Add CMake option to enable expensive line number origin tracking

llvm/CMakeLists.txt

@@ -524,6 +524,10 @@ endif()
 
 option(LLVM_ENABLE_CRASH_DUMPS "Turn on memory dumps on crashes. Currently only implemented on Windows." OFF)
 
+set(LLVM_ENABLE_DEBUGLOC_COVERAGE_TRACKING "DISABLED" CACHE STRING
+  "Enhance debugify's line number coverage tracking; enabling this is abi-breaking. Can be DISABLED, COVERAGE, or COVERAGE_AND_ORIGIN.")
+set_property(CACHE LLVM_ENABLE_DEBUGLOC_COVERAGE_TRACKING PROPERTY STRINGS DISABLED COVERAGE COVERAGE_AND_ORIGIN)
+
 set(WINDOWS_PREFER_FORWARD_SLASH_DEFAULT OFF)
 if (MINGW)
   # Cygwin doesn't identify itself as Windows, and thus gets path::Style::posix

llvm/cmake/modules/HandleLLVMOptions.cmake

@@ -196,6 +196,18 @@ else()
   message(FATAL_ERROR "Unknown value for LLVM_ABI_BREAKING_CHECKS: \"${LLVM_ABI_BREAKING_CHECKS}\"!")
 endif()
 
+string(TOUPPER "${LLVM_ENABLE_DEBUGLOC_COVERAGE_TRACKING}" uppercase_LLVM_ENABLE_DEBUGLOC_COVERAGE_TRACKING)
+
+if( uppercase_LLVM_ENABLE_DEBUGLOC_COVERAGE_TRACKING STREQUAL "COVERAGE" )
+  set( ENABLE_DEBUGLOC_COVERAGE_TRACKING 1 )
+elseif( uppercase_LLVM_ENABLE_DEBUGLOC_COVERAGE_TRACKING STREQUAL "COVERAGE_AND_ORIGIN" )
+  message(FATAL_ERROR "\"COVERAGE_AND_ORIGIN\" setting for LLVM_ENABLE_DEBUGLOC_COVERAGE_TRACKING currently unimplemented.")
+elseif( uppercase_LLVM_ENABLE_DEBUGLOC_COVERAGE_TRACKING STREQUAL "DISABLED" OR NOT DEFINED LLVM_ENABLE_DEBUGLOC_COVERAGE_TRACKING )
+  # The DISABLED setting is default and requires no additional defines.
+else()
+  message(FATAL_ERROR "Unknown value for LLVM_ENABLE_DEBUGLOC_COVERAGE_TRACKING: \"${LLVM_ENABLE_DEBUGLOC_COVERAGE_TRACKING}\"!")
+endif()
+
 if( LLVM_REVERSE_ITERATION )
   set( LLVM_ENABLE_REVERSE_ITERATION 1 )
 endif()

llvm/docs/CMake.rst

@@ -475,6 +475,17 @@ enabled sub-projects. Nearly all of these variable names begin with
 **LLVM_ENABLE_BINDINGS**:BOOL
   If disabled, do not try to build the OCaml bindings.
 
+**LLVM_ENABLE_DEBUGLOC_COVERAGE_TRACKING**:STRING
+  Enhances Debugify's ability to detect line number errors by storing extra
+  information inside Instructions, removing false positives from Debugify's
+  results at the cost of performance. Allowed values are `DISABLED` (default),
+  `COVERAGE`, and `COVERAGE_AND_ORIGIN`. `COVERAGE` tracks whether and why a
+  line number was intentionally dropped or not generated for an instruction,
+  allowing Debugify to avoid reporting these as errors. `COVERAGE_AND_ORIGIN`
+  additionally stores a stacktrace of the point where each DebugLoc is
+  unintentionally dropped, allowing for much easier bug triaging at the cost of
+  a ~10x performance slowdown.
+
 **LLVM_ENABLE_DIA_SDK**:BOOL
   Enable building with MSVC DIA SDK for PDB debugging support. Available
   only with MSVC. Defaults to ON.

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

@@ -19,6 +19,10 @@
 /* Define to 1 to enable crash memory dumps, and to 0 otherwise. */
 #cmakedefine01 LLVM_ENABLE_CRASH_DUMPS
 
+/* Define to 1 to enable expensive checks for debug location coverage checking,
+   and to 0 otherwise. */
+#cmakedefine01 ENABLE_DEBUGLOC_COVERAGE_TRACKING
+
 /* Define to 1 to prefer forward slashes on Windows, and to 0 prefer
    backslashes. */
 #cmakedefine01 LLVM_WINDOWS_PREFER_FORWARD_SLASH