Revert "Add a cmake flag to turn llvm_unreachable() into builtin_trap() when assertions are disabled"

This reverts commit 6316129.

This was implemented with inverted logic.

Author: nikic

llvm/CMakeLists.txt

@@ -465,7 +465,6 @@ option(LLVM_ENABLE_PEDANTIC "Compile with pedantic enabled." ON)
 option(LLVM_ENABLE_WERROR "Fail and stop if a warning is triggered." OFF)
 
 option(LLVM_ENABLE_DUMP "Enable dump functions even when assertions are disabled" OFF)
-option(LLVM_UNREACHABLE_OPTIMIZE "Optimize llvm_unreachable() as undefined behavior (default), guaranteed trap when OFF" ON)
 
 if( NOT uppercase_CMAKE_BUILD_TYPE STREQUAL "DEBUG" )
   option(LLVM_ENABLE_ASSERTIONS "Enable assertions" OFF)

llvm/docs/CMake.rst

@@ -300,12 +300,6 @@ enabled sub-projects. Nearly all of these variable names begin with
   enabled or not.  A version of LLVM built with ABI breaking checks
   is not ABI compatible with a version built without it.
 
-**LLVM_UNREACHABLE_OPTIMIZE**:BOOL
-  This flag controls the behavior of `llvm_unreachable()` in release build
-  (when assertions are disabled in general). When ON (default) then
-  `llvm_unreachable()` is considered "undefined behavior" and optimized as
-  such. When OFF it is instead replaced with a guaranteed "trap".
-
 **LLVM_APPEND_VC_REV**:BOOL
   Embed version control revision info (Git revision id).
   The version info is provided by the ``LLVM_REVISION`` macro in

llvm/include/llvm/Config/llvm-config.h.cmake

@@ -112,8 +112,4 @@
 /* Define if building LLVM with LLVM_FORCE_USE_OLD_TOOLCHAIN_LIBS */
 #cmakedefine LLVM_FORCE_USE_OLD_TOOLCHAIN ${LLVM_FORCE_USE_OLD_TOOLCHAIN}
 
-/* Define if llvm_unreachable should be optimized with undefined behavior
- * in non assert builds */
-#cmakedefine01 LLVM_UNREACHABLE_OPTIMIZE
-
 #endif

llvm/include/llvm/Support/ErrorHandling.h

@@ -124,23 +124,15 @@ llvm_unreachable_internal(const char *msg = nullptr, const char *file = nullptr,
 
 /// Marks that the current location is not supposed to be reachable.
 /// In !NDEBUG builds, prints the message and location info to stderr.
-/// In NDEBUG builds, the behavior is controlled by the CMake flag
-///   -DLLVM_UNREACHABLE_OPTIMIZE
-/// * When "ON" (default) llvm_unreachable() becomes an optimizer hint
-///   that the current location is not supposed to be reachable: the hint
-///   turns such code path into undefined behavior.  On compilers that don't
-///   support such hints, prints a reduced message instead and aborts the
-///   program.
-/// * When "OFF", a builtin_trap is emitted instead of an
-//    optimizer hint or printing a reduced message.
+/// In NDEBUG builds, becomes an optimizer hint that the current location
+/// is not supposed to be reachable.  On compilers that don't support
+/// such hints, prints a reduced message instead and aborts the program.
 ///
 /// Use this instead of assert(0).  It conveys intent more clearly and
 /// allows compilers to omit some unnecessary code.
 #ifndef NDEBUG
 #define llvm_unreachable(msg) \
   ::llvm::llvm_unreachable_internal(msg, __FILE__, __LINE__)
-#elif LLVM_UNREACHABLE_OPTIMIZE
-#define llvm_unreachable(msg) LLVM_BUILTIN_TRAP
 #elif defined(LLVM_BUILTIN_UNREACHABLE)
 #define llvm_unreachable(msg) LLVM_BUILTIN_UNREACHABLE
 #else