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Re: Painful problems with -fpic implementation on powerpc-sysv
- To: law at cygnus dot com, David Edelsohn <dje at watson dot ibm dot com>
- Subject: Re: Painful problems with -fpic implementation on powerpc-sysv
- From: Richard Henderson <rth at cygnus dot com>
- Date: Wed, 26 Aug 1998 12:25:03 -0700
- Cc: Geoff Keating <geoffk at ozemail dot com dot au>, egcs at cygnus dot com, Franz Sirl <Franz dot Sirl-kernel at lauterbach dot com>
- References: <9808211609.AA36466@marc.watson.ibm.com> <783.904115462@hurl.cygnus.com>
- Reply-To: Richard Henderson <rth at cygnus dot com>
On Wed, Aug 26, 1998 at 01:11:02AM -0600, Jeffrey A Law wrote:
> This could work for cases where one is trying to build up a constant,
> but would not work if (for example) reload decided try and put
> (const (plus (symbol_ref) (offset)) into the constant pool. Yes, this
> does really happen and it is painful.
If this happens, it is a bug. With -fpic, a symbol_ref is not a
constant, and will result in a run-time relocation to .rodata.
Not good.
This should instead be reloaded as
(set tmp (mem:PI pic (symbol_ref)))
(set tmp (plus:PI tmp (offset)))
splitting up the first as dictated by -fpic vs -fPIC.
r~