[KeyInstr] Add DISubprogram::keyInstructions bit (#144107)

Patch 1/4 adding bitcode support.

Store whether or not a function is using Key Instructions in its DISubprogram so
that we don't need to rely on the -mllvm flag -dwarf-use-key-instructions to
determine whether or not to interpret Key Instructions metadata to decide
is_stmt placement at DWARF emission time. This makes bitcode support simple and
enables well defined mixing of non-key-instructions and key-instructions
functions in an LTO context.

This patch adds the bit (using DISubprogram::SubclassData1).

PR 144104 and 144103 use it during DWARF emission.
PR 44102 adds bitcode
support.

See pull request for overview of alternative attempts.

1 files changed, 3 insertions, 1 deletions

diff --git a/llvm/lib/Transforms/Utils/Debugify.cpp b/llvm/lib/Transforms/Utils/Debugify.cpp
index c2dbdc5..5f70bc4 100644
--- a/llvm/lib/Transforms/Utils/Debugify.cpp
+++ b/llvm/lib/Transforms/Utils/Debugify.cpp
@@ -123,7 +123,9 @@ bool llvm::applyDebugifyMetadata(
     if (F.hasPrivateLinkage() || F.hasInternalLinkage())
       SPFlags |= DISubprogram::SPFlagLocalToUnit;
     auto SP = DIB.createFunction(CU, F.getName(), F.getName(), File, NextLine,
-                                 SPType, NextLine, DINode::FlagZero, SPFlags);
+                                 SPType, NextLine, DINode::FlagZero, SPFlags,
+                                 nullptr, nullptr, nullptr, nullptr, "",
+                                 /*UseKeyInstructions*/ ApplyAtomGroups);
     F.setSubprogram(SP);
 
     // Helper that inserts a dbg.value before \p InsertBefore, copying the