Commit 7d0fb281fe

Andrew Kelley <superjoe30@gmail.com>
2016-12-08 07:52:57
IR: a bunch of fixes and some additions
* add errorName builtin function * add assertion for generated memcopy being on correct types * respect handle_is_ptr for constant values * fix return codegen to respect sret semantics * remove ArrayLen IR instruction; we already have StructFieldPtr with "len" field * fix gen_const_val for pointers inside aggregates
1 parent a148096
src/all_types.hpp
@@ -128,7 +128,8 @@ struct ConstExprValue {
         ConstBoundFnValue x_bound_fn;
         TypeTableEntry *x_type;
         ConstExprValue *x_maybe;
-        ConstErrValue x_err;
+        ConstErrValue x_err_union;
+        ErrorTableEntry *x_pure_err;
         ConstEnumValue x_enum;
         ConstStructValue x_struct;
         ConstArrayValue x_array;
@@ -1395,6 +1396,7 @@ enum IrInstructionId {
     IrInstructionIdMinValue,
     IrInstructionIdMaxValue,
     IrInstructionIdCompileErr,
+    IrInstructionIdErrName,
 };
 
 struct IrInstruction {
@@ -1811,6 +1813,12 @@ struct IrInstructionCompileErr {
     IrInstruction *msg;
 };
 
+struct IrInstructionErrName {
+    IrInstruction base;
+
+    IrInstruction *value;
+};
+
 enum LValPurpose {
     LValPurposeNone,
     LValPurposeAssign,
src/codegen.cpp
@@ -615,6 +615,9 @@ static LLVMValueRef gen_struct_memcpy(CodeGen *g, LLVMValueRef src, LLVMValueRef
 {
     assert(handle_is_ptr(type_entry));
 
+    assert(LLVMGetTypeKind(LLVMTypeOf(src)) == LLVMPointerTypeKind);
+    assert(LLVMGetTypeKind(LLVMTypeOf(dest)) == LLVMPointerTypeKind);
+
     LLVMTypeRef ptr_u8 = LLVMPointerType(LLVMInt8Type(), 0);
 
     LLVMValueRef src_ptr = LLVMBuildBitCast(g->builder, src, ptr_u8, "");
@@ -669,7 +672,12 @@ static LLVMValueRef ir_llvm_value(CodeGen *g, IrInstruction *instruction) {
         assert(instruction->static_value.special != ConstValSpecialRuntime);
         assert(instruction->type_entry);
         render_const_val(g, instruction->type_entry, &instruction->static_value);
-        instruction->llvm_value = instruction->static_value.llvm_value;
+        if (handle_is_ptr(instruction->type_entry)) {
+            render_const_val_global(g, instruction->type_entry, &instruction->static_value);
+            instruction->llvm_value = instruction->static_value.llvm_global;
+        } else {
+            instruction->llvm_value = instruction->static_value.llvm_value;
+        }
         assert(instruction->llvm_value);
     }
     if (instruction->static_value.special != ConstValSpecialRuntime) {
@@ -681,7 +689,22 @@ static LLVMValueRef ir_llvm_value(CodeGen *g, IrInstruction *instruction) {
 }
 
 static LLVMValueRef ir_render_return(CodeGen *g, IrExecutable *executable, IrInstructionReturn *return_instruction) {
-    LLVMBuildRet(g->builder, ir_llvm_value(g, return_instruction->value));
+    LLVMValueRef value = ir_llvm_value(g, return_instruction->value);
+    TypeTableEntry *return_type = g->cur_fn->type_entry->data.fn.fn_type_id.return_type;
+    bool is_extern = g->cur_fn->type_entry->data.fn.fn_type_id.is_extern;
+    if (handle_is_ptr(return_type)) {
+        if (is_extern) {
+            LLVMValueRef by_val_value = LLVMBuildLoad(g->builder, value, "");
+            LLVMBuildRet(g->builder, by_val_value);
+        } else {
+            assert(g->cur_ret_ptr);
+            gen_assign_raw(g, return_instruction->base.source_node, g->cur_ret_ptr, value,
+                    return_type, return_instruction->value->type_entry);
+            LLVMBuildRetVoid(g->builder);
+        }
+    } else {
+        LLVMBuildRet(g->builder, value);
+    }
     return nullptr;
 }
 
