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
Description
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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Comments and changes to this ticket
-
Peter Johnson June 25th, 2011 @ 07:58 PM
- → Milestone set to “1.2.0”
- → Assigned user set to “Peter Johnson”
-
Peter Johnson July 2nd, 2011 @ 07:49 PM
- → State changed from “new” to “resolved”
HEAD generates a REX prefix for all 64-bit shl's, e.g
shl rax, 32generates:48 C1 E0 20
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