r205646 - Vector [Sema]. Vector "splats" which are truncated should have a warning

[jahanian]

On Apr 4, 2014, at 5:58 PM, Steve Canon <scanon at apple.com> wrote:

> I added a warning with r205521, for this and some other scalar->vector conversions.
> 

Great, thanks. I reverted my patch in r205718.

- Fariborz

> -- Steve
> 
> Sent from my iPhone
> 
>> On Apr 4, 2014, at 8:14 PM, jahanian <fjahanian at apple.com> wrote:
>> 
>> This is strange. Before my patch, there was no warning for my test. This was the reason behind the patch.
>> If my patch is no longer needed due to other changes which took place while I was fixing this,  I can take it out.
>> 
>> - Fariborz
>> 
>> 
>>> On Apr 4, 2014, at 3:05 PM, Stephen Canon <scanon at apple.com> wrote:
>>> 
>>> Hi Fariborz --
>>> 
>>> Before this patch, we were generating the following warning for your test case:
>>> 
>>>   implicit conversion loses integer precision: 'uint32_t' (aka 'unsigned int') to 'ushort16'
>>> 
>>> with your patch, we get the following instead:
>>> 
>>>   implicit conversion loses integer precision: 'uint32_t' (aka 'unsigned int') to 'unsigned short'
>>> 
>>> I have a slight preference for the warning we used to issue, as it refers to the conversion that actually takes place conceptually (scalar -> vector), rather than the "subconversion" that changes the value (scalar -> vector element).  Reasonable people may disagree, of course.
>>> 
>>> – Steve
>>> 
>>>> On Apr 4, 2014, at 3:33 PM, Fariborz Jahanian <fjahanian at apple.com> wrote:
>>>> 
>>>> Author: fjahanian
>>>> Date: Fri Apr  4 14:33:39 2014
>>>> New Revision: 205646
>>>> 
>>>> URL: http://llvm.org/viewvc/llvm-project?rev=205646&view=rev
>>>> Log:
>>>> Vector [Sema]. Vector "splats" which are truncated should have a warning
>>>> with -Wconversion. // rdar://16502418
>>>> 
>>>> Modified:
>>>> cfe/trunk/lib/Sema/SemaChecking.cpp
>>>> cfe/trunk/test/Sema/conversion.c
>>>> 
>>>> Modified: cfe/trunk/lib/Sema/SemaChecking.cpp
>>>> URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/Sema/SemaChecking.cpp?rev=205646&r1=205645&r2=205646&view=diff
>>>> ==============================================================================
>>>> --- cfe/trunk/lib/Sema/SemaChecking.cpp (original)
>>>> +++ cfe/trunk/lib/Sema/SemaChecking.cpp Fri Apr  4 14:33:39 2014
>>>> @@ -6113,11 +6113,20 @@ void CheckConditionalOperator(Sema &S, C
>>>> /// implicit conversions in the given expression.  There are a couple
>>>> /// of competing diagnostics here, -Wconversion and -Wsign-compare.
>>>> void AnalyzeImplicitConversions(Sema &S, Expr *OrigE, SourceLocation CC) {
>>>> -  QualType T = OrigE->getType();
>>>> Expr *E = OrigE->IgnoreParenImpCasts();
>>>> 
>>>> if (E->isTypeDependent() || E->isValueDependent())
>>>>  return;
>>>> +  
>>>> +  QualType T = OrigE->getType();
>>>> +  // Check for conversion from an arithmetic type to a vector of arithmetic
>>>> +  // type elements. Warn if this results in truncation of each vector element.
>>>> +  if (isa<ExtVectorElementExpr>(E)) {
>>>> +    if (ImplicitCastExpr *ICE = dyn_cast<ImplicitCastExpr>(OrigE))
>>>> +      if ((ICE->getCastKind() == CK_VectorSplat) &&
>>>> +          !T.isNull() && T->isExtVectorType())
>>>> +        T = cast<ExtVectorType>(T.getCanonicalType())->getElementType();
>>>> +  }
>>>> 
>>>> // For conditional operators, we analyze the arguments as if they
>>>> // were being fed directly into the output.
>>>> 
>>>> Modified: cfe/trunk/test/Sema/conversion.c
>>>> URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/test/Sema/conversion.c?rev=205646&r1=205645&r2=205646&view=diff
>>>> ==============================================================================
>>>> --- cfe/trunk/test/Sema/conversion.c (original)
>>>> +++ cfe/trunk/test/Sema/conversion.c Fri Apr  4 14:33:39 2014
>>>> @@ -417,3 +417,15 @@ void test26(int si, long sl) {
>>>> si = si / sl;
>>>> si = sl / si; // expected-warning {{implicit conversion loses integer precision: 'long' to 'int'}}
>>>> }
>>>> +
>>>> +// rdar://16502418
>>>> +typedef unsigned short uint16_t;
>>>> +typedef unsigned int uint32_t;
>>>> +typedef __attribute__ ((ext_vector_type(16),__aligned__(32))) uint16_t ushort16;
>>>> +typedef __attribute__ ((ext_vector_type( 8),__aligned__( 32))) uint32_t uint8;
>>>> +
>>>> +void test27(ushort16 constants) {
>>>> +    uint8 pairedConstants = (uint8) constants;
>>>> +    ushort16 crCbScale = pairedConstants.s4; // expected-warning {{implicit conversion loses integer precision: 'uint32_t' (aka 'unsigned int') to 'unsigned short'}}
>>>> +    ushort16 brBias = pairedConstants.s6; // expected-warning {{implicit conversion loses integer precision: 'uint32_t' (aka 'unsigned int') to 'unsigned short'}}
>>>> +}
>>>> 
>>>> 
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>> 

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