[Coverage] Introduce the type `CounterPair` for RegionCounterMap. NFC. (#112724)

`CounterPair` can hold `<uint32_t, uint32_t>` instead of current
`unsigned`, to hold also the counter number of SkipPath. For now, this
change provides the skeleton and only `CounterPair::Executed` is used.

Each counter number can have `None` to suppress emitting counter
increment. 2nd element `Skipped` is initialized as `None` by default,
since most `Stmt*` don't have a pair of counters.

This change also provides stubs for the verifier. I'll provide the impl
of verifier for `+Asserts` later.

`markStmtAsUsed(bool, Stmt*)` may be used to inform that other side
counter may not emitted.

`markStmtMaybeUsed(S)` may be used for the `Stmt` and its inner will be
excluded for emission in the case of skipping by constant folding. I put
it into places where I found.

`verifyCounterMap()` will check the coverage map and the counter map,
and can be used to report inconsistency.

These verifier methods shall be eliminated in `-Asserts`.


https://discourse.llvm.org/t/rfc-integrating-singlebytecoverage-with-branch-coverage/82492

1 files changed, 3 insertions, 0 deletions

diff --git a/clang/lib/CodeGen/CodeGenFunction.cpp b/clang/lib/CodeGen/CodeGenFunction.cpp
index af58fa6..27ec68b 100644
--- a/clang/lib/CodeGen/CodeGenFunction.cpp
+++ b/clang/lib/CodeGen/CodeGenFunction.cpp
@@ -1616,6 +1616,8 @@ void CodeGenFunction::GenerateCode(GlobalDecl GD, llvm::Function *Fn,
   // Emit the standard function epilogue.
   FinishFunction(BodyRange.getEnd());
 
+  PGO.verifyCounterMap();
+
   // If we haven't marked the function nothrow through other means, do
   // a quick pass now to see if we can.
   if (!CurFn->doesNotThrow())
@@ -1738,6 +1740,7 @@ bool CodeGenFunction::ConstantFoldsToSimpleInteger(const Expr *Cond,
   if (!AllowLabels && CodeGenFunction::ContainsLabel(Cond))
     return false;  // Contains a label.
 
+  PGO.markStmtMaybeUsed(Cond);
   ResultInt = Int;
   return true;
 }