change @bitcast to @ptrcast

See #290

Author: andrewrk

doc/langref.md

@@ -634,9 +634,6 @@ calls the public `panic` function exposed in the root source file, or
 if there is not one specified, invokes the one provided in
 `std/special/panic.zig`.
 
-### @bitcast(comptime DestType: type, value: var) -> DestType
+### @ptrcast(comptime DestType: type, value: var) -> DestType
 
-Transmutes memory from one type to another without changing any bits.
-The source and destination types must have the same size. This function
-can be used to, for example, reinterpret a pointer, or convert a `f32` to a
-`u32`.
+Converts a pointer of one type to a pointer of another type.

src/all_types.hpp

@@ -1196,7 +1196,7 @@ enum BuiltinFnId {
     BuiltinFnIdSetGlobalSection,
     BuiltinFnIdSetGlobalLinkage,
     BuiltinFnIdPanic,
-    BuiltinFnIdBitCast,
+    BuiltinFnIdPtrCast,
 };
 
 struct BuiltinFnEntry {
@@ -1720,7 +1720,7 @@ enum IrInstructionId {
     IrInstructionIdFnProto,
     IrInstructionIdTestComptime,
     IrInstructionIdInitEnum,
-    IrInstructionIdBitCast,
+    IrInstructionIdPtrCast,
     IrInstructionIdWidenOrShorten,
     IrInstructionIdIntToPtr,
     IrInstructionIdPtrToInt,
@@ -2370,11 +2370,11 @@ struct IrInstructionInitEnum {
     LLVMValueRef tmp_ptr;
 };
 
-struct IrInstructionBitCast {
+struct IrInstructionPtrCast {
     IrInstruction base;
 
     IrInstruction *dest_type;
-    IrInstruction *target;
+    IrInstruction *ptr;
 };
 
 struct IrInstructionWidenOrShorten {

src/codegen.cpp

@@ -1345,12 +1345,12 @@ static LLVMValueRef ir_render_cast(CodeGen *g, IrExecutable *executable,
     zig_unreachable();
 }
 
-static LLVMValueRef ir_render_bitcast(CodeGen *g, IrExecutable *executable,
-        IrInstructionBitCast *instruction)
+static LLVMValueRef ir_render_ptr_cast(CodeGen *g, IrExecutable *executable,
+        IrInstructionPtrCast *instruction)
 {
     TypeTableEntry *wanted_type = instruction->base.value.type;
-    LLVMValueRef target = ir_llvm_value(g, instruction->target);
-    return LLVMBuildBitCast(g->builder, target, wanted_type->type_ref, "");
+    LLVMValueRef ptr = ir_llvm_value(g, instruction->ptr);
+    return LLVMBuildBitCast(g->builder, ptr, wanted_type->type_ref, "");
 }
 
 static LLVMValueRef ir_render_widen_or_shorten(CodeGen *g, IrExecutable *executable,
@@ -2776,8 +2776,8 @@ static LLVMValueRef ir_render_instruction(CodeGen *g, IrExecutable *executable,
             return ir_render_init_enum(g, executable, (IrInstructionInitEnum *)instruction);
         case IrInstructionIdStructInit:
             return ir_render_struct_init(g, executable, (IrInstructionStructInit *)instruction);
-        case IrInstructionIdBitCast:
-            return ir_render_bitcast(g, executable, (IrInstructionBitCast *)instruction);
+        case IrInstructionIdPtrCast:
+            return ir_render_ptr_cast(g, executable, (IrInstructionPtrCast *)instruction);
         case IrInstructionIdWidenOrShorten:
             return ir_render_widen_or_shorten(g, executable, (IrInstructionWidenOrShorten *)instruction);
         case IrInstructionIdPtrToInt:
@@ -4260,7 +4260,7 @@ static void define_builtin_fns(CodeGen *g) {
     create_builtin_fn(g, BuiltinFnIdSetGlobalSection, "setGlobalSection", 2);
     create_builtin_fn(g, BuiltinFnIdSetGlobalLinkage, "setGlobalLinkage", 2);
     create_builtin_fn(g, BuiltinFnIdPanic, "panic", 1);
-    create_builtin_fn(g, BuiltinFnIdBitCast, "bitcast", 2);
+    create_builtin_fn(g, BuiltinFnIdPtrCast, "ptrcast", 2);
 }
 
 static void add_compile_var(CodeGen *g, const char *name, ConstExprValue *value) {

src/ir.cpp

@@ -480,8 +480,8 @@ static constexpr IrInstructionId ir_instruction_id(IrInstructionInitEnum *) {
     return IrInstructionIdInitEnum;
 }
 
