PGO: Add explicit static initialization
Instead of relying on explicit static initialization from translation
units, create a new file, InstrProfilingRuntime.cc, with an
__llvm_pgo_runtime variable. After this commit (and its pair in clang),
the driver will create a use of this variable. Unless the user defines
their own version, the new object file will get pulled in, including
that C++ static initialization that calls
__llvm_pgo_register_write_atexit.
The result is that, at least on Darwin, static initialization typically
consists of a single function call, which registers a writeout functino
atexit. Furthermore, users can skip even this behaviour by defining
their own __llvm_pgo_runtime.
<rdar://problem/15943240>
llvm-svn: 204380
2014-03-21 03:23:53 +08:00
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//===- InstrProfilingRuntime.cpp - PGO runtime initialization -------------===//
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//
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2019-01-19 16:50:56 +08:00
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// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
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// See https://llvm.org/LICENSE.txt for license information.
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// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
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PGO: Add explicit static initialization
Instead of relying on explicit static initialization from translation
units, create a new file, InstrProfilingRuntime.cc, with an
__llvm_pgo_runtime variable. After this commit (and its pair in clang),
the driver will create a use of this variable. Unless the user defines
their own version, the new object file will get pulled in, including
that C++ static initialization that calls
__llvm_pgo_register_write_atexit.
The result is that, at least on Darwin, static initialization typically
consists of a single function call, which registers a writeout functino
atexit. Furthermore, users can skip even this behaviour by defining
their own __llvm_pgo_runtime.
<rdar://problem/15943240>
llvm-svn: 204380
2014-03-21 03:23:53 +08:00
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//
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//===----------------------------------------------------------------------===//
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extern "C" {
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2014-03-22 02:29:15 +08:00
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#include "InstrProfiling.h"
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PGO: Add explicit static initialization
Instead of relying on explicit static initialization from translation
units, create a new file, InstrProfilingRuntime.cc, with an
__llvm_pgo_runtime variable. After this commit (and its pair in clang),
the driver will create a use of this variable. Unless the user defines
their own version, the new object file will get pulled in, including
that C++ static initialization that calls
__llvm_pgo_register_write_atexit.
The result is that, at least on Darwin, static initialization typically
consists of a single function call, which registers a writeout functino
atexit. Furthermore, users can skip even this behaviour by defining
their own __llvm_pgo_runtime.
<rdar://problem/15943240>
llvm-svn: 204380
2014-03-21 03:23:53 +08:00
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2016-07-22 12:08:16 +08:00
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/* int __llvm_profile_runtime */
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COMPILER_RT_VISIBILITY int INSTR_PROF_PROFILE_RUNTIME_VAR;
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PGO: Add explicit static initialization
Instead of relying on explicit static initialization from translation
units, create a new file, InstrProfilingRuntime.cc, with an
__llvm_pgo_runtime variable. After this commit (and its pair in clang),
the driver will create a use of this variable. Unless the user defines
their own version, the new object file will get pulled in, including
that C++ static initialization that calls
__llvm_pgo_register_write_atexit.
The result is that, at least on Darwin, static initialization typically
consists of a single function call, which registers a writeout functino
atexit. Furthermore, users can skip even this behaviour by defining
their own __llvm_pgo_runtime.
<rdar://problem/15943240>
llvm-svn: 204380
2014-03-21 03:23:53 +08:00
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}
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namespace {
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2014-05-16 09:30:24 +08:00
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class RegisterRuntime {
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PGO: Add explicit static initialization
Instead of relying on explicit static initialization from translation
units, create a new file, InstrProfilingRuntime.cc, with an
__llvm_pgo_runtime variable. After this commit (and its pair in clang),
the driver will create a use of this variable. Unless the user defines
their own version, the new object file will get pulled in, including
that C++ static initialization that calls
__llvm_pgo_register_write_atexit.
The result is that, at least on Darwin, static initialization typically
consists of a single function call, which registers a writeout functino
atexit. Furthermore, users can skip even this behaviour by defining
their own __llvm_pgo_runtime.
<rdar://problem/15943240>
llvm-svn: 204380
2014-03-21 03:23:53 +08:00
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public:
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2014-05-16 09:30:24 +08:00
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RegisterRuntime() {
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2014-05-17 09:27:30 +08:00
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__llvm_profile_initialize_file();
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[profile] Add a mode to continuously sync counter updates to a file
Add support for continuously syncing profile counter updates to a file.
The motivation for this is that programs do not always exit cleanly. On
iOS, for example, programs are usually killed via a signal from the OS.
Running atexit() handlers after catching a signal is unreliable, so some
method for progressively writing out profile data is necessary.
The approach taken here is to mmap() the `__llvm_prf_cnts` section onto
a raw profile. To do this, the linker must page-align the counter and
data sections, and the runtime must ensure that counters are mapped to a
page-aligned offset within a raw profile.
Continuous mode is (for the moment) incompatible with the online merging
mode. This limitation is lifted in https://reviews.llvm.org/D69586.
Continuous mode is also (for the moment) incompatible with value
profiling, as I'm not sure whether there is interest in this and the
implementation may be tricky.
As I have not been able to test extensively on non-Darwin platforms,
only Darwin support is included for the moment. However, continuous mode
may "just work" without modification on Linux and some UNIX-likes. AIUI
the default value for the GNU linker's `--section-alignment` flag is set
to the page size on many systems. This appears to be true for LLD as
well, as its `no_nmagic` option is on by default. Continuous mode will
not "just work" on Fuchsia or Windows, as it's not possible to mmap() a
section on these platforms. There is a proposal to add a layer of
indirection to the profile instrumentation to support these platforms.
rdar://54210980
Differential Revision: https://reviews.llvm.org/D68351
2019-09-20 02:56:43 +08:00
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if (!__llvm_profile_is_continuous_mode_enabled())
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__llvm_profile_register_write_file_atexit();
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2014-05-16 09:30:24 +08:00
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}
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PGO: Add explicit static initialization
Instead of relying on explicit static initialization from translation
units, create a new file, InstrProfilingRuntime.cc, with an
__llvm_pgo_runtime variable. After this commit (and its pair in clang),
the driver will create a use of this variable. Unless the user defines
their own version, the new object file will get pulled in, including
that C++ static initialization that calls
__llvm_pgo_register_write_atexit.
The result is that, at least on Darwin, static initialization typically
consists of a single function call, which registers a writeout functino
atexit. Furthermore, users can skip even this behaviour by defining
their own __llvm_pgo_runtime.
<rdar://problem/15943240>
llvm-svn: 204380
2014-03-21 03:23:53 +08:00
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};
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2014-05-16 09:30:24 +08:00
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RegisterRuntime Registration;
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PGO: Add explicit static initialization
Instead of relying on explicit static initialization from translation
units, create a new file, InstrProfilingRuntime.cc, with an
__llvm_pgo_runtime variable. After this commit (and its pair in clang),
the driver will create a use of this variable. Unless the user defines
their own version, the new object file will get pulled in, including
that C++ static initialization that calls
__llvm_pgo_register_write_atexit.
The result is that, at least on Darwin, static initialization typically
consists of a single function call, which registers a writeout functino
atexit. Furthermore, users can skip even this behaviour by defining
their own __llvm_pgo_runtime.
<rdar://problem/15943240>
llvm-svn: 204380
2014-03-21 03:23:53 +08:00
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}
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