Add llvm assertions trap and no strings (microsoft#6838)

Add option LLVM_ASSERTIONS_NO_STRINGS
    
When defined, drop the stringized expression, __FILE__, and __FUNCTION__
    strings passed to llvm_assert. This dramatically reduces the binary
    size, which is useful when enabling assertions in a non-debug build.

   Add option LLVM_ASSERTIONS_TRAP
    
When enabled, this forces asserts to always trap. Currently, on Windows
    asserts calls RaiseException, while they trap on non-Windows. This
    option makes the assertion behaviour consistent across platforms.

Author: amaiorano

CMakeLists.txt

@@ -325,6 +325,9 @@ else()
   option(LLVM_ENABLE_ASSERTIONS "Enable assertions" ON)
 endif()
 
+option(LLVM_ASSERTIONS_TRAP "Force assertions to always trap, rather than the default unspecified behavior (e.g. RaiseException on Windows)" OFF)
+option(LLVM_ASSERTIONS_NO_STRINGS "Make assertion macro drops strings to reduce binary size" OFF)
+
 set(LLVM_ABI_BREAKING_CHECKS "WITH_ASSERTS" CACHE STRING
   "Enable abi-breaking checks.  Can be WITH_ASSERTS, FORCE_ON or FORCE_OFF.")
 

cmake/modules/HandleLLVMOptions.cmake

@@ -78,6 +78,13 @@ if( LLVM_ENABLE_ASSERTIONS )
         "${flags_var_to_scrub}" "${${flags_var_to_scrub}}")
     endforeach()
   endif()
+
+  if (LLVM_ASSERTIONS_TRAP)
+    add_definitions( -DLLVM_ASSERTIONS_TRAP )
+  endif()
+  if (LLVM_ASSERTIONS_NO_STRINGS)
+    add_definitions( -DLLVM_ASSERTIONS_NO_STRINGS )
+  endif()
 else()
   # Disable assertions in Debug builds
   if( uppercase_CMAKE_BUILD_TYPE STREQUAL "DEBUG" )

include/llvm/llvm_assert/assert.h

@@ -37,8 +37,15 @@ void llvm_assert(const char *Message, const char *File, unsigned Line,
 }
 #endif
 
+// If LLVM_ASSERTIONS_NO_STRINGS is defined, pass empty strings to llvm_assert
+// to reduce binary size.
+#ifdef LLVM_ASSERTIONS_NO_STRINGS
+#define assert(Expression)                                                     \
+  ((void)((!!(Expression)) || (llvm_assert("", "", 0, ""), 0)))
+#else
 #define assert(Expression)                                                     \
   ((void)((!!(Expression)) ||                                                  \
           (llvm_assert(#Expression, __FILE__, __LINE__, __FUNCTION__), 0)))
+#endif
 
 #endif /* NDEBUG */

lib/Support/assert.cpp

@@ -8,29 +8,37 @@
 ///////////////////////////////////////////////////////////////////////////////
 
 #include "assert.h"
+#include "llvm/Support/Compiler.h"
+#include "llvm/Support/raw_ostream.h"
+namespace {
+void llvm_assert_trap(const char *_Message, const char *_File, unsigned _Line,
+                      const char *_Function) {
+  llvm::errs() << "Error: assert(" << _Message << ")\nFile:\n"
+               << _File << "(" << _Line << ")\nFunc:\t" << _Function << "\n";
+  LLVM_BUILTIN_TRAP;
+}
+} // namespace
 
 #ifdef _WIN32
-
 #include "dxc/Support/Global.h"
 #include "windows.h"
 
 void llvm_assert(const char *Message, const char *File, unsigned Line,
                  const char *Function) {
+#ifdef LLVM_ASSERTIONS_TRAP
+  llvm_assert_trap(Message, File, Line, Function);
+#else
   OutputDebugFormatA("Error: assert(%s)\nFile:\n%s(%d)\nFunc:\t%s\n", Message,
                      File, Line, Function);
   RaiseException(STATUS_LLVM_ASSERT, 0, 0, 0);
+#endif
 }
 
-#else
-
-#include "llvm/Support/Compiler.h"
-#include "llvm/Support/raw_ostream.h"
+#else /* _WIN32 */
 
 void llvm_assert(const char *Message, const char *File, unsigned Line,
                  const char *Function) {
-  llvm::errs() << "Error: assert(" << Message << ")\nFile:\n"
-               << File << "(" << Line << ")\nFunc:\t" << Function << "\n";
-  LLVM_BUILTIN_TRAP;
+  llvm_assert_trap(Message, File, Line, Function);
 }
 
-#endif
+#endif /* _WIN32 */