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Re: How to set REX prefix when using RDRAND?
- From: Mason <slash dot tmp at free dot fr>
- To: GCC help <gcc-help at gcc dot gnu dot org>
- Cc: Jeffrey Walton <noloader at gmail dot com>
- Date: Mon, 12 Oct 2015 11:29:14 +0200
- Subject: Re: How to set REX prefix when using RDRAND?
- Authentication-results: sourceware.org; auth=none
- References: <CAH8yC8notjAYqQ4FRMvtP8rV+Ks=G7i83mbae_ttAnBMJz5rEg at mail dot gmail dot com>
On 12/10/2015 10:34, Jeffrey Walton wrote:
> I'm not able to compile a program that uses `rdrand` and a word64 due
> to "Error: operand size mismatch for `rdrand'". If I try to explicitly
> use `rdrandq` and the word64, then it results in
> "Error: invalid instruction suffix for `rdrand'"
(I'm not a gcc developer.)
I think it would be a good idea to provide a minimal example of
what you are compiling, along with the output of
gcc -v source.{c,S}
Regards.