x64: Migrate get_pinned_reg, set_pinned_reg, vconst, and raw_bitcast to ISLE (#4763)

https://github.com/bytecodealliance/wasmtime/pull/4763

cranelift/codegen/src/isa/x64/inst.isle

@@ -1196,6 +1196,10 @@
 (decl temp_writable_xmm () WritableXmm)
 (extern constructor temp_writable_xmm temp_writable_xmm)
 
+;; Fetch the special pinned register.
+(decl pinned_writable_gpr () WritableGpr)
+(extern constructor pinned_writable_gpr pinned_writable_gpr)
+
 ;; Construct a new `XmmMem` from the given `RegMem`.
 ;;
 ;; Asserts that the `RegMem`'s register, if any, is an XMM register.
@@ -3606,6 +3610,17 @@
             (_ Unit (emit_div_or_rem kind ty dst a b)))
         dst))
 
+;;;; Pinned Register ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
+
+(decl read_pinned_gpr () Gpr)
+(rule (read_pinned_gpr)
+      (pinned_writable_gpr))
+
+(decl write_pinned_gpr (Gpr) SideEffectNoResult)
+(rule (write_pinned_gpr val)
+      (let ((dst WritableGpr (pinned_writable_gpr)))
+        (SideEffectNoResult.Inst (gen_move $I64 dst val))))
+
 ;;;; Automatic conversions ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
 
 (convert Gpr InstOutput output_gpr)