better string literal caching implementation

We were caching the ConstExprValue of string literals,
which works if you can never modify ConstExprValues.
This premise is broken with `comptime var ...`.

So I implemented an optimization in ConstExprValue
arrays, where it stores a `Buf *` directly rather
than an array of ConstExprValues for the elements,
and then similar to array of undefined, it is
expanded into the canonical form when necessary.
However many operations can happen directly on the
`Buf *`, which is faster.

Furthermore, before a ConstExprValue array is expanded
into canonical form, it removes itself from the string
literal cache. This fixes the issue, because before an
array element is modified it would have to be expanded.

closes #1076

1 files changed, 27 insertions, 21 deletions

diff --git a/src/codegen.cpp b/src/codegen.cpp
index 91e7c8dde9..6c4b54261c 100644
--- a/src/codegen.cpp
+++ b/src/codegen.cpp
@@ -5336,7 +5336,7 @@ static LLVMValueRef gen_parent_ptr(CodeGen *g, ConstExprValue *val, ConstParent
 
 static LLVMValueRef gen_const_ptr_array_recursive(CodeGen *g, ConstExprValue *array_const_val, size_t index) {
     expand_undef_array(g, array_const_val);
-    ConstParent *parent = &array_const_val->data.x_array.s_none.parent;
+    ConstParent *parent = &array_const_val->data.x_array.data.s_none.parent;
     LLVMValueRef base_ptr = gen_parent_ptr(g, array_const_val, parent);
 
     LLVMTypeKind el_type = LLVMGetTypeKind(LLVMGetElementType(LLVMTypeOf(base_ptr)));
@@ -5716,23 +5716,29 @@ static LLVMValueRef gen_const_val(CodeGen *g, ConstExprValue *const_val, const c
         case ZigTypeIdArray:
             {
                 uint64_t len = type_entry->data.array.len;
-                if (const_val->data.x_array.special == ConstArraySpecialUndef) {
-                    return LLVMGetUndef(type_entry->type_ref);
-                }
-
-                LLVMValueRef *values = allocate<LLVMValueRef>(len);
-                LLVMTypeRef element_type_ref = type_entry->data.array.child_type->type_ref;
-                bool make_unnamed_struct = false;
-                for (uint64_t i = 0; i < len; i += 1) {
-                    ConstExprValue *elem_value = &const_val->data.x_array.s_none.elements[i];
-                    LLVMValueRef val = gen_const_val(g, elem_value, "");
-                    values[i] = val;
-                    make_unnamed_struct = make_unnamed_struct || is_llvm_value_unnamed_type(elem_value->type, val);
-                }
-                if (make_unnamed_struct) {
-                    return LLVMConstStruct(values, len, true);
-                } else {
-                    return LLVMConstArray(element_type_ref, values, (unsigned)len);
+                switch (const_val->data.x_array.special) {
+                    case ConstArraySpecialUndef:
+                        return LLVMGetUndef(type_entry->type_ref);
+                    case ConstArraySpecialNone: {
+                        LLVMValueRef *values = allocate<LLVMValueRef>(len);
+                        LLVMTypeRef element_type_ref = type_entry->data.array.child_type->type_ref;
+                        bool make_unnamed_struct = false;
+                        for (uint64_t i = 0; i < len; i += 1) {
+                            ConstExprValue *elem_value = &const_val->data.x_array.data.s_none.elements[i];
+                            LLVMValueRef val = gen_const_val(g, elem_value, "");
+                            values[i] = val;
+                            make_unnamed_struct = make_unnamed_struct || is_llvm_value_unnamed_type(elem_value->type, val);
+                        }
+                        if (make_unnamed_struct) {
+                            return LLVMConstStruct(values, len, true);
+                        } else {
+                            return LLVMConstArray(element_type_ref, values, (unsigned)len);
+                        }
+                    }
+                    case ConstArraySpecialBuf: {
+                        Buf *buf = const_val->data.x_array.data.s_buf;
+                        return LLVMConstString(buf_ptr(buf), (unsigned)buf_len(buf), true);
+                    }
                 }
             }
         case ZigTypeIdUnion:
@@ -7278,7 +7284,7 @@ void codegen_translate_c(CodeGen *g, Buf *full_path) {
     import->source_code = nullptr;
     import->path = full_path;
     g->root_import = import;
-    import->decls_scope = create_decls_scope(nullptr, nullptr, nullptr, import);
+    import->decls_scope = create_decls_scope(g, nullptr, nullptr, nullptr, import);
 
     init(g);
 
@@ -7352,12 +7358,12 @@ static void create_test_compile_var_and_add_test_runner(CodeGen *g) {
     ConstExprValue *test_fn_array = create_const_vals(1);
     test_fn_array->type = get_array_type(g, struct_type, g->test_fns.length);
     test_fn_array->special = ConstValSpecialStatic;
-    test_fn_array->data.x_array.s_none.elements = create_const_vals(g->test_fns.length);
+    test_fn_array->data.x_array.data.s_none.elements = create_const_vals(g->test_fns.length);
 
     for (size_t i = 0; i < g->test_fns.length; i += 1) {
         ZigFn *test_fn_entry = g->test_fns.at(i);
 
-        ConstExprValue *this_val = &test_fn_array->data.x_array.s_none.elements[i];
+        ConstExprValue *this_val = &test_fn_array->data.x_array.data.s_none.elements[i];
         this_val->special = ConstValSpecialStatic;
         this_val->type = struct_type;
         this_val->data.x_struct.parent.id = ConstParentIdArray;