[PATCH 1/2] [Middle-end] Simplify (trunc)copysign((extend)a, (extend)b) to .COPYSIGN (a, b).

[Joseph Myers]

On Thu, 4 Nov 2021, liuhongt via Gcc-patches wrote:

> a and b are same type as the truncation type and has less precision
> than extend type.

Note that this is not safe with -fsignaling-nans, so needs to be disabled 
for that option (if there isn't already logic somewhere with that effect), 
because the extend will convert a signaling NaN to quiet (raising 
"invalid"), but copysign won't, so this transformation could result in a 
signaling NaN being wrongly returned when the original code would never 
have returned a signaling NaN.

-- 
Joseph S. Myers
joseph@codesourcery.com