@@ -1790,6 +1813,28 @@ static LLVMValueRef ir_render_ref(CodeGen *g, IrExecutable *executable, IrInstru
     }
 }
 
+static LLVMValueRef ir_render_err_name(CodeGen *g, IrExecutable *executable, IrInstructionErrName *instruction) {
+    assert(g->generate_error_name_table);
+
+    if (g->error_decls.length == 1) {
+        LLVMBuildUnreachable(g->builder);
+        return nullptr;
+    }
+
+    LLVMValueRef err_val = ir_llvm_value(g, instruction->value);
+    if (ir_want_debug_safety(g, &instruction->base)) {
+        LLVMValueRef zero = LLVMConstNull(LLVMTypeOf(err_val));
+        LLVMValueRef end_val = LLVMConstInt(LLVMTypeOf(err_val), g->error_decls.length, false);
+        add_bounds_check(g, err_val, LLVMIntNE, zero, LLVMIntULT, end_val);
+    }
+
+    LLVMValueRef indices[] = {
+        LLVMConstNull(g->builtin_types.entry_usize->type_ref),
+        err_val,
+    };
+    return LLVMBuildInBoundsGEP(g->builder, g->err_name_table, indices, 2, "");
+}
+
 static void set_debug_location(CodeGen *g, IrInstruction *instruction) {
     AstNode *source_node = instruction->source_node;
     Scope *scope = instruction->scope;
@@ -1824,6 +1869,7 @@ static LLVMValueRef ir_render_instruction(CodeGen *g, IrExecutable *executable,
         case IrInstructionIdMinValue:
         case IrInstructionIdMaxValue:
         case IrInstructionIdCompileErr:
+        case IrInstructionIdArrayLen:
             zig_unreachable();
         case IrInstructionIdReturn:
             return ir_render_return(g, executable, (IrInstructionReturn *)instruction);
@@ -1871,11 +1917,12 @@ static LLVMValueRef ir_render_instruction(CodeGen *g, IrExecutable *executable,
             return ir_render_phi(g, executable, (IrInstructionPhi *)instruction);
         case IrInstructionIdRef:
             return ir_render_ref(g, executable, (IrInstructionRef *)instruction);
+        case IrInstructionIdErrName:
+            return ir_render_err_name(g, executable, (IrInstructionErrName *)instruction);
         case IrInstructionIdSwitchVar:
         case IrInstructionIdContainerInitList:
         case IrInstructionIdStructInit:
         case IrInstructionIdEnumTag:
-        case IrInstructionIdArrayLen:
             zig_panic("TODO render more IR instructions to LLVM");
     }
     zig_unreachable();
@@ -1919,9 +1966,9 @@ static LLVMValueRef gen_const_val(CodeGen *g, TypeTableEntry *type_entry, ConstE
         case TypeTableEntryIdInt:
             return LLVMConstInt(type_entry->type_ref, bignum_to_twos_complement(&const_val->data.x_bignum), false);
         case TypeTableEntryIdPureError:
-            assert(const_val->data.x_err.err);
+            assert(const_val->data.x_pure_err);
             return LLVMConstInt(g->builtin_types.entry_pure_error->type_ref,
-                    const_val->data.x_err.err->value, false);
+                    const_val->data.x_pure_err->value, false);
         case TypeTableEntryIdFloat:
             if (const_val->data.x_bignum.kind == BigNumKindFloat) {
                 return LLVMConstReal(type_entry->type_ref, const_val->data.x_bignum.data.x_float);
@@ -2045,7 +2092,9 @@ static LLVMValueRef gen_const_val(CodeGen *g, TypeTableEntry *type_entry, ConstE
                 if (index == SIZE_MAX) {
                     render_const_val(g, child_type, const_val->data.x_ptr.base_ptr);
                     render_const_val_global(g, child_type, const_val->data.x_ptr.base_ptr);
-                    return const_val->data.x_ptr.base_ptr->llvm_global;
+                    const_val->llvm_value = const_val->data.x_ptr.base_ptr->llvm_global;
+                    render_const_val_global(g, type_entry, const_val);
+                    return const_val->llvm_value;
                 } else {
                     ConstExprValue *array_const_val = const_val->data.x_ptr.base_ptr;
                     TypeTableEntry *array_type = get_array_type(g, child_type,
@@ -2058,6 +2107,8 @@ static LLVMValueRef gen_const_val(CodeGen *g, TypeTableEntry *type_entry, ConstE
