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| author | Jakub Jelinek <jakub@redhat.com> | 2020-10-09 10:16:57 +0200 |
|---|---|---|
| committer | Jakub Jelinek <jakub@redhat.com> | 2020-10-09 10:18:41 +0200 |
| commit | 600cf1128e49f086522bfddc54490b4e39e30383 (patch) | |
| tree | 394041ef76ed7c8ba90598b84683260a69fae9dd /gcc | |
| parent | 6887244269e0c412afd43474e13fa5ca12c350c4 (diff) | |
| download | gcc-600cf1128e49f086522bfddc54490b4e39e30383.zip gcc-600cf1128e49f086522bfddc54490b4e39e30383.tar.gz gcc-600cf1128e49f086522bfddc54490b4e39e30383.tar.bz2 | |
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 <jakub@redhat.com>
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.
Diffstat (limited to 'gcc')
| -rw-r--r-- | gcc/match.pd | 3 | ||||
| -rw-r--r-- | gcc/testsuite/gcc.c-torture/execute/pr97325.c | 15 |
2 files changed, 17 insertions, 1 deletions
diff --git a/gcc/match.pd b/gcc/match.pd index 952643f..a7032dc 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 0000000..f734c85 --- /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; +} |