Index: lib/Transforms/Instrumentation/SanitizerCoverage.cpp
===================================================================
--- lib/Transforms/Instrumentation/SanitizerCoverage.cpp
+++ lib/Transforms/Instrumentation/SanitizerCoverage.cpp
@@ -384,6 +384,11 @@
   if (Options.NoPrune || &F.getEntryBlock() == BB)
     return true;
 
+  // Do not instrument blocks with no successors and multiple predecessors.
+  if (succ_begin(BB) == succ_end(BB)
+      && BB->getSinglePredecessor() == nullptr)
+    return false;
+
   return !isFullDominator(BB, DT);
 }
 
Index: test/Instrumentation/SanitizerCoverage/coverage.ll
===================================================================
--- test/Instrumentation/SanitizerCoverage/coverage.ll
+++ test/Instrumentation/SanitizerCoverage/coverage.ll
@@ -54,7 +54,7 @@
 ; CHECK_WITH_CHECK: ret void
 ; CHECK_WITH_CHECK-LABEL: define internal void @sancov.module_ctor
 ; CHECK_WITH_CHECK-NOT: ret
-; CHECK_WITH_CHECK: call void @__sanitizer_cov_module_init({{.*}}, i64 4,
+; CHECK_WITH_CHECK: call void @__sanitizer_cov_module_init({{.*}}, i64 3,
 ; CHECK_WITH_CHECK: ret
 
 ; CHECK2-LABEL: define void @foo
@@ -68,7 +68,7 @@
 
 ; CHECK2-LABEL: define internal void @sancov.module_ctor
 ; CHECK2-NOT: ret
-; CHECK2: call void @__sanitizer_cov_module_init({{.*}}, i64 4,
+; CHECK2: call void @__sanitizer_cov_module_init({{.*}}, i64 3,
 ; CHECK2: ret
 
 ; CHECK3-LABEL: define void @foo
@@ -76,7 +76,6 @@
 ; CHECK3: call void @__sanitizer_cov
 ; CHECK3-NOT: ret void
 ; CHECK3: call void @__sanitizer_cov
-; CHECK3: call void @__sanitizer_cov
 ; CHECK3-NOT: call void @__sanitizer_cov
 ; CHECK3: ret void
 
@@ -112,6 +111,5 @@
 ; CHECKPRUNE: call void @__sanitizer_cov
 ; CHECKPRUNE: call void @__sanitizer_cov
 ; CHECKPRUNE: call void @__sanitizer_cov
-; CHECKPRUNE: call void @__sanitizer_cov
 ; CHECKPRUNE-NOT: call void @__sanitizer_cov
 ; CHECKPRUNE: ret void
Index: test/Instrumentation/SanitizerCoverage/tracing.ll
===================================================================
--- test/Instrumentation/SanitizerCoverage/tracing.ll
+++ test/Instrumentation/SanitizerCoverage/tracing.ll
@@ -22,7 +22,6 @@
 ; CHECK_PC: call void @__sanitizer_cov_trace_pc
 ; CHECK_PC: call void @__sanitizer_cov_trace_pc
 ; CHECK_PC: call void @__sanitizer_cov_trace_pc
-; CHECK_PC: call void @__sanitizer_cov_trace_pc
 ; CHECK_PC-NOT: call void @__sanitizer_cov_trace_pc
 ; CHECK_PC: ret void
 ; CHECK_PC-NOT: call void @__sanitizer_cov_module_init
@@ -31,7 +30,6 @@
 ; CHECK_PC_GUARD: call void @__sanitizer_cov_trace_pc_guard
 ; CHECK_PC_GUARD: call void @__sanitizer_cov_trace_pc_guard
 ; CHECK_PC_GUARD: call void @__sanitizer_cov_trace_pc_guard
-; CHECK_PC_GUARD: call void @__sanitizer_cov_trace_pc_guard
 ; CHECK_PC_GUARD-NOT: call void @__sanitizer_cov_trace_pc
 ; CHECK_PC_GUARD: ret void
 ; CHECK_PC_GUARD: call void @__sanitizer_cov_trace_pc_guard_init(i32* bitcast (i32** @__start___sancov_guards to i32*), i32* bitcast (i32** @__stop___sancov_guards to i32*))
@@ -40,7 +38,6 @@
 ; CHECK_PC_GUARD_DARWIN: call void @__sanitizer_cov_trace_pc_guard
 ; CHECK_PC_GUARD_DARWIN: call void @__sanitizer_cov_trace_pc_guard
 ; CHECK_PC_GUARD_DARWIN: call void @__sanitizer_cov_trace_pc_guard
-; CHECK_PC_GUARD_DARWIN: call void @__sanitizer_cov_trace_pc_guard
 ; CHECK_PC_GUARD_DARWIN-NOT: call void @__sanitizer_cov_trace_pc
 ; CHECK_PC_GUARD_DARWIN: ret void
 ; CHECK_PC_GUARD_DARWIN: call void @__sanitizer_cov_trace_pc_guard_init(i32* bitcast (i32** @"\01section$start$__DATA$__sancov_guards" to i32*), i32* bitcast (i32** @"\01section$end$__DATA$__sancov_guards" to i32*))