                         LLVMConstInt(usize->type_ref, index, false),
                     };
                     LLVMValueRef ptr_val = LLVMConstInBoundsGEP(array_const_val->llvm_global, indices, 2);
+                    const_val->llvm_value = ptr_val;
+                    render_const_val_global(g, type_entry, const_val);
                     return ptr_val;
                 }
             }
@@ -2065,17 +2116,17 @@ static LLVMValueRef gen_const_val(CodeGen *g, TypeTableEntry *type_entry, ConstE
             {
                 TypeTableEntry *child_type = type_entry->data.error.child_type;
                 if (!type_has_bits(child_type)) {
-                    uint64_t value = const_val->data.x_err.err ? const_val->data.x_err.err->value : 0;
+                    uint64_t value = const_val->data.x_err_union.err ? const_val->data.x_err_union.err->value : 0;
                     return LLVMConstInt(g->err_tag_type->type_ref, value, false);
                 } else {
                     LLVMValueRef err_tag_value;
                     LLVMValueRef err_payload_value;
-                    if (const_val->data.x_err.err) {
-                        err_tag_value = LLVMConstInt(g->err_tag_type->type_ref, const_val->data.x_err.err->value, false);
+                    if (const_val->data.x_err_union.err) {
+                        err_tag_value = LLVMConstInt(g->err_tag_type->type_ref, const_val->data.x_err_union.err->value, false);
                         err_payload_value = LLVMConstNull(child_type->type_ref);
                     } else {
                         err_tag_value = LLVMConstNull(g->err_tag_type->type_ref);
-                        err_payload_value = gen_const_val(g, child_type, const_val->data.x_err.payload);
+                        err_payload_value = gen_const_val(g, child_type, const_val->data.x_err_union.payload);
                     }
                     LLVMValueRef fields[] = {
                         err_tag_value,
src/eval.cpp
@@ -30,7 +30,7 @@ bool const_values_equal(ConstExprValue *a, ConstExprValue *b, TypeTableEntry *ty
         case TypeTableEntryIdVoid:
             return true;
         case TypeTableEntryIdPureError:
-            return a->data.x_err.err == b->data.x_err.err;
+            return a->data.x_pure_err == b->data.x_pure_err;
         case TypeTableEntryIdFn:
             return a->data.x_fn == b->data.x_fn;
         case TypeTableEntryIdBool:
@@ -351,17 +351,24 @@ void eval_const_expr_implicit_cast(CastOp cast_op,
             const_val->special = ConstValSpecialStatic;
             break;
         case CastOpErrorWrap:
-            const_val->data.x_err.err = nullptr;
-            const_val->data.x_err.payload = other_val;
+            const_val->data.x_err_union.err = nullptr;
+            const_val->data.x_err_union.payload = other_val;
             const_val->special = ConstValSpecialStatic;
             break;
         case CastOpPureErrorWrap:
-            const_val->data.x_err.err = other_val->data.x_err.err;
+            const_val->data.x_err_union.err = other_val->data.x_pure_err;
             const_val->special = ConstValSpecialStatic;
             break;
         case CastOpErrToInt:
             {
-                uint64_t value = other_val->data.x_err.err ? other_val->data.x_err.err->value : 0;
+                uint64_t value;
+                if (other_type->id == TypeTableEntryIdErrorUnion) {
+                    value = other_val->data.x_err_union.err ? other_val->data.x_err_union.err->value : 0;
+                } else if (other_type->id == TypeTableEntryIdPureError) {
+                    value = other_val->data.x_pure_err->value;
+                } else {
+                    zig_unreachable();
+                }
                 bignum_init_unsigned(&const_val->data.x_bignum, value);
                 const_val->special = ConstValSpecialStatic;
                 break;
src/ir.cpp
@@ -318,6 +318,10 @@ static constexpr IrInstructionId ir_instruction_id(IrInstructionCompileErr *) {
     return IrInstructionIdCompileErr;
 }
 
