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Re: -fomit-frame-pointer interaction with alloca - egcs-1.0.1
- To: John Hughes <john at AtlanTech dot COM>
- Subject: Re: -fomit-frame-pointer interaction with alloca - egcs-1.0.1
- From: John Carr <jfc at mit dot edu>
- Date: Fri, 06 Feb 1998 16:04:47 -0500
- cc: egcs-bugs at cygnus dot com
> 1. Why does it do "movl %esp,%eax; pushl %eax" instead of "pushl %esp"
>From combine.c:
/* If I3 has an inc, then give up if I1 or I2 uses the reg that is inc'd.
We used to do this EXCEPT in one case: I3 has a post-inc in an
output operand. However, that exception can give rise to insns like
mov r3,(r3)+
which is a famous insn on the PDP-11 where the value of r3 used as the
source was model-dependent. Avoid this sort of thing. */
I think implementations of the 8086 architecture also disagreed on the
meaning of push %sp.