Implement Expr::StructAtIndex for wasm dev backend

compiler/gen_wasm/src/backend.rs

@@ -22,8 +22,8 @@ use crate::wasm_module::{
     LocalId, Signature, SymInfo, ValueType,
 };
 use crate::{
-    copy_memory, CopyMemoryConfig, Env, BUILTINS_IMPORT_MODULE_NAME, MEMORY_NAME, PTR_TYPE,
+    copy_memory, CopyMemoryConfig, Env, BUILTINS_IMPORT_MODULE_NAME, MEMORY_NAME, PTR_SIZE,
-    STACK_POINTER_GLOBAL_ID, STACK_POINTER_NAME,
+    PTR_TYPE, STACK_POINTER_GLOBAL_ID, STACK_POINTER_NAME,
 };
 
 /// The memory address where the constants data will be loaded during module instantiation.
@@ -540,6 +540,29 @@ impl<'a> WasmBackend<'a> {
 
             Expr::Struct(fields) => self.create_struct(sym, layout, fields),
 
+            Expr::StructAtIndex {
+                index,
+                field_layouts,
+                structure,
+            } => {
+                if let StoredValue::StackMemory { location, .. } = self.storage.get(structure) {
+                    let (local_id, mut offset) =
+                        location.local_and_offset(self.storage.stack_frame_pointer);
+                    for field in field_layouts.iter().take(*index as usize) {
+                        offset += field.stack_size(PTR_SIZE);
+                    }
+                    self.storage.copy_value_from_memory(
+                        &mut self.code_builder,
+                        *sym,
+                        local_id,
+                        offset,
+                    );
+                } else {
+                    unreachable!("Unexpected storage for {:?}", structure)
+                }
+                Ok(())
+            }
+
             x => Err(format!("Expression is not yet implemented {:?}", x)),
         }
     }

compiler/gen_wasm/src/storage.rs

@@ -319,6 +319,67 @@ impl<'a> Storage<'a> {
         }
     }
 
+    /// Generate code to copy a StoredValue from an arbitrary memory location
+    /// (defined by a pointer and offset).
+    pub fn copy_value_from_memory(
+        &mut self,
+        code_builder: &mut CodeBuilder,
+        to_symbol: Symbol,
+        from_ptr: LocalId,
+        from_offset: u32,
+    ) -> u32 {
+        let to_storage = self.get(&to_symbol).to_owned();
+        match to_storage {
+            StoredValue::StackMemory {
+                location,
+                size,
+                alignment_bytes,
+            } => {
+                let (to_ptr, to_offset) = location.local_and_offset(self.stack_frame_pointer);
+                copy_memory(
+                    code_builder,
+                    CopyMemoryConfig {
+                        from_ptr,
+                        from_offset,
+                        to_ptr,
+                        to_offset,
+                        size,
+                        alignment_bytes,
+                    },
+                );
+                size
+            }
+
+            StoredValue::VirtualMachineStack {
+                value_type, size, ..
+            }
+            | StoredValue::Local {
+                value_type, size, ..
+            } => {
+                use crate::wasm_module::Align::*;
+
+                code_builder.get_local(from_ptr);
+                match (value_type, size) {
+                    (ValueType::I64, 8) => code_builder.i64_load(Bytes8, from_offset),
+                    (ValueType::I32, 4) => code_builder.i32_load(Bytes4, from_offset),
+                    (ValueType::I32, 2) => code_builder.i32_load16_s(Bytes2, from_offset),
+                    (ValueType::I32, 1) => code_builder.i32_load8_s(Bytes1, from_offset),
+                    (ValueType::F32, 4) => code_builder.f32_load(Bytes4, from_offset),
+                    (ValueType::F64, 8) => code_builder.f64_load(Bytes8, from_offset),
+                    _ => {
+                        panic!("Cannot store {:?} with alignment of {:?}", value_type, size);
+                    }
+                };
+
+                if let StoredValue::Local { local_id, .. } = to_storage {
+                    code_builder.set_local(local_id);
+                }
+
+                size
+            }
+        }
+    }
+
     /// Generate code to copy from one StoredValue to another
     /// Copies the _entire_ value. For struct fields etc., see `copy_value_to_memory`
     pub fn clone_value(

compiler/test_gen/src/gen_records.rs

@@ -11,7 +11,7 @@ use crate::helpers::wasm::assert_evals_to;
 use indoc::indoc;
 
