Am 04.10.2017 um 05:59 schrieb Matt Turner:
On Tue, Oct 3, 2017 at 11:01 AM, Jochen Rollwagen <joro-2...@t-online.de> wrote:
From 4cebe50a9bade6717923e104c954f3fad75f71bb Mon Sep 17 00:00:00 2001
From: Jochen Rollwagen <joro-2...@t-online.de>
Date: Tue, 3 Oct 2017 19:54:10 +0200
Subject: [PATCH] Replace byte-swapping code with builtins in pack.c
This patch replaces some code for byte-swapping in pack.c with the builtin
functions allowing the compiler to do its optimization magic
---
src/mesa/main/pack.c | 22 ++--------------------
1 file changed, 2 insertions(+), 20 deletions(-)
diff --git a/src/mesa/main/pack.c b/src/mesa/main/pack.c
index 94a6d28..9bfde39 100644
--- a/src/mesa/main/pack.c
+++ b/src/mesa/main/pack.c
@@ -230,26 +230,8 @@ _mesa_pack_bitmap( GLint width, GLint height, const
GLubyte
*source,
}
}
-
-#define SWAP2BYTE(VALUE) \
- { \
- GLubyte *bytes = (GLubyte *) &(VALUE); \
- GLubyte tmp = bytes[0]; \
- bytes[0] = bytes[1]; \
- bytes[1] = tmp; \
- }
-
-#define SWAP4BYTE(VALUE) \
- { \
- GLubyte *bytes = (GLubyte *) &(VALUE); \
- GLubyte tmp = bytes[0]; \
- bytes[0] = bytes[3]; \
- bytes[3] = tmp; \
- tmp = bytes[1]; \
- bytes[1] = bytes[2]; \
- bytes[2] = tmp; \
- }
-
+#define SWAP2BYTE(VALUE) __builtin_bswap16(VALUE)
+#define SWAP4BYTE(VALUE) __builtin_bswap32(VALUE)
In my experience it's much simpler to just write these as
return ((x & 0xff) << 8) | ((x >> 8) & 0xff);
and
return ((x & 0xff) << 24) |
((x & 0xff00) << 8) |
((x & 0xff0000) >> 8) |
((x >> 24) & 0xff);
and not have to deal with compiler intrinsics. Compilers will
recognize these patterns and use the appropriate instructions (rol for
2-bytes and bswap for 4-bytes).
You should be able to count the numbers of those instructions before
and after such a patch to confirm it's working as expected.
Fair enough. I've attached a new patch that optimizes the code on linux
systems only where there is byteswap.h containing (hopefully optimal)
functions. The other systems may be dealt with by a followup patch if
desired.
From 327012410f75f77010b658ce9643a229c45bc308 Mon Sep 17 00:00:00 2001
From: Jochen Rollwagen <joro-2...@t-online.de>
Date: Thu, 5 Oct 2017 20:48:46 +0200
Subject: [PATCH] Simplify byte swapping code in pack.c on Linux systems
This patch replaces the code for byte swapping in pack.c with the
function from
byteswap.h on Linux systems
---
src/mesa/main/pack.c | 8 +++++++-
1 file changed, 7 insertions(+), 1 deletion(-)
diff --git a/src/mesa/main/pack.c b/src/mesa/main/pack.c
index 94a6d28..d8ab267 100644
--- a/src/mesa/main/pack.c
+++ b/src/mesa/main/pack.c
@@ -230,6 +230,12 @@ _mesa_pack_bitmap( GLint width, GLint height, const
GLubyte
*source,
}
}
+#ifdef __linux__
+#include <byteswap.h>
+
+#define SWAP2BYTE(VALUE) bswap_16(VALUE)
+#define SWAP4BYTE(VALUE) bswap_32(VALUE)
+#else
#define SWAP2BYTE(VALUE) \
{ \
@@ -249,7 +255,7 @@ _mesa_pack_bitmap( GLint width, GLint height, const
GLubyte
*source,
bytes[1] = bytes[2]; \
bytes[2] = tmp; \
}
-
+#endif
static void
extract_uint_indexes(GLuint n, GLuint indexes[],
--
1.7.9.5
Cheers
Jochen
>From 327012410f75f77010b658ce9643a229c45bc308 Mon Sep 17 00:00:00 2001
From: Jochen Rollwagen <joro-2...@t-online.de>
Date: Thu, 5 Oct 2017 20:48:46 +0200
Subject: [PATCH] Simplify byte swapping code in pack.c on Linux systems
This patch replaces the code for byte swapping in pack.c with the function from byteswap.h on Linux systems
---
src/mesa/main/pack.c | 8 +++++++-
1 file changed, 7 insertions(+), 1 deletion(-)
diff --git a/src/mesa/main/pack.c b/src/mesa/main/pack.c
index 94a6d28..d8ab267 100644
--- a/src/mesa/main/pack.c
+++ b/src/mesa/main/pack.c
@@ -230,6 +230,12 @@ _mesa_pack_bitmap( GLint width, GLint height, const GLubyte *source,
}
}
+#ifdef __linux__
+#include <byteswap.h>
+
+#define SWAP2BYTE(VALUE) bswap_16(VALUE)
+#define SWAP4BYTE(VALUE) bswap_32(VALUE)
+#else
#define SWAP2BYTE(VALUE) \
{ \
@@ -249,7 +255,7 @@ _mesa_pack_bitmap( GLint width, GLint height, const GLubyte *source,
bytes[1] = bytes[2]; \
bytes[2] = tmp; \
}
-
+#endif
static void
extract_uint_indexes(GLuint n, GLuint indexes[],
--
1.7.9.5
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