AArch64: port load and store operations to ISLE. (#4785)

This retains `lower_amode` in the handwritten code (@akirilov-arm
reports that there is an upcoming patch to port this), but tweaks it
slightly to take a `Value` rather than an `Inst`.

cranelift/codegen/src/ir/dynamic_type.rs

@@ -1,6 +1,7 @@
 //! Dynamic IR types
 
 use crate::ir::entities::DynamicType;
+use crate::ir::types::*;
 use crate::ir::GlobalValue;
 use crate::ir::PrimaryMap;
 use crate::ir::Type;
@@ -36,3 +37,19 @@ impl DynamicTypeData {
 
 /// All allocated dynamic types.
 pub type DynamicTypes = PrimaryMap<DynamicType, DynamicTypeData>;
+
+/// Convert a dynamic-vector type to a fixed-vector type.
+pub fn dynamic_to_fixed(ty: Type) -> Type {
+    match ty {
+        I8X8XN => I8X8,
+        I8X16XN => I8X16,
+        I16X4XN => I16X4,
+        I16X8XN => I16X8,
+        I32X2XN => I32X2,
+        I32X4XN => I32X4,
+        I64X2XN => I64X2,
+        F32X4XN => F32X4,
+        F64X2XN => F64X2,
+        _ => unreachable!("unhandled type: {}", ty),
+    }
+}

cranelift/codegen/src/ir/mod.rs

@@ -35,7 +35,7 @@ pub use crate::ir::builder::{
 };
 pub use crate::ir::constant::{ConstantData, ConstantPool};
 pub use crate::ir::dfg::{DataFlowGraph, ValueDef};
-pub use crate::ir::dynamic_type::{DynamicTypeData, DynamicTypes};
+pub use crate::ir::dynamic_type::{dynamic_to_fixed, DynamicTypeData, DynamicTypes};
 pub use crate::ir::entities::{
     Block, Constant, DynamicStackSlot, DynamicType, FuncRef, GlobalValue, Heap, Immediate, Inst,
     JumpTable, SigRef, StackSlot, Table, UserExternalNameRef, Value,