[NFC][msan] Consolidate clean shadow handling

[vitalybuka]

Summary

Depends on D117276

[vitalybuka]

update

[eugenis]

LGTM

llvm/lib/Transforms/Instrumentation/MemorySanitizer.cpp

if (Argument *A = dyn_cast<Argument>(V)) {
             } 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);
-            setOrigin(A, getCleanOrigin());
-          } else if (MS.EagerChecks && FArg.hasAttribute(Attribute::NoUndef)) {
-            *ShadowPtr = getCleanShadow(V);
-            setOrigin(A, getCleanOrigin());
-            break;
-          } else {
-            if (Overflow) {
-              // ParamTLS overflow.
-              *ShadowPtr = getCleanShadow(V);
-              setOrigin(A, getCleanOrigin());
-            } else {
-              // Shadow over TLS
-              Value *Base = getShadowPtrForArgument(&FArg, EntryIRB, ArgOffset);
-              *ShadowPtr = EntryIRB.CreateAlignedLoad(getShadowTy(&FArg), Base,
-                                                      kShadowTLSAlignment);
-              if (MS.TrackOrigins) {
-                Value *OriginPtr =
-                    getOriginPtrForArgument(&FArg, EntryIRB, ArgOffset);
-                setOrigin(A, EntryIRB.CreateLoad(MS.OriginTy, OriginPtr));
-              }
-            }
-          }
+          }
+
+          if (Overflow || FArg.hasByValAttr() ||
+              (MS.EagerChecks && FArg.hasAttribute(Attribute::NoUndef))) {
           LLVM_DEBUG(dbgs()
                      << "  ARG:    " << FArg << " ==> " << **ShadowPtr << "\n");
           break;
         }
 
         ArgOffset += alignTo(Size, kShadowTLSAlignment);
       }
       assert(*ShadowPtr && "Could not find shadow for an argument");