+static const __DRIextension *brw_driver_extensions[] = {
     &driCoreExtension.base,
     &driDRI2Extension.base,
+    &brw_vtable.base,
     &brw_config_options.base,
     NULL
 };
+
+PUBLIC const __DRIextension **__driDriverGetExtensions_i965(void)
+{
+   globalDriverAPI = &brw_driver_api;
+
+   return brw_driver_extensions;
+}

src/mesa/drivers/dri/i965/intel_screen.h

@@ -67,6 +67,8 @@ extern void intelDestroyContext(__DRIcontext * driContextPriv);
 
 extern GLboolean intelUnbindContext(__DRIcontext * driContextPriv);
 
+PUBLIC const __DRIextension **__driDriverGetExtensions_i965(void);
+
 extern GLboolean
 intelMakeCurrent(__DRIcontext * driContextPriv,
                  __DRIdrawable * driDrawPriv,