[cfe-commits] [PATCH] Use the new APFloat::convertToInt(APSInt) function (issue4728042)

[Jeffrey Yasskin]

On Thu, Jul 14, 2011 at 5:30 PM, Eli Friedman <eli.friedman at gmail.com> wrote:
> On Thu, Jul 14, 2011 at 5:06 PM,  <jyasskin at gmail.com> wrote:
>> Reviewers: cfe-commits_cs.uiuc.edu,
>>
>> Message:
>> Initial diff at
>> http://codereview.appspot.com/download/issue4728042_1.diff.
>>
>> Description:
>> Use the new APFloat::convertToInt(APSInt) function to simplify uses of
>> convertToInt(integerParts*) and make them more reliable.
>>
>> Relies on http://codereview.appspot.com/4738043.
>>
>> Please review this at http://codereview.appspot.com/4728042/
>>
>> Affected files:
>>   M lib/AST/ExprConstant.cpp
>>   M lib/Sema/SemaChecking.cpp
>>
>>
>> Index: lib/AST/ExprConstant.cpp
>> diff --git a/lib/AST/ExprConstant.cpp b/lib/AST/ExprConstant.cpp
>> index
>> 9943222b1dd30d9761731fca984d20d6b578f788..03c0747efba9e8ed9451607b6a33c8b1c9716196
>> 100644
>> --- a/lib/AST/ExprConstant.cpp
>> +++ b/lib/AST/ExprConstant.cpp
>> @@ -223,12 +223,10 @@ static APSInt HandleFloatToIntCast(QualType DestType,
>> QualType SrcType,
>>    // Determine whether we are converting to unsigned or signed.
>>    bool DestSigned = DestType->isSignedIntegerOrEnumerationType();
>>
>> -  // FIXME: Warning for overflow.
>> -  uint64_t Space[4];
>> +  APSInt Result(DestWidth, !DestSigned);
>>    bool ignored;
>> -  (void)Value.convertToInteger(Space, DestWidth, DestSigned,
>> -                               llvm::APFloat::rmTowardZero, &ignored);
>> -  return APSInt(llvm::APInt(DestWidth, 4, Space), !DestSigned);
>> +  (void)Value.convertToInteger(Result, llvm::APFloat::rmTowardZero,
>> &ignored);
>> +  return Result;
>>  }
>
> Why are you removing the "FIXME: Warning for overflow" comment?  The
> issue still exists...

Oops. I thought that was talking about overflowing the 4 slots in
Space. I've put it back.

>>  static APFloat HandleFloatToFloatCast(QualType DestType, QualType SrcType,
>> Index: lib/Sema/SemaChecking.cpp
>> diff --git a/lib/Sema/SemaChecking.cpp b/lib/Sema/SemaChecking.cpp
>> index
>> 267cda8f4016ca935873eac6d22bb82906201051..d1990f3061f353f3152a33d450b971b445d95a10
>> 100644
>> --- a/lib/Sema/SemaChecking.cpp
>> +++ b/lib/Sema/SemaChecking.cpp
>> @@ -2990,17 +2990,15 @@ void DiagnoseFloatingLiteralImpCast(Sema &S,
>> FloatingLiteral *FL, QualType T,
>>    if (&Value.getSemantics() == &llvm::APFloat::PPCDoubleDouble)
>>      return;
>>
>> -  // Try to convert this exactly to an 64-bit integer. FIXME: It would be
>> -  // nice to support arbitrarily large integers here.
>> +  // Try to convert this exactly to an integer.
>>    bool isExact = false;
>> -  uint64_t IntegerPart;
>> -  if (Value.convertToInteger(&IntegerPart, 64, /*isSigned=*/true,
>> +  llvm::APSInt IntegerValue(S.Context.getIntWidth(T),
>> +                            /*isUnsigned=*/false);
>> +  if (Value.convertToInteger(IntegerValue,
>>                               llvm::APFloat::rmTowardZero, &isExact)
>>        != llvm::APFloat::opOK || !isExact)
>>      return;
>>
>> -  llvm::APInt IntegerValue(64, IntegerPart, /*isSigned=*/true);
>> -
>>    std::string LiteralValue = IntegerValue.toString(10, /*isSigned=*/true);
>>    S.Diag(FL->getExprLoc(), diag::note_fix_integral_float_as_integer)
>>      << FixItHint::CreateReplacement(FL->getSourceRange(), LiteralValue);
>
> I was going to ask why you're forcing this to be signed, but then I
> realized it's impossible to write a negative floating-point literal.
> :)

More because the previously-existing code made it signed. I didn't
think hard enough to notice that negative floating literals are
impossible. Using signed integers may actually be a bug, since if the
target is a uint64, and the floating literal doesn't fit in an int64,
this will fail the conversion even though the result would fit.

New patch at http://codereview.appspot.com/download/issue4728042_3001.diff.