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Sat, 04 May 2024 23:58:41 +0000 (GMT) Received: from nasanex01c.na.qualcomm.com (nasanex01c.na.qualcomm.com [10.45.79.139]) by NASANPPMTA01.qualcomm.com (8.17.1.5/8.17.1.5) with ESMTPS id 444Nwf2c032173 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT) for ; Sat, 4 May 2024 23:58:41 GMT Received: from hu-apinski-lv.qualcomm.com (10.49.16.6) by nasanex01c.na.qualcomm.com (10.45.79.139) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.2.1544.9; Sat, 4 May 2024 16:58:40 -0700 From: Andrew Pinski To: CC: Andrew Pinski Subject: [PATCH v3] DCE __cxa_atexit calls where the function is pure/const [PR19661] Date: Sat, 4 May 2024 16:58:26 -0700 Message-ID: <20240504235826.3130451-1-quic_apinski@quicinc.com> X-Mailer: git-send-email 2.34.1 MIME-Version: 1.0 X-Originating-IP: [10.49.16.6] X-ClientProxiedBy: nalasex01c.na.qualcomm.com (10.47.97.35) To nasanex01c.na.qualcomm.com (10.45.79.139) X-QCInternal: smtphost X-Proofpoint-Virus-Version: vendor=nai engine=6200 definitions=5800 signatures=585085 X-Proofpoint-GUID: ud5w9jg382GdWkmu1u1wvZdepNj1Ml3L X-Proofpoint-ORIG-GUID: ud5w9jg382GdWkmu1u1wvZdepNj1Ml3L X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1011,Hydra:6.0.650,FMLib:17.11.176.26 definitions=2024-05-04_18,2024-05-03_02,2023-05-22_02 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 impostorscore=0 mlxscore=0 lowpriorityscore=0 malwarescore=0 adultscore=0 priorityscore=1501 mlxlogscore=999 bulkscore=0 suspectscore=0 clxscore=1015 phishscore=0 spamscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.19.0-2404010003 definitions=main-2405040151 X-Spam-Status: No, score=-13.4 required=5.0 tests=BAYES_00, DKIM_SIGNED, DKIM_VALID, DKIM_VALID_AU, DKIM_VALID_EF, GIT_PATCH_0, SPF_HELO_NONE, SPF_PASS, TXREP autolearn=ham autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on server2.sourceware.org X-BeenThere: gcc-patches@gcc.gnu.org X-Mailman-Version: 2.1.30 Precedence: list List-Id: Gcc-patches mailing list List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: gcc-patches-bounces+incoming=patchwork.ozlabs.org@gcc.gnu.org In C++ sometimes you have a deconstructor function which is "empty", like for an example with unions or with arrays. The front-end might not know it is empty either so this should be done on during optimization.o To implement it I added it to DCE where we mark if a statement is necessary or not. Bootstrapped and tested on x86_64-linux-gnu with no regressions. Changes since v1: * v2: Add support for __aeabi_atexit for arm-*eabi. Add extra comments. Add cxa_atexit-5.C testcase for -fPIC case. * v3: Fix testcases for the __aeabi_atexit (forgot to do in the v2). PR tree-optimization/19661 gcc/ChangeLog: * tree-ssa-dce.cc (is_cxa_atexit): New function. (is_removable_cxa_atexit_call): New function. (mark_stmt_if_obviously_necessary): Don't mark removable cxa_at_exit calls. (mark_all_reaching_defs_necessary_1): Likewise. (propagate_necessity): Likewise. gcc/testsuite/ChangeLog: * g++.dg/tree-ssa/cxa_atexit-1.C: New test. * g++.dg/tree-ssa/cxa_atexit-2.C: New test. * g++.dg/tree-ssa/cxa_atexit-3.C: New