diff --git a/libgcc/ChangeLog b/libgcc/ChangeLog
index a715f0b074e..aeaa6539167 100644
--- a/libgcc/ChangeLog
+++ b/libgcc/ChangeLog
@@ -1,3 +1,10 @@
+2018-04-16  Jakub Jelinek  <jakub@redhat.com>
+
+	PR target/84945
+	* config/i386/cpuinfo.c (set_feature): Wrap into do while (0) to avoid
+	-Wdangling-else warnings.  Mask shift counts to avoid
+	-Wshift-count-negative and -Wshift-count-overflow false positives.
+
 2018-04-06  Ruslan Bukin  <br@bsdpad.com>
 
 	* config.host (riscv*-*-freebsd*): Add RISC-V FreeBSD support.
diff --git a/libgcc/config/i386/cpuinfo.c b/libgcc/config/i386/cpuinfo.c
index 1dac110a79a..86953db2743 100644
--- a/libgcc/config/i386/cpuinfo.c
+++ b/libgcc/config/i386/cpuinfo.c
@@ -275,7 +275,14 @@ get_available_features (unsigned int ecx, unsigned int edx,
     }
 
 #define set_feature(f) \
-  if (f < 32) features |= (1U << f); else features2 |= (1U << (f - 32))
+  do						\
+    {						\
+      if (f < 32)				\
+	features |= (1U << (f & 31));		\
+      else					\
+	features2 |= (1U << ((f - 32) & 31));	\
+    }						\
+  while (0)
 
   if (edx & bit_CMOV)
     set_feature (FEATURE_CMOV);