-static constexpr IrInstructionId ir_instruction_id(IrInstructionBitCast *) {
-    return IrInstructionIdBitCast;
+static constexpr IrInstructionId ir_instruction_id(IrInstructionPtrCast *) {
+    return IrInstructionIdPtrCast;
 }
 
 static constexpr IrInstructionId ir_instruction_id(IrInstructionWidenOrShorten *) {
@@ -1940,16 +1940,16 @@ static IrInstruction *ir_build_init_enum_from(IrBuilder *irb, IrInstruction *old
     return new_instruction;
 }
 
-static IrInstruction *ir_build_bit_cast(IrBuilder *irb, Scope *scope, AstNode *source_node,
-        IrInstruction *dest_type, IrInstruction *target)
+static IrInstruction *ir_build_ptr_cast(IrBuilder *irb, Scope *scope, AstNode *source_node,
+        IrInstruction *dest_type, IrInstruction *ptr)
 {
-    IrInstructionBitCast *instruction = ir_build_instruction<IrInstructionBitCast>(
+    IrInstructionPtrCast *instruction = ir_build_instruction<IrInstructionPtrCast>(
             irb, scope, source_node);
     instruction->dest_type = dest_type;
-    instruction->target = target;
+    instruction->ptr = ptr;
 
     if (dest_type) ir_ref_instruction(dest_type, irb->current_basic_block);
-    ir_ref_instruction(target, irb->current_basic_block);
+    ir_ref_instruction(ptr, irb->current_basic_block);
 
     return &instruction->base;
 }
@@ -2666,12 +2666,12 @@ static IrInstruction *ir_instruction_initenum_get_dep(IrInstructionInitEnum *ins
     }
 }
 
-static IrInstruction *ir_instruction_bitcast_get_dep(IrInstructionBitCast *instruction,
+static IrInstruction *ir_instruction_ptrcast_get_dep(IrInstructionPtrCast *instruction,
         size_t index)
 {
     switch (index) {
         case 0: return instruction->dest_type;
-        case 1: return instruction->target;
+        case 1: return instruction->ptr;
         default: return nullptr;
     }
 }
@@ -2928,8 +2928,8 @@ static IrInstruction *ir_instruction_get_dep(IrInstruction *instruction, size_t
             return ir_instruction_testcomptime_get_dep((IrInstructionTestComptime *) instruction, index);
         case IrInstructionIdInitEnum:
             return ir_instruction_initenum_get_dep((IrInstructionInitEnum *) instruction, index);
-        case IrInstructionIdBitCast:
-            return ir_instruction_bitcast_get_dep((IrInstructionBitCast *) instruction, index);
+        case IrInstructionIdPtrCast:
+            return ir_instruction_ptrcast_get_dep((IrInstructionPtrCast *) instruction, index);
         case IrInstructionIdWidenOrShorten:
             return ir_instruction_widenorshorten_get_dep((IrInstructionWidenOrShorten *) instruction, index);
         case IrInstructionIdIntToPtr:
@@ -4200,7 +4200,7 @@ static IrInstruction *ir_gen_builtin_fn_call(IrBuilder *irb, Scope *scope, AstNo
 
                 return ir_build_panic(irb, scope, node, arg0_value);
             }
-        case BuiltinFnIdBitCast:
+        case BuiltinFnIdPtrCast:
             {
                 AstNode *arg0_node = node->data.fn_call_expr.params.at(0);
                 IrInstruction *arg0_value = ir_gen_node(irb, arg0_node, scope);
@@ -4212,7 +4212,7 @@ static IrInstruction *ir_gen_builtin_fn_call(IrBuilder *irb, Scope *scope, AstNo
                 if (arg1_value == irb->codegen->invalid_instruction)
                     return arg1_value;
 
-                return ir_build_bit_cast(irb, scope, node, arg0_value, arg1_value);
+                return ir_build_ptr_cast(irb, scope, node, arg0_value, arg1_value);
             }
     }
     zig_unreachable();
@@ -12182,34 +12182,36 @@ static TypeTableEntry *ir_analyze_instruction_panic(IrAnalyze *ira, IrInstructio
     return ir_finish_anal(ira, ira->codegen->builtin_types.entry_unreachable);
 }
 
