Add trampoline compilation support for lowered imports (#4206)

* Add trampoline compilation support for lowered imports

This commit adds support to the component model implementation for
compiling trampolines suitable for calling host imports. Currently this
is purely just the compilation side of things, modifying the
wasmtime-cranelift crate and additionally filling out a new
`VMComponentOffsets` type (similar to `VMOffsets`). The actual creation
of a `VMComponentContext` is still not performed and will be a
subsequent PR.

Internally though some tests are actually possible with this where we at
least assert that compilation of a component and creation of everything
in-memory doesn't panic or trip any assertions, so some tests are added
here for that as well.

* Fix some test errors

crates/environ/src/vmoffsets.rs

@@ -95,6 +95,32 @@ pub struct VMOffsets<P> {
 pub trait PtrSize {
     /// Returns the pointer size, in bytes, for the target.
     fn size(&self) -> u8;
+
+    /// The offset of the `func_ptr` field.
+    #[allow(clippy::erasing_op)]
+    #[inline]
+    fn vmcaller_checked_anyfunc_func_ptr(&self) -> u8 {
+        0 * self.size()
+    }
+
+    /// The offset of the `type_index` field.
+    #[allow(clippy::identity_op)]
+    #[inline]
+    fn vmcaller_checked_anyfunc_type_index(&self) -> u8 {
+        1 * self.size()
+    }
+
+    /// The offset of the `vmctx` field.
+    #[inline]
+    fn vmcaller_checked_anyfunc_vmctx(&self) -> u8 {
+        2 * self.size()
+    }
+
+    /// Return the size of `VMCallerCheckedAnyfunc`.
+    #[inline]
+    fn size_of_vmcaller_checked_anyfunc(&self) -> u8 {
+        3 * self.size()
+    }
 }
 
 /// Type representing the size of a pointer for the current compilation host
@@ -310,7 +336,7 @@ impl<P: PtrSize> From<VMOffsetsFields<P>> for VMOffsets<P> {
                 = cmul(ret.num_defined_globals, ret.size_of_vmglobal_definition()),
             size(defined_anyfuncs) = cmul(
                 ret.num_escaped_funcs,
-                ret.size_of_vmcaller_checked_anyfunc(),
+                ret.ptr.size_of_vmcaller_checked_anyfunc(),
             ),
         }
 
@@ -510,35 +536,6 @@ impl<P: PtrSize> VMOffsets<P> {
     }
 }
 
-/// Offsets for `VMCallerCheckedAnyfunc`.
-impl<P: PtrSize> VMOffsets<P> {
-    /// The offset of the `func_ptr` field.
-    #[allow(clippy::erasing_op)]
-    #[inline]
-    pub fn vmcaller_checked_anyfunc_func_ptr(&self) -> u8 {
-        0 * self.pointer_size()
-    }
-
-    /// The offset of the `type_index` field.
-    #[allow(clippy::identity_op)]
-    #[inline]
-    pub fn vmcaller_checked_anyfunc_type_index(&self) -> u8 {
-        1 * self.pointer_size()
-    }
-
-    /// The offset of the `vmctx` field.
-    #[inline]
-    pub fn vmcaller_checked_anyfunc_vmctx(&self) -> u8 {
-        2 * self.pointer_size()
-    }
-
-    /// Return the size of `VMCallerCheckedAnyfunc`.
-    #[inline]
-    pub fn size_of_vmcaller_checked_anyfunc(&self) -> u8 {
-        3 * self.pointer_size()
-    }
-}
-
 /// Offsets for `VMContext`.
 impl<P: PtrSize> VMOffsets<P> {
     /// Return the offset to the `magic` value in this `VMContext`.
@@ -700,7 +697,7 @@ impl<P: PtrSize> VMOffsets<P> {
         assert!(!index.is_reserved_value());
         assert_lt!(index.as_u32(), self.num_escaped_funcs);
         self.vmctx_anyfuncs_begin()
-            + index.as_u32() * u32::from(self.size_of_vmcaller_checked_anyfunc())
+            + index.as_u32() * u32::from(self.ptr.size_of_vmcaller_checked_anyfunc())
     }
 
     /// Return the offset to the `body` field in `*const VMFunctionBody` index `index`.