| Message ID | 20180103205425.GN1833@tucnak |
|---|---|
| State | New |
| Headers | show |
| Series | Update crtl->has_bb_partition if NOTE_INSN_SWITCH_SECTIONS isn't emitted (PR debug/83585) | expand |
On 01/03/2018 01:54 PM, Jakub Jelinek wrote: > Hi! > > My recent dwarf2out.c, dbxout.c and rs6000.c uses of crtl->has_bb_partition > all assume that if it is true then the function actually has 2 partitions > and NOTE_INSN_SWITCH_SECTIONS is present, but as the following testcase > shows, that isn't always the case, crtl->has_bb_partition is set during > bbpart pass if there are 2 partitions, but there are many passes in between > and all bbs of one of the partitions could be optimized away. > > Are there any uses of this flag that would be interested in whether the > function had any partitions in the past (I guess that also means > BB_PARTITION is not unspecified), rather than whether the function has 2 > partitions right now? If yes, instead of this patch we could introduce > a new flag in cfun set by insert_section_boundary_note. If not, the > following patch should be sufficient. > > Bootstrapped/regtested on x86_64-linux and i686-linux. > > 2018-01-03 Jakub Jelinek <jakub@redhat.com> > > PR debug/83585 > * bb-reorder.c (insert_section_boundary_note): Set has_bb_partition > to switched_sections. > > * gcc.dg/pr83585.c: New test. I don't think the question of whether or not there were partitions in the past is particularly interesting -- I could probably conjure up a need, but it wouldn't be based on any actual need I'm aware of. Let's go with this until such time as a port really needs to answer that kind of question. jeff
--- gcc/bb-reorder.c.jj 2018-01-03 10:19:55.303533981 +0100 +++ gcc/bb-reorder.c 2018-01-03 18:16:32.470555769 +0100 @@ -2523,6 +2523,11 @@ insert_section_boundary_note (void) current_partition = BB_PARTITION (bb); } } + + /* Make sure crtl->has_bb_partition matches reality even if bbpart finds + some hot and some cold basic blocks, but later one of those kinds is + optimized away. */ + crtl->has_bb_partition = switched_sections; } namespace { --- gcc/testsuite/gcc.dg/pr83585.c.jj 2018-01-03 18:20:33.685641817 +0100 +++ gcc/testsuite/gcc.dg/pr83585.c 2018-01-03 18:19:29.922619064 +0100 @@ -0,0 +1,18 @@ +/* PR debug/83585 */ +/* { dg-do assemble } */ +/* { dg-options "-std=gnu89 -O2 -g -fno-tree-dce -fno-guess-branch-probability" } */ + +int +foo (int x) +{ + int a, b; + for (a = 0; a < 2; ++a) + if (x != 0) + { + for (b = 0; b < 2; ++b) + ; + return 0; + } + + return; +}