-static TypeTableEntry *ir_analyze_instruction_bit_cast(IrAnalyze *ira, IrInstructionBitCast *instruction) {
+static bool is_ptr_type(TypeTableEntry *t) {
+    return (t->id == TypeTableEntryIdPointer || t->id == TypeTableEntryIdFn ||
+            (t->id == TypeTableEntryIdMaybe && (t->data.maybe.child_type->id == TypeTableEntryIdPointer ||
+                t->data.maybe.child_type->id == TypeTableEntryIdFn)));
+}
+
+static TypeTableEntry *ir_analyze_instruction_ptr_cast(IrAnalyze *ira, IrInstructionPtrCast *instruction) {
     IrInstruction *dest_type_value = instruction->dest_type->other;
     TypeTableEntry *dest_type = ir_resolve_type(ira, dest_type_value);
     if (type_is_invalid(dest_type))
         return ira->codegen->builtin_types.entry_invalid;
 
-    IrInstruction *target = instruction->target->other;
-    TypeTableEntry *src_type = target->value.type;
+    IrInstruction *ptr = instruction->ptr->other;
+    TypeTableEntry *src_type = ptr->value.type;
     if (type_is_invalid(src_type))
         return ira->codegen->builtin_types.entry_invalid;
 
-    ensure_complete_type(ira->codegen, dest_type);
-    ensure_complete_type(ira->codegen, src_type);
+    if (!is_ptr_type(src_type)) {
+        ir_add_error(ira, ptr, buf_sprintf("expected pointer, found '%s'", buf_ptr(&src_type->name)));
+        return ira->codegen->builtin_types.entry_invalid;
+    }
 
-    uint64_t dest_size_bytes = type_size(ira->codegen, dest_type);
-    uint64_t src_size_bytes = type_size(ira->codegen, src_type);
-    if (dest_size_bytes != src_size_bytes) {
-        ir_add_error(ira, &instruction->base,
-            buf_sprintf("destination type '%s' has size %" PRIu64 " but source type '%s' has size %" PRIu64,
-                buf_ptr(&dest_type->name), dest_size_bytes,
-                buf_ptr(&src_type->name), src_size_bytes));
+    if (!is_ptr_type(dest_type)) {
+        ir_add_error(ira, dest_type_value,
+                buf_sprintf("expected pointer, found '%s'", buf_ptr(&dest_type->name)));
         return ira->codegen->builtin_types.entry_invalid;
     }
 
-    if (instr_is_comptime(target) && src_type->id == dest_type->id &&
-        (src_type->id == TypeTableEntryIdPointer || src_type->id == TypeTableEntryIdMaybe))
-    {
-        ConstExprValue *val = ir_resolve_const(ira, target, UndefOk);
+    if (instr_is_comptime(ptr)) {
+        ConstExprValue *val = ir_resolve_const(ira, ptr, UndefOk);
         if (!val)
             return ira->codegen->builtin_types.entry_invalid;
 
@@ -12219,8 +12221,8 @@ static TypeTableEntry *ir_analyze_instruction_bit_cast(IrAnalyze *ira, IrInstruc
         return dest_type;
     }
 
-    IrInstruction *result = ir_build_bit_cast(&ira->new_irb, instruction->base.scope,
-            instruction->base.source_node, nullptr, target);
+    IrInstruction *result = ir_build_ptr_cast(&ira->new_irb, instruction->base.scope,
+            instruction->base.source_node, nullptr, ptr);
     ir_link_new_instruction(result, &instruction->base);
     result->value.type = dest_type;
     return dest_type;
@@ -12464,8 +12466,8 @@ static TypeTableEntry *ir_analyze_instruction_nocast(IrAnalyze *ira, IrInstructi
             return ir_analyze_instruction_decl_ref(ira, (IrInstructionDeclRef *)instruction);
         case IrInstructionIdPanic:
             return ir_analyze_instruction_panic(ira, (IrInstructionPanic *)instruction);
-        case IrInstructionIdBitCast:
-            return ir_analyze_instruction_bit_cast(ira, (IrInstructionBitCast *)instruction);
+        case IrInstructionIdPtrCast:
+            return ir_analyze_instruction_ptr_cast(ira, (IrInstructionPtrCast *)instruction);
         case IrInstructionIdMaybeWrap:
         case IrInstructionIdErrWrapCode:
         case IrInstructionIdErrWrapPayload:
@@ -12637,7 +12639,7 @@ bool ir_has_side_effects(IrInstruction *instruction) {
         case IrInstructionIdFnProto:
         case IrInstructionIdTestComptime:
         case IrInstructionIdInitEnum:
-        case IrInstructionIdBitCast:
+        case IrInstructionIdPtrCast:
         case IrInstructionIdWidenOrShorten:
         case IrInstructionIdPtrToInt:
         case IrInstructionIdIntToPtr:

src/ir_print.cpp

@@ -765,9 +765,13 @@ static void ir_print_init_enum(IrPrint *irp, IrInstructionInitEnum *instruction)
     fprintf(irp->f, "}");
 }
 
