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From: Richard Biener <rguenth@gcc.gnu.org> To: gcc-cvs@gcc.gnu.org Subject: [gcc r13-2817] tree-optimization/106922 - extend same-val clobber FRE Date: Fri, 23 Sep 2022 13:11:15 +0000 (GMT) [thread overview] Message-ID: <20220923131115.9AAC23857357@sourceware.org> (raw) https://gcc.gnu.org/g:af611afe5fcc908a6678b5b205fb5af7d64fbcb2 commit r13-2817-gaf611afe5fcc908a6678b5b205fb5af7d64fbcb2 Author: Richard Biener <rguenther@suse.de> Date: Fri Sep 23 14:28:52 2022 +0200 tree-optimization/106922 - extend same-val clobber FRE The following extends the skipping of same valued stores to handle an arbitrary number of them as long as they are from the same value (which we now record). That's an obvious extension which allows to optimize the m_engaged member of std::optional more reliably. PR tree-optimization/106922 * tree-ssa-sccvn.cc (vn_reference_lookup_3): Allow an arbitrary number of same valued skipped stores. * g++.dg/torture/pr106922.C: New testcase. Diff: --- gcc/testsuite/g++.dg/torture/pr106922.C | 48 +++++++++++++++++++++++++++++++++ gcc/tree-ssa-sccvn.cc | 10 ++++--- 2 files changed, 55 insertions(+), 3 deletions(-) diff --git a/gcc/testsuite/g++.dg/torture/pr106922.C b/gcc/testsuite/g++.dg/torture/pr106922.C new file mode 100644 index 00000000000..046fc6cce76 --- /dev/null +++ b/gcc/testsuite/g++.dg/torture/pr106922.C @@ -0,0 +1,48 @@ +// { dg-do compile } +// { dg-require-effective-target c++17 } +// { dg-additional-options "-Wall" } +// -O1 doesn't iterate VN and thus has bogus uninit diagnostics +// { dg-skip-if "" { *-*-* } { "-O1" } { "" } } + +#include <vector> + +#include <optional> +template <class T> +using Optional = std::optional<T>; + +#include <sstream> + +struct MyOptionalStructWithInt { + int myint; /* works without this */ + Optional<std::vector<std::string>> myoptional; +}; + +struct MyOptionalsStruct { + MyOptionalStructWithInt external1; + MyOptionalStructWithInt external2; +}; + +struct MyStruct { }; +std::ostream &operator << (std::ostream &os, const MyStruct &myStruct); + +std::vector<MyStruct> getMyStructs(); + +void test() +{ + MyOptionalsStruct externals; + MyOptionalStructWithInt internal1; + MyOptionalStructWithInt internal2; + + std::vector<MyStruct> myStructs; + myStructs = getMyStructs(); + + for (const auto& myStruct : myStructs) + { + std::stringstream address_stream; + address_stream << myStruct; + internal1.myint = internal2.myint = 0; + externals.external1 = internal1; + externals.external2 = internal2; + externals.external2 = internal2; + } +} diff --git a/gcc/tree-ssa-sccvn.cc b/gcc/tree-ssa-sccvn.cc index 9c12a8e4f03..2cc2c0e1e34 100644 --- a/gcc/tree-ssa-sccvn.cc +++ b/gcc/tree-ssa-sccvn.cc @@ -2680,7 +2680,6 @@ vn_reference_lookup_3 (ao_ref *ref, tree vuse, void *data_, if (is_gimple_reg_type (TREE_TYPE (lhs)) && types_compatible_p (TREE_TYPE (lhs), vr->type) && (ref->ref || data->orig_ref.ref) - && !data->same_val && !data->mask && data->partial_defs.is_empty () && multiple_p (get_object_alignment @@ -2693,8 +2692,13 @@ vn_reference_lookup_3 (ao_ref *ref, tree vuse, void *data_, a different loop iteration but only to loop invariants. Use CONSTANT_CLASS_P (unvalueized!) as conservative approximation. The one-hop lookup below doesn't have this issue since there's - a virtual PHI before we ever reach a backedge to cross. */ - if (CONSTANT_CLASS_P (rhs)) + a virtual PHI before we ever reach a backedge to cross. + We can skip multiple defs as long as they are from the same + value though. */ + if (data->same_val + && !operand_equal_p (data->same_val, rhs)) + ; + else if (CONSTANT_CLASS_P (rhs)) { if (dump_file && (dump_flags & TDF_DETAILS)) {
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