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[libcxx] Add flag to disable __builtin_assume in _LIBCPP_ASSERT 

Introduce _LIBCPP_ASSERTIONS_DISABLE_ASSUME which makes _LIBCPP_ASSERT
not call __builtin_assume when _LIBCPP_ENABLE_ASSERTIONS == 0.

Calling __builtin_assume was introduced in D122397.

__builtin_assume is generally supposed to improve optimizations, but can
cause regressions when LLVM has trouble handling the calls to
`llvm.assume()` (see comments in D122397).

Reviewed By: philnik

Differential Revision: https://reviews.llvm.org/D123175
This commit is contained in:
Arthur Eubanks 2022-04-05 19:16:39 -07:00
parent 6733590db2
commit 0a77e63322
2 changed files with 10 additions and 9 deletions
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16
libcxx/include/__assert
View File

@ -38,16 +38,14 @@
(__builtin_expect(static_cast<bool>(expression), 1) ? \
(void)0 : \
::std::__libcpp_assertion_handler(__FILE__, __LINE__, #expression, message))
#elif !defined(_LIBCPP_ASSERTIONS_DISABLE_ASSUME) && __has_builtin(__builtin_assume)
# define _LIBCPP_ASSERT(expression, message) \
(_LIBCPP_DIAGNOSTIC_PUSH \
_LIBCPP_CLANG_DIAGNOSTIC_IGNORED("-Wassume") \
__builtin_assume(static_cast<bool>(expression)) \
_LIBCPP_DIAGNOSTIC_POP)
#else
# if __has_builtin(__builtin_assume)
# define _LIBCPP_ASSERT(expression, message) \
(_LIBCPP_DIAGNOSTIC_PUSH \
_LIBCPP_CLANG_DIAGNOSTIC_IGNORED("-Wassume") \
__builtin_assume(static_cast<bool>(expression)) \
_LIBCPP_DIAGNOSTIC_POP)
# else
# define _LIBCPP_ASSERT(expression, message) ((void)0)
# endif
# define _LIBCPP_ASSERT(expression, message) ((void)0)
#endif
_LIBCPP_BEGIN_NAMESPACE_STD

3
libcxx/test/libcxx/assertions/single_expression.sh.cpp
View File

@ -15,6 +15,9 @@
// RUN: %{build} -Wno-macro-redefined -D_LIBCPP_ENABLE_ASSERTIONS=0
// RUN: %{run}
// RUN: %{build} -Wno-macro-redefined -D_LIBCPP_ENABLE_ASSERTIONS=0 -D_LIBCPP_ASSERTIONS_DISABLE_ASSUME
// RUN: %{run}
// We flag uses of the assertion handler in older dylibs at compile-time to avoid runtime
// failures when back-deploying.
// XFAIL: use_system_cxx_lib && target={{.+}}-apple-macosx{{10.9|10.10|10.11|10.12|10.13|10.14|10.15|11.0|12.0}}