[gcc r10-10066] arm: fix vlldm erratum for Armv8.1-m [PR102035]

[gcc r10-10066] arm: fix vlldm erratum for Armv8.1-m [PR102035]

[Richard Earnshaw]

https://gcc.gnu.org/g:08ecab2cce4cbe9a31148cad088473c8af5dbd29

commit r10-10066-g08ecab2cce4cbe9a31148cad088473c8af5dbd29
Author: Richard Earnshaw <rearnsha@arm.com>
Date:   Fri Jun 18 17:18:37 2021 +0100

    arm: fix vlldm erratum for Armv8.1-m [PR102035]
    
    For Armv8.1-m we generate code that emits VLLDM directly and do not
    rely on support code in the library, so emit the mitigation directly
    as well, when required.  In this case, we can use the compiler options
    to determine when to apply the fix and when it is safe to omit it.
    
    gcc:
            PR target/102035
            * config/arm/arm.md (attribute arch): Add fix_vlldm.
            (arch_enabled): Use it.
            * config/arm/vfp.md (lazy_store_multiple_insn): Add alternative to
            use when erratum mitigation is needed.
    (cherry picked from commit 30461cf8dba3d3adb15a125e4da48800eb2b9b8f)

Diff:
---
 gcc/config/arm/arm.md | 11 +++++++++--
 gcc/config/arm/vfp.md | 10 +++++++---
 2 files changed, 16 insertions(+), 5 deletions(-)

diff --git a/gcc/config/arm/arm.md b/gcc/config/arm/arm.md
index a8ee9e1afab..650b0f7f6a4 100644
--- a/gcc/config/arm/arm.md
+++ b/gcc/config/arm/arm.md
@@ -132,9 +132,12 @@
 ; TARGET_32BIT, "t1" or "t2" to specify a specific Thumb mode.  "v6"
 ; for ARM or Thumb-2 with arm_arch6, and nov6 for ARM without
 ; arm_arch6.  "v6t2" for Thumb-2 with arm_arch6 and "v8mb" for ARMv8-M
-; Baseline.  This attribute is used to compute attribute "enabled",
+; Baseline.  "fix_vlldm" is for fixing the v8-m/v8.1-m VLLDM erratum.
+; This attribute is used to compute attribute "enabled",
 ; use type "any" to enable an alternative in all cases.
-(define_attr "arch" "any,a,t,32,t1,t2,v6,nov6,v6t2,v8mb,iwmmxt,iwmmxt2,armv6_or_vfpv3,neon,mve"
+(define_attr "arch" "any, a, t, 32, t1, t2, v6,nov6, v6t2, \
+		     v8mb, fix_vlldm, iwmmxt, iwmmxt2, armv6_or_vfpv3, \
+		     neon, mve"
   (const_string "any"))
 
 (define_attr "arch_enabled" "no,yes"
@@ -177,6 +180,10 @@
 	      (match_test "TARGET_THUMB1 && arm_arch8"))
 	 (const_string "yes")
 
+	 (and (eq_attr "arch" "fix_vlldm")
+	      (match_test "fix_vlldm"))
+	 (const_string "yes")
+
 	 (and (eq_attr "arch" "iwmmxt2")
 	      (match_test "TARGET_REALLY_IWMMXT2"))
 	 (const_string "yes")
diff --git a/gcc/config/arm/vfp.md b/gcc/config/arm/vfp.md
index 0ff3b37e21a..63915478582 100644
--- a/gcc/config/arm/vfp.md
+++ b/gcc/config/arm/vfp.md
@@ -1720,11 +1720,15 @@
 
 (define_insn "lazy_load_multiple_insn"
   [(unspec_volatile
-    [(mem:BLK (match_operand:SI 0 "s_register_operand" "rk"))]
+    [(mem:BLK (match_operand:SI 0 "s_register_operand" "rk,rk"))]
     VUNSPEC_VLLDM)]
   "use_cmse && reload_completed"
-  "vlldm%?\\t%0"
-  [(set_attr "predicable" "yes")
+  "@
+   vscclrm\\t{vpr}\;vlldm\\t%0
+   vlldm\\t%0"
+  [(set_attr "arch" "fix_vlldm,*")
+   (set_attr "predicable" "no")
+   (set_attr "length" "8,4")
    (set_attr "type" "load_4")]
 )