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raise exception on Num.abs overflow
This commit is contained in:
Folkert
parent
2bcaf3921f
commit
51cf54e367
2 changed files with 128 additions and 36 deletions
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@ -2902,7 +2902,7 @@ fn run_low_level<'a, 'ctx, 'env>(
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match arg_builtin {
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Int128 | Int64 | Int32 | Int16 | Int8 => {
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build_int_unary_op(env, arg.into_int_value(), arg_layout, op)
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build_int_unary_op(env, arg.into_int_value(), arg_builtin, op)
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}
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Float128 | Float64 | Float32 | Float16 => {
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build_float_unary_op(env, arg.into_float_value(), op)
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@ -3492,51 +3492,52 @@ fn build_float_binop<'a, 'ctx, 'env>(
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fn build_int_unary_op<'a, 'ctx, 'env>(
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env: &Env<'a, 'ctx, 'env>,
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arg: IntValue<'ctx>,
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arg_layout: &Layout<'a>,
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arg_layout: &Builtin<'a>,
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op: LowLevel,
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) -> BasicValueEnum<'ctx> {
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use roc_module::low_level::LowLevel::*;
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let bd = env.builder;
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let ctx = env.context;
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match op {
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NumNeg => bd.build_int_neg(arg, "negate_int").into(),
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NumAbs => {
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// This is how libc's abs() is implemented - it uses no branching!
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//
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// abs = \arg ->
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// shifted = arg >>> 63
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//
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// (xor arg shifted) - shifted
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use Builtin::*;
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// integer abs overflows when applied to the minimum value of a signed type
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match arg_layout {
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Int128 => {
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let a = i128::MIN as u64;
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let b = (i128::MIN >> 64) as u64;
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let ctx = env.context;
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let shifted_name = "abs_shift_right";
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let shifted_alloca = {
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let bits_to_shift = ((arg_layout.stack_size(env.ptr_bytes) as u64) * 8) - 1;
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let shift_val = ctx.i64_type().const_int(bits_to_shift, false);
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let shifted = bd.build_right_shift(arg, shift_val, true, shifted_name);
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let alloca = bd.build_alloca(
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basic_type_from_layout(env.arena, ctx, arg_layout, env.ptr_bytes),
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"#int_abs_help",
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);
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// shifted = arg >>> 63
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bd.build_store(alloca, shifted);
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alloca
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};
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let xored_arg = bd.build_xor(
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arg,
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bd.build_load(shifted_alloca, shifted_name).into_int_value(),
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"xor_arg_shifted",
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);
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BasicValueEnum::IntValue(bd.build_int_sub(
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xored_arg,
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bd.build_load(shifted_alloca, shifted_name).into_int_value(),
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"sub_xored_shifted",
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))
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int_abs_raise_on_overflow(
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env,
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arg,
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ctx.i128_type().const_int_arbitrary_precision(&[b, a]),
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)
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}
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Int64 => int_abs_raise_on_overflow(
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env,
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arg,
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ctx.i64_type().const_int(i64::MIN as u64, false),
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),
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Int32 => int_abs_raise_on_overflow(
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env,
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arg,
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ctx.i32_type().const_int(i32::MIN as u64, false),
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),
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Int16 => int_abs_raise_on_overflow(
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env,
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arg,
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ctx.i16_type().const_int(i16::MIN as u64, false),
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),
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Int8 => int_abs_raise_on_overflow(
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env,
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arg,
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ctx.i8_type().const_int(i8::MIN as u64, false),
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),
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_ => unreachable!("not an integer type"),
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}
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}
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NumToFloat => {
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// This is an Int, so we need to convert it.
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@ -3553,6 +3554,77 @@ fn build_int_unary_op<'a, 'ctx, 'env>(
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}
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}
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fn int_abs_raise_on_overflow<'a, 'ctx, 'env>(
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env: &Env<'a, 'ctx, 'env>,
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arg: IntValue<'ctx>,
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min_val: IntValue<'ctx>,
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) -> BasicValueEnum<'ctx> {
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let builder = env.builder;
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let condition = builder.build_int_compare(IntPredicate::EQ, arg, min_val, "is_min_val");
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let block = env.builder.get_insert_block().expect("to be in a function");
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let parent = block.get_parent().expect("to be in a function");
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let then_block = env.context.append_basic_block(parent, "then");
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let else_block = env.context.append_basic_block(parent, "else");
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env.builder
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.build_conditional_branch(condition, then_block, else_block);
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builder.position_at_end(then_block);
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throw_exception(
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env,
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"integer absolute overflowed because its argument is the minimum value",
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);
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builder.position_at_end(else_block);
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int_abs_with_overflow(env, arg, Layout::Builtin(Builtin::Int64))
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}
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fn int_abs_with_overflow<'a, 'ctx, 'env>(
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env: &Env<'a, 'ctx, 'env>,
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arg: IntValue<'ctx>,
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arg_layout: Layout<'a>,
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) -> BasicValueEnum<'ctx> {
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// This is how libc's abs() is implemented - it uses no branching!
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//
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// abs = \arg ->
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// shifted = arg >>> 63
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//
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// (xor arg shifted) - shifted
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let bd = env.builder;
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let ctx = env.context;
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let shifted_name = "abs_shift_right";
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let shifted_alloca = {
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let bits_to_shift = ((arg_layout.stack_size(env.ptr_bytes) as u64) * 8) - 1;
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let shift_val = ctx.i64_type().const_int(bits_to_shift, false);
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let shifted = bd.build_right_shift(arg, shift_val, true, shifted_name);
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let alloca = bd.build_alloca(
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basic_type_from_layout(env.arena, ctx, &arg_layout, env.ptr_bytes),
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"#int_abs_help",
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);
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// shifted = arg >>> 63
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bd.build_store(alloca, shifted);
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alloca
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};
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let xored_arg = bd.build_xor(
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arg,
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bd.build_load(shifted_alloca, shifted_name).into_int_value(),
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"xor_arg_shifted",
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);
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BasicValueEnum::IntValue(bd.build_int_sub(
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xored_arg,
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bd.build_load(shifted_alloca, shifted_name).into_int_value(),
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"sub_xored_shifted",
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))
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}
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fn build_float_unary_op<'a, 'ctx, 'env>(
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env: &Env<'a, 'ctx, 'env>,
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arg: FloatValue<'ctx>,
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