Post #2797259

2026-04-14 22:06 UTC

@Doomed_Daniel@mastodon.gamedev.place @zeux@mastodon.gamedev.place @lisyarus@mastodon.gamedev.place Because in the 90s, if you're porting numerical SW to say a PPC, you wouldn't want to not use FMAs, for the most part. That's making a lot of things 2x more expensive because even just basic FP mul and FP add on that HW would execute as FMAs, and their was only one FP arithmetic unit which was the FMA unit! Standards have more recently started to try to tighten down on things but it's just a hard retro-fit due to many historical accidents.

Replies (1)

@rygorous@mastodon.gamedev.place 2026-04-14 22:10

@Doomed_Daniel@mastodon.gamedev.place @zeux@mastodon.gamedev.place @lisyarus@mastodon.gamedev.place FWIW I also agree that FP contractions being enabled by default is very unfortunate these days, but it makes perfect sense for that to be the default given how we got the option in the first place, namely, it was introduced on HW where FMA was the only way to do FP adds or muls and turning contractions off could literally halve your FP throughput.

Open ##2797260