-static void ir_print_bit_cast(IrPrint *irp, IrInstructionBitCast *instruction) {
-    fprintf(irp->f, "@bitcast(");
-    ir_print_other_instruction(irp, instruction->target);
+static void ir_print_ptr_cast(IrPrint *irp, IrInstructionPtrCast *instruction) {
+    fprintf(irp->f, "@ptrcast(");
+    if (instruction->dest_type) {
+        ir_print_other_instruction(irp, instruction->dest_type);
+    }
+    fprintf(irp->f, ",");
+    ir_print_other_instruction(irp, instruction->ptr);
     fprintf(irp->f, ")");
 }
 
@@ -1098,8 +1102,8 @@ static void ir_print_instruction(IrPrint *irp, IrInstruction *instruction) {
         case IrInstructionIdInitEnum:
             ir_print_init_enum(irp, (IrInstructionInitEnum *)instruction);
             break;
-        case IrInstructionIdBitCast:
-            ir_print_bit_cast(irp, (IrInstructionBitCast *)instruction);
+        case IrInstructionIdPtrCast:
+            ir_print_ptr_cast(irp, (IrInstructionPtrCast *)instruction);
             break;
         case IrInstructionIdWidenOrShorten:
             ir_print_widen_or_shorten(irp, (IrInstructionWidenOrShorten *)instruction);

std/debug.zig

@@ -74,7 +74,7 @@ pub fn writeStackTrace(out_stream: &io.OutStream) -> %void {
                 const name = %return compile_unit.die.getAttrString(st, DW.AT_name);
 
                 %return out_stream.printf("{}  -> {}\n", return_address, name);
-                maybe_fp = *@bitcast(&const ?&const u8, fp);
+                maybe_fp = *@ptrcast(&const ?&const u8, fp);
             }
         },
         ObjectFormat.coff => {

std/hash_map.zig

@@ -236,7 +236,7 @@ test "basicHashMapTest" {
 }
 
 fn hash_i32(x: i32) -> u32 {
-    *@bitcast(&u32, &x)
+    *@ptrcast(&u32, &x)
 }
 fn eql_i32(a: i32, b: i32) -> bool {
     a == b

std/mem.zig

@@ -78,7 +78,7 @@ pub const IncrementingAllocator = struct {
     fn alloc(allocator: &Allocator, n: usize) -> %[]u8 {
         // TODO
         //const self = @fieldParentPtr(IncrementingAllocator, "allocator", allocator);
-        const self = @bitcast(&IncrementingAllocator, allocator);
+        const self = @ptrcast(&IncrementingAllocator, allocator);
         const new_end_index = self.end_index + n;
         if (new_end_index > self.bytes.len) {
             return error.NoMem;

std/os/linux.zig

@@ -239,7 +239,7 @@ pub const AF_MAX = PF_MAX;
 
 /// Get the errno from a syscall return value, or 0 for no error.
 pub fn getErrno(r: usize) -> usize {
-    const signed_r = *@bitcast(&isize, &r);
+    const signed_r = *@ptrcast(&isize, &r);
     if (signed_r > -4096 and signed_r < 0) usize(-signed_r) else 0
 }
 

std/special/compiler_rt.zig

@@ -15,7 +15,7 @@ export fn __udivdi3(a: du_int, b: du_int) -> du_int {
 
 fn du_int_to_udwords(x: du_int) -> udwords {
     @setDebugSafety(this, false);
-    return *@bitcast(&udwords, &x);
+    return *@ptrcast(&udwords, &x);
 }
 
