| Message ID | eefab903-071d-a8fe-887d-434f09c36abf@redhat.com |
|---|---|
| State | New |
| Headers | show |
On Thu, Dec 08, 2016 at 01:21:04PM +0100, Bernd Schmidt wrote: > This is another case where an optimization turns a trap_if > unconditional. We have to defer changing the CFG, since the rest of > cprop seems to blow up when we modify things while scanning. > > Bootstrapped and tested on x86_64-linux, and reportedly fixes the > problem on ppc, ok? This fixes PR78626, but not yet PR78727. > @@ -1825,11 +1828,26 @@ one_cprop_pass (void) > insn into a NOTE, or deleted the insn. */ > if (! NOTE_P (insn) && ! insn->deleted ()) > mark_oprs_set (insn); > + > + if (first_uncond_trap == NULL > + && GET_CODE (PATTERN (insn)) == TRAP_IF > + && XEXP (PATTERN (insn), 0) == const1_rtx) > + first_uncond_trap = insn; > } > + if (first_uncond_trap != NULL && first_uncond_trap != BB_END (bb)) > + uncond_traps.safe_push (first_uncond_trap); > } The problem for PR78727 is that we also need to do this for insns that already are the last insn in the block: > + while (!uncond_traps.is_empty ()) > + { > + rtx_insn *insn = uncond_traps.pop (); > + basic_block to_split = BLOCK_FOR_INSN (insn); > + remove_edge (split_block (to_split, insn)); > + emit_barrier_after_bb (to_split); > + } We need that barrier, and we also need the successor edges removed (which split_block+remove_edge does). (PR78727 works fine with just that BB_END test deleted). Segher
On 12/10/2016 08:58 PM, Segher Boessenkool wrote: > On Thu, Dec 08, 2016 at 01:21:04PM +0100, Bernd Schmidt wrote: >> This is another case where an optimization turns a trap_if >> unconditional. We have to defer changing the CFG, since the rest of >> cprop seems to blow up when we modify things while scanning. > The problem for PR78727 is that we also need to do this for insns that > already are the last insn in the block: > >> + while (!uncond_traps.is_empty ()) >> + { >> + rtx_insn *insn = uncond_traps.pop (); >> + basic_block to_split = BLOCK_FOR_INSN (insn); >> + remove_edge (split_block (to_split, insn)); >> + emit_barrier_after_bb (to_split); >> + } > > We need that barrier, and we also need the successor edges removed > (which split_block+remove_edge does). > > (PR78727 works fine with just that BB_END test deleted). Ah, ok. In that case I'll probably also add a test to make sure this is only done for insns that weren't an unconditional trap before. Retesting... Bernd
PR rtl-optimization/78626 * cprop.c (one_cprop_pass): Collect unconditional traps in the middle of a block, and split such blocks after everything else is finished. PR rtl-optimization/78626 * gcc.dg/torture/pr78626.c: New test. Index: gcc/cprop.c =================================================================== --- gcc/cprop.c (revision 243310) +++ gcc/cprop.c (working copy) @@ -1794,7 +1794,7 @@ one_cprop_pass (void) if (set_hash_table.n_elems > 0) { basic_block bb; - rtx_insn *insn; + auto_vec<rtx_insn *> uncond_traps; alloc_cprop_mem (last_basic_block_for_fn (cfun), set_hash_table.n_elems); @@ -1810,6 +1810,9 @@ one_cprop_pass (void) EXIT_BLOCK_PTR_FOR_FN (cfun), next_bb) { + rtx_insn *first_uncond_trap = NULL; + rtx_insn *insn; + /* Reset tables used to keep track of what's still valid [since the start of the block]. */ reset_opr_set_tables (); @@ -1825,11 +1828,26 @@ one_cprop_pass (void) insn into a NOTE, or deleted the insn. */ if (! NOTE_P (insn) && ! insn->deleted ()) mark_oprs_set (insn); + + if (first_uncond_trap == NULL + && GET_CODE (PATTERN (insn)) == TRAP_IF + && XEXP (PATTERN (insn), 0) == const1_rtx) + first_uncond_trap = insn; } + if (first_uncond_trap != NULL && first_uncond_trap != BB_END (bb)) + uncond_traps.safe_push (first_uncond_trap); } changed |= bypass_conditional_jumps (); + while (!uncond_traps.is_empty ()) + { + rtx_insn *insn = uncond_traps.pop (); + basic_block to_split = BLOCK_FOR_INSN (insn); + remove_edge (split_block (to_split, insn)); + emit_barrier_after_bb (to_split); + } + FREE_REG_SET (reg_set_bitmap); free_cprop_mem (); } Index: gcc/testsuite/gcc.dg/torture/pr78626.c =================================================================== --- gcc/testsuite/gcc.dg/torture/pr78626.c (nonexistent) +++ gcc/testsuite/gcc.dg/torture/pr78626.c (working copy) @@ -0,0 +1,27 @@ +/* { dg-do compile } */ + +int qs; + +void +ms (int g1) +{ + int cy; + int *fr = &cy; + + for (;;) + { + *fr = 1; + fr = &g1; + + while (qs != 0) + { + if (qs | cy) + qs = g1 / 0; /* { dg-warning "division" } */ + ++qs; + } + + cy = 1; + while (cy != 0) + cy = 2; + } +}