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wasm: correctly intcast signed integers

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When a signed integer's bitsize is not 32 or 64, but the given
bitsize and wanted bitsize are either both represented by Wasm's i32
or i64, we must either sign extend or wrap the integer.
This commit is contained in:
Luuk de Gram 2023-07-21 21:18:58 +02:00
parent 8924f81d8c
commit 619140c0d2
2 changed files with 29 additions and 2 deletions
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16
src/arch/wasm/CodeGen.zig
View File

@ -4160,7 +4160,7 @@ fn airIntcast(func: *CodeGen, inst: Air.Inst.Index) InnerError!void {
const op_bits = toWasmBits(@as(u16, @intCast(operand_ty.bitSize(mod)))).?; const op_bits = toWasmBits(@as(u16, @intCast(operand_ty.bitSize(mod)))).?;
const wanted_bits = toWasmBits(@as(u16, @intCast(ty.bitSize(mod)))).?; const wanted_bits = toWasmBits(@as(u16, @intCast(ty.bitSize(mod)))).?;
const result = if (op_bits == wanted_bits) const result = if (op_bits == wanted_bits and !ty.isSignedInt(mod))
func.reuseOperand(ty_op.operand, operand) func.reuseOperand(ty_op.operand, operand)
else else
try (try func.intcast(operand, operand_ty, ty)).toLocal(func, ty); try (try func.intcast(operand, operand_ty, ty)).toLocal(func, ty);
@ -4181,7 +4181,19 @@ fn intcast(func: *CodeGen, operand: WValue, given: Type, wanted: Type) InnerErro
const op_bits = toWasmBits(given_bitsize).?; const op_bits = toWasmBits(given_bitsize).?;
const wanted_bits = toWasmBits(wanted_bitsize).?; const wanted_bits = toWasmBits(wanted_bitsize).?;
if (op_bits == wanted_bits) return operand; if (op_bits == wanted_bits) {
if (given.isSignedInt(mod)) {
if (given_bitsize < wanted_bitsize) {
// signed integers are stored as two's complement,
// when we upcast from a smaller integer to larger
// integers, we must get its absolute value similar to
// i64_extend_i32_s instruction.
return func.signAbsValue(operand, given);
}
return func.wrapOperand(operand, wanted);
}
return operand;
}
if (op_bits > 32 and op_bits <= 64 and wanted_bits == 32) { if (op_bits > 32 and op_bits <= 64 and wanted_bits == 32) {
try func.emitWValue(operand); try func.emitWValue(operand);

15
test/behavior/cast_int.zig
View File

@ -14,3 +14,18 @@ test "@intCast i32 to u7" {
var z = x >> @as(u7, @intCast(y)); var z = x >> @as(u7, @intCast(y));
try expect(z == 0xff); try expect(z == 0xff);
} }
test "coerce i8 to i32 and @intCast back" {
if (builtin.zig_backend == .stage2_aarch64) return error.SkipZigTest; // TODO
if (builtin.zig_backend == .stage2_arm) return error.SkipZigTest; // TODO
if (builtin.zig_backend == .stage2_sparc64) return error.SkipZigTest; // TODO
if (builtin.zig_backend == .stage2_spirv64) return error.SkipZigTest;
var x: i8 = -5;
var y: i32 = -5;
try expect(y == x);
var x2: i32 = -5;
var y2: i8 = -5;
try expect(y2 == @as(i8, @intCast(x2)));
}