On Wed, 11 Nov 2020 01:38:04 +0100
Charlene Wendling <juliana...@posteo.jp> wrote:
> On Tue, 10 Nov 2020 07:50:26 +0100
> Charlene Wendling wrote:
>
> New diff with aja's and sthen's suggestions. I tested on macppc and, even
> if it has no impact there, amd64.
I built webkitgtk4 on macppc after you committed your fixes, and with
one more change: I deleted the -mlongcall flag. I suggest to keep
-mlongcall for now, but the next person to edit webkitgtk4/Makefile
should remove -mlongcall at the same time.
Below the diff, I explain -mlongcall and -Wl,--relax flags.
Index: Makefile
===================================================================
RCS file: /cvs/ports/www/webkitgtk4/Makefile,v
retrieving revision 1.130
diff -u -p -r1.130 Makefile
--- Makefile 11 Nov 2020 21:27:03 -0000 1.130
+++ Makefile 13 Nov 2020 20:45:24 -0000
@@ -119,8 +119,6 @@ LDFLAGS += -Wl,--no-keep-memory
.if ${MACHINE_ARCH} == "powerpc"
# XXX fix colors being off, it would be nice to fix the code
CONFIGURE_ARGS += -DENABLE_GRAPHICS_CONTEXT_GL=OFF
-CFLAGS += -mlongcall
-CXXFLAGS += -mlongcall
LDFLAGS += -Wl,--relax
PATCH_LIST = patch-* powerpc-patch-*
.endif
In powerpc and powerpc64 code, the "bl" instruction for a direct
function call uses a signed 26-bit offset. This limits the branch
distance to plus or minus 32 megabytes. This works well when each
program or shared lib has less than 32M of code.
libwebkit2gtk-4.0.so.3.3 is too big, because its LOAD segment with
the E flag (for code) has size > 32M = 0x2_000_000 bytes:
$ readelf -l libwebkit2gtk-4.0.so.3.3|head
...
Type Offset VirtAddr PhysAddr FileSiz MemSiz Flg Align
LOAD 0x000000 0x00000000 0x00000000 0x2e979e4 0x2e979e4 R E 0x10000
With cc -mlongcall, each function call is indirect through a function
pointer. This would get around the 32M limit, but it doesn't work
because /usr/lib/crt*.o don't use -mlongcall. My test program with
code over 32M got linker errors from crtbegin.o and crt0.o.
With cc -Wl,--relax, the linker ld.bfd can pass the 32M limit by
inserting a thunk (or branch island) between the "bl" and its
destination. This doesn't need -mlongcall and does work with crt*.o.
We use -Wl,--relax without -mlongcall in devel/llvm on powerpc.
cc -Wl,--relax causes an error with ld.lld on powerpc64 (or with
cc -fuse-ld=lld on powerpc), but lld inserts thunks (branch islands)
by default. If macppc switches to lld, we would remove -Wl,--relax
from ports. --George
