[Assignment Tracking][NFC] Replace LLVM command line option with a module flag

Remove LLVM flag -experimental-assignment-tracking. Assignment tracking is
still enabled from Clang with the command line -Xclang
-fexperimental-assignment-tracking which tells Clang to ask LLVM to run the
pass declare-to-assign. That pass converts conventional debug intrinsics to
assignment tracking metadata. With this patch it now also sets a module flag
debug-info-assignment-tracking with the value `i1 true` (using the flag conflict
rule `Max` since enabling assignment tracking on IR that contains only
conventional debug intrinsics should cause no issues).

Update the docs and tests too.

Reviewed By: CarlosAlbertoEnciso

Differential Revision: https://reviews.llvm.org/D142027

1 files changed, 3 insertions, 0 deletions

diff --git a/llvm/lib/CodeGen/AssignmentTrackingAnalysis.cpp b/llvm/lib/CodeGen/AssignmentTrackingAnalysis.cpp
index ba51c3b..16782a3 100644
--- a/llvm/lib/CodeGen/AssignmentTrackingAnalysis.cpp
+++ b/llvm/lib/CodeGen/AssignmentTrackingAnalysis.cpp
@@ -2389,6 +2389,9 @@ static void analyzeFunction(Function &Fn, const DataLayout &Layout,
 }
 
 bool AssignmentTrackingAnalysis::runOnFunction(Function &F) {
+  if (!isAssignmentTrackingEnabled(*F.getParent()))
+    return false;
+
   LLVM_DEBUG(dbgs() << "AssignmentTrackingAnalysis run on " << F.getName()
                     << "\n");
   auto DL = std::make_unique<DataLayout>(F.getParent());