diff options
| -rw-r--r-- | doc/langref.html.in | 11 | ||||
| -rw-r--r-- | src/ir.cpp | 24 | ||||
| -rw-r--r-- | test/compile_errors.zig | 11 | ||||
| -rw-r--r-- | test/stage1/behavior/truncate.zig | 23 |
4 files changed, 56 insertions, 13 deletions
diff --git a/doc/langref.html.in b/doc/langref.html.in index dfea8e1e04..779eb6a31b 100644 --- a/doc/langref.html.in +++ b/doc/langref.html.in @@ -6381,14 +6381,14 @@ fn List(comptime T: type) type { {#header_close#} {#header_open|@truncate#} - <pre>{#syntax#}@truncate(comptime T: type, integer) T{#endsyntax#}</pre> + <pre>{#syntax#}@truncate(comptime T: type, integer: var) T{#endsyntax#}</pre> <p> This function truncates bits from an integer type, resulting in a smaller integer type. </p> <p> - The following produces a crash in debug mode and undefined behavior in - release mode: + The following produces a crash in {#link|Debug#} mode and {#link|Undefined Behavior#} in + {#link|ReleaseFast#} mode: </p> <pre>{#syntax#}const a: u16 = 0xabcd; const b: u8 = u8(a);{#endsyntax#}</pre> @@ -6402,7 +6402,10 @@ const b: u8 = @truncate(u8, a); This function always truncates the significant bits of the integer, regardless of endianness on the target platform. </p> - + <p> + If {#syntax#}T{#endsyntax#} is {#syntax#}comptime_int{#endsyntax#}, + then this is semantically equivalent to an {#link|implicit cast|Implicit Casts#}. + </p> {#header_close#} {#header_open|@typeId#} diff --git a/src/ir.cpp b/src/ir.cpp index d87486bbdd..5d4013b4b9 100644 --- a/src/ir.cpp +++ b/src/ir.cpp @@ -18491,7 +18491,22 @@ static IrInstruction *ir_analyze_instruction_truncate(IrAnalyze *ira, IrInstruct return ira->codegen->invalid_instruction; } - if (src_type->data.integral.bit_count == 0) { + if (dest_type->id == ZigTypeIdComptimeInt) { + return ir_implicit_cast(ira, target, dest_type); + } + + if (instr_is_comptime(target)) { + ConstExprValue *val = ir_resolve_const(ira, target, UndefBad); + if (val == nullptr) + return ira->codegen->invalid_instruction; + + IrInstruction *result = ir_const(ira, &instruction->base, dest_type); + bigint_truncate(&result->value.data.x_bigint, &val->data.x_bigint, + dest_type->data.integral.bit_count, dest_type->data.integral.is_signed); + return result; + } + + if (src_type->data.integral.bit_count == 0 || dest_type->data.integral.bit_count == 0) { IrInstruction *result = ir_const(ira, &instruction->base, dest_type); bigint_init_unsigned(&result->value.data.x_bigint, 0); return result; @@ -18507,13 +18522,6 @@ static IrInstruction *ir_analyze_instruction_truncate(IrAnalyze *ira, IrInstruct return ira->codegen->invalid_instruction; } - if (target->value.special == ConstValSpecialStatic) { - IrInstruction *result = ir_const(ira, &instruction->base, dest_type); - bigint_truncate(&result->value.data.x_bigint, &target->value.data.x_bigint, - dest_type->data.integral.bit_count, dest_type->data.integral.is_signed); - return result; - } - IrInstruction *new_instruction = ir_build_truncate(&ira->new_irb, instruction->base.scope, instruction->base.source_node, dest_type_value, target); new_instruction->value.type = dest_type; diff --git a/test/compile_errors.zig b/test/compile_errors.zig index de01a5ac45..b47cdf2ed1 100644 --- a/test/compile_errors.zig +++ b/test/compile_errors.zig @@ -2,6 +2,15 @@ const tests = @import("tests.zig"); pub fn addCases(cases: *tests.CompileErrorContext) void { cases.addTest( + "@truncate undefined value", + \\export fn entry() void { + \\ var z = @truncate(u8, u16(undefined)); + \\} + , + ".tmp_source.zig:2:30: error: use of undefined value", + ); + + cases.addTest( "return invalid type from test", \\test "example" { return 1; } , @@ -3335,7 +3344,7 @@ pub fn addCases(cases: *tests.CompileErrorContext) void { cases.add( "truncate sign mismatch", \\fn f() i8 { - \\ const x: u32 = 10; + \\ var x: u32 = 10; \\ return @truncate(i8, x); \\} \\ diff --git a/test/stage1/behavior/truncate.zig b/test/stage1/behavior/truncate.zig index c195b64cbf..568346369f 100644 --- a/test/stage1/behavior/truncate.zig +++ b/test/stage1/behavior/truncate.zig @@ -6,3 +6,26 @@ test "truncate u0 to larger integer allowed and has comptime known result" { const y = @truncate(u8, x); comptime expect(y == 0); } + +test "truncate.u0.literal" { + var z = @truncate(u0, 0); + expect(z == 0); +} + +test "truncate.u0.const" { + const c0: usize = 0; + var z = @truncate(u0, c0); + expect(z == 0); +} + +test "truncate.u0.var" { + var d: u8 = 2; + var z = @truncate(u0, d); + expect(z == 0); +} + +test "truncate sign mismatch but comptime known so it works anyway" { + const x: u32 = 10; + var result = @truncate(i8, x); + expect(result == 10); +} |