[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, 2 insertions, 1 deletions

diff --git a/llvm/lib/Transforms/Utils/BasicBlockUtils.cpp b/llvm/lib/Transforms/Utils/BasicBlockUtils.cpp
index d14e5b8..9b35faf1 100644
--- a/llvm/lib/Transforms/Utils/BasicBlockUtils.cpp
+++ b/llvm/lib/Transforms/Utils/BasicBlockUtils.cpp
@@ -531,7 +531,8 @@ bool llvm::RemoveRedundantDbgInstrs(BasicBlock *BB) {
   // getting (2) out of the way, the foward scan will remove (3) since "x"
   // already is described as having the value V1 at (1).
   MadeChanges |= removeRedundantDbgInstrsUsingBackwardScan(BB);
-  if (BB->isEntryBlock() && getEnableAssignmentTracking())
+  if (BB->isEntryBlock() &&
+      isAssignmentTrackingEnabled(*BB->getParent()->getParent()))
     MadeChanges |= remomveUndefDbgAssignsFromEntryBlock(BB);
   MadeChanges |= removeRedundantDbgInstrsUsingForwardScan(BB);