http://gcc.gnu.org/bugzilla/show_bug.cgi?id=47685
Summary: Tail call doesn't work for thumb2
Product: gcc
Version: 4.5.2
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c
AssignedTo: unassig...@gcc.gnu.org
ReportedBy: alexandre.nu...@gmail.com
Created attachment 23298
--> http://gcc.gnu.org/bugzilla/attachment.cgi?id=23298
testcase.
When compiling the attached test program for i.e. -mcpu=cortex-a9 -marm the
tail call mechanism works correctly ... if you replace -marm for -mthumb then
the result is a traditional stack frame, for which i couldn't find any switches
to turn it off.
For example, this was taken from the example code for -mthumb:
func_c:
@ args = 0, pretend = 0, frame = 0
@ frame_needed = 0, uses_anonymous_args = 0
push {lr}
movs r3, #33
bl func_a
pop {pc}
.size func_c, .-func_c
And this for -marm:
func_c:
@ args = 0, pretend = 0, frame = 0
@ frame_needed = 0, uses_anonymous_args = 0
@ link register save eliminated.
mov r3, #33
b func_a
.size func_c, .-func_c
This is more relevant for example to -mcpu=cortex-m3 where we have no ram to
waste.
