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/s390x/lower/isle.rs

@@ -13,12 +13,12 @@ use crate::machinst::isle::*;
 use crate::settings::Flags;
 use crate::{
     ir::{
-        condcodes::*, immediates::*, types::*, AtomicRmwOp, Endianness, ExternalName, Inst,
-        InstructionData, StackSlot, TrapCode, Value, ValueLabel, ValueList,
+        condcodes::*, immediates::*, types::*, AtomicRmwOp, Endianness, Inst, InstructionData,
+        StackSlot, TrapCode, Value, ValueLabel, ValueList,
     },
     isa::s390x::inst::s390x_map_regs,
     isa::unwind::UnwindInst,
-    machinst::{InsnOutput, LowerCtx, RelocDistance},
+    machinst::{InsnOutput, LowerCtx},
 };
 use std::boxed::Box;
 use std::cell::Cell;
@@ -127,18 +127,6 @@ where
         }
     }
 
-    #[inline]
-    fn symbol_value_data(&mut self, inst: Inst) -> Option<(BoxExternalName, RelocDistance, i64)> {
-        let (name, dist, offset) = self.lower_ctx.symbol_value(inst)?;
-        Some((Box::new(name.clone()), dist, offset))
-    }
-
-    #[inline]
-    fn call_target_data(&mut self, inst: Inst) -> Option<(BoxExternalName, RelocDistance)> {
-        let (name, dist) = self.lower_ctx.call_target(inst)?;
-        Some((Box::new(name.clone()), dist))
-    }
-
     #[inline]
     fn writable_gpr(&mut self, regno: u8) -> WritableReg {
         super::writable_gpr(regno)
@@ -404,15 +392,6 @@ where
         vec[usize::from(index)]
     }
 
-    #[inline]
-    fn reloc_distance_near(&mut self, dist: &RelocDistance) -> Option<()> {
-        if *dist == RelocDistance::Near {
-            Some(())
-        } else {
-            None
-        }
-    }
-
     #[inline]
     fn zero_offset(&mut self) -> Offset32 {
         Offset32::new(0)
@@ -443,6 +422,11 @@ where
         }
     }
 
+    #[inline]
+    fn box_external_name(&mut self, name: ExternalName) -> BoxExternalName {
+        Box::new(name)
+    }
+
     #[inline]
     fn memflags_trusted(&mut self) -> MemFlags {
         MemFlags::trusted()
@@ -459,9 +443,9 @@ where
     }
 
     #[inline]
-    fn memarg_symbol(&mut self, name: BoxExternalName, offset: i32, flags: MemFlags) -> MemArg {
+    fn memarg_symbol(&mut self, name: ExternalName, offset: i32, flags: MemFlags) -> MemArg {
         MemArg::Symbol {
-            name,
+            name: Box::new(name),
             offset,
             flags,
         }

cranelift/codegen/src/isa/s390x/lower/isle/generated_code.manifest

@@ -1,4 +1,4 @@
 src/clif.isle 9ea75a6f790b5c03
-src/prelude.isle 6aaf8ce0f5a5c2ec
-src/isa/s390x/inst.isle 1ae3c0f9c956affd
-src/isa/s390x/lower.isle d18ee0bff12cad4e
+src/prelude.isle 73285cd431346d53
+src/isa/s390x/inst.isle 87a2d7c0c69d0324
+src/isa/s390x/lower.isle 3c124e26bc411983