`Word.toInt` does not raise an exception when out of range

[Skyb0rg007]

Version

110.99.7.1 (Latest)

Operating System

• Any
• Linux
• macOS
• Windows
• Other Unix

OS Version

Ubuntu on Windows 11 WSL

Processor

• Any
• Arm (using Rosetta)
• PowerPC
• Sparc
• x86 (32-bit)
• x86-64 (64-bit)
• Other

System Component

Basis Library

Severity

Minor

Description

Word.toInt produces values outside the range [0,2^(wordSize-1))

Transcript

- Word.toInt ~1;
val it = 0wx7FFFFFFFFFFFFFFF : word
- Word.fromInt ~1 = 0wx7FFFFFFFFFFFFFFF;
val it = false : bool

Expected Behavior

- Word.toInt ~1;
val it = 0wx7FFFFFFFFFFFFFFF : word
- Word.fromInt ~1 = 0wx7FFFFFFFFFFFFFFF;
val it = true : bool

Steps to Reproduce

Type the above code

Additional Information

I believe this is an issue in conversion: (W63)9223372036854775807 is converted to (I63t)9223372036854775807 when it should be converted to (I63t)~1.

[After fcontract+eta ...]

v5{1} : (FCT)  =
  FN([v11{0} : ???],
    v1{2} = PRIMOP(copy_63_63, <I63> -f-> <I63>, []) [(I63)~1]
    [v3{1}] = IF PRIMOP(=u63, <I63,I63> -f-> <VOID>, []) [v1,(W63)9223372036854775807]
               THEN
                   v8{1} = WRAP(I63, (I63)1)
                   RETURN [v8]
               ELSE
                   v10{1} = WRAP(I63, (I63)0)
                   RETURN [v10]
    v6{1} = STRUCT [v3,v1,(W63)9223372036854775807]
    RETURN [v6])


[After convert ...]

std v5(v13[C],v11[PR0]) =
   v17(v18[PV]) =
      v17("bogus")
   v12(v19[PV]) =
      v17("bogus")
   copy_63_63((I63t)~1) -> v1[I]
   v15(v14[PV]) =
      {v14,v1,(I63t)9223372036854775807} -> v6
      v13(v6)
   if u63=(v1,(I63t)9223372036854775807) [v16] then
      wrap_i63((I63t)1) -> v8[PV]
      v15(v8)
   else
      wrap_i63((I63t)0) -> v10[PV]
      v15(v10)

Email address

ssoss AT uchicago DOT edu

[Skyb0rg007]

This is where the optimizer goes wrong: the stage between cpstrans and lowering performs constant propagation which replaces the comparison between (I63t)~1 and (I63t)9223372036854775807 with 0.

[After cpstrans ...]

std v5(v13[C],v11[PR0]) =
   v17(v18[PV]) =
      v17("bogus")
   v12(v19[PV]) =
      v17("bogus")
   copy_63_63((I63t)~1) -> v1[I]
   v15(v14[PV]) =
      {v14,v1,(I63t)9223372036854775807} -> v6
      v13(v6)
   if u63=(v1,(I63t)9223372036854775807) [v16] then
      v15((I63t)1)
   else
      v15((I63t)0)



[Before lowering]

std v5(v13[C],v11[PR0]) =
   {(I63t)0,(I63t)~1,(I63t)9223372036854775807} -> v6
   v13(v6)

[JohnReppy]

The example is not correct SML, since ~1 has type int, not word.

- Word.toInt ~1;
stdIn:1.2-1.15 Error: operator and operand do not agree [overload - bad instantiation]
  operator domain: word
  operand:         'Z[INT]
  in expression:
    Word.toInt ~1

and if I try writing ~1 as a word value, I get the expected exception:

- Word.toInt 0wx7fffffffffffffff;

uncaught exception Overflow [overflow]
  raised at: <file stdIn>

[JohnReppy]

There does seem to be a bug in that

Word.fromInt ~1 = 0wx7FFFFFFFFFFFFFFF;
val it = false : bool

should be true. I created a Issue #341 for the constant folding of equality bug and I'm leaving this one open until we can resolve the question of what the bug actually is.

[Skyb0rg007]

Actual

- Word64.toInt (Word64.fromInt ~1);
val it = ~1 : int

Expected

- Word64.toInt (Word64.fromInt ~1);
error

[JohnReppy]

Fixed for 110.99.8