On 7/11/19 5:26 AM, Richard Henderson wrote: > On 7/10/19 8:21 PM, Jan Bobek wrote: >> Doesn't B8 (without REX.W) work for x86_64, too? It zeroes the upper >> part of the destination, so it's effectively zero-extending, and it's >> one byte shorter than C7 (no ModR/M byte needed). > > Sorry, I shouldn't have been quite so terse. What I meant is > > if (!$is_x86_64 || (0 <= $imm && $imm <= 0xffffffff)) > > so that 32-bit always uses the 5-byte encoding instead of the 6-byte.
Oh, I see. I double-checked my new code and it never uses the C7 move in 32-bit mode, but thanks for pointing it out. -Jan
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