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.

diff --git a/gcc/config/arm/arm.md b/gcc/config/arm/arm.md
index 064604808cccb2a9d747e1f3055d757217a08db2..5d3f21b91c4e931270b9a7c532abef15a1e82260 100644 (file)
--- 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 9961f9389fedb5778ef7e9876eea38a071d37714..f0030a8c36a4493e920f332866e26cbb711ea3dc 100644 (file)
--- 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")]
 )