[Bug target/102522] Multiplication by scalar on arm-v7 seems to generate scalar code

[pinskia at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=102522

Andrew Pinski <pinskia at gcc dot gnu.org> changed:

           What    |Removed                     |Added
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         Resolution|---                         |INVALID
             Status|UNCONFIRMED                 |RESOLVED

--- Comment #1 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
(In reply to Denis Yaroshevskiy from comment #0)
> ARM-V7 Neon has intrinsics like vmulq_n_u32 that are suppose to generate one
> mul instruction.

Read the outputed code again.

you need to move the argument x which is currently in r0 into a SIMD register.
GCC zeros out the other parts of the register just because.
And then it does the multiple.


        vmov.i32        d7, #0  @ v2si // d7 = {0,0}
        vmov.32 d7[0], r0              // d7 = {x, 0}
        vmul.i32        q0, q0, d7[0]  // q0 *= d7[0] (or rather q0 *= x)