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From: frederic.recoules@univ-grenoble-alpes.fr
To: alsa-devel@alsa-project.org
Cc: "Frédéric Recoules" <frederic.recoules@orange.fr>
Subject: [PATCH v3 2/5] pcm_dmix assembly: fix the interface for safety
Date: Wed,  6 May 2020 19:19:21 +0200	[thread overview]
Message-ID: <20200506171924.2644-2-frederic.recoules@univ-grenoble-alpes.fr> (raw)
In-Reply-To: <20200506171924.2644-1-frederic.recoules@univ-grenoble-alpes.fr>

From: Frédéric Recoules <frederic.recoules@orange.fr>

- move 'size' and 'old_ebx' in the output section
  since they are clobbered;
- add the "memory" clobber since input pointers
  are accessed;
- (minor) add the "cc" clobber since flags are
  clobbered.

  The compiler is missing some dataflow information
  about the execution of the assembly chunks.
  For instance, it assumes that 'size' remains unchanged
  and that no input pointer is accessed.
  The compiler optimizer may take advantage of these
  assumption and produce a wrong code.

Note: currently produces the same binary output.

Signed-off-by: Frédéric Recoules <frederic.recoules@orange.fr>
---
 src/pcm/pcm_dmix_i386.h   | 45 +++++++++++++++++----------------------
 src/pcm/pcm_dmix_x86_64.h | 27 +++++++++++------------
 2 files changed, 32 insertions(+), 40 deletions(-)

diff --git a/src/pcm/pcm_dmix_i386.h b/src/pcm/pcm_dmix_i386.h
index e816d5e0..3ea0737d 100644
--- a/src/pcm/pcm_dmix_i386.h
+++ b/src/pcm/pcm_dmix_i386.h
@@ -142,12 +142,11 @@ static void MIX_AREAS_16(unsigned int size,
 		"7:"
 		"\tmovl %[old_ebx], %%ebx\n"	/* ebx is GOT pointer (-fPIC) */
 
-		: /* no output regs */
-		: [size] "m" (size),
-		  [dst] "m" (dst), [src] "m" (src), [sum] "m" (sum),
+		: [size] "+m" (size), [old_ebx] "=m" (old_ebx)
+		: [dst] "m" (dst), [src] "m" (src), [sum] "m" (sum),
 		  [dst_step] "m" (dst_step),  [src_step] "m" (src_step),
-		  [sum_step] "m" (sum_step), [old_ebx] "m" (old_ebx)
-		: "esi", "edi", "edx", "ecx", "eax"
+		  [sum_step] "m" (sum_step)
+		: "esi", "edi", "edx", "ecx", "eax", "memory", "cc"
 	);
 }
 
@@ -233,12 +232,11 @@ static void MIX_AREAS_16_MMX(unsigned int size,
                 "5:"
 		"\tmovl %[old_ebx], %%ebx\n"	/* ebx is GOT pointer (-fPIC) */
 
-		: /* no output regs */
-		: [size] "m" (size),
-		  [dst] "m" (dst), [src] "m" (src), [sum] "m" (sum),
+	        : [size] "+m" (size), [old_ebx] "=m" (old_ebx)
+		: [dst] "m" (dst), [src] "m" (src), [sum] "m" (sum),
 		  [dst_step] "m" (dst_step),  [src_step] "m" (src_step),
-		  [sum_step] "m" (sum_step), [old_ebx] "m" (old_ebx)
-		: "esi", "edi", "edx", "ecx", "eax"
+		  [sum_step] "m" (sum_step)
+		: "esi", "edi", "edx", "ecx", "eax", "memory", "cc"
 	);
 }
 
@@ -347,12 +345,11 @@ static void MIX_AREAS_32(unsigned int size,
 		"6:"
 		"\tmovl %[old_ebx], %%ebx\n"	/* ebx is GOT pointer (-fPIC) */
 
-		: /* no output regs */
-		: [size] "m" (size),
-		  [dst] "m" (dst), [src] "m" (src), [sum] "m" (sum),
+		: [size] "+m" (size), [old_ebx] "=m" (old_ebx)
+		: [dst] "m" (dst), [src] "m" (src), [sum] "m" (sum),
 		  [dst_step] "m" (dst_step),  [src_step] "m" (src_step),
-		  [sum_step] "m" (sum_step), [old_ebx] "m" (old_ebx)
-		: "esi", "edi", "edx", "ecx", "eax"
+		  [sum_step] "m" (sum_step)
+		: "esi", "edi", "edx", "ecx", "eax", "memory", "cc"
 	);
 }
 
@@ -454,12 +451,11 @@ static void MIX_AREAS_24(unsigned int size,
 		"6:"
 		"\tmovl %[old_ebx], %%ebx\n"	/* ebx is GOT pointer (-fPIC) */
 
-		: /* no output regs */
-		: [size] "m" (size),
-		  [dst] "m" (dst), [src] "m" (src), [sum] "m" (sum),
+	        : [size] "+m" (size), [old_ebx] "=m" (old_ebx)
+		: [dst] "m" (dst), [src] "m" (src), [sum] "m" (sum),
 		  [dst_step] "m" (dst_step),  [src_step] "m" (src_step),
-		  [sum_step] "m" (sum_step), [old_ebx] "m" (old_ebx)
-		: "esi", "edi", "edx", "ecx", "eax"
+		  [sum_step] "m" (sum_step)
+		: "esi", "edi", "edx", "ecx", "eax", "memory", "cc"
 	);
 }
 
