[PATCH] Allow encoded 8-bit floating point constants in ARM vmov instructions

Renato Golin renato.golin at linaro.org
Wed Dec 18 04:13:38 PST 2013


On 17 December 2013 21:58, Jim Grosbach <grosbach at apple.com> wrote:

> What does the ARM documentation indicate? Either way, you’re right that we
> should clean up the implementation so that if we reject or accept the
> different forms of constants, we do so intentionally and not inadvertently.
>

ARM docs mention that both VFPv3+ and NEON VMOV.f32 Rn, #imm support
encoded floating-point constants. Tables A7-15 and A7-18 (ARMv7-AR):

"The bit pattern represents the floating-point number (–1)S × 2exp ×
mantissa, where S = UInt(a), exp = UInt(NOT(b):c:d)-3 and mantissa =
(16+UInt(e:f:g:h))/16."

cheers,
--renato
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