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From: | Richard Henderson |
Subject: | Re: [Qemu-devel] [PATCH RFC 7/9] tcg: replace ext/u_i32_i64 by a mov when not implemented |
Date: | Fri, 17 Jul 2015 07:30:52 +0100 |
User-agent: | Mozilla/5.0 (X11; Linux x86_64; rv:38.0) Gecko/20100101 Thunderbird/38.0.1 |
On 07/15/2015 12:03 PM, Aurelien Jarno wrote:
When ext_i32_i64 and extu_i32_i64 ops are not implemented, this means that the register is already properly zero/sign extended, so we can simply replace it by a mov. In practice it means at least one of the two ops should always be implemented on 64-bit targets. Cc: Paolo Bonzini<address@hidden> Cc: Richard Henderson<address@hidden> Signed-off-by: Aurelien Jarno<address@hidden> --- tcg/tcg-op.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-)
If we're going to do this (and of course pick a solution for all of the other backends), I think perhaps x86 should choose trunc + exts as the two that should be implemented, leaving extu the one that can be folded away.
Something to experiment with... r~
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