@@ -554,11 +550,10 @@ static void MIX_AREAS_24_CMOV(unsigned int size,
 		"6:"
 		"\tmovl %[old_ebx], %%ebx\n"	/* ebx is GOT pointer (-fPIC) */
 
-		: /* no output regs */
-		: [size] "m" (size),
-		  [dst] "m" (dst), [src] "m" (src), [sum] "m" (sum),
+	        : [size] "+m" (size), [old_ebx] "=m" (old_ebx)
+		: [dst] "m" (dst), [src] "m" (src), [sum] "m" (sum),
 		  [dst_step] "m" (dst_step),  [src_step] "m" (src_step),
-		  [sum_step] "m" (sum_step), [old_ebx] "m" (old_ebx)
-		: "esi", "edi", "edx", "ecx", "eax"
+		  [sum_step] "m" (sum_step)
+		: "esi", "edi", "edx", "ecx", "eax", "memory", "cc"
 	);
 }
diff --git a/src/pcm/pcm_dmix_x86_64.h b/src/pcm/pcm_dmix_x86_64.h
index dc433b35..7f711547 100644
--- a/src/pcm/pcm_dmix_x86_64.h
+++ b/src/pcm/pcm_dmix_x86_64.h
@@ -114,12 +114,11 @@ static void MIX_AREAS_16(unsigned int size,
 		"\temms\n"
 		"\tmovq %[old_rbx], %%rbx\n"
 
-		: /* no output regs */
-	        : [size] "m" (size),
-		  [dst] "m" (dst), [src] "m" (src), [sum] "m" (sum),
+		: [size] "+m" (size), [old_rbx] "=m" (old_rbx)
+	        : [dst] "m" (dst), [src] "m" (src), [sum] "m" (sum),
 		  [dst_step] "m" (dst_step),  [src_step] "m" (src_step),
-		  [sum_step] "m" (sum_step), [old_rbx] "m" (old_rbx)
-		: "rsi", "rdi", "edx", "ecx", "eax"
+		  [sum_step] "m" (sum_step)
+		: "rsi", "rdi", "edx", "ecx", "eax", "memory", "cc"
 	);
 }
 
@@ -230,12 +229,11 @@ static void MIX_AREAS_32(unsigned int size,
 		"6:"
 		"\tmovq %[old_rbx], %%rbx\n"
 
-		: /* no output regs */
-	        : [size] "m" (size),
-		  [dst] "m" (dst), [src] "m" (src), [sum] "m" (sum),
+		: [size] "+m" (size), [old_rbx] "=m" (old_rbx)
+	        : [dst] "m" (dst), [src] "m" (src), [sum] "m" (sum),
 		  [dst_step] "m" (dst_step),  [src_step] "m" (src_step),
-		  [sum_step] "m" (sum_step), [old_rbx] "m" (old_rbx)
-		: "rsi", "rdi", "edx", "ecx", "eax"
+		  [sum_step] "m" (sum_step)
+		: "rsi", "rdi", "edx", "ecx", "eax", "memory", "cc"
 	);
 }
 
@@ -334,11 +332,10 @@ static void MIX_AREAS_24(unsigned int size,
 		"6:"
 		"\tmovq %[old_rbx], %%rbx\n"
 
-		: /* no output regs */
-	        : [size] "m" (size),
-		  [dst] "m" (dst), [src] "m" (src), [sum] "m" (sum),
+		: [size] "+m" (size), [old_rbx] "=m" (old_rbx)
+	        : [dst] "m" (dst), [src] "m" (src), [sum] "m" (sum),
 		  [dst_step] "m" (dst_step),  [src_step] "m" (src_step),
-		  [sum_step] "m" (sum_step), [old_rbx] "m" (old_rbx)
-		: "rsi", "rdi", "edx", "ecx", "eax"
+		  [sum_step] "m" (sum_step)
+		: "rsi", "rdi", "edx", "ecx", "eax", "memory", "cc"
 	);
 }
-- 
2.17.1


  reply	other threads:[~2020-05-06 17:23 UTC|newest]

Thread overview: 7+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-05-06 17:19 [PATCH v3 1/5] pcm_dmix assembly: change the token by symbolic names frederic.recoules
2020-05-06 17:19 ` frederic.recoules [this message]
2020-05-06 17:19 ` [PATCH v3 3/5] pcm_dmix assembly: fix the interface for safety (mmx) frederic.recoules
2020-05-06 17:19 ` [PATCH v3 4/5] pcm_dmix assembly: refactor the PIC mode frederic.recoules
2020-05-06 17:19 ` [PATCH v3 5/5] pcm_dmix assembly: give more freedom over the constraints frederic.recoules
2020-05-06 20:36 ` [PATCH v3 1/5] pcm_dmix assembly: change the token by symbolic names Takashi Iwai
2020-05-14 17:33   ` FRÉDÉRIC RECOULES

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