Index: llvm/trunk/lib/Transforms/Instrumentation/SanitizerCoverage.cpp
===================================================================
--- llvm/trunk/lib/Transforms/Instrumentation/SanitizerCoverage.cpp
+++ llvm/trunk/lib/Transforms/Instrumentation/SanitizerCoverage.cpp
@@ -101,10 +101,10 @@
                                       "instructions"),
                              cl::Hidden, cl::init(false));
 
-static cl::opt<bool> ClPruneBlocks(
-    "sanitizer-coverage-prune-blocks",
-    cl::desc("Reduce the number of instrumented blocks (experimental)"),
-    cl::Hidden, cl::init(false));
+static cl::opt<bool>
+    ClPruneBlocks("sanitizer-coverage-prune-blocks",
+                  cl::desc("Reduce the number of instrumented blocks"),
+                  cl::Hidden, cl::init(true));
 
 // Experimental 8-bit counters used as an additional search heuristic during
 // coverage-guided fuzzing.
Index: llvm/trunk/test/Instrumentation/SanitizerCoverage/coverage.ll
===================================================================
--- llvm/trunk/test/Instrumentation/SanitizerCoverage/coverage.ll
+++ llvm/trunk/test/Instrumentation/SanitizerCoverage/coverage.ll
@@ -56,7 +56,7 @@
 ; 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
@@ -64,20 +64,18 @@
 ; CHECK2: call void asm sideeffect "", ""()
 ; CHECK2: call void @__sanitizer_cov
 ; CHECK2: call void asm sideeffect "", ""()
-; CHECK2: call void @__sanitizer_cov
 ; CHECK2: call void asm sideeffect "", ""()
 ; CHECK2-NOT: call void @__sanitizer_cov
 ; CHECK2: ret void
 
 ; 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
 ; CHECK3: call void @__sanitizer_cov
 ; CHECK3: call void @__sanitizer_cov
-; CHECK3: call void @__sanitizer_cov
 ; CHECK3-NOT: ret void
 ; CHECK3: call void @__sanitizer_cov
 ; CHECK3-NOT: call void @__sanitizer_cov
Index: llvm/trunk/test/Instrumentation/SanitizerCoverage/coverage2-dbg.ll
===================================================================
--- llvm/trunk/test/Instrumentation/SanitizerCoverage/coverage2-dbg.ll
+++ llvm/trunk/test/Instrumentation/SanitizerCoverage/coverage2-dbg.ll
@@ -19,11 +19,9 @@
 ; CHECK-LABEL:_Z3fooPi
 ; CHECK: call void @__sanitizer_cov(i32*{{.*}}), !dbg [[A:!.*]]
 ; CHECK: call void @__sanitizer_cov(i32*{{.*}}), !dbg [[B:!.*]]
-; CHECK: call void @__sanitizer_cov(i32*{{.*}}), !dbg [[C:!.*]]
 ; CHECK: ret void
 ; CHECK: [[A]] = !DILocation(line: 1, scope: !{{.*}})
 ; CHECK: [[B]] = !DILocation(line: 3, column: 5, scope: !{{.*}})
-; CHECK: [[C]] = !DILocation(line: 4, column: 1, scope: !{{.*}})
 
 define void @_Z3fooPi(i32* %a) #0 !dbg !4 {
 entry:
Index: llvm/trunk/test/Instrumentation/SanitizerCoverage/tracing.ll
===================================================================
--- llvm/trunk/test/Instrumentation/SanitizerCoverage/tracing.ll
+++ llvm/trunk/test/Instrumentation/SanitizerCoverage/tracing.ll
@@ -21,7 +21,6 @@
 ; CHECK1-LABEL: define void @foo
 ; CHECK1: call void @__sanitizer_cov_trace_func_enter
 ; CHECK1: call void @__sanitizer_cov_trace_basic_block
-; CHECK1: call void @__sanitizer_cov_trace_basic_block
 ; CHECK1-NOT: call void @__sanitizer_cov_trace_basic_block
 ; CHECK1: ret void
 
@@ -29,7 +28,6 @@
 ; CHECK3: call void @__sanitizer_cov_trace_func_enter
 ; CHECK3: call void @__sanitizer_cov_trace_basic_block
 ; CHECK3: call void @__sanitizer_cov_trace_basic_block
-; CHECK3: call void @__sanitizer_cov_trace_basic_block
 ; CHECK3-NOT: call void @__sanitizer_cov_trace_basic_block
 ; CHECK3: ret void
 
@@ -37,7 +35,6 @@
 ; 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