On 9 October 2012 14:44, Jubi Taneja <jubitan...@gmail.com> wrote:
>
>
> On Tue, Oct 9, 2012 at 5:21 PM, Matthew Gretton-Dann
> <matthew.gretton-d...@linaro.org> wrote:
>>
>> >> /* arm-none-linux-gnueabi-gcc -mcpu=cortex-a15 -mfpu=vfpv4 -S -o-
>> >> /tmp/fma.c -mfloat-abi=hard -O2 */
>> >> float f(float a, float b, float c)
>> >> {
>> >> return a * b + c;
>> >> }
>> >> /* end of tmp.c */
>> >>
>> >> (Note that -mfloat-abi=softfp will also work in this example. Which
>> >> one you want to use depends on whether you have configured your system
>> >> for hard or soft-float ABIs).
>> >>
>> > I checked both with -mfpu=vfpv3 and -mfpu=vfpv4 and it generates the
>> > same
>> > assembly code. VMLA insn is emitted for both the cases. I was wondering
>> > if I
>> > can get any test case so that I may observe the difference in the two
>> > objdumps.
>>
>> Which compiler are you using? VFMA support is only in trunk FSF GCC.
>> Linaro has not yet backported support to 4.7.
>
>
> I am using FSF GCC only.
What version of GCC (what does arm-none-linux-gneabi-gcc -v report?).
When I compile the test case above with a recent (within last month or
so) trunk GCC I get the following output which uses vfma:
$
/work/builds/gcc-fsf-arm-none-linux-gnueabi/tools/bin/arm-none-linux-gnueabi-gcc
-mcpu=cortex-a15 -mfpu=vfpv4 -S -o- /tmp/fma.c -mfloat-abi=hard -O2
.cpu cortex-a15
.eabi_attribute 27, 3
.eabi_attribute 28, 1
.fpu vfpv4
.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 34, 1
.eabi_attribute 18, 4
.file "fma.c"
.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.
vfma.f32 s2, s0, s1
fcpys s0, s2
bx lr
.size f, .-f
.ident "GCC: (GNU) 4.8.0 20120913 (experimental)"
.section .note.GNU-stack,"",%progbits
--
Matthew Gretton-Dann
Linaro Toolchain Working Group
matthew.gretton-d...@linaro.org
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