[cmake] Disable GCC lifetime DSE

[xry111]

Summary

LLVM data structures like llvm::User and llvm::MDNode rely on
the value of object storage persisting beyond the lifetime of the
object (#24952). This is not standard compliant and causes a runtime
crash if LLVM is built with GCC and LTO enabled (#57740). Until
these issues are fixed, we need to disable dead store eliminations
eliminations based on object lifetime.

The previous version (D150505) also exploited an issue in the
clang-tidy test suite. The test trivially-destructible.cpp is filtered
into a temporary file, and when clang-tidy operates on the file, the
compile_commands.json file in the build directory will be read and
the compiler options in it will be used. If LLVM is not built with Clang,
some of the options may be unsupported, causing a test failure. Fix
it by adding "-p %s" into the test command to force clang-tidy to
search the compiler option DB file in the source directory, where there
is none.

Bug: https://github.com/llvm/llvm-project/issues/24952
Bug: https://github.com/llvm/llvm-project/issues/57740
Link: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=106943

[MaskRay]

I think the correct fix for trivially-destructible.cpp is to append --. No -p or comment is needed.

[xry111]

Closing as https://reviews.llvm.org/rG626849c71e85d546a004cc91866beab610222194 is already landed and we just need to reopen D150505.

clang-tools-extra/test/clang-tidy/checkers/performance/trivially-destructible.cpp

 // RUN: %check_clang_tidy %s performance-trivially-destructible %t
 // RUN: grep -Ev "// *[A-Z-]+:" %s > %t.cpp
-// RUN: clang-tidy %t.cpp -checks='-*,performance-trivially-destructible' -fix
-// RUN: clang-tidy %t.cpp -checks='-*,performance-trivially-destructible' -warnings-as-errors='-*,performance-trivially-destructible'
+// RUN: clang-tidy -p %S %t.cpp -checks='-*,performance-trivially-destructible' -fix
+// RUN: clang-tidy -p %S %t.cpp -checks='-*,performance-trivially-destructible' -warnings-as-errors='-*,performance-trivially-destructible'
+
+// The "-p %S" in the clang-tidy command lines above is used for overriding
+// the detection of the `compile_commands.json` file.  As %t.cpp is in the
+// build directory, by default the `compile_commands.json` file created by
+// cmake for LLVM itself will be used.  But the file may contains options
+// not recognized by Clang if the LLVM project is built with another
+// compiler.
 
 struct TriviallyDestructible1 {
   int a;
 };
 
 struct TriviallyDestructible2 : TriviallyDestructible1 {
   ~TriviallyDestructible2() = default;
   TriviallyDestructible1 b;

llvm/cmake/modules/HandleLLVMOptions.cmake

 endif( LLVM_COMPILER_IS_GCC_COMPATIBLE )
 
 # Specific default warnings-as-errors for compilers accepting GCC-compatible warning flags:
 if ( LLVM_COMPILER_IS_GCC_COMPATIBLE OR CMAKE_CXX_COMPILER_ID MATCHES "XL" )
   add_flag_if_supported("-Werror=date-time" WERROR_DATE_TIME)
   add_flag_if_supported("-Werror=unguarded-availability-new" WERROR_UNGUARDED_AVAILABILITY_NEW)
 endif( LLVM_COMPILER_IS_GCC_COMPATIBLE OR CMAKE_CXX_COMPILER_ID MATCHES "XL" )
 
+if ( LLVM_COMPILER_IS_GCC_COMPATIBLE )
+  # LLVM data structures like llvm::User and llvm::MDNode rely on
+  # the value of object storage persisting beyond the lifetime of the
+  # object (#24952).  This is not standard compliant and causes a runtime
+  # crash if LLVM is built with GCC and LTO enabled (#57740).  Until
+  # these bugs are fixed, we need to disable dead store eliminations
+  # based on object lifetime.
+  add_flag_if_supported("-fno-lifetime-dse" CMAKE_CXX_FLAGS)
+endif ( LLVM_COMPILER_IS_GCC_COMPATIBLE )
+
 # Modules enablement for GCC-compatible compilers:
 if ( LLVM_COMPILER_IS_GCC_COMPATIBLE AND LLVM_ENABLE_MODULES )
   set(OLD_CMAKE_REQUIRED_FLAGS ${CMAKE_REQUIRED_FLAGS})
   set(module_flags "-fmodules -fmodules-cache-path=${PROJECT_BINARY_DIR}/module.cache")
   if (${CMAKE_SYSTEM_NAME} MATCHES "Darwin")
     # On Darwin -fmodules does not imply -fcxx-modules.
     set(module_flags "${module_flags} -fcxx-modules")
   endif()