2007/11/3, Kenneth Zadeck wrote: > I believe that this is something new and is most likely fallout from > diego's reworking of the tree to rtl converter. > > To fix this will require a round of copy propagation, most likely in > concert with some induction variable detection, since the most > profitable place for this will be in loops. > > I wonder if any of this effects the rtl level induction variable > discovery? > > > Hi, Ramana, > > I tried the trunk version with/without your patch. It still produces > > the same code as gcc4.2.2 does. In auto-inc-dec.c, the comments say > > > > *a > > ... > > a <- a + c > > > > becomes > > > > *(a += c) post > > > > But the problem is after Tree-SSA pass, there is no > > a <- a + c > > But something like > > a_1 <- a + c > > > > Unless the auto-inc-dec.c can reverse a_1 <- a + c to a <- a + c. I > > don't see this transformation is applicable in most scenarios. Any > > comments? > > > > Cheers, > > Bingfeng
They need to add an algorithm post-SSA that the code reuse the variables converting a_j <- phi(a_i,...) to a_k <- phi(a_k,...). The algorithms of POST_INC and POST_DEC are very specific, so an above general algorithm is sufficient. J.C. Pizarro
