[sancov] enabling coverage edge pruning by default.

[eugenis]

LGTM

lib/Transforms/Instrumentation/SanitizerCoverage.cpp

static cl::opt<bool> ClExperimentalTracePC("sanitizer-coverage-trace-pc",
                                            cl::Hidden, cl::init(false));
 
 static cl::opt<bool>
     ClExperimentalCMPTracing("sanitizer-coverage-experimental-trace-compares",
                              cl::desc("Experimental tracing of CMP and similar "
                                       "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.
 // The counters are not thread-friendly:
 //   - contention on these counters may cause significant slowdown;
 //   - the counter updates are racy and the results may be inaccurate.
 // They are also inaccurate due to 8-bit integer overflow.
 static cl::opt<bool> ClUse8bitCounters("sanitizer-coverage-8bit-counters",

test/Instrumentation/SanitizerCoverage/coverage.ll

 ; CHECK1: call void @__sanitizer_cov_module_init({{.*}}, i64 2,
 ; CHECK1: ret
 
 ; CHECK_WITH_CHECK-LABEL: define void @foo
 ; CHECK_WITH_CHECK: __sanitizer_cov_with_check
 ; 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
 ; CHECK2: call void @__sanitizer_cov
 ; 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
 ; CHECK3: ret void
 
 ; test -sanitizer-coverage-8bit-counters=1
 ; CHECK-8BIT-LABEL: define void @foo
 

test/Instrumentation/SanitizerCoverage/coverage2-dbg.ll

 target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"
 target triple = "x86_64-unknown-linux-gnu"
 
 ; Check that __sanitizer_cov call has !dgb pointing to the beginning
 ; of appropriate basic blocks.
 ; 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:
   tail call void @llvm.dbg.value(metadata i32* %a, i64 0, metadata !11, metadata !DIExpression()), !dbg !15
   %tobool = icmp eq i32* %a, null, !dbg !16
   br i1 %tobool, label %if.end, label %if.then, !dbg !16
 
 if.then:                                          ; preds = %entry

test/Instrumentation/SanitizerCoverage/tracing.ll

entry:
 
   if.end:                                           ; preds = %entry, %if.then
   ret void
 }
 
 ; 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
 
 ; CHECK3-LABEL: define void @foo
 ; 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
 
 ; CHECK_PC-LABEL: define void @foo
 ; 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