simd - Why there is no pmulluw, pslad and pslaw commands in MMX? -



simd - Why there is no pmulluw, pslad and pslaw commands in MMX? -

why there no pmulluw, pslad , pslaw commands in mmx? , why there no movb , movw commands?

there totally pmulluw, it's called pmullw. since keeps low half, there no difference between signed , unsigned.

for related reason, pslad , pslaw pslld , psllw respectively. left shift left shift, signedness doesn't come in picture, shift (assuming shift 1) second-to-highest bit highest, nil else makes sense (the cases in signed-overflows exactly cases in "full result" cannot represented anyway, trying somehow preserve sign useless). right shift has signed , unsigned versions.

simd cpu-architecture mmx

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