+static constexpr IrInstructionId ir_instruction_id(IrInstructionErrName *) {
+    return IrInstructionIdErrName;
+}
+
 template<typename T>
 static T *ir_create_instruction(IrExecutable *exec, Scope *scope, AstNode *source_node) {
     T *special_instruction = allocate<T>(1);
@@ -508,8 +512,8 @@ static IrInstruction *ir_build_const_bound_fn(IrBuilder *irb, Scope *scope, AstN
     return &const_instruction->base;
 }
 
-static IrInstruction *ir_build_const_str_lit(IrBuilder *irb, Scope *scope, AstNode *source_node, Buf *str) {
-    IrInstructionConst *const_instruction = ir_build_instruction<IrInstructionConst>(irb, scope, source_node);
+static IrInstruction *ir_create_const_str_lit(IrBuilder *irb, Scope *scope, AstNode *source_node, Buf *str) {
+    IrInstructionConst *const_instruction = ir_create_instruction<IrInstructionConst>(irb->exec, scope, source_node);
     TypeTableEntry *u8_type = irb->codegen->builtin_types.entry_u8;
     TypeTableEntry *type_entry = get_array_type(irb->codegen, u8_type, buf_len(str));
     const_instruction->base.type_entry = type_entry;
@@ -526,6 +530,11 @@ static IrInstruction *ir_build_const_str_lit(IrBuilder *irb, Scope *scope, AstNo
 
     return &const_instruction->base;
 }
+static IrInstruction *ir_build_const_str_lit(IrBuilder *irb, Scope *scope, AstNode *source_node, Buf *str) {
+    IrInstruction *instruction = ir_create_const_str_lit(irb, scope, source_node, str);
+    ir_instruction_append(irb->current_basic_block, instruction);
+    return instruction;
+}
 
 static IrInstruction *ir_build_const_c_str_lit(IrBuilder *irb, Scope *scope, AstNode *source_node, Buf *str) {
     // first we build the underlying array
@@ -1229,15 +1238,6 @@ static IrInstruction *ir_build_array_len(IrBuilder *irb, Scope *scope, AstNode *
     return &instruction->base;
 }
 
-static IrInstruction *ir_build_array_len_from(IrBuilder *irb, IrInstruction *old_instruction,
-        IrInstruction *array_value)
-{
-    IrInstruction *new_instruction = ir_build_array_len(irb, old_instruction->scope,
-            old_instruction->source_node, array_value);
-    ir_link_new_instruction(new_instruction, old_instruction);
-    return new_instruction;
-}
-
 static IrInstruction *ir_build_ref(IrBuilder *irb, Scope *scope, AstNode *source_node, IrInstruction *value) {
     IrInstructionRef *instruction = ir_build_instruction<IrInstructionRef>(irb, scope, source_node);
     instruction->value = value;
@@ -1280,6 +1280,22 @@ static IrInstruction *ir_build_compile_err(IrBuilder *irb, Scope *scope, AstNode
     return &instruction->base;
 }
 
