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* [gcc r13-4806] Don't use PHI equivalences in range-on-entry.
@ 2022-12-20 14:27 Andrew Macleod
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From: Andrew Macleod @ 2022-12-20 14:27 UTC (permalink / raw)
To: gcc-cvs
https://gcc.gnu.org/g:0bdd2261c254f08b0f4437c156b79711d68c6e7f
commit r13-4806-g0bdd2261c254f08b0f4437c156b79711d68c6e7f
Author: Andrew MacLeod <amacleod@redhat.com>
Date: Fri Dec 16 16:53:31 2022 -0500
Don't use PHI equivalences in range-on-entry.
If there is only one argument to a PHI which is defined, an equivalency is
created between the def and the argument. It is safe to consider the def
equal to the argument, but it is dangerous to assume the argument is also
equivalent to the def as there may be branches which change the range on the
path to the PHI on that argument
This patch avoid using that relation in range-on-entry calculations.
PR tree-optimization/108139
gcc/
* gimple-range-cache.cc (ranger_cache::fill_block_cache): Do not
use equivalences originating from PHIS.
gcc/testsuite/
* gcc.dg/pr108139.c: New.
Diff:
---
gcc/gimple-range-cache.cc | 7 +++++++
gcc/testsuite/gcc.dg/pr108139.c | 18 ++++++++++++++++++
2 files changed, 25 insertions(+)
diff --git a/gcc/gimple-range-cache.cc b/gcc/gimple-range-cache.cc
index ce5a0c8155e..9848d140242 100644
--- a/gcc/gimple-range-cache.cc
+++ b/gcc/gimple-range-cache.cc
@@ -1235,6 +1235,13 @@ ranger_cache::fill_block_cache (tree name, basic_block bb, basic_block def_bb)
if (!m_gori.has_edge_range_p (equiv_name))
continue;
+ // PR 108139. It is hazardous to assume an equivalence with
+ // a PHI is the same value. The PHI may be an equivalence
+ // via UNDEFINED arguments which is really a one way equivalence.
+ // PHIDEF == name, but name may not be == PHIDEF.
+ if (is_a<gphi *> (SSA_NAME_DEF_STMT (equiv_name)))
+ continue;
+
// Check if the equiv definition dominates this block
if (equiv_bb == bb ||
(equiv_bb && !dominated_by_p (CDI_DOMINATORS, bb, equiv_bb)))
diff --git a/gcc/testsuite/gcc.dg/pr108139.c b/gcc/testsuite/gcc.dg/pr108139.c
new file mode 100644
index 00000000000..6f224e3ce62
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/pr108139.c
@@ -0,0 +1,18 @@
+/* { dg-do compile { target int128 } } */
+/* { dg-options "-O1 -ftree-vrp -fdump-tree-vrp" } */
+
+int a, b;
+int main() {
+ int c;
+ if (a > 1)
+ a++;
+ while (a)
+ if (c == b)
+ c = a;
+ return 0;
+}
+
+
+/* { dg-final { scan-tree-dump-not "Folding predicate" "vrp2" } } */
+
+
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