 #[test]
-#[cfg(any(feature = "gen-llvm", feature = "gen-dev"))]
+#[cfg(any(feature = "gen-llvm", feature = "gen-dev", feature = "gen-wasm"))]
 fn basic_record() {
     assert_evals_to!(
         indoc!(
@@ -45,7 +45,7 @@ fn basic_record() {
 }
 
 #[test]
-#[cfg(any(feature = "gen-llvm", feature = "gen-dev"))]
+#[cfg(any(feature = "gen-llvm", feature = "gen-dev", feature = "gen-wasm"))]
 fn f64_record() {
     assert_evals_to!(
         indoc!(
@@ -137,7 +137,7 @@ fn fn_record() {
 }
 
 #[test]
-#[cfg(any(feature = "gen-llvm", feature = "gen-dev"))]
+#[cfg(any(feature = "gen-llvm", feature = "gen-dev", feature = "gen-wasm"))]
 fn def_record() {
     assert_evals_to!(
         indoc!(
@@ -192,7 +192,7 @@ fn when_on_record() {
 }
 
 #[test]
-#[cfg(any(feature = "gen-llvm", feature = "gen-dev"))]
+#[cfg(any(feature = "gen-llvm", feature = "gen-dev", feature = "gen-wasm"))]
 fn when_record_with_guard_pattern() {
     assert_evals_to!(
         indoc!(
@@ -207,7 +207,7 @@ fn when_record_with_guard_pattern() {
 }
 
 #[test]
-#[cfg(any(feature = "gen-llvm", feature = "gen-dev"))]
+#[cfg(any(feature = "gen-llvm", feature = "gen-dev", feature = "gen-wasm"))]
 fn let_with_record_pattern() {
     assert_evals_to!(
         indoc!(
@@ -223,7 +223,7 @@ fn let_with_record_pattern() {
 }
 
 #[test]
-#[cfg(any(feature = "gen-llvm", feature = "gen-dev"))]
+#[cfg(any(feature = "gen-llvm", feature = "gen-dev", feature = "gen-wasm"))]
 fn record_guard_pattern() {
     assert_evals_to!(
         indoc!(
@@ -239,7 +239,7 @@ fn record_guard_pattern() {
 }
 
 #[test]
-#[cfg(any(feature = "gen-llvm", feature = "gen-dev"))]
+#[cfg(any(feature = "gen-llvm", feature = "gen-dev", feature = "gen-wasm"))]
 fn twice_record_access() {
     assert_evals_to!(
         indoc!(
@@ -254,7 +254,7 @@ fn twice_record_access() {
     );
 }
 #[test]
-#[cfg(any(feature = "gen-llvm", feature = "gen-dev", feature = "gen-dev"))]
+#[cfg(any(feature = "gen-llvm", feature = "gen-dev"))]
 fn empty_record() {
     assert_evals_to!(
         indoc!(
@@ -873,7 +873,7 @@ fn update_single_element_record() {
 }
 
 #[test]
-#[cfg(any(feature = "gen-llvm"))]
+#[cfg(any(feature = "gen-llvm", feature = "gen-wasm"))]
 fn booleans_in_record() {
     assert_evals_to!(
         indoc!("{ x: 1 == 1, y: 1 == 1 }"),
@@ -908,7 +908,7 @@ fn alignment_in_record() {
 }
 
 #[test]
-#[cfg(any(feature = "gen-llvm"))]
+#[cfg(any(feature = "gen-llvm", feature = "gen-wasm"))]
 fn blue_and_present() {
     assert_evals_to!(
         indoc!(
@@ -927,7 +927,7 @@ fn blue_and_present() {
 }
 
 #[test]
-#[cfg(any(feature = "gen-llvm"))]
+#[cfg(any(feature = "gen-llvm", feature = "gen-wasm"))]
 fn blue_and_absent() {
     assert_evals_to!(
         indoc!(