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

llvm-svn: 241127

2 files changed, 16 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,
diff --git a/llvm/test/Instrumentation/SanitizerCoverage/coverage.ll b/llvm/test/Instrumentation/SanitizerCoverage/coverage.ll
index b2f0ab0680b..659c03040f2 100644
--- a/llvm/test/Instrumentation/SanitizerCoverage/coverage.ll
+++ b/llvm/test/Instrumentation/SanitizerCoverage/coverage.ll
@@ -119,3 +119,12 @@ entry:
 ; CHECK4: call void @__sanitizer_cov_indir_call16({{.*}},[[CACHE:.*]])
 ; CHECK4-NOT: call void @__sanitizer_cov_indir_call16({{.*}},[[CACHE]])
 ; CHECK4: ret void
+
+define void @call_unreachable() uwtable sanitize_address {
+entry:
+  unreachable
+}
+
+; CHECK4-LABEL: define void @call_unreachable
+; CHECK4-NOT: __sanitizer_cov
+; CHECK4: unreachable