[NFC][msan] Reorder branches in complex if

[vitalybuka]

update

[eugenis]

LGTM

llvm/lib/Transforms/Instrumentation/MemorySanitizer.cpp

if (Argument *A = dyn_cast<Argument>(V)) {
       unsigned ArgOffset = 0;
       const DataLayout &DL = F->getParent()->getDataLayout();
       for (auto &FArg : F->args()) {
         if (!FArg.getType()->isSized()) {
           LLVM_DEBUG(dbgs() << "Arg is not sized\n");
           continue;
         }
 
-        bool FArgByVal = FArg.hasByValAttr();
-        unsigned Size = FArgByVal
+        unsigned Size = FArg.hasByValAttr()
                             ? DL.getTypeAllocSize(FArg.getParamByValType())
                             : DL.getTypeAllocSize(FArg.getType());
 
         if (A == &FArg) {
           bool Overflow = ArgOffset + Size > kParamTLSSize;
-          bool FArgEagerCheck = MS.EagerChecks && !FArgByVal &&
-                                FArg.hasAttribute(Attribute::NoUndef);
-
-          if (FArgEagerCheck) {
-            *ShadowPtr = getCleanShadow(V);
-            setOrigin(A, getCleanOrigin());
-            break;
-          } else if (FArgByVal) {
+          if (FArg.hasByValAttr()) {
             // ByVal pointer itself has clean shadow. We copy the actual
             // argument shadow to the underlying memory.
             // Figure out maximal valid memcpy alignment.
             const Align ArgAlign = DL.getValueOrABITypeAlignment(
                 MaybeAlign(FArg.getParamAlignment()), FArg.getParamByValType());
             Value *CpShadowPtr =
                 getShadowOriginPtr(V, EntryIRB, EntryIRB.getInt8Ty(), ArgAlign,
                                    /*isStore*/ true)
                     .first;
             // TODO(glider): need to copy origins.
             if (Overflow) {
               // ParamTLS overflow.
               EntryIRB.CreateMemSet(
                   CpShadowPtr, Constant::getNullValue(EntryIRB.getInt8Ty()),
                   Size, ArgAlign);
             } else {
               Value *Base = getShadowPtrForArgument(&FArg, EntryIRB, ArgOffset);
               const Align CopyAlign = std::min(ArgAlign, kShadowTLSAlignment);
               Value *Cpy = EntryIRB.CreateMemCpy(CpShadowPtr, CopyAlign, Base,
                                                  CopyAlign, Size);
               LLVM_DEBUG(dbgs() << "  ByValCpy: " << *Cpy << "\n");
               (void)Cpy;
             }
             *ShadowPtr = getCleanShadow(V);
+          } else if (MS.EagerChecks && FArg.hasAttribute(Attribute::NoUndef)) {
+            *ShadowPtr = getCleanShadow(V);
+            setOrigin(A, getCleanOrigin());
+            break;
           } else {
             if (Overflow) {
               // ParamTLS overflow.
               *ShadowPtr = getCleanShadow(V);
             } else {
               // Shadow over TLS
               Value *Base = getShadowPtrForArgument(&FArg, EntryIRB, ArgOffset);
               *ShadowPtr = EntryIRB.CreateAlignedLoad(getShadowTy(&FArg), Base,