Use same CompiledCode for import replacement (#478)

This commit allows CompiledCode to be re-used regardless of
the existence of import replacement configs for instantiation.

In order to achieve this, we introduce ModuleID, which is sha256
checksum calculated on source bytes, as a key for module compilation
cache. Previously, we used*wasm.Module as keys for caches which
differ before/after import replacement.

Signed-off-by: Takeshi Yoneda takeshi@tetrate.io

builder_test.go

@@ -346,8 +346,11 @@ func TestNewModuleBuilder_Build(t *testing.T) {
 			b := tc.input(NewRuntime()).(*moduleBuilder)
 			m, err := b.Build()
 			require.NoError(t, err)
+
 			requireHostModuleEquals(t, tc.expected, m.module)
 
+			require.Equal(t, b.r.store.Engine, m.compiledEngine)
+
 			// Built module must be instantiable by Engine.
 			_, err = b.r.InstantiateModule(m)
 			require.NoError(t, err)