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Chandler Carruth
1d904556ef
These appear to be causing some subtle misinteractions with MSan that we don't understand, and may be a compiler bug. =/ Fortunately, they weren't essential to the performance gains so just remove them for now. When benchmarked on an x86 server, where I would expect this to be more important due to relatively few named registers, the performance change appears to be either an improvement or in the noise. Huge credit to Jon for tracking down that this is related to the MSan issues.
57 lines
2.3 KiB
C++
57 lines
2.3 KiB
C++
// Part of the Carbon Language project, under the Apache License v2.0 with LLVM
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// Exceptions. See /LICENSE for license information.
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// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
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#ifndef CARBON_COMMON_VLOG_H_
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#define CARBON_COMMON_VLOG_H_
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#include "common/ostream.h"
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#include "common/template_string.h"
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#include "llvm/Support/FormatVariadic.h"
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namespace Carbon::Internal {
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// Implements verbose logging.
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//
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// This is designed to minimize the overhead in callers by being a
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// forcibly-outlined routine that takes a minimal number of parameters.
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//
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// Internally uses `llvm::formatv` to render the format string with any value
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// arguments, and streams the result to the provided stream.
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template <TemplateString FormatStr, typename... Ts>
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[[clang::noinline]] auto VLogImpl(llvm::raw_ostream* stream, Ts&&... values)
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-> void {
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*stream << llvm::formatv(FormatStr.c_str(), std::forward<Ts>(values)...);
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}
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} // namespace Carbon::Internal
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// Logs when verbose logging is enabled. CARBON_VLOG_TO uses a provided stream;
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// CARBON_VLOG requires a member named `vlog_stream_`.
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//
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// For example:
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// CARBON_VLOG_TO(vlog_stream, "Verbose message: {0}", "extra information");
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// CARBON_VLOG("Verbose message: {0}", "extra information");
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//
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// The first argument must be a string literal format string valid for passing
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// to `llvm::formatv`. If it contains any substitutions, those should be passed
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// as subsequent arguments.
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//
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// Also supports a legacy syntax where no arguments are passed and the desired
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// logging is streamed into the call:
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// CARBON_VLOG() << "Legacy verbose message";
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//
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// However, the streaming syntax has higher overhead and can inhibit inlining.
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// Code should prefer the format string form, and eventually when all code has
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// migrated the streaming interface will be removed.
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#define CARBON_VLOG_TO(Stream, FormatStr, ...) \
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__builtin_expect(Stream == nullptr, true) \
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? (void)0 \
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: Carbon::Internal::VLogImpl<"" FormatStr>(Stream __VA_OPT__(, ) \
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__VA_ARGS__)
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#define CARBON_VLOG(FormatStr, ...) \
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CARBON_VLOG_TO(vlog_stream_, FormatStr, __VA_ARGS__)
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#endif // CARBON_COMMON_VLOG_H_
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