From 619140c0d2abd22da668747820f0ee80b497eb24 Mon Sep 17 00:00:00 2001 From: Luuk de Gram Date: Fri, 21 Jul 2023 21:18:58 +0200 Subject: wasm: correctly intcast signed integers 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. --- src/arch/wasm/CodeGen.zig | 16 ++++++++++++++-- 1 file changed, 14 insertions(+), 2 deletions(-) (limited to 'src') diff --git a/src/arch/wasm/CodeGen.zig b/src/arch/wasm/CodeGen.zig index 14d2cf95c4..af54043f7a 100644 --- a/src/arch/wasm/CodeGen.zig +++ b/src/arch/wasm/CodeGen.zig @@ -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 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) else 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 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) { try func.emitWValue(operand); -- cgit v1.2.3