test. * g++.dg/tree-ssa/cxa_atexit-4.C: New test. * g++.dg/tree-ssa/cxa_atexit-5.C: New test. * g++.dg/tree-ssa/cxa_atexit-6.C: New test. Signed-off-by: Andrew Pinski --- gcc/testsuite/g++.dg/tree-ssa/cxa_atexit-1.C | 20 +++++++ gcc/testsuite/g++.dg/tree-ssa/cxa_atexit-2.C | 21 +++++++ gcc/testsuite/g++.dg/tree-ssa/cxa_atexit-3.C | 19 +++++++ gcc/testsuite/g++.dg/tree-ssa/cxa_atexit-4.C | 20 +++++++ gcc/testsuite/g++.dg/tree-ssa/cxa_atexit-5.C | 39 +++++++++++++ gcc/testsuite/g++.dg/tree-ssa/cxa_atexit-6.C | 24 ++++++++ gcc/tree-ssa-dce.cc | 58 ++++++++++++++++++++ 7 files changed, 201 insertions(+) create mode 100644 gcc/testsuite/g++.dg/tree-ssa/cxa_atexit-1.C create mode 100644 gcc/testsuite/g++.dg/tree-ssa/cxa_atexit-2.C create mode 100644 gcc/testsuite/g++.dg/tree-ssa/cxa_atexit-3.C create mode 100644 gcc/testsuite/g++.dg/tree-ssa/cxa_atexit-4.C create mode 100644 gcc/testsuite/g++.dg/tree-ssa/cxa_atexit-5.C create mode 100644 gcc/testsuite/g++.dg/tree-ssa/cxa_atexit-6.C diff --git a/gcc/testsuite/g++.dg/tree-ssa/cxa_atexit-1.C b/gcc/testsuite/g++.dg/tree-ssa/cxa_atexit-1.C new file mode 100644 index 00000000000..82ff3d2b778 --- /dev/null +++ b/gcc/testsuite/g++.dg/tree-ssa/cxa_atexit-1.C @@ -0,0 +1,20 @@ +/* { dg-do compile } */ +/* { dg-options "-O2 -fdump-tree-cddce1-details -fdump-tree-optimized" } */ +// { dg-require-effective-target cxa_atexit } +/* PR tree-optimization/19661 */ + +/* The call to axexit should be removed as A::~A() is a pure/const function call + and there is no visible effect if A::~A() call does not happen. */ + +struct A { + A(); + ~A() {} +}; + +void foo () { + static A a; +} + +/* { dg-final { scan-tree-dump-times "Deleting : (?:__cxxabiv1::__cxa_atexit|__aeabiv1::__aeabi_atexit)" 1 "cddce1" } } */ +/* { dg-final { scan-tree-dump-not "__cxa_atexit|__aeabi_atexit" "optimized" } } */ + diff --git a/gcc/testsuite/g++.dg/tree-ssa/cxa_atexit-2.C b/gcc/testsuite/g++.dg/tree-ssa/cxa_atexit-2.C new file mode 100644 index 00000000000..726b6d7f156 --- /dev/null +++ b/gcc/testsuite/g++.dg/tree-ssa/cxa_atexit-2.C @@ -0,0 +1,21 @@ +/* { dg-do compile { target c++11 } } */ +/* { dg-options "-O2 -fdump-tree-cddce1-details -fdump-tree-optimized" } */ +// { dg-require-effective-target cxa_atexit } +/* PR tree-optimization/19661 */ + +/* The call to axexit should be not removed as A::~A() as it marked with noipa. */ + +struct A { + A(); + ~A(); +}; + +[[gnu::noipa]] A::~A() {} + +void foo () { + static A a; +} + +/* { dg-final { scan-tree-dump-not "Deleting : (?:__cxxabiv1::__cxa_atexit|__aeabiv1::__aeabi_atexit)" "cddce1" } } */ +/* { dg-final { scan-tree-dump-times "(?:__cxa_atexit|__aeabi_atexit)" 1 "optimized" } } */ + diff --git a/gcc/testsuite/g++.dg/tree-ssa/cxa_atexit-3.C b/gcc/testsuite/g++.dg/tree-ssa/cxa_atexit-3.C new file mode 100644 index 00000000000..42cc7ccb11b --- /dev/null +++ b/gcc/testsuite/g++.dg/tree-ssa/cxa_atexit-3.C @@ -0,0 +1,19 @@ +/* { dg-do compile } */ +/* { dg-options "-O2 -fdump-tree-cddce1-details -fdump-tree-optimized" } */ +// { dg-require-effective-target cxa_atexit } +/* PR tree-optimization/19661 */ + +/* We should not remove the call to atexit as A::~A is unknown. */ + +struct A { + A(); + ~A(); +}; + +void foo () { + static A a; +} + +/* { dg-final { scan-tree-dump-not "Deleting : (?:__cxxabiv1::__cxa_atexit|__aeabiv1::__aeabi_atexit)" "cddce1" } } */ +/* { dg-final { scan-tree-dump-times "(?:__cxa_atexit|__aeabi_atexit)" 1 "optimized" } } */ + diff --git a/gcc/testsuite/g++.dg/tree-ssa/cxa_atexit-4.C b/gcc/testsuite/g++.dg/tree-ssa/cxa_atexit-4.C new file mode 100644 index 00000000000..591c1c0552a --- /dev/null +++ b/gcc/testsuite/g++.dg/tree-ssa/cxa_atexit-4.C @@ -0,0 +1,20 @@ +/* { dg-do compile { target c++11 } } */ +/* { dg-options "-O2 -fdump-tree-cddce1-details -fdump-tree-optimized -w" } */ +// { dg-require-effective-target cxa_atexit } +/* PR tree-optimization/19661 */ + +/* The call to axexit should be removed as A::~A() is a pure/const function call + and there is no visible effect if A::~A() call does not happen. */ + +struct A { + A(); + [[gnu::pure]] ~A(); +}; + +void foo () { + static A a; +} + +/* { dg-final { scan-tree-dump-times "Deleting : (?:__cxxabiv1::__cxa_atexit|__aeabiv1::__aeabi_atexit)" 1 "cddce1" } } */ +/* { dg-final { scan-tree-dump-not "(?:__cxa_atexit|__aeabi_atexit)" "optimized" } } */ + diff --git a/gcc/testsuite/g++.dg/tree-ssa/cxa_atexit-5.C b/gcc/testsuite/g++.dg/tree-ssa/cxa_atexit-5.C new file mode 100644 index 00000000000..e59f70c1ed4 --- /dev/null +++ b/gcc/testsuite/g++.dg/tree-ssa/cxa_atexit-5.C @@ -0,0 +1,39 @@ +/* { dg-do compile { target c++20 } } */ +/* { dg-options "-O2 -fdump-tree-dce2-details -fdump-tree-optimized" } */ +// { dg-require-effective-target cxa_atexit } +/* PR tree-optimization/19661 */ + +/* The call to axexit should be removed as constant_init::~constant_init is a pure/const function call + and there is no visible effect if constant_init::~constant_init() call does not happen. */ +/* This takes until DCE2 as constant_init::~constant_init is not figured out being pure/const until late. */ + +extern "C" int puts(const char*); + +struct A +{ + constexpr A() { } + ~A() { puts("bye"); } +}; + +namespace +{ + struct constant_init + { + union { + A obj; + }; + constexpr constant_init() : obj() { } + + ~constant_init() { /* do nothing, union member is not destroyed */ } + }; + + + // Single-threaded fallback buffer. + constinit constant_init global; +} + +extern "C" A* get() { return &global.obj; } + +/* { dg-final { scan-tree-dump-times "Deleting : (?:__cxxabiv1::__cxa_atexit|__aeabiv1::__aeabi_atexit)" 1 "dce2" } } */ +/* { dg-final { scan-tree-dump-not "(?:__cxa_atexit|__aeabi_atexit)" "optimized" } } */ + diff --git a/gcc/testsuite/g++.dg/tree-ssa/cxa_atexit-6.C b/gcc/testsuite/g++.dg/tree-ssa/cxa_atexit-6.C new file mode 100644 index 00000000000..f6599a3c9f4 --- /dev/null +++ b/gcc/testsuite/g++.dg/tree-ssa/cxa_atexit-6.C @@ -0,0 +1,24 @@ +/* { dg-do compile } */ +/* { dg-require-effective-target fpic } */ +/* { dg-options "-O2 -fdump-tree-cddce1-details -fdump-tree-optimized -fPIC" } */ +// { dg-require-effective-target cxa_atexit } +/* PR tree-optimization/19661 */ + +/* The call to axexit should not be removed as A::~A() cannot be figured if it + is a pure/const function call as the function