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| author | law <law@138bc75d-0d04-0410-961f-82ee72b054a4> | 2005-12-16 07:03:12 +0000 |
|---|---|---|
| committer | law <law@138bc75d-0d04-0410-961f-82ee72b054a4> | 2005-12-16 07:03:12 +0000 |
| commit | 2b9070b6074f3138196132879507cab903308feb (patch) | |
| tree | 88a7799c9f4d7f31317de3ae132949f5dde781d1 /gcc/tree-ssa-dse.c | |
| parent | c4503c0a24b13382f88c58711cf142064ec51e26 (diff) | |
| download | gcc-2b9070b6074f3138196132879507cab903308feb.tar.gz | |
* 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.
git-svn-id: svn+ssh://gcc.gnu.org/svn/gcc/trunk@108630 138bc75d-0d04-0410-961f-82ee72b054a4
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 fa3ba960a28..f1cc22ae310 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)) |