MSan: Use `createSanitizerCtor` to create ctor, and call `__msan_init`

[ismailp]

• createSanitizerCtor renamed to createSanitizerCtorAndInitFunctions to match with changes in D8777
• Added simple check to ensure MSan's ctor is added to module ctors, and __msan_init is called from ctor

[samsonov]

LGTM

test/Instrumentation/MemorySanitizer/msan_basic.ll

881 ↗

(On Diff #25235)

CHECK-LABEL

lib/Transforms/Instrumentation/MemorySanitizer.cpp

 
 // This is an experiment to enable handling of cases where shadow is a non-zero
 // compile-time constant. For some unexplainable reason they were silently
 // ignored in the instrumentation.
 static cl::opt<bool> ClCheckConstantShadow("msan-check-constant-shadow",
        cl::desc("Insert checks for constant shadow values"),
        cl::Hidden, cl::init(false));
 
+static const char *const kMsanModuleCtorName = "msan.module_ctor";
+static const char *const kMsanInitName = "__msan_init";
+
 namespace {
 
 // Memory map parameters used in application-to-shadow address calculation.
 // Offset = (Addr & ~AndMask) ^ XorMask
 // Shadow = ShadowBase + Offset
 // Origin = OriginBase + Offset
 struct MemoryMapParams {
   uint64_t AndMask;
private:
   /// \brief Memory map parameters used in application-to-shadow calculation.
   const MemoryMapParams *MapParams;
 
   MDNode *ColdCallWeights;
   /// \brief Branch weights for origin store.
   MDNode *OriginStoreWeights;
   /// \brief An empty volatile inline asm that prevents callback merge.
   InlineAsm *EmptyAsm;
+  Function *MsanCtorFunction;
 
   friend struct MemorySanitizerVisitor;
   friend struct VarArgAMD64Helper;
   friend struct VarArgMIPS64Helper;
 };
 }  // namespace
 
 char MemorySanitizer::ID = 0;
bool MemorySanitizer::doInitialization(Module &M) {
   C = &(M.getContext());
   IRBuilder<> IRB(*C);
   IntptrTy = IRB.getIntPtrTy(DL);
   OriginTy = IRB.getInt32Ty();
 
   ColdCallWeights = MDBuilder(*C).createBranchWeights(1, 1000);
   OriginStoreWeights = MDBuilder(*C).createBranchWeights(1, 1000);
 
-  // Insert a call to __msan_init/__msan_track_origins into the module's CTORs.
-  appendToGlobalCtors(M, cast<Function>(M.getOrInsertFunction(
-                      "__msan_init", IRB.getVoidTy(), nullptr)), 0);
+  MsanCtorFunction = createSanitizerCtor(M, kMsanModuleCtorName, kMsanInitName);
+
+  appendToGlobalCtors(M, MsanCtorFunction, 0);
 
   if (TrackOrigins)
     new GlobalVariable(M, IRB.getInt32Ty(), true, GlobalValue::WeakODRLinkage,
                        IRB.getInt32(TrackOrigins), "__msan_track_origins");
 
   if (ClKeepGoing)
     new GlobalVariable(M, IRB.getInt32Ty(), true, GlobalValue::WeakODRLinkage,
                        IRB.getInt32(ClKeepGoing), "__msan_keep_going");
else if (TargetTriple.getArch() == llvm::Triple::mips64 ||
     return new VarArgMIPS64Helper(Func, Msan, Visitor);
   else
     return new VarArgNoOpHelper(Func, Msan, Visitor);
 }
 
 }  // namespace
 
 bool MemorySanitizer::runOnFunction(Function &F) {
+  if (&F == MsanCtorFunction)
+    return false;
   MemorySanitizerVisitor Visitor(F, *this);
 
   // Clear out readonly/readnone attributes.
   AttrBuilder B;
   B.addAttribute(Attribute::ReadOnly)
     .addAttribute(Attribute::ReadNone);
   F.removeAttributes(AttributeSet::FunctionIndex,
                      AttributeSet::get(F.getContext(),
                                        AttributeSet::FunctionIndex, B));
 
   return Visitor.runOnFunction();
 }