diff mbox

[FFmpeg-devel] Fix missing used attribute for inline assembly variables

Message ID 20171112162437.18878-1-tkoeppe@google.com
State New
Headers show

Commit Message

Thomas Köppe Nov. 12, 2017, 4:24 p.m. UTC 
Variables used in inline assembly need to be marked with attribute((used)).
Static constants already were, via the define of DECLARE_ASM_CONST.
But DECLARE_ALIGNED does not add this attribute, and some of the variables
defined with it are const only used in inline assembly, and therefore
appeared dead. This change adds a macro DECLARE_ASM_ALIGNED that marks
variables as used.

This change makes FFMPEG work with Clang's ThinLTO.
---
 libavcodec/cabac.c         |  2 +-
 libavcodec/x86/constants.c | 20 ++++++++++----------
 libavutil/mem.h            | 17 +++++++++++++++++
 libswscale/x86/swscale.c   | 12 ++++++------
 4 files changed, 34 insertions(+), 17 deletions(-)

Comments

Michael Niedermayer Nov. 13, 2017, 2:46 a.m. UTC | #1 
On Sun, Nov 12, 2017 at 04:24:37PM +0000, Thomas Köppe wrote:
> Variables used in inline assembly need to be marked with attribute((used)).
> Static constants already were, via the define of DECLARE_ASM_CONST.
> But DECLARE_ALIGNED does not add this attribute, and some of the variables
> defined with it are const only used in inline assembly, and therefore
> appeared dead. This change adds a macro DECLARE_ASM_ALIGNED that marks
> variables as used.
> 
> This change makes FFMPEG work with Clang's ThinLTO.
> ---
>  libavcodec/cabac.c         |  2 +-
>  libavcodec/x86/constants.c | 20 ++++++++++----------
>  libavutil/mem.h            | 17 +++++++++++++++++
>  libswscale/x86/swscale.c   | 12 ++++++------
>  4 files changed, 34 insertions(+), 17 deletions(-)

will apply

thanks

[...]
diff mbox

Patch

diff --git a/libavcodec/cabac.c b/libavcodec/cabac.c
index dd2b057c6d..e51139de3b 100644
--- a/libavcodec/cabac.c
+++ b/libavcodec/cabac.c
@@ -32,7 +32,7 @@ 
 #include "cabac.h"
 #include "cabac_functions.h"
 
