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| From | Philipp Klaus Krause <pkk@spth.de> |
|---|---|
| Newsgroups | comp.std.c |
| Subject | Re: Why is shifting too far undefined behvaior? |
| Date | 2021-09-21 20:12 +0200 |
| Message-ID | <sid79l$d35$1@solani.org> (permalink) |
| References | <siceh0$1lm$1@solani.org> <87tuidolj1.fsf@nosuchdomain.example.com> |
Am 21.09.21 um 20:01 schrieb Keith Thompson: > > I looked at my Interdata 8/32 manual (1975), which describes > a 32-bit machine, and was amused to find, under the > "Shift Left Logical" instruction, > > "... the shift count is specified by the least significant > five bits of the second operand." The modern Z80N (a Z80 variant used in the ZX Spectrum Next) has a "shift left arithmetic" that shifts 16-bit register de left by the number specified in the lower 5 bits of 8-bit register b. So in SDCC when targeting the Z80N, left-shifting a 16-bit value could, depending on which register the shifted value gets allocated to, shift either by the lower 5 bits of the right operand (is the Z80N instruction is used) or the lower 8 bits of the right operand (if normal code for Z80 left shift is generated) or by the actual right operand (if the value of the right operand can be determined at compile time).
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Why is shifting too far undefined behvaior? Philipp Klaus Krause <pkk@spth.de> - 2021-09-21 13:09 +0200
Re: Why is shifting too far undefined behvaior? Ike Naar <ike@faeroes.freeshell.org> - 2021-09-21 11:33 +0000
Re: Why is shifting too far undefined behvaior? Richard Kettlewell <invalid@invalid.invalid> - 2021-09-21 12:47 +0100
Re: Why is shifting too far undefined behvaior? Richard Damon <Richard@Damon-Family.org> - 2021-09-21 08:29 -0400
Re: Why is shifting too far undefined behvaior? Vincent Lefevre <vincent-news@vinc17.net> - 2021-09-22 01:17 +0000
Re: Why is shifting too far undefined behvaior? Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2021-09-21 19:05 -0700
Re: Why is shifting too far undefined behvaior? James Kuyper <jameskuyper@alumni.caltech.edu> - 2021-09-22 00:02 -0400
Re: Why is shifting too far undefined behvaior? Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2021-09-21 21:12 -0700
Re: Why is shifting too far undefined behvaior? James Kuyper <jameskuyper@alumni.caltech.edu> - 2021-09-22 09:42 -0400
Re: Why is shifting too far undefined behvaior? Richard Damon <Richard@Damon-Family.org> - 2021-09-22 07:08 -0400
Re: Why is shifting too far undefined behvaior? James Kuyper <jameskuyper@alumni.caltech.edu> - 2021-09-22 09:42 -0400
Re: Why is shifting too far undefined behvaior? James Kuyper <jameskuyper@alumni.caltech.edu> - 2021-09-23 12:18 -0400
Re: Why is shifting too far undefined behvaior? Vincent Lefevre <vincent-news@vinc17.net> - 2021-09-23 11:10 +0000
Re: Why is shifting too far undefined behvaior? James Kuyper <jameskuyper@alumni.caltech.edu> - 2021-09-23 12:22 -0400
Re: Why is shifting too far undefined behvaior? Vincent Lefevre <vincent-news@vinc17.net> - 2021-09-23 11:08 +0000
Re: Why is shifting too far undefined behvaior? Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2021-09-21 11:01 -0700
Re: Why is shifting too far undefined behvaior? Philipp Klaus Krause <pkk@spth.de> - 2021-09-21 20:12 +0200
Re: Why is shifting too far undefined behvaior? Vincent Lefevre <vincent-news@vinc17.net> - 2021-09-22 01:13 +0000
Re: Why is shifting too far undefined behvaior? David Brown <david.brown@hesbynett.no> - 2021-09-22 14:25 +0200
Re: Why is shifting too far undefined behvaior? Vincent Lefevre <vincent-news@vinc17.net> - 2021-09-23 11:17 +0000
Re: Why is shifting too far undefined behvaior? Tim Rentsch <txr@shamko.com> - 2021-10-09 04:27 -0700
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