call g does not bind locally. */ + +__attribute__((noinline)) +void g() {} + +struct A { + A(); + ~A() { g(); } +}; + +void foo () { + static A a; +} + +/* { dg-final { scan-tree-dump-not "Deleting : (?:__cxxabiv1::__cxa_atexit|__aeabiv1::__aeabi_atexit)" "cddce1" } } */ +/* { dg-final { scan-tree-dump-times "(?:__cxa_atexit|__aeabi_atexit)" 1 "optimized" } } */ + diff --git a/gcc/tree-ssa-dce.cc b/gcc/tree-ssa-dce.cc index 636c471d4c8..69249c73013 100644 --- a/gcc/tree-ssa-dce.cc +++ b/gcc/tree-ssa-dce.cc @@ -124,6 +124,55 @@ keep_all_vdefs_p () return optimize_debug; } +/* 1 if CALLEE is the function __cxa_atexit. + 2 if CALLEE is the function __aeabi_atexit. + 0 otherwise. */ + +static inline int +is_cxa_atexit (const_tree callee) +{ + if (callee != NULL_TREE + && strcmp (IDENTIFIER_POINTER (DECL_NAME (callee)), "__cxa_atexit") == 0) + return 1; + if (callee != NULL_TREE + && strcmp (IDENTIFIER_POINTER (DECL_NAME (callee)), "__aeabi_atexit") == 0) + return 2; + return 0; +} + +/* True if STMT is a call to __cxa_atexit (or __aeabi_atexit) + and the function argument to that call is a const or pure + non-looping function decl. */ + +static inline bool +is_removable_cxa_atexit_call (gimple *stmt) +{ + tree callee = gimple_call_fndecl (stmt); + int functype = is_cxa_atexit (callee); + if (!functype) + return false; + if (gimple_call_num_args (stmt) != 3) + return false; + + /* The function argument is the 1st argument for __cxa_atexit + or the 2nd argument for __eabi_atexit. */ + tree arg = gimple_call_arg (stmt, functype == 2 ? 1 : 0); + if (TREE_CODE (arg) != ADDR_EXPR) + return false; + arg = TREE_OPERAND (arg, 0); + if (TREE_CODE (arg) != FUNCTION_DECL) + return false; + int flags = flags_from_decl_or_type (arg); + + /* If the function is noreturn then it cannot be removed. */ + if (flags & ECF_NORETURN) + return false; + + /* The function needs to be const or pure and non looping. */ + return (flags & (ECF_CONST|ECF_PURE)) + && !(flags & ECF_LOOPING_CONST_OR_PURE); +} + /* If STMT is not already marked necessary, mark it, and add it to the worklist if ADD_TO_WORKLIST is true. */ @@ -251,6 +300,10 @@ mark_stmt_if_obviously_necessary (gimple *stmt, bool aggressive) && DECL_IS_REPLACEABLE_OPERATOR_NEW_P (callee)) return; + /* For __cxa_atexit calls, don't mark as necessary right away. */ + if (is_removable_cxa_atexit_call (stmt)) + return; + /* IFN_GOACC_LOOP calls are necessary in that they are used to represent parameter (i.e. step, bound) of a lowered OpenACC partitioned loop. But this kind of partitioned loop might not @@ -626,6 +679,8 @@ mark_all_reaching_defs_necessary_1 (ao_ref *ref ATTRIBUTE_UNUSED, || DECL_IS_OPERATOR_DELETE_P (callee)) && gimple_call_from_new_or_delete (call)) return false; + if (is_removable_cxa_atexit_call (call)) + return false; } if (! gimple_clobber_p (def_stmt)) @@ -930,6 +985,9 @@ propagate_necessity (bool aggressive) && gimple_call_from_new_or_delete (call)) continue; + if (is_removable_cxa_atexit_call (call)) + continue; + /* Calls implicitly load from memory, their arguments in addition may explicitly perform memory loads. */ mark_all_reaching_defs_necessary (call);