Merge pull request herd#1846 from murzinv/fix-x12

[gen][AArch64] Properly reserve X12 for SME

Author: ShaleXIONG

gen/AArch64Compile_gen.ml

@@ -50,16 +50,7 @@ module Make(Cfg:Config) : XXXCompile_gen.S =
     (* Reserve SME's slice index register *)
     let x12 = Ireg R12
 
-    let next_reg x =
-      if do_sme then
-        begin
-          let r,x = A64.alloc_reg x in
-          match r with
-          | Ireg R12 -> A64.alloc_reg x
-          | _ -> r,x
-        end
-      else
-        A64.alloc_reg x
+    let next_reg x = A64.alloc_reg x
 
     let next_reg2 x =
       let r1,x = next_reg x in

gen/common/AArch64Arch_gen.ml

@@ -1109,6 +1109,13 @@ let is_valid_rmw rmw_list =
   List.length atomic_st_list = List.length (Util.List.uniq ~eq:atomic_op_equal atomic_st_list)
 end
 
+let free_registers =
+  if do_sme then
+    (* Reserve SME's slice index register *)
+    List.filter ( fun r -> r != Ireg R12) allowed_for_symb
+  else
+    allowed_for_symb
+
 include
     ArchExtra_gen.Make
     (struct
@@ -1119,7 +1126,7 @@ include
         | _ -> false
 
       let pp_reg = pp_reg
-      let free_registers = allowed_for_symb
+      let free_registers = free_registers
 
       type special = reg
       type special2 = reg