-const uint8_t ff_h264_cabac_tables[512 + 4*2*64 + 4*64 + 63] = {
+DECLARE_ASM_ALIGNED(1, const uint8_t, ff_h264_cabac_tables)[512 + 4*2*64 + 4*64 + 63] = {
     9,8,7,7,6,6,6,6,5,5,5,5,5,5,5,5,
     4,4,4,4,4,4,4,4,4,4,4,4,4,4,4,4,
     3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,
diff --git a/libavcodec/x86/constants.c b/libavcodec/x86/constants.c
index 11002ee61e..47905c74a1 100644
--- a/libavcodec/x86/constants.c
+++ b/libavcodec/x86/constants.c
@@ -26,23 +26,23 @@  DECLARE_ALIGNED(32, const ymm_reg,  ff_pw_1)    = { 0x0001000100010001ULL, 0x000
                                                     0x0001000100010001ULL, 0x0001000100010001ULL };
 DECLARE_ALIGNED(32, const ymm_reg,  ff_pw_2)    = { 0x0002000200020002ULL, 0x0002000200020002ULL,
                                                     0x0002000200020002ULL, 0x0002000200020002ULL };
-DECLARE_ALIGNED(16, const xmm_reg,  ff_pw_3)    = { 0x0003000300030003ULL, 0x0003000300030003ULL };
-DECLARE_ALIGNED(32, const ymm_reg,  ff_pw_4)    = { 0x0004000400040004ULL, 0x0004000400040004ULL,
+DECLARE_ASM_ALIGNED(16, const xmm_reg,  ff_pw_3)    = { 0x0003000300030003ULL, 0x0003000300030003ULL };
+DECLARE_ASM_ALIGNED(32, const ymm_reg,  ff_pw_4)    = { 0x0004000400040004ULL, 0x0004000400040004ULL,
                                                     0x0004000400040004ULL, 0x0004000400040004ULL };
-DECLARE_ALIGNED(16, const xmm_reg,  ff_pw_5)    = { 0x0005000500050005ULL, 0x0005000500050005ULL };
+DECLARE_ASM_ALIGNED(16, const xmm_reg,  ff_pw_5)    = { 0x0005000500050005ULL, 0x0005000500050005ULL };
 DECLARE_ALIGNED(16, const xmm_reg,  ff_pw_8)    = { 0x0008000800080008ULL, 0x0008000800080008ULL };
-DECLARE_ALIGNED(16, const xmm_reg,  ff_pw_9)    = { 0x0009000900090009ULL, 0x0009000900090009ULL };
+DECLARE_ASM_ALIGNED(16, const xmm_reg,  ff_pw_9)    = { 0x0009000900090009ULL, 0x0009000900090009ULL };
 DECLARE_ALIGNED(8,  const uint64_t, ff_pw_15)   =   0x000F000F000F000FULL;
 DECLARE_ALIGNED(16, const xmm_reg,  ff_pw_16)   = { 0x0010001000100010ULL, 0x0010001000100010ULL };
 DECLARE_ALIGNED(16, const xmm_reg,  ff_pw_17)   = { 0x0011001100110011ULL, 0x0011001100110011ULL };
-DECLARE_ALIGNED(16, const xmm_reg,  ff_pw_18)   = { 0x0012001200120012ULL, 0x0012001200120012ULL };
+DECLARE_ASM_ALIGNED(16, const xmm_reg,  ff_pw_18)   = { 0x0012001200120012ULL, 0x0012001200120012ULL };
 DECLARE_ALIGNED(16, const xmm_reg,  ff_pw_20)   = { 0x0014001400140014ULL, 0x0014001400140014ULL };
 DECLARE_ALIGNED(16, const xmm_reg,  ff_pw_32)   = { 0x0020002000200020ULL, 0x0020002000200020ULL };
-DECLARE_ALIGNED(8,  const uint64_t, ff_pw_42)   =   0x002A002A002A002AULL;
-DECLARE_ALIGNED(8,  const uint64_t, ff_pw_53)   =   0x0035003500350035ULL;
-DECLARE_ALIGNED(16, const xmm_reg,  ff_pw_64)   = { 0x0040004000400040ULL, 0x0040004000400040ULL };
-DECLARE_ALIGNED(8,  const uint64_t, ff_pw_96)   =   0x0060006000600060ULL;
-DECLARE_ALIGNED(8,  const uint64_t, ff_pw_128)  =   0x0080008000800080ULL;
+DECLARE_ASM_ALIGNED(8,  const uint64_t, ff_pw_42)   =   0x002A002A002A002AULL;
+DECLARE_ASM_ALIGNED(8,  const uint64_t, ff_pw_53)   =   0x0035003500350035ULL;
+DECLARE_ASM_ALIGNED(16, const xmm_reg,  ff_pw_64)   = { 0x0040004000400040ULL, 0x0040004000400040ULL };
+DECLARE_ASM_ALIGNED(8,  const uint64_t, ff_pw_96)   =   0x0060006000600060ULL;
+DECLARE_ASM_ALIGNED(8,  const uint64_t, ff_pw_128)  =   0x0080008000800080ULL;
 DECLARE_ALIGNED(32, const ymm_reg,  ff_pw_255)  = { 0x00ff00ff00ff00ffULL, 0x00ff00ff00ff00ffULL,
                                                     0x00ff00ff00ff00ffULL, 0x00ff00ff00ff00ffULL };
 DECLARE_ALIGNED(32, const ymm_reg,  ff_pw_256)  = { 0x0100010001000100ULL, 0x0100010001000100ULL,
diff --git a/libavutil/mem.h b/libavutil/mem.h
index e5ca8299dc..9e344bd2c3 100644
--- a/libavutil/mem.h
+++ b/libavutil/mem.h
@@ -73,6 +73,19 @@ 
  * @param v Name of the variable
  */
 
+/**
+ * @def DECLARE_ASM_ALIGNED(n,t,v)
+ * Declare an aligned variable appropriate for use in inline assembly code.
+ *
+ * @code{.c}
+ * DECLARE_ASM_ALIGNED(16, uint64_t, pw_08) = UINT64_C(0x0008000800080008);
+ * @endcode
+ *
+ * @param n Minimum alignment in bytes
+ * @param t Type of the variable (or array element)
+ * @param v Name of the variable
+ */
+
 /**
  * @def DECLARE_ASM_CONST(n,t,v)
  * Declare a static constant aligned variable appropriate for use in inline
@@ -89,18 +102,22 @@ 
 