+static IrInstruction *ir_build_err_name(IrBuilder *irb, Scope *scope, AstNode *source_node, IrInstruction *value) {
+    IrInstructionErrName *instruction = ir_build_instruction<IrInstructionErrName>(irb, scope, source_node);
+    instruction->value = value;
+
+    ir_ref_instruction(value);
+
+    return &instruction->base;
+}
+
+static IrInstruction *ir_build_err_name_from(IrBuilder *irb, IrInstruction *old_instruction, IrInstruction *value) {
+    IrInstruction *new_instruction = ir_build_err_name(irb, old_instruction->scope,
+            old_instruction->source_node, value);
+    ir_link_new_instruction(new_instruction, old_instruction);
+    return new_instruction;
+}
+
 
 static void ir_gen_defers_for_block(IrBuilder *irb, Scope *inner_scope, Scope *outer_scope,
         bool gen_error_defers, bool gen_maybe_defers)
@@ -1946,6 +1962,15 @@ static IrInstruction *ir_gen_builtin_fn_call(IrBuilder *irb, Scope *scope, AstNo
 
                 return ir_build_compile_err(irb, scope, node, arg0_value);
             }
+        case BuiltinFnIdErrName:
+            {
+                AstNode *arg0_node = node->data.fn_call_expr.params.at(0);
+                IrInstruction *arg0_value = ir_gen_node(irb, arg0_node, scope);
+                if (arg0_value == irb->codegen->invalid_instruction)
+                    return arg0_value;
+
+                return ir_build_err_name(irb, scope, node, arg0_value);
+            }
         case BuiltinFnIdMemcpy:
         case BuiltinFnIdMemset:
         case BuiltinFnIdAlignof:
@@ -1958,7 +1983,6 @@ static IrInstruction *ir_gen_builtin_fn_call(IrBuilder *irb, Scope *scope, AstNo
         case BuiltinFnIdCDefine:
         case BuiltinFnIdCUndef:
         case BuiltinFnIdCImport:
-        case BuiltinFnIdErrName:
         case BuiltinFnIdBreakpoint:
         case BuiltinFnIdReturnAddress:
         case BuiltinFnIdFrameAddress:
@@ -2834,6 +2858,11 @@ static IrInstruction *ir_gen_type_literal(IrBuilder *irb, Scope *scope, AstNode
     return ir_build_const_type(irb, scope, node, irb->codegen->builtin_types.entry_type);
 }
 
+static IrInstruction *ir_gen_error_type(IrBuilder *irb, Scope *scope, AstNode *node) {
+    assert(node->type == NodeTypeErrorType);
+    return ir_build_const_type(irb, scope, node, irb->codegen->builtin_types.entry_pure_error);
+}
+
 static IrInstruction *ir_gen_defer(IrBuilder *irb, Scope *parent_scope, AstNode *node) {
     assert(node->type == NodeTypeDefer);
 
