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* [gcc r13-4357] tree-optimization/107493 - SCEV analysis with conversions
@ 2022-11-28 10:17 Richard Biener
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From: Richard Biener @ 2022-11-28 10:17 UTC (permalink / raw)
To: gcc-cvs
https://gcc.gnu.org/g:2b293a949c0fbe21e47c4bc99f807dc941c02bb6
commit r13-4357-g2b293a949c0fbe21e47c4bc99f807dc941c02bb6
Author: Richard Biener <rguenther@suse.de>
Date: Mon Nov 28 10:25:44 2022 +0100
tree-optimization/107493 - SCEV analysis with conversions
This shows another case where trying to validate conversions during
the CHREC SCC analysis fails because said analysis assumes we are
converting a complete SCC. Like the constraint on the initial
conversion seen restrict all conversions handled to sign-changes.
PR tree-optimization/107493
* tree-scalar-evolution.cc (scev_dfs::follow_ssa_edge_expr):
Only handle no-op and sign-changing conversions.
* gcc.dg/torture/pr107493.c: New testcase.
Diff:
---
gcc/testsuite/gcc.dg/torture/pr107493.c | 13 +++++++++++++
gcc/tree-scalar-evolution.cc | 10 ++++++++--
2 files changed, 21 insertions(+), 2 deletions(-)
diff --git a/gcc/testsuite/gcc.dg/torture/pr107493.c b/gcc/testsuite/gcc.dg/torture/pr107493.c
new file mode 100644
index 00000000000..b36692133d8
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/torture/pr107493.c
@@ -0,0 +1,13 @@
+/* { dg-do run { target int32plus } } */
+
+int a;
+int b(int c) { return c; }
+int main()
+{
+ a = -21;
+ for (; a <= 0; a = (unsigned short)(b(a + 2) + 8))
+ ;
+ if (a != 65525)
+ __builtin_abort();
+ return 0;
+}
diff --git a/gcc/tree-scalar-evolution.cc b/gcc/tree-scalar-evolution.cc
index 60060337804..f75398afb7c 100644
--- a/gcc/tree-scalar-evolution.cc
+++ b/gcc/tree-scalar-evolution.cc
@@ -1227,10 +1227,16 @@ scev_dfs::follow_ssa_edge_expr (gimple *at_stmt, tree expr,
{
CASE_CONVERT:
{
- /* This assignment is under the form "a_1 = (cast) rhs. */
+ /* This assignment is under the form "a_1 = (cast) rhs. We cannot
+ validate any precision altering conversion during the SCC
+ analysis, so don't even try. */
+ if (!tree_nop_conversion_p (type, TREE_TYPE (rhs0)))
+ return t_false;
t_bool res = follow_ssa_edge_expr (at_stmt, rhs0,
evolution_of_loop, limit);
- *evolution_of_loop = chrec_convert (type, *evolution_of_loop, at_stmt);
+ if (res == t_true)
+ *evolution_of_loop = chrec_convert (type, *evolution_of_loop,
+ at_stmt);
return res;
}
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