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camel-cdr 2 months ago

> The great joy of basic x86 encoding is that you don't actually need to put things in registers to operate on them.

That's just spilling with fewer steps. The executed uops should be the same.

timewizard 2 months ago | parent [-]

> That's just spilling with fewer steps.

Another way to say this is it's "more efficient."

> The executed uops should be the same.

And "more densely coded."

camel-cdr 2 months ago | parent [-]

hm, I was wondering how the density compares with x86 having more complex encodings in general.

vaddps zmm1,zmm0,ZMMWORD PTR [r14]

takes six bytes to encode:

62 d1 7c 48 58 0e

In SVE and RVV a load+add takes 8 bytes to encode.