Add reference types R32 and R64

-Add resumable_trap, safepoint, isnull, and null instructions
-Add Stackmap struct and StackmapSink trait

Co-authored-by: Mir Ahmed <mirahmed753@gmail.com>
Co-authored-by: Dan Gohman <sunfish@mozilla.com>

cranelift/codegen/src/isa/riscv/binemit.rs

@@ -2,7 +2,7 @@
 
 use crate::binemit::{bad_encoding, CodeSink, Reloc};
 use crate::ir::{Function, Inst, InstructionData};
-use crate::isa::{RegUnit, StackBaseMask, StackRef};
+use crate::isa::{RegUnit, StackBaseMask, StackRef, TargetIsa};
 use crate::predicates::is_signed_int;
 use crate::regalloc::RegDiversions;
 use core::u32;

cranelift/codegen/src/isa/riscv/mod.rs

@@ -115,11 +115,11 @@ impl TargetIsa for Isa {
         divert: &mut regalloc::RegDiversions,
         sink: &mut dyn CodeSink,
     ) {
-        binemit::emit_inst(func, inst, divert, sink)
+        binemit::emit_inst(func, inst, divert, sink, self)
     }
 
     fn emit_function_to_memory(&self, func: &ir::Function, sink: &mut MemoryCodeSink) {
-        emit_function(func, binemit::emit_inst, sink)
+        emit_function(func, binemit::emit_inst, sink, self)
     }
 }