On Tue, Nov 25, 2014 at 3:59 PM, Tom de Vries <tom_devr...@mentor.com> wrote: > On 25-11-14 10:28, Richard Biener wrote: >> >> On Tue, Nov 25, 2014 at 1:01 AM, Tom de Vries <tom_devr...@mentor.com> >> wrote: >>> >>> Richard, >>> >>> I ran into a problem with my oacc kernels directive patch series where >>> tail-merge added another entry into a region that was previously >>> single-entry-single-exit. >>> >>> That resulted in hitting this assert in calc_dfs_tree: >>> ... >>> /* This aborts e.g. when there is _no_ path from ENTRY to EXIT at all. >>> */ >>> gcc_assert (di->nodes == (unsigned int) n_basic_blocks_for_fn (cfun) - >>> 1); >>> ... >>> during a call to move_sese_region_to_fn. >>> >>> This patch makes sure that we abort earlier, with a clearer message of >>> what >>> is actually wrong. >>> >>> Bootstrapped and reg-tested on x86_64. >>> >>> OK for trunk/stage3? >> >> >> I believe someone made the function work for SEME regions and I believe >> it is actually used to copy loops with multiple exits > > > This is the first part of the function comment for move_sese_region_to_fn: > ... > /* Move a single-entry, single-exit region delimited by ENTRY_BB and > EXIT_BB to function DEST_CFUN. The whole region is replaced by a > single basic block in the original CFG and the new basic block is > returned. DEST_CFUN must not have a CFG yet. > > Note that the region need not be a pure SESE region. Blocks inside > the region may contain calls to abort/exit. The only restriction > is that ENTRY_BB should be the only entry point and it must > dominate EXIT_BB. > ... > > I'm guessing you're referring to the 'not pure SESE region' bit? > > So in fact, it's not a single-entry-single-exit region, but more a > single-entry-at-most-one-continuation region. [ Note that in case of f.i. an > eternal loop, we can also have single entry, no continuation. ] > >> so I don't see how the >> patch can work in these cases? >> > > The bbs with calls to abort/exit don't have any successor edges. verify_sese > doesn't assert anything specific about suchs bbs.
Ah, indeed. Patch is ok then. Thanks, Richard. > Thanks, > - Tom >
