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Re: Change to readonly conflict handling
- To: geoffk at cygnus dot com
- Subject: Re: Change to readonly conflict handling
- From: kenner at vlsi1 dot ultra dot nyu dot edu (Richard Kenner)
- Date: Sun, 17 Sep 00 20:30:50 EDT
- Cc: gcc at gcc dot gnu dot org
This code is actually not valid C; neither of the two assignments are
valid, because they change p->a and q->a which are 'const'.
Yes, I know, but I don't think there's any way to get it from valid C. This
was meant to be as close I could get the actual case, which was from Ada.
Actually, what I get is _both_ words of *p and *q being stored with
/u. On powerpc (so the fields are SImode):
Right, I get that too. I even think I see why, though it is a bug.
(insn 16 15 19 (set (mem/s/u:DI (reg/v:SI 82) 0)
(reg:DI 86)) -1 (nil)
(nil))
(insn 19 16 20 (set (reg:DI 87)
(mem/s:DI (reg/v:SI 82) 0)) -1 (nil)
(nil))
But *this* is key: it's being stored *with* the "/u", but loaded without.
That will cause these two loads to be marked non-conflicting, which may
have them scheduled in the wrong order (how I ran into the bug).