Cranelift(aarch64): Use an existing extractor instead of a new pure constructor (#5273)

cranelift/codegen/src/isa/aarch64/inst.isle

@@ -1614,9 +1614,6 @@
 (decl imm12_from_u64 (Imm12) u64)
 (extern extractor imm12_from_u64 imm12_from_u64)
 
-(decl pure make_imm12_from_u64 (u64) Imm12)
-(extern constructor make_imm12_from_u64 make_imm12_from_u64)
-
 (decl u8_into_uimm5 (u8) UImm5)
 (extern constructor u8_into_uimm5 u8_into_uimm5)
 
@@ -3483,12 +3480,12 @@
 (rule (lower_icmp_const (IntCC.UnsignedGreaterThanOrEqual) a b ty)
       (if (ty_int_ref_scalar_64 ty))
       (if-let $true (u64_is_odd b))
-      (if-let imm (make_imm12_from_u64 (u64_sub b 1)))
+      (if-let (imm12_from_u64 imm) (u64_sub b 1))
   (flags_and_cc (cmp_imm (operand_size ty) a imm) (IntCC.UnsignedGreaterThan)))
 (rule (lower_icmp_const (IntCC.SignedGreaterThanOrEqual) a b ty)
       (if (ty_int_ref_scalar_64 ty))
       (if-let $true (u64_is_odd b))
-      (if-let imm (make_imm12_from_u64 (u64_sub b 1)))
+      (if-let (imm12_from_u64 imm) (u64_sub b 1))
   (flags_and_cc (cmp_imm (operand_size ty) a imm) (IntCC.SignedGreaterThan)))
 
 (rule -1 (lower_icmp_const cond rn (imm12_from_u64 c) ty)

cranelift/codegen/src/isa/aarch64/lower/isle.rs

@@ -129,10 +129,6 @@ impl Context for IsleContext<'_, '_, MInst, Flags, IsaFlags, 6> {
         Imm12::maybe_from_u64(n)
     }
 
-    fn make_imm12_from_u64(&mut self, n: u64) -> Option<Imm12> {
-        Imm12::maybe_from_u64(n)
-    }
-
     fn imm12_from_negated_u64(&mut self, n: u64) -> Option<Imm12> {
         Imm12::maybe_from_u64((n as i64).wrapping_neg() as u64)
     }