Why can't I assemble this single FPU instruction with GNU as?

Question

I'm trying to retrieve the binary representation of a few FPU instructions for the Cortex-M4 processor. I resolved to put the code I need to retrieve in a file like this

.syntax unified
vsub.f32 s0, s1, s2    ; or any other instruction

and then call

arm-none-eabi-as -o /dev/null -mcpu=cortex-m4 -march=armv7e-m -mfloat-abi=hard -al -EB <file>

However, for FPU instructions, it fails telling me

Assembler messages:
Error: invalid instruction shape -- `vsub.f32 s0,s1,s2'

What am I doing wrong? Thanks

Answer 1

Apparently, the -mfpu flag is needed too (in this case, -mfpu=fpv4-sp-d16):

[alessandro@commodoroII src]$ arm-none-eabi-as -o /dev/null -mcpu=cortex-m4 -march=armv7e-m -mfloat-abi=hard -al -EB /tmp/temp-julia.s
/tmp/temp-julia.s: Assembler messages:
/tmp/temp-julia.s:2: Error: invalid instruction shape -- `vsub.f32 s0,s1,s2'
ARM GAS  /tmp/temp-julia.s                      page 1


   1                    .syntax unified
   2                    vsub.f32 s0, s1, s2
[alessandro@commodoroII src]$ arm-none-eabi-as -o /dev/null -mcpu=cortex-m4 -march=armv7e-m -mfloat-abi=hard -mfpu=fpv4-sp-d16 -al -EB /tmp/temp-julia.s
ARM GAS  /tmp/temp-julia.s                      page 1


   1                    .syntax unified
   2 0000 EE300AC1      vsub.f32 s0, s1, s2