From: "Radim Krčmář" <rkrcmar@redhat.com>
To: Paolo Bonzini <pbonzini@redhat.com>
Cc: Michael Walle <michael@walle.cc>,
Paolo Bonzini <paolo.bonzini@gmail.com>,
qemu-devel@nongnu.org
Subject: Re: [Qemu-devel] [PATCH 2/2] milkymist-pfpu: fix GCC 5.0.0 aggressive-loop-optimizations warning
Date: Fri, 20 Feb 2015 16:48:12 +0100 [thread overview]
Message-ID: <20150220154811.GC3974@potion.brq.redhat.com> (raw)
In-Reply-To: <54E74AFE.6030004@redhat.com>
2015-02-20 15:55+0100, Paolo Bonzini:
>
>
> On 20/02/2015 15:52, Michael Walle wrote:
> >>>
> >>> - i = 0;
> >>> - while (pfpu_decode_insn(s)) {
> >>> - /* decode at most MICROCODE_WORDS instructions */
> >>> - if (i++ >= MICROCODE_WORDS) {
> >>
> >> Isn't the fix just to say "++i" instead of "i++"?
> >
> > In the first run, s->regs[R_PC] may have any value, therefore the "insn
> > = s->microcode[pc]" from above may access out of bounds.
>
> Then should pfpu_decode_insn access s->microcode[pc & (MICROCODE_WORDS -
> 1)]? That's likely what happens in hardware, and the purpose of the
> error is just to avoid an infinite loop in device code.
http://www.milkymist.org/socdoc/pfpu.pdf is dead, but the source isn't:
https://github.com/m-labs/milkymist/blob/master/cores/pfpu/doc/pfpu.tex
I don't see the PC register mentioned in interface, so hiding it would
probably be a good start.
next prev parent reply other threads:[~2015-02-20 15:48 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-02-20 14:18 [Qemu-devel] [PATCH 0/2] Fix GCC 5.0.0 build errors Radim Krčmář
2015-02-20 14:18 ` [Qemu-devel] [PATCH 1/2] fix GCC 5.0.0 logical-not-parentheses warnings Radim Krčmář
2015-02-20 14:38 ` Paolo Bonzini
2015-02-20 15:43 ` Radim Krčmář
2015-02-20 14:18 ` [Qemu-devel] [PATCH 2/2] milkymist-pfpu: fix GCC 5.0.0 aggressive-loop-optimizations warning Radim Krčmář
2015-02-20 14:24 ` Radim Krčmář
2015-02-20 14:36 ` Paolo Bonzini
2015-02-20 14:52 ` Michael Walle
2015-02-20 14:55 ` Paolo Bonzini
2015-02-20 15:48 ` Radim Krčmář [this message]
2015-02-20 14:40 ` Peter Maydell
2015-02-20 15:37 ` Radim Krčmář
2015-02-20 16:10 ` Michael Walle
-- strict thread matches above, loose matches on Subject: below --
2015-02-20 16:06 [Qemu-devel] [PATCH 0/2] Fix GCC 5.0.0 build errors Radim Krčmář
2015-02-20 16:06 ` [Qemu-devel] [PATCH 2/2] milkymist-pfpu: fix GCC 5.0.0 aggressive-loop-optimizations warning Radim Krčmář
2015-02-23 17:32 ` Michael Walle
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