https://gcc.gnu.org/bugzilla/show_bug.cgi?id=67856
Richard Biener changed:
What|Removed |Added
Status|NEW |ASSIGNED
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=67856
Segher Boessenkool changed:
What|Removed |Added
Status|ASSIGNED|NEW
--- Comment #6 from Segher
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=67856
Andrew Pinski changed:
What|Removed |Added
Keywords||missed-optimization
CC|
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=67856
Segher Boessenkool changed:
What|Removed |Added
Status|NEW |ASSIGNED
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=67856
--- Comment #4 from Andy Lutomirski ---
I don't want to comment on how code generation works in GCC, but in terms of
what works in the output:
x86_64 generally has a 16-byte stack alignment in user code, which is two
slots. (In the kernel, we
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=67856
--- Comment #5 from Segher Boessenkool ---
The prologue does a lot of separate things:
- Save non-volatile registers;
- Do whatever needs to be done to be able to call things (save the
return address, align the stack, whatever; different per
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=67856
Segher Boessenkool changed:
What|Removed |Added
Status|UNCONFIRMED |NEW
Last reconfirmed|
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=67856
--- Comment #2 from Andy Lutomirski ---
(In reply to Segher Boessenkool from comment #1)
> The call to "a" needs the prologue, maybe to align the stack?
The "subq $8, %rsp" is for stack alignment, and whether it's emitted depends on
the parity
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=67856
--- Comment #3 from Segher Boessenkool ---
Currently, shrink-wrapping does not allow any call to happen without
prologue (see shrink-wrap.c:requires_stack_frame_p).
On x86-64, if you do not have a prologue but do do a call, the called
function
