ISLE: Common accessors for some insn data fields (#3781)

Add accessors to prelude.isle to access data fields of
`func_addr` and `symbol_value` instructions.

These are based on similar versions I had added to the s390x
back-end, but are a bit more straightforward to use.

- func_ref_data: Extract SigRef, ExternalName, and RelocDistance
  fields given a FuncRef.

- symbol_value_data: Extract ExternalName, RelocDistance, and
  offset fields given a GlobalValue representing a Symbol.

- reloc_distance_near: Test for RelocDistance::Near.

The s390x back-end is changed to use these common versions.

Note that this exposed a bug in common isle code: This extractor:

(extractor (load_sym inst)
  (and inst
       (load _ (def_inst (symbol_value
                           (symbol_value_data _
                             (reloc_distance_near) offset)))
               (i64_from_offset
                 (memarg_symbol_offset_sum <offset _)))))

would raise an assertion in sema.rs due to a supposed cycle in
extractor definitions.  But there was no actual cycle, it was
simply that the extractor tree refers twice to the `insn_data`
extractor (once via the `load` and once via the `symbol_value`
extractor).  Fixed by checking for pre-existing definitions only
along one path in the tree, not across the whole tree.

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

@@ -65,6 +65,12 @@ pub trait Context {
     fn trap_code_integer_overflow(&mut self) -> TrapCode;
     fn trap_code_bad_conversion_to_integer(&mut self) -> TrapCode;
     fn avoid_div_traps(&mut self, arg0: Type) -> Option<()>;
+    fn func_ref_data(&mut self, arg0: FuncRef) -> (SigRef, ExternalName, RelocDistance);
+    fn symbol_value_data(
+        &mut self,
+        arg0: GlobalValue,
+    ) -> Option<(ExternalName, RelocDistance, i64)>;
+    fn reloc_distance_near(&mut self, arg0: RelocDistance) -> Option<()>;
     fn move_wide_const_from_u64(&mut self, arg0: u64) -> Option<MoveWideConst>;
     fn move_wide_const_from_negated_u64(&mut self, arg0: u64) -> Option<MoveWideConst>;
     fn imm_logic_from_u64(&mut self, arg0: u64, arg1: Type) -> Option<ImmLogic>;
@@ -96,19 +102,19 @@ pub trait Context {
     fn rotr_opposite_amount(&mut self, arg0: Type, arg1: ImmShift) -> ImmShift;
 }
 
-/// Internal type SideEffectNoResult: defined at src/prelude.isle line 307.
+/// Internal type SideEffectNoResult: defined at src/prelude.isle line 308.
 #[derive(Clone, Debug)]
 pub enum SideEffectNoResult {
     Inst { inst: MInst },
 }
 
-/// Internal type ProducesFlags: defined at src/prelude.isle line 326.
+/// Internal type ProducesFlags: defined at src/prelude.isle line 327.
 #[derive(Clone, Debug)]
 pub enum ProducesFlags {
     ProducesFlags { inst: MInst, result: Reg },
 }
 
-/// Internal type ConsumesFlags: defined at src/prelude.isle line 329.
+/// Internal type ConsumesFlags: defined at src/prelude.isle line 330.
 #[derive(Clone, Debug)]
 pub enum ConsumesFlags {
     ConsumesFlags { inst: MInst, result: Reg },
@@ -1019,7 +1025,7 @@ pub fn constructor_value_regs_none<C: Context>(
         inst: ref pattern1_0,
     } = pattern0_0
     {
-        // Rule at src/prelude.isle line 312.
+        // Rule at src/prelude.isle line 313.
         let expr0_0 = C::emit(ctx, &pattern1_0);
         let expr1_0 = C::value_regs_invalid(ctx);
         return Some(expr1_0);
@@ -1037,7 +1043,7 @@ pub fn constructor_safepoint<C: Context>(
         inst: ref pattern1_0,
     } = pattern0_0
     {
-        // Rule at src/prelude.isle line 318.
+        // Rule at src/prelude.isle line 319.
         let expr0_0 = C::emit_safepoint(ctx, &pattern1_0);
         let expr1_0 = C::value_regs_invalid(ctx);
         return Some(expr1_0);
@@ -1063,7 +1069,7 @@ pub fn constructor_with_flags<C: Context>(
             result: pattern3_1,
         } = pattern2_0
         {
-            // Rule at src/prelude.isle line 339.
+            // Rule at src/prelude.isle line 340.
             let expr0_0 = C::emit(ctx, &pattern1_0);
             let expr1_0 = C::emit(ctx, &pattern3_0);
             let expr2_0 = C::value_regs(ctx, pattern1_1, pattern3_1);
@@ -1091,7 +1097,7 @@ pub fn constructor_with_flags_1<C: Context>(
             result: pattern3_1,
         } = pattern2_0
         {
-            // Rule at src/prelude.isle line 347.
+            // Rule at src/prelude.isle line 348.
             let expr0_0 = C::emit(ctx, &pattern1_0);
             let expr1_0 = C::emit(ctx, &pattern3_0);
             return Some(pattern3_1);
@@ -1125,7 +1131,7 @@ pub fn constructor_with_flags_2<C: Context>(
                 result: pattern5_1,
             } = pattern4_0
             {
-                // Rule at src/prelude.isle line 357.
+                // Rule at src/prelude.isle line 358.
                 let expr0_0 = C::emit(ctx, &pattern1_0);
                 let expr1_0 = C::emit(ctx, &pattern5_0);
                 let expr2_0 = C::emit(ctx, &pattern3_0);