This backport contains 1 patch from gcc main stream tree.
The commit id of these patchs list as following in the order of time.

0001-re-PR-debug-83666-ICE-SIGFPE-with-O2-g-param-sccvn-m.patch
c54af0682ce0881ecde74a3b7502287a53ced378

diff -Nurp a/gcc/cfgexpand.c b/gcc/cfgexpand.c
--- a/gcc/cfgexpand.c	2021-06-20 21:43:53.568000000 -0400
+++ b/gcc/cfgexpand.c	2021-06-20 22:04:33.432000000 -0400
@@ -4516,7 +4516,7 @@ expand_debug_expr (tree exp)
         if (bitpos < 0)
           return NULL;
 
-	if (GET_MODE (op0) == BLKmode)
+	if (GET_MODE (op0) == BLKmode || mode == BLKmode)
 	  return NULL;
 
 	if ((bitpos % BITS_PER_UNIT) == 0
diff -Nurp a/gcc/testsuite/gcc.dg/pr83666.c b/gcc/testsuite/gcc.dg/pr83666.c
--- a/gcc/testsuite/gcc.dg/pr83666.c	1969-12-31 19:00:00.000000000 -0500
+++ b/gcc/testsuite/gcc.dg/pr83666.c	2021-06-20 22:04:33.432000000 -0400
@@ -0,0 +1,28 @@
+/* PR debug/83666 */
+/* { dg-do compile } */
+/* { dg-options "-O2 -g --param=sccvn-max-scc-size=10 -Wno-psabi" } */
+
+typedef int __attribute__ ((vector_size (64))) V;
+
+int c, d;
+short e;
+V g;
+
+V
+bar (void)
+{
+  g[1] = d;
+  do
+    {
+      e += c;
+      g = g > 0;
+    }
+  while (g[1]);
+  return g;
+}
+
+void
+foo (void)
+{
+  int x = bar ()[3];
+}