diff --git a/gcc/expr.cc b/gcc/expr.cc
index 4d1a6f3dd1c..ba00226c4e7 100644
--- a/gcc/expr.cc
+++ b/gcc/expr.cc
@@ -5976,9 +5976,9 @@ mem_ref_refers_to_non_mem_p (tree ref)
 static bool
 store_field_updates_msb_p (poly_int64 bitpos, poly_int64 bitsize, rtx to_rtx)
 {
-  poly_int64 to_size = GET_MODE_SIZE (GET_MODE (to_rtx));
-  poly_int64 bitnum = BYTES_BIG_ENDIAN ? to_size - bitsize - bitpos : bitpos;
-  return maybe_eq (bitnum + bitsize, to_size);
+  return (BYTES_BIG_ENDIAN
+	  ? maybe_le (bitpos, 0)
+	  : maybe_ge (bitpos + bitsize, GET_MODE_BITSIZE (GET_MODE (to_rtx))));
 }
 
 /* Expand an assignment that stores the value of FROM into TO.  If NONTEMPORAL
diff --git a/gcc/testsuite/gcc.dg/torture/pr124435.c b/gcc/testsuite/gcc.dg/torture/pr124435.c
new file mode 100644
index 00000000000..d9e1edf9f62
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/torture/pr124435.c
@@ -0,0 +1,18 @@
+/* { dg-do run { target le } } */
+
+short c;
+
+__attribute__((__noipa__)) short
+foo (short s)
+{
+  __builtin_memmove (1 + (char *) &s, &c, 1);
+  return s >> 10;
+}
+
+int
+main ()
+{
+  short x = foo (-6);
+  if (x)
+    __builtin_abort();
+}