Re: [FFmpeg-devel] [PATCH] avutil/intmath: use bzhi gcc builtin in av_mod_uintp2()

2015-06-27 Thread James Almer 
On 26/06/15 8:14 PM, James Almer wrote:
 Signed-off-by: James Almer jamr...@gmail.com
 ---
 Now making sure it's not used with ICC.

Pushed the original. Oked by Cehoyos who confirmed ICC never reaches this code
to begin with.
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[FFmpeg-devel] [PATCH] avutil/intmath: use bzhi gcc builtin in av_mod_uintp2()

2015-06-26 Thread James Almer 
Signed-off-by: James Almer jamr...@gmail.com
---
 libavutil/x86/intmath.h | 7 +++
 1 file changed, 7 insertions(+)

diff --git a/libavutil/x86/intmath.h b/libavutil/x86/intmath.h
index c42fa83..85f15a4 100644
--- a/libavutil/x86/intmath.h
+++ b/libavutil/x86/intmath.h
@@ -39,6 +39,12 @@
 
 #if defined(__BMI2__)
 
+#if AV_GCC_VERSION_AT_LEAST(5,1)
+#define av_mod_uintp2 __builtin_ia32_bzhi_si
+#else
+/* GCC releases before 5.1.0 have a broken bzhi builtin, so for those we
+ * implement it using inline assembly
+ */
 #define av_mod_uintp2 av_mod_uintp2_bmi2
 static av_always_inline av_const unsigned av_mod_uintp2_bmi2(unsigned a, 
unsigned p)
 {
@@ -50,6 +56,7 @@ static av_always_inline av_const unsigned 
av_mod_uintp2_bmi2(unsigned a, unsigne
 return x;
 }
 }
+#endif /* AV_GCC_VERSION_AT_LEAST */
 
 #endif /* __BMI2__ */
 
-- 
2.4.4

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Re: [FFmpeg-devel] [PATCH] avutil/intmath: use bzhi gcc builtin in av_mod_uintp2()

2015-06-26 Thread James Almer 
On 26/06/15 4:56 PM, Carl Eugen Hoyos wrote:
 On Friday 26 June 2015 09:52:31 pm James Almer wrote:
 
 +#if AV_GCC_VERSION_AT_LEAST(5,1)
 +#define av_mod_uintp2 __builtin_ia32_bzhi_si
 
 Since there are compilers != gcc that define GCC 
 (for example icc), this needs a configure check imo.

Does it define __GNUC__ with a value =5 like I'm checking above? And
if it defines __GNUC__, shouldn't it support the relevant builtins or
defines?

 
 What is the advantage over the inline version?

The bzhi instruction sets the ZF flag among others, but GCC apparently
doesn't take it into consideration when it's used inside the __asm__()
block, so something like if (av_mod_uintp2(foo, bar)) will result in
a bzhi instruction followed by a test instruction.
This doesn't happen if you use the builtin.

 
 Carl Eugen
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Re: [FFmpeg-devel] [PATCH] avutil/intmath: use bzhi gcc builtin in av_mod_uintp2()

2015-06-26 Thread Carl Eugen Hoyos 
On Friday 26 June 2015 09:52:31 pm James Almer wrote:

 +#if AV_GCC_VERSION_AT_LEAST(5,1)
 +#define av_mod_uintp2 __builtin_ia32_bzhi_si

Since there are compilers != gcc that define GCC 
(for example icc), this needs a configure check imo.

What is the advantage over the inline version?

Carl Eugen
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[FFmpeg-devel] [PATCH] avutil/intmath: use bzhi gcc builtin in av_mod_uintp2()

2015-06-26 Thread James Almer 
Signed-off-by: James Almer jamr...@gmail.com
---
Now making sure it's not used with ICC.

 libavutil/x86/intmath.h | 7 +++
 1 file changed, 7 insertions(+)

diff --git a/libavutil/x86/intmath.h b/libavutil/x86/intmath.h
index c42fa83..8127e10 100644
--- a/libavutil/x86/intmath.h
+++ b/libavutil/x86/intmath.h
@@ -39,6 +39,12 @@
 
 #if defined(__BMI2__)
 
+#if AV_GCC_VERSION_AT_LEAST(5,1)  !defined(__INTEL_COMPILER)
+#define av_mod_uintp2 __builtin_ia32_bzhi_si
+#else
+/* GCC releases before 5.1.0 have a broken bzhi builtin, so for those we
+ * implement it using inline assembly
+ */
 #define av_mod_uintp2 av_mod_uintp2_bmi2
 static av_always_inline av_const unsigned av_mod_uintp2_bmi2(unsigned a, 
unsigned p)
 {
@@ -50,6 +56,7 @@ static av_always_inline av_const unsigned 
av_mod_uintp2_bmi2(unsigned a, unsigne
 return x;
 }
 }
+#endif /* AV_GCC_VERSION_AT_LEAST */
 
 #endif /* __BMI2__ */
 
-- 
2.4.4

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