diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index 856ce684b79..b7c0fbeaa9d 100644
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,3 +1,9 @@
+2019-08-27  Richard Earnshaw  <rearnsha@arm.com>
+
+	* config/arm/arm.md (stack_protect_set_insn): Add security-related
+	comment.
+	* config/aarch64/aarch64.md (stack_protect_set_<mode>): Likewise.
+
 2019-08-27  Martin Liska  <mliska@suse.cz>
 
 	* cgraph.c (cgraph_node::remove): Remove dead assignment before
diff --git a/gcc/config/aarch64/aarch64.md b/gcc/config/aarch64/aarch64.md
index 9a07f631010..88e04df6a80 100644
--- a/gcc/config/aarch64/aarch64.md
+++ b/gcc/config/aarch64/aarch64.md
@@ -7016,13 +7016,15 @@
  }
  [(set_attr "type" "mrs")])
 
+;; DO NOT SPLIT THIS PATTERN.  It is important for security reasons that the
+;; canary value does not live beyond the life of this sequence.
 (define_insn "stack_protect_set_<mode>"
   [(set (match_operand:PTR 0 "memory_operand" "=m")
 	(unspec:PTR [(match_operand:PTR 1 "memory_operand" "m")]
 	 UNSPEC_SP_SET))
    (set (match_scratch:PTR 2 "=&r") (const_int 0))]
   ""
-  "ldr\\t%<w>2, %1\;str\\t%<w>2, %0\;mov\t%<w>2,0"
+  "ldr\\t%<w>2, %1\;str\\t%<w>2, %0\;mov\t%<w>2, 0"
   [(set_attr "length" "12")
    (set_attr "type" "multiple")])
 
diff --git a/gcc/config/arm/arm.md b/gcc/config/arm/arm.md
index ed49c4beda1..f138d31f012 100644
--- a/gcc/config/arm/arm.md
+++ b/gcc/config/arm/arm.md
@@ -8208,6 +8208,8 @@
   [(set_attr "arch" "t1,32")]
 )
 
+;; DO NOT SPLIT THIS INSN.  It's important for security reasons that the
+;; canary value does not live beyond the life of this sequence.
 (define_insn "*stack_protect_set_insn"
   [(set (match_operand:SI 0 "memory_operand" "=m,m")
 	(unspec:SI [(mem:SI (match_operand:SI 1 "register_operand" "+&l,&r"))]
@@ -8215,8 +8217,8 @@
    (clobber (match_dup 1))]
   ""
   "@
-   ldr\\t%1, [%1]\;str\\t%1, %0\;movs\t%1,#0
-   ldr\\t%1, [%1]\;str\\t%1, %0\;mov\t%1,#0"
+   ldr\\t%1, [%1]\;str\\t%1, %0\;movs\t%1, #0
+   ldr\\t%1, [%1]\;str\\t%1, %0\;mov\t%1, #0"
   [(set_attr "length" "8,12")
    (set_attr "conds" "clob,nocond")
    (set_attr "type" "multiple")