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From: Richard Biener <rguenth@gcc.gnu.org> To: gcc-cvs@gcc.gnu.org Subject: [gcc r13-6113] Fix wrong-code issue in VN Date: Fri, 17 Feb 2023 11:31:58 +0000 (GMT) [thread overview] Message-ID: <20230217113158.2AC4A382E69E@sourceware.org> (raw) https://gcc.gnu.org/g:417e95263ca4d7a6623783ad664cf6305d8d3fad commit r13-6113-g417e95263ca4d7a6623783ad664cf6305d8d3fad Author: Richard Biener <rguenther@suse.de> Date: Fri Feb 17 09:30:49 2023 +0100 Fix wrong-code issue in VN The following fixes the wrong removed dead store discovered on the PR108657 testcase when the reported DSE issue is not fixed. The issue is we were using ssa_undefined_value_p on virtual operands which returns a result based on the real definition of the definition statement. That doesn't make sense so this patch guards the calls properly and makes sure nobody else does the same mistake. * tree-ssa.cc (ssa_undefined_value_p): Assert we are not called on virtual operands. * tree-ssa-sccvn.cc (vn_phi_lookup): Guard ssa_undefined_value_p calls. (vn_phi_insert): Likewise. (set_ssa_val_to): Likewise. (visit_phi): Avoid extra work with equivalences for virtual operand PHIs. Diff: --- gcc/tree-ssa-sccvn.cc | 20 +++++++++++++++----- gcc/tree-ssa.cc | 2 ++ 2 files changed, 17 insertions(+), 5 deletions(-) diff --git a/gcc/tree-ssa-sccvn.cc b/gcc/tree-ssa-sccvn.cc index 8ee77fd2b78..d5b081a309f 100644 --- a/gcc/tree-ssa-sccvn.cc +++ b/gcc/tree-ssa-sccvn.cc @@ -4824,7 +4824,8 @@ vn_phi_lookup (gimple *phi, bool backedges_varying_p) if (TREE_CODE (def) == SSA_NAME && (!backedges_varying_p || !(e->flags & EDGE_DFS_BACK))) { - if (ssa_undefined_value_p (def, false)) + if (!virtual_operand_p (def) + && ssa_undefined_value_p (def, false)) def = VN_TOP; else def = SSA_VAL (def); @@ -4877,7 +4878,8 @@ vn_phi_insert (gimple *phi, tree result, bool backedges_varying_p) if (TREE_CODE (def) == SSA_NAME && (!backedges_varying_p || !(e->flags & EDGE_DFS_BACK))) { - if (ssa_undefined_value_p (def, false)) + if (!virtual_operand_p (def) + && ssa_undefined_value_p (def, false)) def = VN_TOP; else def = SSA_VAL (def); @@ -5059,6 +5061,7 @@ set_ssa_val_to (tree from, tree to) } curr_invariant = is_gimple_min_invariant (currval); curr_undefined = (TREE_CODE (currval) == SSA_NAME + && !virtual_operand_p (currval) && ssa_undefined_value_p (currval, false)); if (currval != VN_TOP && !curr_invariant @@ -5081,6 +5084,7 @@ set_ssa_val_to (tree from, tree to) else if (currval != VN_TOP && !curr_undefined && TREE_CODE (to) == SSA_NAME + && !virtual_operand_p (to) && ssa_undefined_value_p (to, false)) { if (dump_file && (dump_flags & TDF_DETAILS)) @@ -5116,6 +5120,7 @@ set_and_exit: PR82320 for a testcase were we'd otherwise not terminate iteration. */ && !(curr_undefined && TREE_CODE (to) == SSA_NAME + && !virtual_operand_p (to) && ssa_undefined_value_p (to, false)) /* ??? For addresses involving volatile objects or types operand_equal_p does not reliably detect ADDR_EXPRs as equal. We know we are only @@ -5880,7 +5885,14 @@ visit_phi (gimple *phi, bool *inserted, bool backedges_varying_p) sameval = def; sameval_e = e; } - else if (!expressions_equal_p (def, sameval)) + else if (expressions_equal_p (def, sameval)) + sameval_e = NULL; + else if (virtual_operand_p (def)) + { + sameval = NULL_TREE; + break; + } + else { /* We know we're arriving only with invariant addresses here, try harder comparing them. We can do some caching here @@ -5957,8 +5969,6 @@ visit_phi (gimple *phi, bool *inserted, bool backedges_varying_p) sameval = NULL_TREE; break; } - else - sameval_e = NULL; } /* If the value we want to use is flowing over the backedge and we diff --git a/gcc/tree-ssa.cc b/gcc/tree-ssa.cc index 5126020d40f..a5cad2d344e 100644 --- a/gcc/tree-ssa.cc +++ b/gcc/tree-ssa.cc @@ -1320,6 +1320,8 @@ ssa_undefined_value_p (tree t, bool partial) { gimple *def_stmt; + gcc_checking_assert (!virtual_operand_p (t)); + if (ssa_defined_default_def_p (t)) return false;
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