@@ -2903,6 +2932,8 @@ static IrInstruction *ir_gen_node_raw(IrBuilder *irb, AstNode *node, Scope *scop
             return ir_lval_wrap(irb, scope, ir_gen_goto(irb, scope, node), lval);
         case NodeTypeTypeLiteral:
             return ir_lval_wrap(irb, scope, ir_gen_type_literal(irb, scope, node), lval);
+        case NodeTypeErrorType:
+            return ir_lval_wrap(irb, scope, ir_gen_error_type(irb, scope, node), lval);
         case NodeTypeBreak:
             return ir_lval_wrap(irb, scope, ir_gen_break(irb, scope, node), lval);
         case NodeTypeContinue:
@@ -2913,7 +2944,6 @@ static IrInstruction *ir_gen_node_raw(IrBuilder *irb, AstNode *node, Scope *scop
         case NodeTypeSliceExpr:
         case NodeTypeCharLiteral:
         case NodeTypeZeroesLiteral:
-        case NodeTypeErrorType:
         case NodeTypeVarLiteral:
         case NodeTypeRoot:
         case NodeTypeFnProto:
@@ -5564,7 +5594,20 @@ static TypeTableEntry *ir_analyze_instruction_field_ptr(IrAnalyze *ira, IrInstru
                 return ira->codegen->builtin_types.entry_invalid;
             }
         } else if (child_type->id == TypeTableEntryIdPureError) {
-            zig_panic("TODO error type field");
+            auto err_table_entry = ira->codegen->error_table.maybe_get(field_name);
+            if (err_table_entry) {
+                ConstExprValue *const_val = allocate<ConstExprValue>(1);
+                const_val->special = ConstValSpecialStatic;
+                const_val->data.x_pure_err = err_table_entry->value;
+
+                bool depends_on_compile_var = container_ptr->static_value.depends_on_compile_var;
+                return ir_analyze_const_ptr(ira, &field_ptr_instruction->base, const_val,
+                        child_type, depends_on_compile_var, ConstPtrSpecialNone);
+            }
+
+            ir_add_error(ira, &field_ptr_instruction->base,
+                buf_sprintf("use of undeclared error value '%s'", buf_ptr(field_name)));
+            return ira->codegen->builtin_types.entry_invalid;
         } else if (child_type->id == TypeTableEntryIdInt) {
             zig_panic("TODO integer type field");
         } else {
@@ -6525,7 +6568,12 @@ static TypeTableEntry *ir_analyze_instruction_array_len(IrAnalyze *ira,
                         len_val->data.x_bignum.data.x_uint, depends_on_compile_var);
             }
         }
-        ir_build_array_len_from(&ira->new_irb, &array_len_instruction->base, array_value);
+        TypeStructField *field = find_struct_type_field(canon_type, buf_create_from_str("len"));
+        assert(field);
+        IrInstruction *len_ptr = ir_build_struct_field_ptr(&ira->new_irb, array_len_instruction->base.scope,
+                array_len_instruction->base.source_node, array_value, field);
+        len_ptr->type_entry = get_pointer_to_type(ira->codegen, ira->codegen->builtin_types.entry_usize, true);
+        ir_build_load_ptr_from(&ira->new_irb, &array_len_instruction->base, len_ptr);
         return ira->codegen->builtin_types.entry_usize;
     } else {
         add_node_error(ira->codegen, array_len_instruction->base.source_node,
@@ -6814,6 +6862,31 @@ static TypeTableEntry *ir_analyze_instruction_compile_err(IrAnalyze *ira,
     return ira->codegen->builtin_types.entry_invalid;
 }
 
