[patch] Fix powerpc 64 alignment problem for lwa instruction

[Dale Johannesen]

On Nov 7, 2006, at 3:13 PM, Andrew Pinski wrote:
>> #pragma pack(push, 2)
>> struct FixedRectangle {
>>   int left;
>>   int top;
>>   int right;
>>   int bottom;
>> };
>> #pragma pack(pop)
>>
>> long getLeft (struct FixedRectangle *a)
>> {
>>   return ((struct FixedRectangle*)(((char*)a)+4))->top;
>> }
>>
>> Compile at -Os -m64, we should still get a lwa but with your patch  
>> we get a
>> lwz and a extsw.
>>
>> The following patch keeps this regression from showing up and also  
>> fixes your orginal
>> testcase:
>> Index: predicates.md
>> ===================================================================
>> --- predicates.md       (revision 118565)
>> +++ predicates.md       (working copy)
>> @@ -654,7 +654,9 @@ (define_predicate "lwa_operand"
>>         && GET_CODE (XEXP (inner, 0)) != PRE_DEC
>>         && (GET_CODE (XEXP (inner, 0)) != PLUS
>>             || GET_CODE (XEXP (XEXP (inner, 0), 1)) != CONST_INT
>> -           || INTVAL (XEXP (XEXP (inner, 0), 1)) % 4 == 0));
>> +           || INTVAL (XEXP (XEXP (inner, 0), 1)) % 4 == 0)
>> +       && (GET_CODE (XEXP (inner, 0)) != LO_SUM
>> +           || (MEM_ALIGN (inner) % 32) == 0));
>>  })
>>
>>  ;; Return 1 if the operand, used inside a MEM, is a SYMBOL_REF.

(I forgot about this thread, sorry.)  While the original patch is  
conservatively correct
I agree this one is better.