From 600cf1128e49f086522bfddc54490b4e39e30383 Mon Sep 17 00:00:00 2001 From: Jakub Jelinek Date: Fri, 9 Oct 2020 10:16:57 +0200 Subject: [PATCH] match.pd: Fix up FFS -> CTZ + 1 optimization [PR97325] And no testcase was included, I'm including one below. Anyway, this PR and the other CTZ related discussions led me to discover a bug I've made earlier, CLZ/CTZ builtins have unsigned arguments and e.g. both the vr-values.cc and now gimple-range.cc code heavily relies on that, but __builtin_ffs has a signed operand and this optimization was incorrectly making the operand signed too, so I guess it would greatly confuse VRP in some cases. 2020-10-09 Jakub Jelinek PR tree-optimization/97325 * match.pd (FFS(nonzero) -> CTZ(nonzero) + 1): Cast argument to corresponding unsigned type. * gcc.c-torture/execute/pr97325.c: New test. --- gcc/match.pd | 3 ++- gcc/testsuite/gcc.c-torture/execute/pr97325.c | 15 +++++++++++++++ 2 files changed, 17 insertions(+), 1 deletion(-) create mode 100644 gcc/testsuite/gcc.c-torture/execute/pr97325.c diff --git a/gcc/match.pd b/gcc/match.pd index 952643f3c6d..a7032dcae29 100644 --- a/gcc/match.pd +++ b/gcc/match.pd @@ -6196,7 +6196,8 @@ DEFINE_INT_AND_FLOAT_ROUND_FN (RINT) (if (INTEGRAL_TYPE_P (TREE_TYPE (@0)) && direct_internal_fn_supported_p (IFN_CTZ, TREE_TYPE (@0), OPTIMIZE_FOR_SPEED)) - (plus (CTZ:type @0) { build_one_cst (type); }))) + (with { tree utype = unsigned_type_for (TREE_TYPE (@0)); } + (plus (CTZ:type (convert:utype @0)) { build_one_cst (type); })))) #endif (for ffs (BUILT_IN_FFS BUILT_IN_FFSL BUILT_IN_FFSLL diff --git a/gcc/testsuite/gcc.c-torture/execute/pr97325.c b/gcc/testsuite/gcc.c-torture/execute/pr97325.c new file mode 100644 index 00000000000..f734c85c711 --- /dev/null +++ b/gcc/testsuite/gcc.c-torture/execute/pr97325.c @@ -0,0 +1,15 @@ +/* PR tree-optimization/97325 */ + +unsigned long long +foo (unsigned long long c) +{ + return c ? __builtin_ffs (-(unsigned short) c) : 0; +} + +int +main () +{ + if (foo (2) != 2) + __builtin_abort (); + return 0; +} -- 2.30.2