On Mon, Jul 25, 2011 at 1:09 PM, Ira Rosen <ira.ro...@linaro.org> wrote: > On 25 July 2011 13:57, Richard Guenther <richard.guent...@gmail.com> wrote: >> On Mon, Jul 25, 2011 at 12:52 PM, Ira Rosen <ira.ro...@linaro.org> wrote: >>> On 25 July 2011 12:39, Richard Guenther <richard.guent...@gmail.com> wrote: >>>> On Mon, Jul 25, 2011 at 11:10 AM, Ulrich Weigand <uweig...@de.ibm.com> >>>> wrote: >>>>> Richard Guenther wrote: >>>>>> On Sun, Jul 24, 2011 at 2:02 PM, Ira Rosen <ira.ro...@linaro.org> wrote: >>>>>> > On 21 July 2011 15:19, Ira Rosen <ira.ro...@linaro.org> wrote: >>>>>> >> I reproduced the failure. It occurs without Richard's >>>>>> >> (http://gcc.gnu.org/ml/gcc-patches/2011-07/msg01022.html) and this >>>>>> >> patches too. Obviously the vectorized loop is executed, but at the >>>>>> >> moment I don't understand why. I'll have a better look on Sunday. >>>>>> > >>>>>> > Actually it doesn't choose the vectorized code. But the scalar version >>>>>> > gets optimized in a harmful way for SPU, AFAIU. >>>>>> > Here is the scalar loop after vrp2 >>>>>> > >>>>>> > <bb 8>: >>>>>> > # ivtmp.42_50 = PHI <ivtmp.42_59(3), ivtmp.42_45(10)> >>>>>> > D.4593_42 = (void *) ivtmp.53_32; >>>>>> > D.4520_33 = MEM[base: D.4593_42, offset: 0B]; >>>>>> > D.4521_34 = D.4520_33 + 1; >>>>>> > MEM[symbol: a, index: ivtmp.42_50, offset: 0B] = D.4521_34; >>>>>> > ivtmp.42_45 = ivtmp.42_50 + 4; >>>>>> > if (ivtmp.42_45 != 16) >>>>>> > goto <bb 10>; >>>>>> > else >>>>>> > goto <bb 5>; >>>>>> > >>>>>> > and the load is changed by dom2 to: >>>>>> > >>>>>> > <bb 4>: >>>>>> > ... >>>>>> > D.4520_33 = MEM[base: vect_pa.9_19, offset: 0B]; >>>>>> > ... >>>>>> > >>>>>> > where vector(4) int * vect_pa.9; >>>>>> > >>>>>> > And the scalar loop has no rotate for that load: >>>>>> >>>>>> Hum. This smells like we are hiding sth from the tree optimizers? >>>>> >>>>> Well, the back-end assumes a pointer to vector type is always >>>>> naturally aligned, and therefore the data it points to can be >>>>> accessed via a simple load, with no extra rotate needed. >>>> >>>> I can't see any use of VECTOR_TYPE in config/spu/, and assuming >>>> anything about alignment just because of the kind of the pointer >>>> is bogus - the scalar code does a scalar read using that pointer. >>>> So the backend better should look at the memory operation, not >>>> at the pointer type. That said, I can't find any code that looks >>>> suspicious in the spu backend. >>>> >>>>> It seems what happened here is that somehow, a pointer to int >>>>> gets replaced by a pointer to vector, even though their alignment >>>>> properties are different. >>>> >>>> No, they are not. They get replaced if they are value-equivalent >>>> in which case they are also alignment-equivalent. But well, the >>>> dump snippet wasn't complete and I don't feel like building a >>>> SPU cross to verify myself. >>> >>> I am attaching the complete file. >> >> The issue seems to be that the IV in question, vect_pa.9_19, is >> defined as >> >> vect_pa.9_19 = (vector(4) int *) ivtmp.53_32; >> >> but ivtmp.53_32 does not have a definition at all. >> > > I am sorry, it's my fault, resending the file.
Seems perfectly valid to me. Or well - I suppose we might run into the issue that the vectorizer sets alignment data at the wrong spot? You can check alignment info when dumping with the -alias flag. Building a spu cross now. Richard.
