implement @bitSizeOf

Author: Vexu

doc/langref.html.in

@@ -6815,6 +6815,19 @@ async fn func(y: *i32) void {
       </p>
       {#header_close#}
 
+      {#header_open|@bitSizeOf#}
+      <pre>{#syntax#}@bitSizeOf(comptime T: type) comptime_int{#endsyntax#}</pre>
+      <p>
+      This function returns the number of bits it takes to store {#syntax#}T{#endsyntax#} in memory.
+      The result is a target-specific compile time constant.
+      </p>
+      <p>
+      This function measures the size at runtime. For types that are disallowed at runtime, such as
+      {#syntax#}comptime_int{#endsyntax#} and {#syntax#}type{#endsyntax#}, the result is {#syntax#}0{#endsyntax#}.
+      </p>
+      {#see_also|@sizeOf|@typeInfo#}
+      {#header_close#}
+
       {#header_open|@breakpoint#}
       <pre>{#syntax#}@breakpoint(){#endsyntax#}</pre>
       <p>
@@ -8044,7 +8057,7 @@ test "@setRuntimeSafety" {
       This function measures the size at runtime. For types that are disallowed at runtime, such as
       {#syntax#}comptime_int{#endsyntax#} and {#syntax#}type{#endsyntax#}, the result is {#syntax#}0{#endsyntax#}.
       </p>
-      {#see_also|@typeInfo#}
+      {#see_also|@bitSizeOf|@typeInfo#}
       {#header_close#}
 
       {#header_open|@sliceToBytes#}

src/all_types.hpp

@@ -358,6 +358,8 @@ struct LazyValueSizeOf {
 
     IrAnalyze *ira;
     IrInstruction *target_type;
+
+    bool bit_size;
 };
 
 struct LazyValueSliceType {
@@ -1754,6 +1756,7 @@ enum BuiltinFnId {
     BuiltinFnIdFrameSize,
     BuiltinFnIdAs,
     BuiltinFnIdCall,
+    BuiltinFnIdBitSizeof,
 };
 
 struct BuiltinFnEntry {
@@ -3146,6 +3149,7 @@ struct IrInstructionAsmGen {
 struct IrInstructionSizeOf {
     IrInstruction base;
 
+    bool bit_size;
     IrInstruction *type_value;
 };
 

src/codegen.cpp

@@ -8299,6 +8299,7 @@ static void define_builtin_fns(CodeGen *g) {
     create_builtin_fn(g, BuiltinFnIdFrameSize, "frameSize", 1);
     create_builtin_fn(g, BuiltinFnIdAs, "as", 2);
     create_builtin_fn(g, BuiltinFnIdCall, "call", 3);
+    create_builtin_fn(g, BuiltinFnIdBitSizeof, "bitSizeOf", 1);
 }
 
 static const char *bool_to_str(bool b) {

src/ir.cpp

@@ -2392,9 +2392,10 @@ static IrInstruction *ir_build_asm_gen(IrAnalyze *ira, Scope *scope, AstNode *so
     return &instruction->base;
 }
 
-static IrInstruction *ir_build_size_of(IrBuilder *irb, Scope *scope, AstNode *source_node, IrInstruction *type_value) {
+static IrInstruction *ir_build_size_of(IrBuilder *irb, Scope *scope, AstNode *source_node, IrInstruction *type_value, bool bit_size) {
     IrInstructionSizeOf *instruction = ir_build_instruction<IrInstructionSizeOf>(irb, scope, source_node);
     instruction->type_value = type_value;
+    instruction->bit_size = bit_size;
 
     ir_ref_instruction(type_value, irb->current_basic_block);
 
@@ -5249,13 +5250,14 @@ static IrInstruction *ir_gen_builtin_fn_call(IrBuilder *irb, Scope *scope, AstNo
                 return ir_lval_wrap(irb, scope, set_float_mode, lval, result_loc);
             }
         case BuiltinFnIdSizeof:
+        case BuiltinFnIdBitSizeof:
             {
                 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;
 
-                IrInstruction *size_of = ir_build_size_of(irb, scope, node, arg0_value);
+                IrInstruction *size_of = ir_build_size_of(irb, scope, node, arg0_value, builtin_fn->id == BuiltinFnIdBitSizeof);
                 return ir_lval_wrap(irb, scope, size_of, lval, result_loc);
             }
         case BuiltinFnIdImport:
@@ -21065,6 +21067,7 @@ static IrInstruction *ir_analyze_instruction_size_of(IrAnalyze *ira, IrInstructi
     lazy_size_of->ira = ira; ira_ref(ira);
     result->value->data.x_lazy = &lazy_size_of->base;
     lazy_size_of->base.id = LazyValueIdSizeOf;
+    lazy_size_of->bit_size = instruction->bit_size;
 
     lazy_size_of->target_type = instruction->type_value->child;
     if (ir_resolve_type_lazy(ira, lazy_size_of->target_type) == nullptr)
@@ -29415,7 +29418,10 @@ static Error ir_resolve_lazy_raw(AstNode *source_node, ZigValue *val) {
 
             val->special = ConstValSpecialStatic;
             assert(val->type->id == ZigTypeIdComptimeInt || val->type->id == ZigTypeIdInt);
-            bigint_init_unsigned(&val->data.x_bigint, abi_size);
+            if (lazy_size_of->bit_size)
+                bigint_init_unsigned(&val->data.x_bigint, size_in_bits);
+            else
+                bigint_init_unsigned(&val->data.x_bigint, abi_size);
 
             // We can't free the lazy value here, because multiple other ZigValues might be pointing to it.
             return ErrorNone;

src/ir_print.cpp

@@ -1039,7 +1039,10 @@ static void ir_print_asm_gen(IrPrint *irp, IrInstructionAsmGen *instruction) {
 }
 
 static void ir_print_size_of(IrPrint *irp, IrInstructionSizeOf *instruction) {
-    fprintf(irp->f, "@sizeOf(");
+    if (instruction->bit_size)
+        fprintf(irp->f, "@bitSizeOf(");
+    else
+        fprintf(irp->f, "@sizeOf(");
     ir_print_other_instruction(irp, instruction->type_value);
     fprintf(irp->f, ")");
 }

test/stage1/behavior/sizeof_and_typeof.zig

@@ -124,3 +124,14 @@ fn fn1(alpha: bool) void {
 test "lazy @sizeOf result is checked for definedness" {
     const f = fn1;
 }
+
+test "@bitSizeOf" {
+    expect(@bitSizeOf(u2) == 2);
+    expect(@bitSizeOf(u8) == @sizeOf(u8) * 8);
+    expect(@bitSizeOf(struct {
+        a: u2
+    }) == 8);
+    expect(@bitSizeOf(packed struct {
+        a: u2
+    }) == 2);
+}