[Bug target/42017] gcc compiling C for ARM has stopped using r14 in leaf functions?
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=42017 Wilco changed: What|Removed |Added Status|NEW |RESOLVED CC||wilco at gcc dot gnu.org Resolution|--- |WORKSFORME --- Comment #6 from Wilco --- This has been fixed since at least GCC5.4: https://www.godbolt.org/z/6IAGfh
[Bug target/42017] gcc compiling C for ARM has stopped using r14 in leaf functions?
--- Comment #5 from ramana at gcc dot gnu dot org 2009-11-16 09:58 --- Confirmed. LR could have been used instead of using the stack here. -- ramana at gcc dot gnu dot org changed: What|Removed |Added Status|WAITING |NEW Ever Confirmed|0 |1 Last reconfirmed|-00-00 00:00:00 |2009-11-16 09:58:48 date|| http://gcc.gnu.org/bugzilla/show_bug.cgi?id=42017
[Bug target/42017] gcc compiling C for ARM has stopped using r14 in leaf functions?
--- Comment #4 from nickpelling at nanodome dot com 2009-11-14 16:50 --- Actually, I am targeting ARM (not Thumb1). I don't currently have easy access to 4.2.1 and 4.3.2, but I am assured that the former does indeed use r14 and the latter does indeed not use r14. -- http://gcc.gnu.org/bugzilla/show_bug.cgi?id=42017
[Bug target/42017] gcc compiling C for ARM has stopped using r14 in leaf functions?
--- Comment #3 from nickpelling at nanodome dot com 2009-11-14 16:48 --- Created an attachment (id=19018) --> (http://gcc.gnu.org/bugzilla/attachment.cgi?id=19018&action=view) This is the assembler file generated by gcc 4.4.1 for the C test file Note the presence of "[sp, #0]" in the listing at the points where it really ought to be using the lr register (AKA r14). -- http://gcc.gnu.org/bugzilla/show_bug.cgi?id=42017
[Bug target/42017] gcc compiling C for ARM has stopped using r14 in leaf functions?
--- Comment #2 from nickpelling at nanodome dot com 2009-11-14 16:45 --- Created an attachment (id=19017) --> (http://gcc.gnu.org/bugzilla/attachment.cgi?id=19017&action=view) Test C file for which gcc -O3 should (but currently doesn't) use r14 -- http://gcc.gnu.org/bugzilla/show_bug.cgi?id=42017
[Bug target/42017] gcc compiling C for ARM has stopped using r14 in leaf functions?
--- Comment #1 from ramana at gcc dot gnu dot org 2009-11-13 17:32 ---
(In reply to comment #0)
> In gcc4.2.1 targeting ARM processors, pure leaf functions were able to make
> use
> of r14 / lr (the link register). However, in gcc4.3.2 and gcc4.4.1 (and
> presumably since then, since I can't find it mentioned in any gcc bug
> reports),
> this now uses the stack instead rather than this spare register (boo, hiss).
Can you post specifically what output you got with 4.2.1, what you get with 4.3
and what you get with 4.4 ?
Presumably you are targetting Thumb1 but you need to make that explicit.
>
> Here's some C test code: when compiled with the -O3 option, this uses lr on
> gcc4.2.1 but [sp] on gcc4.3.2 and gcc4.4.1.
>
> int foo(int r0) {
> int r1,r2,r3,r4,r5,r6,r7,r8,r9,r10,r11,r12,r13,r14;
>
> r1 = 0;
>
> for(r2=0;r2 for(r3=0;r3 for(r4=0;r4 for(r5=0;r5 for(r6=0;r6 for(r7=0;r7 for(r8=0;r8 for(r9=0;r9 for(r10=0;r10 for(r11=0;r11 for(r12=0;r12 for(r13=0;r13 for(r14=0;r14 r1++;
>
> return r1;
> }
>
> PS: my guess is that this might have got broken when Thumb2 and ARMv7 support
> was added in (round about gcc4.3)...
>
--
ramana at gcc dot gnu dot org changed:
What|Removed |Added
Status|UNCONFIRMED |WAITING
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=42017
[Bug target/42017] gcc compiling C for ARM has stopped using r14 in leaf functions?
-- nickpelling at nanodome dot com changed: What|Removed |Added Severity|normal |minor GCC target triplet||ARM http://gcc.gnu.org/bugzilla/show_bug.cgi?id=42017
[Bug target/42017] gcc compiling C for ARM has stopped using r14 in leaf functions?
-- nickpelling at nanodome dot com changed: What|Removed |Added Severity|minor |normal http://gcc.gnu.org/bugzilla/show_bug.cgi?id=42017