+static TypeTableEntry *ir_analyze_instruction_err_name(IrAnalyze *ira, IrInstructionErrName *instruction) {
+    IrInstruction *value = instruction->value->other;
+    if (value->type_entry->id == TypeTableEntryIdInvalid)
+        return ira->codegen->builtin_types.entry_invalid;
+
+    IrInstruction *casted_value = ir_get_casted_value(ira, value, value->type_entry);
+    if (casted_value->type_entry->id == TypeTableEntryIdInvalid)
+        return ira->codegen->builtin_types.entry_invalid;
+
+    TypeTableEntry *str_type = get_slice_type(ira->codegen, ira->codegen->builtin_types.entry_u8, true);
+    if (casted_value->static_value.special == ConstValSpecialStatic) {
+        ErrorTableEntry *err = casted_value->static_value.data.x_pure_err;
+        IrInstruction *new_instruction = ir_create_const_str_lit(&ira->new_irb, instruction->base.scope,
+                instruction->base.source_node, &err->name);
+        ir_link_new_instruction(new_instruction, &instruction->base);
+        new_instruction->static_value.special = ConstValSpecialStatic;
+        new_instruction->static_value.depends_on_compile_var = casted_value->static_value.depends_on_compile_var;
+        return str_type;
+    }
+
+    ira->codegen->generate_error_name_table = true;
+    ir_build_err_name_from(&ira->new_irb, &instruction->base, value);
+    return str_type;
+}
+
 static TypeTableEntry *ir_analyze_instruction_nocast(IrAnalyze *ira, IrInstruction *instruction) {
     switch (instruction->id) {
         case IrInstructionIdInvalid:
@@ -6904,6 +6977,8 @@ static TypeTableEntry *ir_analyze_instruction_nocast(IrAnalyze *ira, IrInstructi
             return ir_analyze_instruction_max_value(ira, (IrInstructionMaxValue *)instruction);
         case IrInstructionIdCompileErr:
             return ir_analyze_instruction_compile_err(ira, (IrInstructionCompileErr *)instruction);
+        case IrInstructionIdErrName:
+            return ir_analyze_instruction_err_name(ira, (IrInstructionErrName *)instruction);
         case IrInstructionIdCast:
         case IrInstructionIdStructFieldPtr:
         case IrInstructionIdEnumFieldPtr:
@@ -7033,6 +7108,7 @@ bool ir_has_side_effects(IrInstruction *instruction) {
         case IrInstructionIdRef:
         case IrInstructionIdMinValue:
         case IrInstructionIdMaxValue:
+        case IrInstructionIdErrName:
             return false;
         case IrInstructionIdAsm:
             {
@@ -7103,25 +7179,6 @@ bool ir_has_side_effects(IrInstruction *instruction) {
 //    return resolve_expr_const_val_as_import(g, node, child_import);
 //}
 //
-//static TypeTableEntry *analyze_err_name(CodeGen *g, ImportTableEntry *import,
-//        BlockContext *context, AstNode *node)
-//{
-//    assert(node->type == NodeTypeFnCallExpr);
-//
-//    AstNode *err_value = node->data.fn_call_expr.params.at(0);
-//    TypeTableEntry *resolved_type = analyze_expression(g, import, context,
-//            g->builtin_types.entry_pure_error, err_value);
-//
-//    if (resolved_type->id == TypeTableEntryIdInvalid) {
-//        return resolved_type;
-//    }
-//
-//    g->generate_error_name_table = true;
-//
-//    TypeTableEntry *str_type = get_slice_type(g, g->builtin_types.entry_u8, true);
-//    return str_type;
-//}
-//
 //static TypeTableEntry *analyze_embed_file(CodeGen *g, ImportTableEntry *import,
 //        BlockContext *context, AstNode *node)
 //{
@@ -7533,8 +7590,6 @@ bool ir_has_side_effects(IrInstruction *instruction) {
 //            return analyze_import(g, import, context, node);
 //        case BuiltinFnIdCImport:
 //            return analyze_c_import(g, import, context, node);
-//        case BuiltinFnIdErrName:
-//            return analyze_err_name(g, import, context, node);
 //        case BuiltinFnIdBreakpoint:
 //            mark_impure_fn(g, context, node);
 //            return g->builtin_types.entry_void;
@@ -7927,21 +7982,6 @@ bool ir_has_side_effects(IrInstruction *instruction) {
 //    }
 //}
 //
-//static TypeTableEntry *analyze_error_literal_expr(CodeGen *g, ImportTableEntry *import,
-//        BlockContext *context, AstNode *node, Buf *err_name)
-//{
-//    auto err_table_entry = g->error_table.maybe_get(err_name);
-//
-//    if (err_table_entry) {
-//        return resolve_expr_const_val_as_err(g, node, err_table_entry->value);
-//    }
-//
-//    add_node_error(g, node,
-//            buf_sprintf("use of undeclared error value '%s'", buf_ptr(err_name)));
-//
-//    return g->builtin_types.entry_invalid;
-//}
-//
 //static void validate_voided_expr(CodeGen *g, AstNode *source_node, TypeTableEntry *type_entry) {
 //    if (type_entry->id == TypeTableEntryIdMetaType) {
 //        add_node_error(g, first_executing_node(source_node), buf_sprintf("expected expression, found type"));
@@ -7952,32 +7992,6 @@ bool ir_has_side_effects(IrInstruction *instruction) {
 //
 
