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Re: Possible patches for bug 27565


Ian Lance Taylor <iant@google.com> writes:

> "Joseph S. Myers" <joseph@codesourcery.com> writes:

> > but LOCAL_ALIGNMENT is defined as
> > 
> > #define LOCAL_ALIGNMENT(TYPE, ALIGN)                            \
> >   ((TARGET_ALTIVEC && TREE_CODE (TYPE) == VECTOR_TYPE) ? 128 :  \
> >     (TARGET_E500_DOUBLE && TYPE_MODE (TYPE) == DFmode) ? 64 : \
> >     (TARGET_SPE && TREE_CODE (TYPE) == VECTOR_TYPE) ? 64 : ALIGN)
> > 
> > which reduces the alignment from BIGGEST_ALIGNMENT (128) to 64 so causing 
> > an assertion failure.
> 
> I don't understand why we check this condition.
> 
> In general we assume that the alignment of BLKmode is BITS_PER_UNIT.
> There is no other assumption that we can make.  In particular, we
> certainly can't assume that a BLKmode value is aligned to
> BIGGEST_ALIGNMENT.  So why do we insist on that here?

Of course, this also leads to the question of why LOCAL_ALIGNMENT
should return anything other than ALIGN when TYPE_MODE (TYPE) ==
BLKmode.  Or: why is the mode BLKmode here?

Ian


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