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| author | Jeff Law <law@redhat.com> | 2005-12-16 00:03:12 -0700 |
|---|---|---|
| committer | Jeff Law <law@gcc.gnu.org> | 2005-12-16 00:03:12 -0700 |
| commit | 7d48c9e2cc0d77630d365efe8fa1803a224a9a0a (patch) | |
| tree | 88a7799c9f4d7f31317de3ae132949f5dde781d1 /gcc/tree-ssa-dse.c | |
| parent | 9a8ce21f3b47a109b9ac35239e21198bb36e1146 (diff) | |
| download | gcc-7d48c9e2cc0d77630d365efe8fa1803a224a9a0a.zip gcc-7d48c9e2cc0d77630d365efe8fa1803a224a9a0a.tar.gz gcc-7d48c9e2cc0d77630d365efe8fa1803a224a9a0a.tar.bz2 | |
tree-ssa-dse.c (dse_optimize_stmt): Correctly handle PHI nodes which represent a use and definition of the same...
* tree-ssa-dse.c (dse_optimize_stmt): Correctly handle PHI nodes which
represent a use and definition of the same SSA_NAME.
* gcc.dg/tree-ssa/ssa-dse-8.c: New test.
From-SVN: r108630
Diffstat (limited to 'gcc/tree-ssa-dse.c')
| -rw-r--r-- | gcc/tree-ssa-dse.c | 9 |
1 files changed, 9 insertions, 0 deletions
diff --git a/gcc/tree-ssa-dse.c b/gcc/tree-ssa-dse.c index fa3ba96..f1cc22a 100644 --- a/gcc/tree-ssa-dse.c +++ b/gcc/tree-ssa-dse.c @@ -309,6 +309,15 @@ dse_optimize_stmt (struct dom_walk_data *walk_data, && TREE_CODE (use_stmt) == PHI_NODE && bitmap_bit_p (dse_gd->stores, get_stmt_uid (use_stmt))) { + /* A PHI node can both define and use the same SSA_NAME if + the PHI is at the top of a loop and the PHI_RESULT is + a loop invariant and copies have not been fully propagated. + + The safe thing to do is exit assuming no optimization is + possible. */ + if (SSA_NAME_DEF_STMT (PHI_RESULT (use_stmt)) == use_stmt) + return; + /* Skip past this PHI and loop again in case we had a PHI chain. */ if (single_imm_use (PHI_RESULT (use_stmt), &use_p, &use_stmt)) |