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| author | Jeff Law <law@redhat.com> | 2016-10-10 14:40:59 -0600 |
|---|---|---|
| committer | Jeff Law <law@gcc.gnu.org> | 2016-10-10 14:40:59 -0600 |
| commit | d30078b8e7dc6f94dbd8aa1b56f59bdf479303a8 (patch) | |
| tree | 066715968cbe99237d25613412f7aaa6312ca3c3 /gcc/tree-ssa-dom.c | |
| parent | db62593447dd61532f7b7411d603d844498fc0a9 (diff) | |
| download | gcc-d30078b8e7dc6f94dbd8aa1b56f59bdf479303a8.zip gcc-d30078b8e7dc6f94dbd8aa1b56f59bdf479303a8.tar.gz gcc-d30078b8e7dc6f94dbd8aa1b56f59bdf479303a8.tar.bz2 | |
re PR tree-optimization/71947 (x ^ y not folded to 0 if x == y by DOM)
PR tree-optimization/71947
* tree-ssa-dom.c (cprop_into_stmt): Avoid replacing A with B, then
B with A within a single statement.
PR tree-optimization/71947
* gcc.dg/tree-ssa/pr71947-1.c: New test.
* gcc.dg/tree-ssa/pr71947-2.c: New test.
* gcc.dg/tree-ssa/pr71947-3.c: New test.
* gcc.dg/tree-ssa/pr71947-4.c: New test.
* gcc.dg/tree-ssa/pr71947-5.c: New test.
* gcc.dg/tree-ssa/pr71947-6.c: New test.
From-SVN: r240947
Diffstat (limited to 'gcc/tree-ssa-dom.c')
| -rw-r--r-- | gcc/tree-ssa-dom.c | 19 |
1 files changed, 18 insertions, 1 deletions
diff --git a/gcc/tree-ssa-dom.c b/gcc/tree-ssa-dom.c index b007388..5376ff9 100644 --- a/gcc/tree-ssa-dom.c +++ b/gcc/tree-ssa-dom.c @@ -1731,9 +1731,26 @@ cprop_into_stmt (gimple *stmt) { use_operand_p op_p; ssa_op_iter iter; + tree last_copy_propagated_op = NULL; FOR_EACH_SSA_USE_OPERAND (op_p, stmt, iter, SSA_OP_USE) - cprop_operand (stmt, op_p); + { + tree old_op = USE_FROM_PTR (op_p); + + /* If we have A = B and B = A in the copy propagation tables + (due to an equality comparison), avoid substituting B for A + then A for B in the trivially discovered cases. This allows + optimization of statements were A and B appear as input + operands. */ + if (old_op != last_copy_propagated_op) + { + cprop_operand (stmt, op_p); + + tree new_op = USE_FROM_PTR (op_p); + if (new_op != old_op && TREE_CODE (new_op) == SSA_NAME) + last_copy_propagated_op = new_op; + } + } } /* Optimize the statement in block BB pointed to by iterator SI |