[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, 6 insertions, 0 deletions

diff --git a/llvm/lib/IR/Verifier.cpp b/llvm/lib/IR/Verifier.cpp
index 9cab88b..96eb4ef 100644
--- a/llvm/lib/IR/Verifier.cpp
+++ b/llvm/lib/IR/Verifier.cpp
@@ -3178,6 +3178,12 @@ void Verifier::visitFunction(const Function &F) {
     CheckDI(SP->describes(&F),
             "!dbg attachment points at wrong subprogram for function", N, &F,
             &I, DL, Scope, SP);
+
+    if (DL->getAtomGroup())
+      CheckDI(DL->getScope()->getSubprogram()->getKeyInstructionsEnabled(),
+              "DbgLoc uses atomGroup but DISubprogram doesn't have Key "
+              "Instructions enabled",
+              DL, DL->getScope()->getSubprogram());
   };
   for (auto &BB : F)
     for (auto &I : BB) {