tree-optimization/107935 - fixup equivalence handling in PHI VN
Commit Message
The following makes sure to honor the backedge processing logic
that forces VARYING there.
Bootstrapped and tested on x86_64-unknown-linux-gnu, pushed.
PR tree-optimization/107935
* tree-ssa-sccvn.cc (visit_phi): Honor forced VARYING on
backedges.
* gcc.dg/torture/pr107935.c: New testcase.
---
gcc/testsuite/gcc.dg/torture/pr107935.c | 18 ++++++++++++++++++
gcc/tree-ssa-sccvn.cc | 7 ++++++-
2 files changed, 24 insertions(+), 1 deletion(-)
create mode 100644 gcc/testsuite/gcc.dg/torture/pr107935.c
new file mode 100644
@@ -0,0 +1,18 @@
+/* { dg-do compile } */
+
+int *a, **b;
+int main() {
+ int d = 0, *e = &d;
+ L:
+ *e = d;
+ if (a) {
+ int *g = e = *b;
+ if (!e)
+ __builtin_abort();
+ if (**b)
+ return 0;
+ *g = 1;
+ goto L;
+ }
+ return 0;
+}
@@ -5861,7 +5861,12 @@ visit_phi (gimple *phi, bool *inserted, bool backedges_varying_p)
continue;
}
/* There's also the possibility to use equivalences. */
- if (!FLOAT_TYPE_P (TREE_TYPE (def)))
+ if (!FLOAT_TYPE_P (TREE_TYPE (def))
+ /* But only do this if we didn't force any of sameval or
+ val to VARYING because of backedge processing rules. */
+ && (TREE_CODE (sameval) != SSA_NAME
+ || SSA_VAL (sameval) == sameval)
+ && (TREE_CODE (def) != SSA_NAME || SSA_VAL (def) == def))
{
vn_nary_op_t vnresult;
tree ops[2];