https://gcc.gnu.org/bugzilla/show_bug.cgi?id=81766
--- Comment #2 from rguenther at suse dot de <rguenther at suse dot de> --- On Tue, 8 Aug 2017, jakub at gcc dot gnu.org wrote: > https://gcc.gnu.org/bugzilla/show_bug.cgi?id=81766 > > --- Comment #1 from Jakub Jelinek <jakub at gcc dot gnu.org> --- > If contemplating reversion, perhaps: > --- gcc/function.c.jj 2017-08-07 18:50:09.000000000 +0200 > +++ gcc/function.c 2017-08-08 11:11:25.506239318 +0200 > @@ -6073,17 +6073,16 @@ thread_prologue_and_epilogue_insns (void > if (prologue_insn > && BLOCK_FOR_INSN (prologue_insn) == NULL) > prologue_insn = NULL; > - if (split_prologue_insn || prologue_insn) > - { > - auto_sbitmap blocks (last_basic_block_for_fn (cfun)); > - bitmap_clear (blocks); > - if (split_prologue_insn) > - bitmap_set_bit (blocks, > - BLOCK_FOR_INSN (split_prologue_insn)->index); > - if (prologue_insn) > - bitmap_set_bit (blocks, BLOCK_FOR_INSN (prologue_insn)->index); > - find_many_sub_basic_blocks (blocks); > - } > + auto_sbitmap blocks (last_basic_block_for_fn (cfun)); > + bitmap_clear (blocks); > + if (split_prologue_insn) > + bitmap_set_bit (blocks, > + BLOCK_FOR_INSN (split_prologue_insn)->index); > + if (prologue_insn) > + bitmap_set_bit (blocks, BLOCK_FOR_INSN (prologue_insn)->index); > + bitmap_set_bit (blocks, entry_edge->dest->index); > + bitmap_set_bit (blocks, orig_entry_edge->dest->index); > + find_many_sub_basic_blocks (blocks); > } > > default_rtl_profile (); > > should be safe too (which does what we used to do before and additionally > marks > the new blocks if needed and different from the old ones. > Can't test it right now though. And, I really need to debug why we need to > find_many_sub_basic_blocks when split_prologue_seq is NULL and prologue_seq is > just > (note 17 0 0 NOTE_INSN_PROLOGUE_END) > alone. Perhaps something inserts insns elsewhere. find_many_sub_basic_blocks just splits the BB after NOTE_INSN_PROLOGUE_END because there's a label there(?). So commit_one_edge_insertion fails to split the edge? There's NOTE_INSN_BASIC_BLOCK before the label and the fn expects it the other way around(?). "Fixing" that doesn't help (NOTE_INSN_PROLOGUE_END after the L12: label) OTOH maybe add_branch_dependences is just bougus. The label is inserted by #1 0x0000000001147df5 in ix86_init_pic_reg () at /space/rguenther/src/svn/gcc-7-branch/gcc/config/i386/i386.c:8513 8513 insert_insn_on_edge (seq, entry_edge); so maybe that is the real issue. Either we can't insert labels that way or we need to handle it? Don't know enough about RTL internals.
