The two bank-crossing quadword moves take the mandatory prefix by
direction: the toolchain renders F3 0F D6 as MOVQ2DQ with the MMX
source and F2 0F D6 as MOVDQ2Q with the XMM source, and the encoder
emitted F2 for both, so MOVQ2DQ encoded MOVDQ2Q.
Assisted-by: GLM 5.3 Flash
The toolchain's disassembler prints the segment-prefixed disp32
absolute as FS:0, but the bare-name branch read the segment register
alone and dropped the offset, so MOVQ FS:0, DX silently encoded a
register move. The colon-offset form now lowers to the same
segment-absolute operand the 0(FS) spelling takes.
Assisted-by: GLM 5.3 Flash
petrbalvin