https://gcc.gnu.org/bugzilla/show_bug.cgi?id=109257
Jakub Jelinek <jakub at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
CC| |hjl.tools at gmail dot com,
| |jakub at gcc dot gnu.org,
| |jbeulich at suse dot com
--- Comment #1 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
It isn't just for sibcalls, but also for calls:
extern int (*foo) (int, int);
int bar (int a, int b) { return foo (a, b); }
int baz (int a, int b) { foo (a, b); return 0; }
gcc emits
jmp [QWORD PTR foo[rip]]
and
call [QWORD PTR foo[rip]]
icc emits
mov rax, QWORD PTR foo[rip] #2.33
jmp rax #2.33
and
call QWORD PTR foo[rip] #3.26
clang emits
mov rax, qword ptr [rip + foo]
jmp rax # TAILCALL
and
call qword ptr [rip + foo]
gas testsuite doesn't have any tests with the []s around the whole thing, but
accepts it the same as without those.
And on the gcc side it is hardcoded that way in lots of spots:
grep '\[[QD]\?WORD' i386.cc i386.md
i386.cc: xasm = "{%p0@GOTPCREL(%%rip)|[QWORD PTR
%p0@GOTPCREL[rip]]}";
i386.cc: xasm = "%!jmp\t{*%p0@GOTPCREL(%%rip)|[QWORD PTR
%p0@GOTPCREL[rip]]}";
i386.cc: xasm = "{%p0@GOT|[DWORD PTR %p0@GOT]}";
i386.cc: xasm = "%!jmp\t{*%p0@GOT|[DWORD PTR %p0@GOT]}";
i386.cc: xasm = "{%p0@GOTPCREL(%%rip)|[QWORD PTR
%p0@GOTPCREL[rip]]}";
i386.cc: xasm = "%!call\t{*%p0@GOTPCREL(%%rip)|[QWORD PTR
%p0@GOTPCREL[rip]]}";
i386.cc: xasm = "{%p0@GOT|[DWORD PTR %p0@GOT]}";
i386.cc: xasm = "%!call\t{*%p0@GOT|[DWORD PTR %p0@GOT]}";
i386.md: return "call\t{*%p3@GOT(%1)|[DWORD PTR %p3@GOT[%1]]}";
i386.md: return "call\t{*%p2@GOTPCREL(%%rip)|[QWORD PTR %p2@GOTPCREL[rip]]}";
i386.md: return "call\t{*%p2@GOT(%1)|[DWORD PTR %p2@GOT[%1]]}";
i386.md: return "call\t{*%p1@GOTPCREL(%%rip)|[QWORD PTR %p1@GOTPCREL[rip]]}";
i386.md: "call\t{*%a1@TLSCALL(%2)|[DWORD PTR [%2+%a1@TLSCALL]]}"
i386.md: "call\t{*%a1@TLSCALL(%2)|[QWORD PTR [%2+%a1@TLSCALL]]}"
and I'm sure I'm missing some.
