[llvm-commits] [llvm] r66366 - in /llvm/trunk: lib/Transforms/Scalar/ScalarReplAggregates.cpp test/Transforms/ScalarRepl/2008-06-22-LargeArray.ll test/Transforms/ScalarRepl/vector_memcpy.ll
baldrick at free.fr
Sun Mar 8 12:44:51 PDT 2009
> >> + // If this is a memcpy or memmove into or out of the whole
> >> allocation, we
> >> + // can handle it like a load or store of the scalar type.
> > a load+store of a floating point type might trap, while a memcpy/
> > memmove would
> > not.
> How so? Load of double works on any bit pattern, so long as the
> address is correct and the alignment is right etc.
what about trapping NaNs (maybe they're called signalling NaN's,
> > Also, a memcpy/memmove of i33 may not the same as a load+store, due
> > to
> > the extra bits off the end (load of an i33 is only defined if the
> > original
> > value was stored using an i33 store - this way we can assume any
> > extra bits
> > are zero, because the store puts zero there; if someone wanted to
> > avoid this
> > undefinedness they might have used memcpy/memmove).
> This is converting a memcpy to a load/store of the same size, so it
> must be a multiple of a byte in size.
How is the size measured? By getTypeSizeInBits, getTypeStoreSizeInBits
or getTypePaddedSizeInBits? The first one is ok, the others not.
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