[PATCH] tsan: handle vptr loads specially

[Dmitry Vyukov]

Hi kcc,

This is required to determine ctor/dtor vs virtual call races.


http://llvm-reviews.chandlerc.com/D566

Files:
  lib/Transforms/Instrumentation/ThreadSanitizer.cpp
  test/Instrumentation/ThreadSanitizer/vptr_read.ll

Index: lib/Transforms/Instrumentation/ThreadSanitizer.cpp
===================================================================
--- lib/Transforms/Instrumentation/ThreadSanitizer.cpp
+++ lib/Transforms/Instrumentation/ThreadSanitizer.cpp
@@ -63,6 +63,7 @@
           "Number of reads ignored due to following writes");
 STATISTIC(NumAccessesWithBadSize, "Number of accesses with bad size");
 STATISTIC(NumInstrumentedVtableWrites, "Number of vtable ptr writes");
+STATISTIC(NumInstrumentedVtableReads, "Number of vtable ptr reads");
 STATISTIC(NumOmittedReadsFromConstantGlobals,
           "Number of reads from constant globals");
 STATISTIC(NumOmittedReadsFromVtable, "Number of vtable reads");
@@ -108,6 +109,7 @@
   Function *TsanAtomicThreadFence;
   Function *TsanAtomicSignalFence;
   Function *TsanVptrUpdate;
+  Function *TsanVptrLoad;
 };
 }  // namespace
 
@@ -196,6 +198,8 @@
   TsanVptrUpdate = checkInterfaceFunction(M.getOrInsertFunction(
       "__tsan_vptr_update", IRB.getVoidTy(), IRB.getInt8PtrTy(),
       IRB.getInt8PtrTy(), NULL));
+  TsanVptrLoad = checkInterfaceFunction(M.getOrInsertFunction(
+      "__tsan_vptr_read", IRB.getVoidTy(), IRB.getInt8PtrTy(), NULL));
   TsanAtomicThreadFence = checkInterfaceFunction(M.getOrInsertFunction(
       "__tsan_atomic_thread_fence", IRB.getVoidTy(), OrdTy, NULL));
   TsanAtomicSignalFence = checkInterfaceFunction(M.getOrInsertFunction(
@@ -386,6 +390,12 @@
     NumInstrumentedVtableWrites++;
     return true;
   }
+  if (!IsWrite && isVtableAccess(I)) {
+    IRB.CreateCall(TsanVptrLoad,
+                   IRB.CreatePointerCast(Addr, IRB.getInt8PtrTy()));
+    NumInstrumentedVtableReads++;
+    return true;
+  }
   Value *OnAccessFunc = IsWrite ? TsanWrite[Idx] : TsanRead[Idx];
   IRB.CreateCall(OnAccessFunc, IRB.CreatePointerCast(Addr, IRB.getInt8PtrTy()));
   if (IsWrite) NumInstrumentedWrites++;
Index: test/Instrumentation/ThreadSanitizer/vptr_read.ll
===================================================================
--- test/Instrumentation/ThreadSanitizer/vptr_read.ll
+++ test/Instrumentation/ThreadSanitizer/vptr_read.ll
@@ -0,0 +1,13 @@
+; RUN: opt < %s -tsan -S | FileCheck %s
+; Check that vptr reads are treated in a special way.
+target datalayout = "e-p:64:64:64-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:64:64-f32:32:32-f64:64:64-v64:64:64-v128:128:128-a0:0:64-s0:64:64-f80:128:128-n8:16:32:64-S128"
+
+define i8 @Foo(i8* %a) nounwind uwtable {
+entry:
+; CHECK: call void @__tsan_vptr_read
+  %0 = load i8* %a, align 8, !tbaa !0
+  ret i8 %0
+}
+!0 = metadata !{metadata !"vtable pointer", metadata !1}
+!1 = metadata !{metadata !"Simple C/C++ TBAA", null}
+
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