[dfsan] Fix getShadowAddress computation (llvm#162864)

Fix getShadowAddress computation by adding ShadowBase if it is not zero.

Co-authored-by: anoopkg6 <[email protected]>

Author: 2 people

llvm/lib/Transforms/Instrumentation/DataFlowSanitizer.cpp

@@ -1957,8 +1957,12 @@ Value *DataFlowSanitizer::getShadowAddress(Value *Addr,
 Value *DataFlowSanitizer::getShadowAddress(Value *Addr,
                                            BasicBlock::iterator Pos) {
   IRBuilder<> IRB(Pos->getParent(), Pos);
-  Value *ShadowOffset = getShadowOffset(Addr, IRB);
-  return getShadowAddress(Addr, Pos, ShadowOffset);
+  Value *ShadowAddr = getShadowOffset(Addr, IRB);
+  uint64_t ShadowBase = MapParams->ShadowBase;
+  if (ShadowBase != 0)
+    ShadowAddr =
+        IRB.CreateAdd(ShadowAddr, ConstantInt::get(IntptrTy, ShadowBase));
+  return getShadowAddress(Addr, Pos, ShadowAddr);
 }
 
 Value *DFSanFunction::combineShadowsThenConvert(Type *T, Value *V1, Value *V2,