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Update Value.intTrunc to use new big int truncate

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This commit is contained in:
Robin Voetter
2021-09-26 07:40:40 +02:00
parent b58cf6dab6
commit a733692444
2 changed files with 19 additions and 7 deletions
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2
src/Sema.zig
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@@ -9017,7 +9017,7 @@ fn zirTruncate(sema: *Sema, block: *Block, inst: Zir.Inst.Index) CompileError!Ai
if (try sema.resolveMaybeUndefVal(block, operand_src, operand)) |val| {
if (val.isUndef()) return sema.addConstUndef(dest_ty);
return sema.addConstant(dest_ty, try val.intTrunc(sema.arena, dest_info.bits));
return sema.addConstant(dest_ty, try val.intTrunc(sema.arena, dest_info.signedness, dest_info.bits));
}
try sema.requireRuntimeBlock(block, src);

24
src/value.zig
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@@ -2136,12 +2136,24 @@ pub const Value = extern union {
}
}
pub fn intTrunc(val: Value, arena: *Allocator, bits: u16) !Value {
const x = val.toUnsignedInt(); // TODO: implement comptime truncate on big ints
if (bits == 64) return val;
const mask = (@as(u64, 1) << @intCast(u6, bits)) - 1;
const truncated = x & mask;
return Tag.int_u64.create(arena, truncated);
pub fn intTrunc(val: Value, allocator: *Allocator, signedness: std.builtin.Signedness, bits: u16) !Value {
var val_space: Value.BigIntSpace = undefined;
const val_bigint = val.toBigInt(&val_space);
const limbs = try allocator.alloc(
std.math.big.Limb,
std.math.big.int.calcTwosCompLimbCount(bits),
);
var result_bigint = BigIntMutable{ .limbs = limbs, .positive = undefined, .len = undefined };
result_bigint.truncate(val_bigint, signedness, bits);
const result_limbs = result_bigint.limbs[0..result_bigint.len];
if (result_bigint.positive) {
return Value.Tag.int_big_positive.create(allocator, result_limbs);
} else {
return Value.Tag.int_big_negative.create(allocator, result_limbs);
}
}
pub fn shl(lhs: Value, rhs: Value, allocator: *Allocator) !Value {