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Re: [PATCH v6 5/7] x86: control memset() and memcpy() inlining
- To: Jan Beulich <jbeulich@xxxxxxxx>, "xen-devel@xxxxxxxxxxxxxxxxxxxx" <xen-devel@xxxxxxxxxxxxxxxxxxxx>
- From: Jason Andryuk <jason.andryuk@xxxxxxx>
- Date: Tue, 24 Jun 2025 17:00:01 -0400
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- Cc: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>, Roger Pau Monné <roger.pau@xxxxxxxxxx>
- Delivery-date: Tue, 24 Jun 2025 21:00:08 +0000
- List-id: Xen developer discussion <xen-devel.lists.xenproject.org>
On 2025-06-16 09:01, Jan Beulich wrote:
Stop the compiler from inlining non-trivial memset() and memcpy() (for
memset() see e.g. map_vcpu_info() or kimage_load_segments() for
examples). This way we even keep the compiler from using REP STOSQ /
REP MOVSQ when we'd prefer REP STOSB / REP MOVSB (when ERMS is
available).
With gcc10 this yields a modest .text size reduction (release build) of
around 2k.
Unfortunately these options aren't understood by the clang versions I
have readily available for testing with; I'm unaware of equivalents.
Note also that using cc-option-add is not an option here, or at least I
couldn't make things work with it (in case the option was not supported
by the compiler): The embedded comma in the option looks to be getting
in the way.
Requested-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>
Reviewed-by: Jason Andryuk <jason.andryuk@xxxxxxx>
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