[libcxx-commits] [libcxx] 0a77e63 - [libcxx] Add flag to disable __builtin_assume in _LIBCPP_ASSERT

[Arthur Eubanks via libcxx-commits]

Author: Arthur Eubanks
Date: 2022-04-07T09:00:31-07:00
New Revision: 0a77e633226b5598e426603c03e54d62ed275670

URL: https://github.com/llvm/llvm-project/commit/0a77e633226b5598e426603c03e54d62ed275670
DIFF: https://github.com/llvm/llvm-project/commit/0a77e633226b5598e426603c03e54d62ed275670.diff

LOG: [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

Added: 
    

Modified: 
    libcxx/include/__assert
    libcxx/test/libcxx/assertions/single_expression.sh.cpp

Removed: 
    


################################################################################
diff  --git a/libcxx/include/__assert b/libcxx/include/__assert
index cb397e41980f5..a9096d92bb888 100644
--- a/libcxx/include/__assert
+++ b/libcxx/include/__assert
@@ -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

diff  --git a/libcxx/test/libcxx/assertions/single_expression.sh.cpp b/libcxx/test/libcxx/assertions/single_expression.sh.cpp
index 76635d6a7e61f..fb661103b6de6 100644
--- a/libcxx/test/libcxx/assertions/single_expression.sh.cpp
+++ b/libcxx/test/libcxx/assertions/single_expression.sh.cpp
@@ -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}}