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='2019-01-15 16:46:45 +0100'>2019-01-15</span></td><td><a href='/guix/commit/gnu/packages/fpga.scm?id=9210a6c082cb201b46aa50eea9aecc4334ead83a'>gnu: yosys: Update to 0.8.</a><span class='msg-avail'>...</span></td><td>Danny Milosavljevic</td></tr>
<tr><td><span title='2019-01-15 16:46:45 +0100'>2019-01-15</span></td><td><a href='/guix/commit/gnu/packages/fpga.scm?id=eccd3f6d2ef09fcfccf5e4e09be13b79089c60d1'>gnu: arachne-pnr: Fix tests.</a><span class='msg-avail'>...</span></td><td>Danny Milosavljevic</td></tr>
<tr><td><span title='2019-01-15 16:46:45 +0100'>2019-01-15</span></td><td><a href='/guix/commit/gnu/packages/fpga.scm?id=72dd271cee8d38349b43d8a1a4fd5b6942952a42'>gnu: icestorm: Update to 0.0-2-c0cbae88a.</a><span class='msg-avail'>...</span></td><td>Danny Milosavljevic</td></tr>
<tr><td><span title='2019-01-15 16:46:43 +0100'>2019-01-15</span></td><td><a href='/guix/commit/gnu/packages/fpga.scm?id=e82baf69f18f42b58e8929000ca4b665a74d86b4'>gnu: arachne-pnr: Update to 840bdfdeb.</a><span class='msg-avail'>...</span></td><td>Amin Bandali</td></tr>
<tr><td><span title='2018-10-30 23:40:43 +0100'>2018-10-30</span></td><td><a href='/guix/commit/gnu/packages/fpga.scm?id=21fc352bad21c786ad334edc78fadf74c9a9bb0f'>gnu: yosys: Don't use unstable tarball.</a><span class='msg-avail'>...</span></td><td>Tobias Geerinckx-Rice</td></tr>
<tr><td><span title='2018-07-05 02:35:02 +0200'>2018-07-05</span></td><td><a href='/guix/commit/gnu/packages/fpga.scm?id=1e6191bb55afd1173a3ce3a8a7116b5332aedf52'>gnu: gtkwave: Mark up description.</a><span class='msg-avail'>...</span></td><td>Tobias Geerinckx-Rice</td></tr>
<tr><td><span title='2018-07-04 02:45:39 +0200'>2018-07-04</span></td><td><a href='/guix/commit/gnu/packages/fpga.scm?id=55e3e1ceb9ba0fc1b85485e66a26fa52a4146744'>gnu: gtkwave: Update to 3.3.91.</a><span class='msg-avail'>...</span></td><td>Tobias Geerinckx-Rice</td></tr>
<tr><td><span title='2018-06-26 02:17:02 +0200'>2018-06-26</span></td><td><a href='/guix/commit/gnu/packages/fpga.scm?id=99f6ef9ab4b508e5081b5bf6e031054a7e04cec1'>gnu: yosys: Return #t from all phases.</a><span class='msg-avail'>...</span></td><td>Tobias Geerinckx-Rice</td></tr>
<tr><td><span title='2018-03-16 09:08:31 -0400'>2018-03-16</span></td><td><a href='/guix/commit/gnu/packages/fpga.scm?id=6cbee49d6668eb7fd738080666f66febfce8c7e8'>gnu: All snippets report errors using exceptions, else return #t.</a><span class='msg-avail'>...</span></td><td>Mark H Weaver</td></tr>
<tr><td><span title='2018-02-19 06:00:33 +0100'>2018-02-19</span></td><td><a href='/guix/commit/gnu/packages/fpga.scm?id=77659ff3ad58c779209737dfd542cf4d6ecc057e'>gnu: iverilog: Use Texinfo in description.</a><span class='msg-avail'>...</span></td><td>Tobias Geerinckx-Rice</td></tr>
<tr><td><span title='2018-02-19 06:00:32 +0100'>2018-02-19</span></td><td><a href='/guix/commit/gnu/packages/fpga.scm?id=c046904d7470027f2666d5ba652d8385f719c779'>gnu: iverilog: Update to 10.2.</a><span class='msg-avail'>...</span></td><td>Tobias Geerinckx-Rice</td></tr>
<tr><td><span title='2017-10-03 17:07:54 +0200'>2017-10-03</span></td><td><a href='/guix/commit/gnu/packages/fpga.scm?id=d109b1e85c5c1438e66dfc05ea4a018418edaf19'>Update e-mail for Theodoros Foradis.</a><span class='msg-avail'>...</span></td><td>Theodoros Foradis</td></tr>
<tr><td><span title='2017-07-29 23:03:47 +0200'>2017-07-29</span></td><td><a href='/guix/commit/gnu/packages/fpga.scm?id=85cdab64c672c228069cd9d74d737de61db2f3e9'>gnu: yosys: Add dependency on z3.</a><span class='msg-avail'>...</span></td><td>Theodoros Foradis</td></tr>
<tr><td><span title='2017-06-20 18:10:35 +0530'>2017-06-20</span></td><td><a href='/guix/commit/gnu/packages/fpga.scm?id=148585c240f848ad08f6541ede7db3fca3411007'>gnu: Move contents of zip module into compression module.</a><span class='msg-avail'>...</span></td><td>Arun Isaac</td></tr>