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Do not use llvm.smul.with.overflow.i64 anymore #2693

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May 16, 2018
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Do not use llvm.smul.with.overflow.i64 anymore #2693

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52 changes: 36 additions & 16 deletions packages/builtin/signed.pony
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Original file line number Diff line number Diff line change
Expand Up @@ -161,7 +161,8 @@ primitive I64 is _SignedInteger[I64, U64]
@"llvm.ssub.with.overflow.i64"[(I64, Bool)](this, y)

fun mulc(y: I64): (I64, Bool) =>
@"llvm.smul.with.overflow.i64"[(I64, Bool)](this, y)
_SignedCheckedArithmetic._mulc[U64, I64](this, y)


primitive ILong is _SignedInteger[ILong, ULong]
new create(value: ILong) => value
Expand Down Expand Up @@ -248,7 +249,7 @@ primitive ILong is _SignedInteger[ILong, ULong]
ifdef ilp32 or llp64 then
@"llvm.smul.with.overflow.i32"[(ILong, Bool)](this, y)
else
@"llvm.smul.with.overflow.i64"[(ILong, Bool)](this, y)
_SignedCheckedArithmetic._mulc[ULong, ILong](this, y)
end

primitive ISize is _SignedInteger[ISize, USize]
Expand Down Expand Up @@ -335,7 +336,7 @@ primitive ISize is _SignedInteger[ISize, USize]
ifdef ilp32 then
@"llvm.smul.with.overflow.i32"[(ISize, Bool)](this, y)
else
@"llvm.smul.with.overflow.i64"[(ISize, Bool)](this, y)
_SignedCheckedArithmetic._mulc[USize, ISize](this, y)
end

primitive I128 is _SignedInteger[I128, U128]
Expand Down Expand Up @@ -525,25 +526,44 @@ primitive I128 is _SignedInteger[I128, U128]
// See this bug for reference:
// the following implementation is more or less exactly was __muloti4 is
// doing
let result = this * y
if this == I128.min_value() then
return (result, (y != 0) and (y != 1))
_SignedCheckedArithmetic._mulc[U128, I128](this, y)

type Signed is (I8 | I16 | I32 | I64 | I128 | ILong | ISize)


primitive _SignedCheckedArithmetic
fun _mulc[U: _UnsignedInteger[U] val, T: (Signed & _SignedInteger[T, U] val)](x: T, y: T): (T, Bool) =>
"""
basically exactly what the runtime functions __muloti4, mulodi4 etc. are doing
and roughly as fast as these.

Additionally on (at least some) 32 bit systems, the runtime function for checked 64 bit integer addition __mulodi4 is not available.
So we shouldn't use: `@"llvm.smul.with.overflow.i64"[(I64, Bool)](this, y)`

Also see https://bugs.llvm.org/show_bug.cgi?id=14469

That's basically why we rolled our own.
"""
let result = x * y
if x == T.min_value() then
return (result, (y != T.from[I8](0)) and (y != T.from[I8](1)))
end
if y == I128.min_value() then
return (result, (this != 0) and (this != 1))
if y == T.min_value() then
return (result, (x != T.from[I8](0)) and (x != T.from[I8](1)))
end
let this_neg = this >> (this.bitwidth() - 1)
let this_abs = (this xor this_neg) - this_neg
let y_neg = y >> (this.bitwidth() - 1)
let x_neg = x >> (x.bitwidth() - U.from[U8](1))
let x_abs = (x xor x_neg) - x_neg
let y_neg = y >> (x.bitwidth() - U.from[U8](1))
let y_abs = (y xor y_neg) - y_neg

if ((this_abs < 2) or (y_abs < 2)) then
if ((x_abs < T.from[I8](2)) or (y_abs < T.from[I8](2))) then
return (result, false)
end
if (this_neg == y_neg) then
(result, (this_abs > (I128.max_value() / y_abs)))
if (x_neg == y_neg) then
(result, (x_abs > (T.max_value() / y_abs)))
else
(result, (this_abs > (I128.min_value() / -y_abs)))
(result, (x_abs > (T.min_value() / -y_abs)))
end

type Signed is (I8 | I16 | I32 | I64 | I128 | ILong | ISize)