diff --git a/enzyme/tools/enzyme-tblgen/blas-tblgen.cpp b/enzyme/tools/enzyme-tblgen/blas-tblgen.cpp
index 69dfdfa6cc39..45f891eecd18 100644
--- a/enzyme/tools/enzyme-tblgen/blas-tblgen.cpp
+++ b/enzyme/tools/enzyme-tblgen/blas-tblgen.cpp
@@ -57,6 +57,29 @@ bool hasDiffeRet(Init *resultTree) {
   return false;
 }
 
+bool hasAdjoint(Init *resultTree, StringRef argName) {
+  if (DagInit *resultRoot = dyn_cast<DagInit>(resultTree)) {
+    auto opName = resultRoot->getOperator()->getAsString();
+    auto Def = cast<DefInit>(resultRoot->getOperator())->getDef();
+    if (Def->isSubClassOf("adj")) {
+      auto name = Def->getValueAsString("name");
+      return name == argName;
+    }
+    for (auto arg : resultRoot->getArgs()) {
+      if (hasAdjoint(arg, argName))
+        return true;
+    }
+  }
+  if (DefInit *DefArg = dyn_cast<DefInit>(resultTree)) {
+    auto Def = DefArg->getDef();
+    if (Def->isSubClassOf("adj")) {
+      auto name = Def->getValueAsString("name");
+      return name == argName;
+    }
+  }
+  return false;
+}
+
 static void checkBlasCallsInDag(const RecordKeeper &RK,
                                 ArrayRef<Record *> blasPatterns,
                                 StringRef blasName, const DagInit *toSearch) {
diff --git a/enzyme/tools/enzyme-tblgen/blas-tblgen.h b/enzyme/tools/enzyme-tblgen/blas-tblgen.h
index e0c2c966e008..f9726b396561 100644
--- a/enzyme/tools/enzyme-tblgen/blas-tblgen.h
+++ b/enzyme/tools/enzyme-tblgen/blas-tblgen.h
@@ -1,2 +1,3 @@
 void emitBlasDerivatives(const llvm::RecordKeeper &RK, llvm::raw_ostream &os);
 bool hasDiffeRet(llvm::Init *resultTree);
+bool hasAdjoint(llvm::Init *resultTree, llvm::StringRef argName);
diff --git a/enzyme/tools/enzyme-tblgen/blasDiffUseUpdater.h b/enzyme/tools/enzyme-tblgen/blasDiffUseUpdater.h
index 439ddc583bfe..e071222ea19a 100644
--- a/enzyme/tools/enzyme-tblgen/blasDiffUseUpdater.h
+++ b/enzyme/tools/enzyme-tblgen/blasDiffUseUpdater.h
@@ -60,7 +60,7 @@ void emit_BLASDiffUse(TGPattern &pattern, llvm::raw_ostream &os) {
     auto name = nameVec[arg];
     os << "  bool active_" << name << " = !gutils->isConstantValue(arg_" << name
        << ");\n";
-    os << "  if (EnzymeRuntimeActivityCheck && active_" << name
+    os << "  if (!shadow && EnzymeRuntimeActivityCheck && active_" << name
        << ") return true;\n";
   }
 
@@ -68,10 +68,53 @@ void emit_BLASDiffUse(TGPattern &pattern, llvm::raw_ostream &os) {
 
   for (size_t argPos = (lv23 ? 1 : 0); argPos < typeMap.size(); argPos++) {
     auto users = argUsers.lookup(argPos);
-    auto name = nameVec[argPos];
-    os << "  if (val == arg_" << name << " && need_" << name << " && !cache_"
-       << name << ")\n"
-       << "     return true;\n";
+    auto argname = nameVec[argPos];
+
+    os << "  if (val == arg_" << argname << ") {\n";
+
+    // We need the shadow of the value we're updating
+    if (typeMap[argPos] == ArgType::fp) {
+      os << "    if (shadow && byRef && active_" << argname
+         << ") return true;\n";
+    } else if (typeMap[argPos] == ArgType::vincData ||
+               typeMap[argPos] == ArgType::mldData) {
+      for (auto derivOp : pattern.getRules()) {
+        if (hasAdjoint(derivOp.getRuleDag(), argname)) {
+          os << "    if (shadow && active_"
+             << nameVec[derivOp.getHandledArgIdx()] << ") return true;\n";
+        } else {
+          bool isNoop = false;
+          if (DagInit *resultRoot = dyn_cast<DagInit>(derivOp.getRuleDag())) {
+            auto opName = resultRoot->getOperator()->getAsString();
+            auto Def = cast<DefInit>(resultRoot->getOperator())->getDef();
+            if (Def->getName() == "noop" || Def->getName() == "inactive") {
+              isNoop = true;
+            }
+          }
+          if (DefInit *DefArg = dyn_cast<DefInit>(derivOp.getRuleDag())) {
+            auto Def = DefArg->getDef();
+            if (Def->getName() == "noop" || Def->getName() == "inactive") {
+              isNoop = true;
+            }
+          }
+          // updates to a vector/matrix must definitionally use the shadow of
+          // the input, unless a noop-update
+          if (!isNoop) {
+            if (derivOp.getHandledArgIdx() == argPos) {
+              llvm::errs() << " fnname: " << name << " argPos: " << argPos
+                           << " argname: " << argname
+                           << " rule: " << *derivOp.getRuleDag() << "\n";
+            }
+            assert(derivOp.getHandledArgIdx() != argPos);
+          }
+        }
+      }
+    }
+
+    os << "    if (!shadow && need_" << argname << " && !cache_" << argname
+       << ")\n"
+       << "      return true;\n";
+    os << "  }\n";
   }
 
   // If any of the rule uses DiffeRet, the primary function has a ret val