From: Richard Henderson <rth@twiddle.net>
To: Aurelien Jarno <aurelien@aurel32.net>
Cc: qemu-devel@nongnu.org
Subject: Re: [Qemu-devel] [PATCH 2/9] tcg/optimizer: check types in copy propagation
Date: Wed, 19 Sep 2012 14:33:46 -0700 [thread overview]
Message-ID: <505A3A3A.5070002@twiddle.net> (raw)
In-Reply-To: <1348084823-18277-3-git-send-email-aurelien@aurel32.net>
On 09/19/2012 01:00 PM, Aurelien Jarno wrote:
> The copy propagation doesn't check the types of the temps during copy
> propagation. However TCG is using the mov_i32 for the i64 to i32
> conversion and thus the two are not equivalent.
>
> With this patch tcg_opt_gen_mov() doesn't consider two temps with
> different types as copies anymore.
>
> So far it seems the optimization was not aggressive enough to trigger
> this bug, but it will be triggered later in this series once the copy
> propagation is improved.
Exactly where/how does this manifest as problematic?
We do this mov_i32 trick from i64->i32 when we're truncating.
Given that we're not (yet) targeting mips64 and having to
maintain 32-bit sign-extended quantities, I can't see how
that would matter.
We do the i32->i64 trick immediately before a proper extension.
In either case I can't see how plain copy propagation should
matter until some other operation is involved. So, do we have
some other data propagation bug that is being masked here?
r~
next prev parent reply other threads:[~2012-09-19 21:33 UTC|newest]
Thread overview: 22+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-09-19 20:00 [Qemu-devel] [PATCH 0/9] tcg/optimize: rework copy propagation Aurelien Jarno
2012-09-19 20:00 ` [Qemu-devel] [PATCH 1/9] tcg/optimizer: remove TCG_TEMP_ANY Aurelien Jarno
2012-09-19 21:25 ` Richard Henderson
2012-09-19 20:00 ` [Qemu-devel] [PATCH 2/9] tcg/optimizer: check types in copy propagation Aurelien Jarno
2012-09-19 21:33 ` Richard Henderson [this message]
2012-09-20 5:54 ` Aurelien Jarno
2012-09-20 14:00 ` Richard Henderson
2012-09-19 20:00 ` [Qemu-devel] [PATCH 3/9] tcg/optimizer: rework copy progagation Aurelien Jarno
2012-09-19 21:41 ` Richard Henderson
2012-09-19 20:00 ` [Qemu-devel] [PATCH 4/9] tcg/optimize: do copy propagation for all operations Aurelien Jarno
2012-09-19 21:43 ` Richard Henderson
2012-09-19 20:00 ` [Qemu-devel] [PATCH 5/9] tcg/optimize: optimize "op r, a, a => mov r, a" Aurelien Jarno
2012-09-19 21:43 ` Richard Henderson
2012-09-19 20:00 ` [Qemu-devel] [PATCH 6/9] tcg/optimize: optimize "op r, a, a => movi r, 0" Aurelien Jarno
2012-09-19 21:46 ` Richard Henderson
2012-09-19 20:00 ` [Qemu-devel] [PATCH 7/9] tcg/optimize: further optimize brcond/setcond Aurelien Jarno
2012-09-19 21:48 ` Richard Henderson
2012-09-19 20:00 ` [Qemu-devel] [PATCH 8/9] tcg/optimize: prefer the "op a, a, b" form for commutative ops Aurelien Jarno
2012-09-19 21:49 ` Richard Henderson
2012-09-19 20:00 ` [Qemu-devel] [PATCH 9/9] tcg: remove #ifdef #endif around TCGOpcode tests Aurelien Jarno
2012-09-19 21:50 ` Richard Henderson
2012-09-21 12:36 ` [Qemu-devel] [PATCH 0/9] tcg/optimize: rework copy propagation Laurent Desnogues
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