Move CompiledBlob to a new file

cranelift/simplejit/src/compiled_blob.rs

@@ -0,0 +1,55 @@
+use cranelift_codegen::binemit::Reloc;
+use cranelift_codegen::ir::ExternalName;
+use cranelift_module::RelocRecord;
+
+#[derive(Clone)]
+pub(crate) struct CompiledBlob {
+    pub(crate) ptr: *mut u8,
+    pub(crate) size: usize,
+    pub(crate) relocs: Vec<RelocRecord>,
+}
+
+impl CompiledBlob {
+    pub(crate) fn perform_relocations(&self, get_definition: impl Fn(&ExternalName) -> *const u8) {
+        use std::ptr::write_unaligned;
+
+        for &RelocRecord {
+            reloc,
+            offset,
+            ref name,
+            addend,
+        } in &self.relocs
+        {
+            debug_assert!((offset as usize) < self.size);
+            let at = unsafe { self.ptr.offset(offset as isize) };
+            let base = get_definition(name);
+            // TODO: Handle overflow.
+            let what = unsafe { base.offset(addend as isize) };
+            match reloc {
+                Reloc::Abs4 => {
+                    // TODO: Handle overflow.
+                    #[cfg_attr(feature = "cargo-clippy", allow(clippy::cast_ptr_alignment))]
+                    unsafe {
+                        write_unaligned(at as *mut u32, what as u32)
+                    };
+                }
+                Reloc::Abs8 => {
+                    #[cfg_attr(feature = "cargo-clippy", allow(clippy::cast_ptr_alignment))]
+                    unsafe {
+                        write_unaligned(at as *mut u64, what as u64)
+                    };
+                }
+                Reloc::X86PCRel4 | Reloc::X86CallPCRel4 => {
+                    // TODO: Handle overflow.
+                    let pcrel = ((what as isize) - (at as isize)) as i32;
+                    #[cfg_attr(feature = "cargo-clippy", allow(clippy::cast_ptr_alignment))]
+                    unsafe {
+                        write_unaligned(at as *mut i32, pcrel)
+                    };
+                }
+                Reloc::X86GOTPCRel4 | Reloc::X86CallPLTRel4 => panic!("unexpected PIC relocation"),
+                _ => unimplemented!(),
+            }
+        }
+    }
+}