[Coverage] Emit a gap region to cover switch bodies

Emit a gap region beginning where the switch body begins. This sets line
execution counts in the areas between non-overlapping cases to 0.

This also removes some special handling of the first case in a switch:
these are now treated like any other case.

This does not resolve an outstanding issue with case statement regions
that do not end when a region is terminated. But it should address
llvm.org/PR44011.

Differential Revision: https://reviews.llvm.org/D70571

1 files changed, 2 insertions, 2 deletions

diff --git a/clang/lib/CodeGen/CoverageMappingGen.cpp b/clang/lib/CodeGen/CoverageMappingGen.cpp
index 0a7a4fe33ac..bdecff39c88 100644
--- a/clang/lib/CodeGen/CoverageMappingGen.cpp
+++ b/clang/lib/CodeGen/CoverageMappingGen.cpp
@@ -1114,8 +1114,8 @@ struct CounterCoverageMappingBuilder
         // Make a region for the body of the switch.  If the body starts with
         // a case, that case will reuse this region; otherwise, this covers
         // the unreachable code at the beginning of the switch body.
-        size_t Index =
-            pushRegion(Counter::getZero(), getStart(CS->body_front()));
+        size_t Index = pushRegion(Counter::getZero(), getStart(CS));
+        getRegion().setGap(true);
         for (const auto *Child : CS->children())
           Visit(Child);