Commit `c90a97f9be`

Luuk de Gram <luuk@degram.dev>

2022-05-23 18:24:03

codegen: Order error union fields per alignment

Based on the size of the payload the native backends will lower the error union with its fields (errorset & payload) in the correct order. e.g. ErrorA!u8 will first lower the error set's value and then the payload. In the event of ErrorA!u32 will lower the payload first.

master

1 parent 3264abe

Changed files (1)

src

codegen.zig

@@ -702,16 +702,50 @@ pub fn generateSymbol(
         .ErrorUnion => {
             const error_ty = typed_value.ty.errorUnionSet();
             const payload_ty = typed_value.ty.errorUnionPayload();
+
+            if (error_ty.errorSetCardinality() == .zero) {
+                const payload_val = typed_value.val.castTag(.eu_payload).?.data;
+                return generateSymbol(bin_file, src_loc, .{
+                    .ty = payload_ty,
+                    .val = payload_val,
+                }, code, debug_output, reloc_info);
+            }
+
             const is_payload = typed_value.val.errorUnionIsPayload();
 
+            if (!payload_ty.hasRuntimeBitsIgnoreComptime()) {
+                const err_val = if (!is_payload) typed_value.val else Value.initTag(.zero);
+                return generateSymbol(bin_file, src_loc, .{
+                    .ty = error_ty,
+                    .val = err_val,
+                }, code, debug_output, reloc_info);
+            }
+
+            const payload_align = payload_ty.abiAlignment(target);
+            const error_align = Type.anyerror.abiAlignment(target);
             const abi_align = typed_value.ty.abiAlignment(target);
 
+            // error value first when its type is larger than the error union's payload
+            if (error_align > payload_align) {
+                switch (try generateSymbol(bin_file, src_loc, .{
+                    .ty = error_ty,
+                    .val = if (is_payload) Value.initTag(.zero) else typed_value.val,
+                }, code, debug_output, reloc_info)) {
+                    .appended => {},
+                    .externally_managed => |external_slice| {
+                        code.appendSliceAssumeCapacity(external_slice);
+                    },
+                    .fail => |em| return Result{ .fail = em },
+                }
+            }
+
+            // emit payload part of the error union
             {
-                const error_val = if (!is_payload) typed_value.val else Value.initTag(.zero);
                 const begin = code.items.len;
+                const payload_val = if (typed_value.val.castTag(.eu_payload)) |val| val.data else Value.initTag(.undef);
                 switch (try generateSymbol(bin_file, src_loc, .{
-                    .ty = error_ty,
-                    .val = error_val,
+                    .ty = payload_ty,
+                    .val = payload_val,
                 }, code, debug_output, reloc_info)) {
                     .appended => {},
                     .externally_managed => |external_slice| {
@@ -728,12 +762,12 @@ pub fn generateSymbol(
                 }
             }
 
-            if (payload_ty.hasRuntimeBits()) {
+            // Payload size is larger than error set, so emit our error set last
+            if (error_align < payload_align) {
                 const begin = code.items.len;
-                const payload_val = if (typed_value.val.castTag(.eu_payload)) |val| val.data else Value.initTag(.undef);
                 switch (try generateSymbol(bin_file, src_loc, .{
-                    .ty = payload_ty,
-                    .val = payload_val,
+                    .ty = error_ty,
+                    .val = if (is_payload) Value.initTag(.zero) else typed_value.val,
                 }, code, debug_output, reloc_info)) {
                     .appended => {},
                     .externally_managed => |external_slice| {

Commit c90a97f9be

Commit `c90a97f9be`