On Sat, May 7, 2011 at 12:39 AM, Nicolas Pitre <[email protected]> wrote:
> On Fri, 6 May 2011, Ramana Radhakrishnan wrote:
>
>> On 6 May 2011 16:06, Ken Werner <[email protected]> wrote:
>> >
>> > Currently the GCC ARM backend doesn't provide a pattern to inline 64bit
>> > __sync_* functions but the compiler emits __sync_*_8 function calls [1].
>> > The
>> > libgcc does not provide these symbols via the usual thin wrapper around the
>> > kernel helper [2] because the ARM Linux __kernel_cmpxchg supports 32bit
>> > only.
>> > My understanding is that for ARMv7 the GCC backend could be enhanced to
>> > inline
>> > the __sync_* functions by using the LDREXD and STREXD instructions. But for
>> > ARMv5 we would still rely on a new kernel helper.
>>
>> It's a bit tricky with when you want to use the kernel helper for v5t,
>> so we've got to find a way of turning this on only with special knobs
>> and not by default and that's a bit tricky.
>
> What is the problem with v5t?
Hi, when I run the following on my jaunty (for armv5), I get the following
echo "void f(){__sync_synchronize();}" | gcc -O2 -x c -Wall -dA -S - -o -
.arch armv6
.eabi_attribute 27, 3
.fpu vfp
.eabi_attribute 20, 1
.eabi_attribute 21, 1
.eabi_attribute 23, 3
.eabi_attribute 24, 1
.eabi_attribute 25, 1
.eabi_attribute 26, 2
.eabi_attribute 30, 2
.eabi_attribute 18, 4
.file ""
.text
.align 2
.global f
.type f, %function
f:
@ args = 0, pretend = 0, frame = 0
@ frame_needed = 0, uses_anonymous_args = 0
@ link register save eliminated.
@ basic block 2
bx lr
.size f, .-f
.ident "GCC: (Ubuntu 4.4.1-4ubuntu9) 4.4.1"
.section .note.GNU-stack,"",%progbits
but I can see (with debugger) that the kernel helper functions are
reached. any idea how?
saeed
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