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.
Bootstrapped and tested on x86_64-unknown-linux-gnu, pushed. 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. --- gcc/testsuite/gcc.dg/torture/pr107493.c | 13 +++++++++++++ gcc/tree-scalar-evolution.cc | 10 ++++++++-- 2 files changed, 21 insertions(+), 2 deletions(-) create mode 100644 gcc/testsuite/gcc.dg/torture/pr107493.c 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; } -- 2.35.3