[gcc r12-3110] arm: Fix general issues with patterns for VLLDM and VLSTM

[Richard Earnshaw <rearnsha@gcc.gnu.org>]

https://gcc.gnu.org/g:4702d3cf044924970a9a00142542da1edacfd76c

commit r12-3110-g4702d3cf044924970a9a00142542da1edacfd76c
Author: Richard Earnshaw <rearnsha@arm.com>
Date:   Fri Jun 11 17:18:12 2021 +0100

    arm: Fix general issues with patterns for VLLDM and VLSTM
    
    Both lazy_store_multiple_insn and lazy_load_multiple_insn contain
    invalid RTL (eg they contain a post_inc statement outside of a mem).
    What's more, the instructions concerned do not modify their input
    address register.  We probably got away with this because they are
    generated so late in the compilation that no subsequent pass needed to
    understand them.  Nevertheless, this could cause problems someday, so
    fixed to use a simple legal unspec.
    
    gcc:
            * config/arm/vfp.md (lazy_store_multiple_insn): Rewrite as valid RTL.
            (lazy_load_multiple_insn): Likewise.

Diff:
---
 gcc/config/arm/vfp.md | 21 +++++++++++----------
 1 file changed, 11 insertions(+), 10 deletions(-)

diff --git a/gcc/config/arm/vfp.md b/gcc/config/arm/vfp.md
index 93e963696da..9961f9389fe 100644
--- a/gcc/config/arm/vfp.md
+++ b/gcc/config/arm/vfp.md
@@ -1703,12 +1703,15 @@
    (set_attr "type" "mov_reg")]
 )
 
+;; Both this and the next instruction are treated by GCC in the same
+;; way as a blockage pattern.  That's perhaps stronger than it needs
+;; to be, but we do not want accesses to the VFP register bank to be
+;; moved across either instruction.
+
 (define_insn "lazy_store_multiple_insn"
-  [(set (match_operand:SI 0 "s_register_operand" "+&rk")
-	(post_dec:SI (match_dup 0)))
-   (unspec_volatile [(const_int 0)
-		     (mem:SI (post_dec:SI (match_dup 0)))]
-		    VUNSPEC_VLSTM)]
+  [(unspec_volatile
+    [(mem:BLK (match_operand:SI 0 "s_register_operand" "rk"))]
+    VUNSPEC_VLSTM)]
   "use_cmse && reload_completed"
   "vlstm%?\\t%0"
   [(set_attr "predicable" "yes")
@@ -1716,11 +1719,9 @@
 )
 
 (define_insn "lazy_load_multiple_insn"
-  [(set (match_operand:SI 0 "s_register_operand" "+&rk")
-	(post_inc:SI (match_dup 0)))
-   (unspec_volatile:SI [(const_int 0)
-			(mem:SI (match_dup 0))]
-		       VUNSPEC_VLLDM)]
+  [(unspec_volatile
+    [(mem:BLK (match_operand:SI 0 "s_register_operand" "rk"))]
+    VUNSPEC_VLLDM)]
   "use_cmse && reload_completed"
   "vlldm%?\\t%0"
   [(set_attr "predicable" "yes")