 #if defined(__INTEL_COMPILER) && __INTEL_COMPILER < 1110 || defined(__SUNPRO_C)
     #define DECLARE_ALIGNED(n,t,v)      t __attribute__ ((aligned (n))) v
+    #define DECLARE_ASM_ALIGNED(n,t,v)  t __attribute__ ((aligned (n))) v
     #define DECLARE_ASM_CONST(n,t,v)    const t __attribute__ ((aligned (n))) v
 #elif defined(__DJGPP__)
     #define DECLARE_ALIGNED(n,t,v)      t __attribute__ ((aligned (FFMIN(n, 16)))) v
     #define DECLARE_ASM_CONST(n,t,v)    static const t av_used __attribute__ ((aligned (FFMIN(n, 16)))) v
 #elif defined(__GNUC__) || defined(__clang__)
     #define DECLARE_ALIGNED(n,t,v)      t __attribute__ ((aligned (n))) v
+    #define DECLARE_ASM_ALIGNED(n,t,v)  t av_used __attribute__ ((aligned (n))) v
     #define DECLARE_ASM_CONST(n,t,v)    static const t av_used __attribute__ ((aligned (n))) v
 #elif defined(_MSC_VER)
     #define DECLARE_ALIGNED(n,t,v)      __declspec(align(n)) t v
+    #define DECLARE_ASM_ALIGNED(n,t,v)  __declspec(align(n)) t v
     #define DECLARE_ASM_CONST(n,t,v)    __declspec(align(n)) static const t v
 #else
     #define DECLARE_ALIGNED(n,t,v)      t v
+    #define DECLARE_ASM_ALIGNED(n,t,v)  t v
     #define DECLARE_ASM_CONST(n,t,v)    static const t v
 #endif
 
diff --git a/libswscale/x86/swscale.c b/libswscale/x86/swscale.c
index 869e7fb176..7dc2d70574 100644
--- a/libswscale/x86/swscale.c
+++ b/libswscale/x86/swscale.c
@@ -53,13 +53,13 @@  DECLARE_ASM_CONST(8, uint64_t, b15Mask)=   0x001F001F001F001FLL;
 DECLARE_ASM_CONST(8, uint64_t, g15Mask)=   0x03E003E003E003E0LL;
 DECLARE_ASM_CONST(8, uint64_t, r15Mask)=   0x7C007C007C007C00LL;
 
-DECLARE_ALIGNED(8, const uint64_t, ff_M24A)         = 0x00FF0000FF0000FFLL;
-DECLARE_ALIGNED(8, const uint64_t, ff_M24B)         = 0xFF0000FF0000FF00LL;
-DECLARE_ALIGNED(8, const uint64_t, ff_M24C)         = 0x0000FF0000FF0000LL;
+DECLARE_ASM_ALIGNED(8, const uint64_t, ff_M24A)         = 0x00FF0000FF0000FFLL;
+DECLARE_ASM_ALIGNED(8, const uint64_t, ff_M24B)         = 0xFF0000FF0000FF00LL;
+DECLARE_ASM_ALIGNED(8, const uint64_t, ff_M24C)         = 0x0000FF0000FF0000LL;
 
-DECLARE_ALIGNED(8, const uint64_t, ff_bgr2YOffset)  = 0x1010101010101010ULL;
-DECLARE_ALIGNED(8, const uint64_t, ff_bgr2UVOffset) = 0x8080808080808080ULL;
-DECLARE_ALIGNED(8, const uint64_t, ff_w1111)        = 0x0001000100010001ULL;
+DECLARE_ASM_ALIGNED(8, const uint64_t, ff_bgr2YOffset)  = 0x1010101010101010ULL;
+DECLARE_ASM_ALIGNED(8, const uint64_t, ff_bgr2UVOffset) = 0x8080808080808080ULL;
+DECLARE_ASM_ALIGNED(8, const uint64_t, ff_w1111)        = 0x0001000100010001ULL;
 
 
 //MMX versions