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ircd: Add branchless optimistic assertion instrument --with-assert=opt

This commit is contained in:
Jason Volk 2022-07-16 13:09:14 -07:00
parent e4d517415b
commit b2d451b74d
4 changed files with 88 additions and 27 deletions
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4
configure.ac
View File

@ -235,6 +235,10 @@ AM_COND_IF(ASSERT,
RB_DEFINE([ASSERT_INTRINSIC], [1], [Intrinsic assertion behavior])
fi
if [[ "$assert_type" == "opt" ]]; then
RB_DEFINE([ASSERT_OPTIMISTIC], [1], [Optimistic assertion behavior])
fi
fi
])

94
include/ircd/assert.h
View File

@ -19,13 +19,13 @@
#pragma once
#define HAVE_IRCD_ASSERT_H
/// This file has to be included prior to the standard library assert headers
// This file has to be included prior to the standard library assert headers
#if defined(RB_ASSERT) && defined(_ASSERT_H_DECLS) && defined(RB_DEBUG)
#error "Do not include <assert.h> or <cassert> first."
#endif
/// Define an indicator for whether we override standard assert() behavior in
/// this build if the conditions are appropriate.
// Define an indicator for whether we override standard assert() behavior in
// this build if the conditions are appropriate.
#if defined(RB_ASSERT) && !defined(NDEBUG)
#define _ASSERT_H_DECLS
#endif
@ -34,57 +34,99 @@
namespace ircd
{
void debugtrap() noexcept;
template<class expr> void always_assert(expr&&) noexcept;
[[gnu::cold]] void print_assertion(const char *, const char *, const unsigned, const char *) noexcept;
template<class expr>
void always_assert(expr&&) noexcept;
[[gnu::cold]]
void print_assertion(const char *, const char *, const unsigned, const char *) noexcept;
#if defined(RB_ASSERT_OPTIMISTIC)
struct assertion extern assertion;
#endif
}
/// Override the standard assert behavior to take one of several different
/// actions as defined in our internal assert.cc unit. When trapping assert
/// is disabled this path will be used instead.
///
#if defined(RB_ASSERT) && !defined(RB_ASSERT_INTRINSIC)
// Alternative declaration of __assert_fail() which may return; our definitions
// take on different behaviors depending on the value of RB_ASSERT.
#if defined(RB_ASSERT)
extern "C" void
__attribute__((visibility("default")))
__assert_fail(const char *__assertion,
const char *__file,
unsigned int __line,
const char *__function);
const char *__function) noexcept;
#endif
// Custom assert
#if defined(RB_ASSERT) && defined(RB_ASSERT_INTRINSIC) && !defined(NDEBUG)
#if defined(RB_ASSERT_INTRINSIC) && !defined(NDEBUG)
#undef assert
#define assert(expr) \
({ \
if(__builtin_expect(!static_cast<bool>(expr), 0)) \
__assert_fail(#expr, __FILE__, __LINE__, __FUNCTION__); \
#define assert(expr) \
({ \
if(__builtin_expect(!static_cast<bool>(expr), 0)) \
__assert_fail(#expr, __FILE__, __LINE__, __FUNCTION__); \
})
#elif defined(RB_ASSERT_OPTIMISTIC) && !defined(NDEBUG)
#undef assert
#define assert(expr) \
({ \
ircd::assertion.ok &= static_cast<bool>(expr); \
})
#endif
// Custom addl cases to avoid any trouble w/ clang
#if defined(RB_ASSERT) && defined(__clang__) && !defined(assert)
#ifdef NDEBUG
#define assert(expr) (static_cast<void>(0))
#endif
#if defined(RB_ASSERT) && defined(__clang__) && !defined(assert) && defined(NDEBUG)
#define assert(expr) (static_cast<void>(0))
#endif
/// Override the standard assert behavior, if enabled, to trap into the
/// debugger as close as possible to the offending site.
///
#if defined(RB_ASSERT) && defined(RB_ASSERT_INTRINSIC)
#if defined(RB_ASSERT_OPTIMISTIC)
/// State structure for optimistic assertion mode.
struct ircd::assertion
{
bool ok alignas(8) {true};
const char *__assertion;
const char *__file;
unsigned int __line;
const char *__function;
bool point();
};
#endif
#if defined(RB_ASSERT_OPTIMISTIC)
/// Test-and-reset for pending assertion.
[[gnu::hot]]
inline bool
ircd::assertion::point()
{
if(__builtin_expect(!ok, 0))
{
#if defined(__SSE2__) && defined(__clang__)
asm volatile ("lfence");
#endif
__assert_fail(__assertion, __file, __line, __function);
ok = true;
return true;
}
else return false;
}
#endif
#if defined(RB_ASSERT_INTRINSIC)
extern "C" // for clang
{
/// Override the standard assert behavior, if enabled, to trap into the
/// debugger as close as possible to the offending site.
extern inline void
__attribute__((cold, flatten, always_inline, gnu_inline, artificial))
__assert_fail(const char *const __assertion,
const char *const __file,
unsigned int __line,
const char *const __function)
noexcept
{
#if defined(__SSE2__) && defined(__clang__)
asm volatile ("lfence");
asm volatile ("lfence");
#endif
ircd::print_assertion(__assertion, __file, __line, __function);
ircd::debugtrap();
}

12
ircd/assert.cc
View File

@ -10,6 +10,12 @@
#include <RB_INC_SIGNAL_H
#if defined(RB_ASSERT_OPTIMISTIC)
decltype(ircd::assertion)
ircd::assertion
alignas(64);
#endif
#if defined(RB_ASSERT) && !defined(RB_ASSERT_INTRINSIC)
#ifdef __clang__
#pragma clang diagnostic push
@ -21,6 +27,7 @@ __assert_fail(const char *__assertion,
const char *__file,
unsigned int __line,
const char *__function)
noexcept
{
ircd::print_assertion(__assertion, __file, __line, __function);
@ -30,6 +37,9 @@ __assert_fail(const char *__assertion,
if(strcmp(RB_ASSERT, "quit") == 0)
ircd::quit();
else if(strcmp(RB_ASSERT, "opt") == 0)
ircd::debugtrap();
else if(strcmp(RB_ASSERT, "trap") == 0)
ircd::debugtrap();
@ -79,7 +89,7 @@ ircd::print_assertion(const char *const __assertion,
const char *const __function)
noexcept
{
if(strcmp(__assertion, "critical") == 0)
if(__assertion && strcmp(__assertion, "critical") == 0)
return;
fprintf(stderr, "\nassertion failed [%s +%u] %s :%s\n",

5
ircd/ios.cc
View File

@ -609,6 +609,11 @@ noexcept
};
assert(handler::current == handler);
#if defined(RB_ASSERT_OPTIMISTIC)
ircd::assertion.point();
#endif
handler::current = nullptr;
}