From: LIU Hao <lh_mouse@126.com>
To: Xi Ruoyao <xry111@xry111.site>
Cc: gcc-help@gcc.gnu.org
Subject: Re: optimizer discards sign information
Date: Wed, 10 Apr 2024 18:07:48 +0800 [thread overview]
Message-ID: <ceabca26-1adc-41bf-b38e-d59927d296e4@126.com> (raw)
In-Reply-To: <5f1da8b7829b4b1a445aac2216f50aba2fb5dac5.camel@xry111.site>
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在 2024-04-10 17:52, Xi Ruoyao via Gcc-help 写道:
> No, the OP is still thinking it's a wrong-code.
Would you read the Subject please?
u32 x = a * b;
u64 r = x;
return r;
This is same as
u32 x = (int) a * (int) b;
u64 r = x;
return r;
and
return (u64)(u32) ((int) a * (int) b);
The code requests an `int` be zero-extended to a `u64` (if the result is written to EAX then this is
no-op), but GCC performs sign extension anyway. Do you still consider it not a bug?
--
Best regards,
LIU Hao
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next prev parent reply other threads:[~2024-04-10 10:07 UTC|newest]
Thread overview: 20+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-04-10 8:52 stefan
2024-04-10 9:16 ` Alexander Monakov
2024-04-10 9:19 ` Xi Ruoyao
2024-04-10 9:40 ` LIU Hao
2024-04-10 9:44 ` Xi Ruoyao
2024-04-10 9:51 ` LIU Hao
2024-04-10 9:52 ` Xi Ruoyao
2024-04-10 10:07 ` LIU Hao [this message]
2024-04-10 10:17 ` Xi Ruoyao
2024-04-10 10:03 ` AW: " stefan
2024-04-10 10:34 ` Xi Ruoyao
2024-04-10 9:24 ` stefan
2024-04-10 9:49 ` stefan
2024-04-10 9:54 ` Xi Ruoyao
2024-04-10 9:57 ` LIU Hao
2024-04-10 10:03 ` Xi Ruoyao
2024-04-10 11:52 ` David Brown
2024-04-10 14:25 ` Stefan Franke
2024-04-10 16:51 ` David Brown
2024-04-11 0:32 ` Oleg Endo
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