[SanitizerCoverage] Don't add instrumentation to unreachable blocks.

llvm-svn: 241127

1 files changed, 7 insertions, 0 deletions

diff --git a/llvm/lib/Transforms/Instrumentation/SanitizerCoverage.cpp b/llvm/lib/Transforms/Instrumentation/SanitizerCoverage.cpp
index dff39efa5b9..7a5b4cb0178 100644
--- a/llvm/lib/Transforms/Instrumentation/SanitizerCoverage.cpp
+++ b/llvm/lib/Transforms/Instrumentation/SanitizerCoverage.cpp
@@ -375,6 +375,13 @@ void SanitizerCoverageModule::SetNoSanitizeMetadata(Instruction *I) {
 
 void SanitizerCoverageModule::InjectCoverageAtBlock(Function &F, BasicBlock &BB,
                                                     bool UseCalls) {
+  // Don't insert coverage for unreachable blocks: we will never call
+  // __sanitizer_cov() for them, so counting them in
+  // NumberOfInstrumentedBlocks() might complicate calculation of code coverage
+  // percentage. Also, unreachable instructions frequently have no debug
+  // locations.
+  if (isa<UnreachableInst>(BB.getTerminator()))
+    return;
   BasicBlock::iterator IP = BB.getFirstInsertionPt(), BE = BB.end();
   // Skip static allocas at the top of the entry block so they don't become
   // dynamic when we split the block.  If we used our optimized stack layout,