commit dd5c7f9313ca9b1ec9c4f49c1af03d2835f02ac1
author Kostya Serebryany <kcc@google.com> Thu Jul 14 17:59:01 2016 +0000
committer Kostya Serebryany <kcc@google.com> Thu Jul 14 17:59:01 2016 +0000
tree ed02dddd8fb00dc81d5ed04b0a730f1a5829a629
parent cb7d6e955d74fc58b1a537023aef0f566d412c42

[sanitizer-coverage] make sure that calls to __sanitizer_cov_trace_pc are not merged (otherwise different calls get the same PC and confuse fuzzers)

llvm-svn: 275449

llvm/lib/Transforms/Instrumentation/SanitizerCoverage.cpp

diff --git a/llvm/lib/Transforms/Instrumentation/SanitizerCoverage.cpp b/llvm/lib/Transforms/Instrumentation/SanitizerCoverage.cpp
index 1315e19..7d40447 100644
--- a/llvm/lib/Transforms/Instrumentation/SanitizerCoverage.cpp
+++ b/llvm/lib/Transforms/Instrumentation/SanitizerCoverage.cpp
@@ -544,7 +544,8 @@
   Type *Int32PtrTy = PointerType::getUnqual(IRB.getInt32Ty());
   GuardP = IRB.CreateIntToPtr(GuardP, Int32PtrTy);
   if (Options.TracePC) {
-    IRB.CreateCall(SanCovTracePC);
+    IRB.CreateCall(SanCovTracePC); // gets the PC using GET_CALLER_PC.
+    IRB.CreateCall(EmptyAsm, {}); // Avoids callback merge.
   } else if (Options.TraceBB) {
     IRB.CreateCall(IsEntryBB ? SanCovTraceEnter : SanCovTraceBB, GuardP);
   } else if (UseCalls) {