[FFmpeg-devel] [PATCH] avcodec/mathops: Set hidden visibility where advantageous

[FFmpeg-devel] [PATCH] avcodec/mathops: Set hidden visibility where advantageous

[Andreas Rheinhardt]

It is advantageous for ff_crop_tab, as the base pointer used to
access this table is not the first element of it. But the real
base pointer is still at a constant offset from the code/the GOT
and can therefore be accessed relative to the instruction pointer
(if supported by the arch) or relative to the GOT; without this,
one has to first load address of ff_crop_tab (potentially via
the GOT) and then offset manually (which is what the earlier code
did).

Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@outlook.com>
---
 libavcodec/mathops.h | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/libavcodec/mathops.h b/libavcodec/mathops.h
index f81d21f9c4..c89054d6ed 100644
--- a/libavcodec/mathops.h
+++ b/libavcodec/mathops.h
@@ -24,6 +24,7 @@
 
 #include <stdint.h>
 
+#include "libavutil/attributes_internal.h"
 #include "libavutil/common.h"
 #include "config.h"
 
@@ -32,7 +33,7 @@
 extern const uint32_t ff_inverse[257];
 extern const uint8_t ff_log2_run[41];
 extern const uint8_t ff_sqrt_tab[256];
-extern const uint8_t ff_crop_tab[256 + 2 * MAX_NEG_CROP];
+extern const uint8_t attribute_visibility_hidden ff_crop_tab[256 + 2 * MAX_NEG_CROP];
 extern const uint8_t ff_zigzag_direct[64];
 extern const uint8_t ff_zigzag_scan[16+1];
 
-- 
2.34.1

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Re: [FFmpeg-devel] [PATCH] avcodec/mathops: Set hidden visibility where advantageous

[Martin Storsjö]

On Sat, 3 Sep 2022, Andreas Rheinhardt wrote:

> It is advantageous for ff_crop_tab, as the base pointer used to
> access this table is not the first element of it. But the real
> base pointer is still at a constant offset from the code/the GOT
> and can therefore be accessed relative to the instruction pointer
> (if supported by the arch) or relative to the GOT; without this,
> one has to first load address of ff_crop_tab (potentially via
> the GOT) and then offset manually (which is what the earlier code
> did).
>
> Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@outlook.com>
> ---
> libavcodec/mathops.h | 3 ++-
> 1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/libavcodec/mathops.h b/libavcodec/mathops.h
> index f81d21f9c4..c89054d6ed 100644
> --- a/libavcodec/mathops.h
> +++ b/libavcodec/mathops.h
> @@ -24,6 +24,7 @@
>
> #include <stdint.h>
>
> +#include "libavutil/attributes_internal.h"
> #include "libavutil/common.h"
> #include "config.h"
>
> @@ -32,7 +33,7 @@
> extern const uint32_t ff_inverse[257];
> extern const uint8_t ff_log2_run[41];
> extern const uint8_t ff_sqrt_tab[256];
> -extern const uint8_t ff_crop_tab[256 + 2 * MAX_NEG_CROP];
> +extern const uint8_t attribute_visibility_hidden ff_crop_tab[256 + 2 * MAX_NEG_CROP];
> extern const uint8_t ff_zigzag_direct[64];
> extern const uint8_t ff_zigzag_scan[16+1];
>
> -- 
> 2.34.1

LGTM

// Martin

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