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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<tr><td><span title='2020-01-22 22:12:34 +0100'>2020-01-22</span></td><td><a href='/guix/commit/gnu/packages/tcl.scm?id=4bd428a7ce382f623784a3ff8186aadc3cebca91'>gnu: Replace uses of 'libjpeg' with 'libjpeg-turbo'.</a><span class='msg-avail'>...</span></td><td>Marius Bakke</td></tr>
<tr><td><span title='2019-12-19 09:51:56 +0100'>2019-12-19</span></td><td><a href='/guix/commit/gnu/packages/tcl.scm?id=8a0e29d8b9da4a277c8f9613be85df16de9e8898'>gnu: tcl: Fix cross-compilation.</a><span class='msg-avail'>...</span></td><td>Mathieu Othacehe</td></tr>
<tr><td><span title='2019-12-05 17:59:01 +0100'>2019-12-05</span></td><td><a href='/guix/commit/gnu/packages/tcl.scm?id=72c7788fcf0d619fb5e99c7da0c087af8edbd6bb'>gnu: Tcl/Tk: Update to 8.6.10.</a><span class='msg-avail'>...</span></td><td>Marius Bakke</td></tr>
<tr><td><span title='2019-10-14 10:03:19 +0200'>2019-10-14</span></td><td><a href='/guix/commit/gnu/packages/tcl.scm?id=c206f1914e9299b3f9a8b8be295a02f14acc67b3'>Merge remote-tracking branch 'signed/master' into core-updates</a></td><td>Mathieu Othacehe</td></tr>
<tr><td><span title='2019-10-13 18:35:59 +0200'>2019-10-13</span></td><td><a href='/guix/commit/gnu/packages/tcl.scm?id=068d0a1c345104983a9b43f5e2cf4f7e70ab3c07'>gnu: tcl: Update home page.</a><span class='msg-avail'>...</span></td><td>Marius Bakke</td></tr>
<tr><td><span title='2019-09-24 08:12:54 +0200'>2019-09-24</span></td><td><a href='/guix/commit/gnu/packages/tcl.scm?id=ee4c8c899b91ff5a691213cb79ff181bc13fe76c'>gnu: tk: Fix cross-compilation.</a><span class='msg-avail'>...</span></td><td>Mathieu Othacehe</td></tr>
<tr><td><span title='2019-09-24 08:12:53 +0200'>2019-09-24</span></td><td><a href='/guix/commit/gnu/packages/tcl.scm?id=2ce30a37ad5d74e368a8db4a1f38877ee9759a02'>gnu: tcl: Fix cross-compilation.</a><span class='msg-avail'>...</span></td><td>Mathieu Othacehe</td></tr>
<tr><td><span title='2019-06-27 23:33:48 +0200'>2019-06-27</span></td><td><a href='/guix/commit/gnu/packages/tcl.scm?id=5cc1075a76392666d3d733837f5c6252b1e48002'>Merge branch 'master' into core-updates</a></td><td>Ludovic Courtès</td></tr>
<tr><td><span title='2019-06-22 17:11:27 +0200'>2019-06-22</span></td><td><a href='/guix/commit/gnu/packages/tcl.scm?id=a5c86aa0fbb8a9fa7f5e1b79d652df54ff83229c'>gnu: Add go-github.com-nsf-gothic.</a><span class='msg-avail'>...</span></td><td>Julien Lepiller</td></tr>
<tr><td><span title='2019-06-22 17:10:48 +0200'>2019-06-22</span></td><td><a href='/guix/commit/gnu/packages/tcl.scm?id=d9d836c3231be0122355f42f52f6779d07776720'>gnu: Use license: prefix in tcl.scm.</a><span class='msg-avail'>...</span></td><td>Julien Lepiller</td></tr>
<tr><td><span title='2019-03-01 17:40:51 +0100'>2019-03-01</span></td><td><a href='/guix/commit/gnu/packages/tcl.scm?id=f5e563e50a232492e57d609a95d96081a060ea17'>Merge branch 'staging' into core-updates</a></td><td>Marius Bakke</td></tr>
<tr><td><span title='2019-02-25 02:10:55 +0100'>2019-02-25</span></td><td><a href='/guix/commit/gnu/packages/tcl.scm?id=345eec8203a3e784bd692a19bf2dc23728569297'>gnu: tcllib: Update to 1.19.</a><span class='msg-avail'>...</span></td><td>Tobias Geerinckx-Rice</td></tr>
<tr><td><span title='2019-02-25 02:10:55 +0100'>2019-02-25</span></td><td><a href='/guix/commit/gnu/packages/tcl.scm?id=f86f1531c95fe05f65183e034f1ca37fff4b0a55'>gnu: tcllib: Don't use NAME in source URI.</a><span class='msg-avail'>...</span></td><td>Tobias Geerinckx-Rice</td></tr>