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Article #50149Incompatibility with long right shifts not in the info pages
From: Nick Haines
Date: Wed, 17 Nov 1993 13:45
Date: Wed, 17 Nov 1993 13:45
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1243 bytes
On SPARCs, the sra instruction shifts right by the nominal amount modulo 32. And yet this instruction is generated by gcc (2.3.3) for (x >> y) (where y is unknown). So for y>=32, one obtains a result incompatible with ISO C, which specifies simply floor(x/2^y). I don't know if this is true under any other architectures. I assume this is known about, since for known y (e.g. x >> 48) the instruction generated has an immediate value of y mod 32, (sra %o1,0x10,%o1 in this case), presumably for compatibility with the "unknown y" case. So why isn't it in the info pages? Nick Haines nickh@harlequin.co.uk
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X-Google-Language: ENGLISH,ASCII-7-bit X-Google-Thread: 11318c,f753af2a6e079d94,start X-Google-Attributes: gid11318c,public X-Google-ArrivalTime: 1993-11-17 08:21:23 PST Path: arc1-ca.pugleaf.net!gmd.de!xlink.net!howland.reston.ans.net!math.ohio-state.edu!magnus.acs.ohio-state.edu!cis.ohio-state.edu!harlequin.co.UK!nickh From: nickh@harlequin.co.UK (Nick Haines) Newsgroups: gnu.gcc.help Subject: Incompatibility with long right shifts not in the info pages Date: 17 Nov 1993 08:45:16 -0500 Organization: GNUs Not Usenet Lines: 15 Sender: daemon@cis.ohio-state.edu Distribution: gnu Message-ID: <7452.753543647@gamgee>