Right shift vs. divide

[Utah]

In article <974 at brl-tgr.ARPA> Schauble at mit-multics.arpa (Paul Schauble) writes:
>
>BTW, is >> defined to be a sign-extended shift or a zero extended shift
>and under what circumstances.
>  
>                                    Paul
>                                    Schauble @ MIT-Multics

The way that I interpreted this when generating machine code (68000) for a >> X
was that if a was 'signed' (char, short, int, and long in our implementation)
the compiler generated an arithmetic shift.  If a was 'unsigned'
(unsigned char, unsigned short, unsigned int, unsigned long), it generated
a bitwise (logical?) shift.

BTW, most C compilers I have seen do not fold the following constant expression
correctly:	((unsigned long)0xFFFFFFFF) >> 1 /* or anything w/sign bit on */
Seems like the constant folding function in the compiler only does arithmetic
shifts.
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