 
-//static LLVMValueRef gen_err_name(CodeGen *g, AstNode *node) {
-//    assert(node->type == NodeTypeFnCallExpr);
-//    assert(g->generate_error_name_table);
-//
-//    if (g->error_decls.length == 1) {
-//        LLVMBuildUnreachable(g->builder);
-//        return nullptr;
-//    }
-//
-//
-//    AstNode *err_val_node = node->data.fn_call_expr.params.at(0);
-//    LLVMValueRef err_val = gen_expr(g, err_val_node);
-//
-//    if (want_debug_safety(g, node)) {
-//        LLVMValueRef zero = LLVMConstNull(LLVMTypeOf(err_val));
-//        LLVMValueRef end_val = LLVMConstInt(LLVMTypeOf(err_val), g->error_decls.length, false);
-//        add_bounds_check(g, err_val, LLVMIntNE, zero, LLVMIntULT, end_val);
-//    }
-//
-//    LLVMValueRef indices[] = {
-//        LLVMConstNull(g->builtin_types.entry_usize->type_ref),
-//        err_val,
-//    };
-//    return LLVMBuildInBoundsGEP(g->builder, g->err_name_table, indices, 2, "");
-//}
-//
 //static LLVMValueRef gen_cmp_exchange(CodeGen *g, AstNode *node) {
 //    assert(node->type == NodeTypeFnCallExpr);
 //
@@ -8179,8 +8193,6 @@ bool ir_has_side_effects(IrInstruction *instruction) {
 //            zig_unreachable();
 //        case BuiltinFnIdCompileVar:
 //            return nullptr;
-//        case BuiltinFnIdErrName:
-//            return gen_err_name(g, node);
 //        case BuiltinFnIdBreakpoint:
 //            return LLVMBuildCall(g->builder, g->trap_fn_val, nullptr, 0, "");
 //        case BuiltinFnIdFrameAddress:
src/ir_print.cpp
@@ -676,6 +676,12 @@ static void ir_print_compile_err(IrPrint *irp, IrInstructionCompileErr *instruct
     fprintf(irp->f, ")");
 }
 
+static void ir_print_err_name(IrPrint *irp, IrInstructionErrName *instruction) {
+    fprintf(irp->f, "@errorName(");
+    ir_print_other_instruction(irp, instruction->value);
+    fprintf(irp->f, ")");
+}
+
 static void ir_print_instruction(IrPrint *irp, IrInstruction *instruction) {
     ir_print_prefix(irp, instruction);
     switch (instruction->id) {
@@ -822,6 +828,9 @@ static void ir_print_instruction(IrPrint *irp, IrInstruction *instruction) {
         case IrInstructionIdCompileErr:
             ir_print_compile_err(irp, (IrInstructionCompileErr *)instruction);
             break;
+        case IrInstructionIdErrName:
+            ir_print_err_name(irp, (IrInstructionErrName *)instruction);
+            break;
     }
     fprintf(irp->f, "\n");
 }
test/self_hosted2.zig
@@ -238,6 +238,26 @@ fn testMinValueAndMaxValue() {
     assert(@minValue(i64) == -9223372036854775808);
 }
 
+fn first4KeysOfHomeRow() -> []const u8 {
+    "aoeu"
+}
+
+fn testReturnStringFromFunction() {
+    assert(memeql(first4KeysOfHomeRow(), "aoeu"));
+}
+
+pub fn memeql(a: []const u8, b: []const u8) -> bool {
+    sliceEql(u8, a, b)
+}
+
+pub fn sliceEql(inline T: type, a: []const T, b: []const T) -> bool {
+    if (a.len != b.len) return false;
+    for (a) |item, index| {
+        if (b[index] != item) return false;
+    }
+    return true;
+}
+
 fn assert(ok: bool) {
     if (!ok)
         @unreachable();
@@ -263,6 +283,7 @@ fn runAllTests() {
     testStaticAddOne();
     testInlineVarsAgain();
     testMinValueAndMaxValue();
+    testReturnStringFromFunction();
 }
 
 export nakedcc fn _start() -> unreachable {