 export fn __udivmoddi4(a: du_int, b: du_int, maybe_rem: ?&du_int) -> du_int {
@@ -66,7 +66,7 @@ export fn __udivmoddi4(a: du_int, b: du_int, maybe_rem: ?&du_int) -> du_int {
             if (var rem ?= maybe_rem) {
                 r[high] = n[high] % d[high];
                 r[low] = 0;
-                *rem = *@bitcast(&du_int, &r[0]);
+                *rem = *@ptrcast(&du_int, &r[0]);
             }
             return n[high] / d[high];
         }
@@ -78,7 +78,7 @@ export fn __udivmoddi4(a: du_int, b: du_int, maybe_rem: ?&du_int) -> du_int {
             if (var rem ?= maybe_rem) {
                 r[low] = n[low];
                 r[high] = n[high] & (d[high] - 1);
-                *rem = *@bitcast(&du_int, &r[0]);
+                *rem = *@ptrcast(&du_int, &r[0]);
             }
             return n[high] >> @ctz(d[high]);
         }
@@ -89,7 +89,7 @@ export fn __udivmoddi4(a: du_int, b: du_int, maybe_rem: ?&du_int) -> du_int {
         // 0 <= sr <= n_uword_bits - 2 or sr large
         if (sr > n_uword_bits - 2) {
             if (var rem ?= maybe_rem) {
-                *rem = *@bitcast(&du_int, &n[0]);
+                *rem = *@ptrcast(&du_int, &n[0]);
             }
             return 0;
         }
@@ -113,12 +113,12 @@ export fn __udivmoddi4(a: du_int, b: du_int, maybe_rem: ?&du_int) -> du_int {
                     *rem = n[low] & (d[low] - 1);
                 }
                 if (d[low] == 1) {
-                    return *@bitcast(&du_int, &n[0]);
+                    return *@ptrcast(&du_int, &n[0]);
                 }
                 sr = @ctz(d[low]);
                 q[high] = n[high] >> sr;
                 q[low] = (n[high] << (n_uword_bits - sr)) | (n[low] >> sr);
-                return *@bitcast(&du_int, &q[0]);
+                return *@ptrcast(&du_int, &q[0]);
             }
             // K X
             // ---
@@ -154,7 +154,7 @@ export fn __udivmoddi4(a: du_int, b: du_int, maybe_rem: ?&du_int) -> du_int {
             // 0 <= sr <= n_uword_bits - 1 or sr large
             if (sr > n_uword_bits - 1) {
                 if (var rem ?= maybe_rem) {
-                    *rem = *@bitcast(&du_int, &n[0]);
+                    *rem = *@ptrcast(&du_int, &n[0]);
                 }
                 return 0;
             }
@@ -191,17 +191,17 @@ export fn __udivmoddi4(a: du_int, b: du_int, maybe_rem: ?&du_int) -> du_int {
         //      r.all -= d.all;
         //      carry = 1;
         // }
-        const s: di_int = (di_int)(*@bitcast(&du_int, &d[0]) - *@bitcast(&du_int, &r[0]) - 1) >> (n_udword_bits - 1);
+        const s: di_int = (di_int)(*@ptrcast(&du_int, &d[0]) - *@ptrcast(&du_int, &r[0]) - 1) >> (n_udword_bits - 1);
         carry = su_int(s & 1);
-        *@bitcast(&du_int, &r[0]) -= *@bitcast(&du_int, &d[0]) & u64(s);
+        *@ptrcast(&du_int, &r[0]) -= *@ptrcast(&du_int, &d[0]) & u64(s);
 
         sr -= 1;
     }
-    *@bitcast(&du_int, &q[0]) = (*@bitcast(&du_int, &q[0]) << 1) | u64(carry);
+    *@ptrcast(&du_int, &q[0]) = (*@ptrcast(&du_int, &q[0]) << 1) | u64(carry);
     if (var rem ?= maybe_rem) {
-        *rem = *@bitcast(&du_int, &r[0]);
+        *rem = *@ptrcast(&du_int, &r[0]);
     }
-    return *@bitcast(&du_int, &q[0]);
+    return *@ptrcast(&du_int, &q[0]);
 }
 
 export fn __umoddi3(a: du_int, b: du_int) -> du_int {

test/cases/cast.zig

@@ -15,7 +15,7 @@ test "numLitIntToPtrCast" {
 test "pointerReinterpretConstFloatToInt" {
     const float: f64 = 5.99999999999994648725e-01;
     const float_ptr = &float;
-    const int_ptr = @bitcast(&i32, float_ptr);
+    const int_ptr = @ptrcast(&i32, float_ptr);
     const int_val = *int_ptr;
     assert(int_val == 858993411);
 }