#217 ✓resolved
Peter Johnson

REX prefix missing in shl

Reported by Peter Johnson | June 25th, 2011 @ 07:52 PM | in 1.2.0 (closed)

Originally posted on Trac by post@MartinSander.de
Original Trac Ticket


In the shl, shr, sal, sar commands, the count is normally masked to 5 bits, i.e., it is limited to a number between 0 and 31. This is true also for the 64-bit registers. Only with a REX.W prefix, the full range of 0..63 can be used. This REX prefix seems not to be emitted by YASM, as the line

shl rax, 32

just performs nothing (showing that the bit masking changes the immediate 32 into 0).

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