asan: optimization experiments

The experiments can be used to evaluate potential optimizations that remove
instrumentation (assess false negatives). Instead of completely removing
some instrumentation, you set Exp to a non-zero value (mask of optimization
experiments that want to remove instrumentation of this instruction).
If Exp is non-zero, this pass will emit special calls into runtime
(e.g. __asan_report_exp_load1 instead of __asan_report_load1). These calls
make runtime terminate the program in a special way (with a different
exit status). Then you run the new compiler on a buggy corpus, collect
the special terminations (ideally, you don't see them at all -- no false
negatives) and make the decision on the optimization.

The exact reaction to experiments in runtime is not implemented in this patch.
It will be defined and implemented in a subsequent patch.

http://reviews.llvm.org/D8198



git-svn-id: https://llvm.org/svn/llvm-project/compiler-rt/trunk@232501 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 7 insertions, 0 deletions

diff --git a/lib/sanitizer_common/sanitizer_coverage_libcdep.cc b/lib/sanitizer_common/sanitizer_coverage_libcdep.cc
index 112e4896c..08f1f9cad 100644
--- a/lib/sanitizer_common/sanitizer_coverage_libcdep.cc
+++ b/lib/sanitizer_common/sanitizer_coverage_libcdep.cc
@@ -806,6 +806,13 @@ void CoverageUpdateMapping() {
 }  // namespace __sanitizer
 
 extern "C" {
+SANITIZER_INTERFACE_ATTRIBUTE WEAK
+void __sanitizer_cov_hint(uptr g, u64 c, u64 v) {
+  (void)g;
+  (void)c;
+  (void)v;
+}
+
 SANITIZER_INTERFACE_ATTRIBUTE void __sanitizer_cov(u32 *guard) {
   coverage_data.Add(StackTrace::GetPreviousInstructionPc(GET_CALLER_PC()),
                     guard);