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

[jahanian]

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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