Copied from Debian.

From: Dave Martin
Subject: "rsc" doesnt exist anymore in thumb2

diff --git a/fixed.h b/fixed.h
index 4b58abf..ba4bc26 100644
--- a/fixed.h
+++ b/fixed.h
@@ -275,12 +275,25 @@ mad_fixed_t mad_f_mul_inline(mad_fixed_t x, mad_fixed_t y)
 	 : "+r" (lo), "+r" (hi)  \
 	 : "%r" (x), "r" (y))
 
+#ifdef __thumb__
+/* In Thumb-2, the RSB-immediate instruction is only allowed with a zero
+	operand.  If needed this code can also support Thumb-1 
+	(simply append "s" to the end of the second two instructions). */
+#  define MAD_F_MLN(hi, lo)  \
+    asm ("rsbs        %0, %0, #0\n\t"  \
+	 "sbc   %1, %1, %1\n\t"  \
+	 "sub   %1, %1, %2"  \
+	 : "+&r" (lo), "=&r" (hi)  \
+	 : "r" (hi)  \
+	 : "cc")
+#else /* ! __thumb__ */
 #  define MAD_F_MLN(hi, lo)  \
     asm ("rsbs	%0, %2, #0\n\t"  \
 	 "rsc	%1, %3, #0"  \
-	 : "=r" (lo), "=r" (hi)  \
+	 : "=&r" (lo), "=r" (hi)  \
 	 : "0" (lo), "1" (hi)  \
 	 : "cc")
+#endif /* __thumb__ */
 
 #  define mad_f_scale64(hi, lo)  \
     ({ mad_fixed_t __result;  \
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<div class='path'>path: <a href='/guix/log/?id=018cf270a3f59d3f060d78719fdf1ffab1bea559'>root</a>/<a href='/guix/log/gnu?id=018cf270a3f59d3f060d78719fdf1ffab1bea559'>gnu</a>/<a href='/guix/log/gnu/tests?id=018cf270a3f59d3f060d78719fdf1ffab1bea559'>tests</a>/<a href='/guix/log/gnu/tests/audio.scm?id=018cf270a3f59d3f060d78719fdf1ffab1bea559'>audio.scm</a></div><div class='content'><table class='list nowrap'><tr class='nohover'><th class='left'>Age</th><th class='left'>Commit message (<a href='/guix/log/gnu/tests/audio.scm?id=018cf270a3f59d3f060d78719fdf1ffab1bea559&amp;showmsg=1'>Expand</a>)</th><th class='left'>Author</th></tr>
<tr><td><span title='2017-08-13 07:36:32 +0100'>2017-08-13</span></td><td><a href='/guix/commit/gnu/tests/audio.scm?id=06465d2ba4291eb2046c90c3977a295a9b7c434b'>gnu: Add mpd service.</a><span class='msg-avail'>...</span></td><td>Peter Mikkelsen</td></tr>