From 8b9a03d644fb55566180aeec291b64ca23f3c77b Mon Sep 17 00:00:00 2001 From: David Malcolm Date: Thu, 8 Mar 2018 12:17:36 +0000 Subject: [PATCH] tree-if-conv.c: fix ICE seen with -fno-tree-forwprop (PR tree-optimization/84178) PR tree-optimization/84178 reports a couple of source files that ICE inside ifcvt when compiled with -03 -fno-tree-forwprop (trunk and gcc 7). Both cases involve problems with ifcvt's per-BB gimplified predicates. Testcase 1 fails this assertion within release_bb_predicate during cleanup: 283 if (flag_checking) 284 for (gimple_stmt_iterator i = gsi_start (stmts); 285 !gsi_end_p (i); gsi_next (&i)) 286 gcc_assert (! gimple_use_ops (gsi_stmt (i))); The testcase contains a division in the loop, which leads to if_convertible_loop_p returning false (due to gimple_could_trap_p being true for the division). This happens *after* the per-BB gimplified predicates have been created in predicate_bbs (loop). Hence tree_if_conversion bails out to "cleanup", but the gimplified predicates exist and make use of SSA names; for example this conjunction for two BB conditions: _4 = h4.1_112 != 0; _175 = (signed char) _117; _176 = _175 >= 0; _174 = _4 & _176; is using SSA names. This assertion was added in r236498 (aka c3deca2519d97c55876869c57cf11ae1e5c6cf8b): 2016-05-20 Richard Biener * tree-if-conv.c (add_bb_predicate_gimplified_stmts): Use gimple_seq_add_seq_without_update. (release_bb_predicate): Assert we have no operands to free. (if_convertible_loop_p_1): Calculate post dominators later. Do not free BB predicates here. (combine_blocks): Do not recompute BB predicates. (version_loop_for_if_conversion): Save BB predicates around loop versioning. * gcc.dg/tree-ssa/ifc-cd.c: Adjust. The following patch fixes this by adding a call to gimple_seq_discard to release_bb_predicate. It also updates the assertion, so that instead of asserting the stmts have no imm uses, instead assert that they weren't added to a bb before discarding them (otherwise discarding them would be a bug). We know this is the case because insert_gimplified_predicates has: /* Once the sequence is code generated, set it to NULL. */ set_bb_predicate_gimplified_stmts (bb, NULL); but asserting it seems appropriate as a double-check. The patch doesn't address the 2nd issue within PR tree-optimization/84178. gcc/ChangeLog: PR tree-optimization/84178 * tree-if-conv.c (release_bb_predicate): Remove the the assertion that the stmts have NULL use_ops. Discard the statements, asserting that they haven't yet been added to a BB. gcc/testsuite/ChangeLog: PR tree-optimization/84178 * gcc.c-torture/compile/pr84178-1.c: New test. From-SVN: r258363 --- gcc/ChangeLog | 8 ++++++++ gcc/testsuite/ChangeLog | 5 +++++ .../gcc.c-torture/compile/pr84178-1.c | 18 ++++++++++++++++++ gcc/tree-if-conv.c | 8 +++++--- 4 files changed, 36 insertions(+), 3 deletions(-) create mode 100644 gcc/testsuite/gcc.c-torture/compile/pr84178-1.c diff --git a/gcc/ChangeLog b/gcc/ChangeLog index 380b023270e..e1c40c310a0 100644 --- a/gcc/ChangeLog +++ b/gcc/ChangeLog @@ -1,3 +1,11 @@ +2018-03-08 David Malcolm + + PR tree-optimization/84178 + * tree-if-conv.c (release_bb_predicate): Remove the + the assertion that the stmts have NULL use_ops. + Discard the statements, asserting that they haven't + yet been added to a BB. + 2018-03-08 Richard Biener PR tree-optimization/84746 diff --git a/gcc/testsuite/ChangeLog b/gcc/testsuite/ChangeLog index 3d12b6b2a47..eb8ade6cb68 100644 --- a/gcc/testsuite/ChangeLog +++ b/gcc/testsuite/ChangeLog @@ -1,3 +1,8 @@ +2018-03-08 David Malcolm + + PR tree-optimization/84178 + * gcc.c-torture/compile/pr84178-1.c: New test. + 2018-03-08 Thomas Schwinge * lib/target-supports.exp: Do not return zero from a ifunc diff --git a/gcc/testsuite/gcc.c-torture/compile/pr84178-1.c b/gcc/testsuite/gcc.c-torture/compile/pr84178-1.c new file mode 100644 index 00000000000..49f2c893054 --- /dev/null +++ b/gcc/testsuite/gcc.c-torture/compile/pr84178-1.c @@ -0,0 +1,18 @@ +/* { dg-options "-fno-tree-forwprop" } */ + +int zy, h4; + +void +r8 (long int mu, int *jr, int *fi, short int dv) +{ + do + { + int tx; + + tx = !!h4 ? (zy / h4) : 1; + mu = tx; + *jr = (((unsigned char) mu > (254 >> dv)) ? 0 : (unsigned char) tx) + *fi; + } while (*jr == 0); + + r8 (mu, jr, fi, 1); +} diff --git a/gcc/tree-if-conv.c b/gcc/tree-if-conv.c index cac3fd75d54..5467f3fa4e0 100644 --- a/gcc/tree-if-conv.c +++ b/gcc/tree-if-conv.c @@ -271,8 +271,7 @@ init_bb_predicate (basic_block bb) set_bb_predicate (bb, boolean_true_node); } -/* Release the SSA_NAMEs associated with the predicate of basic block BB, - but don't actually free it. */ +/* Release the SSA_NAMEs associated with the predicate of basic block BB. */ static inline void release_bb_predicate (basic_block bb) @@ -280,11 +279,14 @@ release_bb_predicate (basic_block bb) gimple_seq stmts = bb_predicate_gimplified_stmts (bb); if (stmts) { + /* Ensure that these stmts haven't yet been added to a bb. */ if (flag_checking) for (gimple_stmt_iterator i = gsi_start (stmts); !gsi_end_p (i); gsi_next (&i)) - gcc_assert (! gimple_use_ops (gsi_stmt (i))); + gcc_assert (! gimple_bb (gsi_stmt (i))); + /* Discard them. */ + gimple_seq_discard (stmts); set_bb_predicate_gimplified_stmts (bb, NULL); } } -- 2.30.2