[forwardmode] handle multi store on active store (#1564)

Author: wsmoses

enzyme/Enzyme/AdjointGenerator.h

@@ -1026,23 +1026,26 @@ class AdjointGenerator
     if (Mode == DerivativeMode::ForwardMode) {
 
       auto dt = vd[{-1}];
-      for (size_t i = 0; i < storeSize; ++i) {
-        bool Legal = true;
-        dt.checkedOrIn(vd[{(int)i}], /*PointerIntSame*/ true, Legal);
-        if (!Legal) {
-          std::string str;
-          raw_string_ostream ss(str);
-          ss << "Cannot deduce single type of store " << I << vd.str()
-             << " size: " << storeSize;
-          if (CustomErrorHandler) {
-            CustomErrorHandler(str.c_str(), wrap(&I), ErrorType::NoType,
-                               &TR.analyzer, nullptr, wrap(&BuilderZ));
-          } else {
-            EmitFailure("CannotDeduceType", I.getDebugLoc(), &I, ss.str());
+      // Only need the full type in forward mode, if storing a constant
+      // and therefore may need to zero some floats.
+      if (constantval)
+        for (size_t i = 0; i < storeSize; ++i) {
+          bool Legal = true;
+          dt.checkedOrIn(vd[{(int)i}], /*PointerIntSame*/ true, Legal);
+          if (!Legal) {
+            std::string str;
+            raw_string_ostream ss(str);
+            ss << "Cannot deduce single type of store " << I << vd.str()
+               << " size: " << storeSize;
+            if (CustomErrorHandler) {
+              CustomErrorHandler(str.c_str(), wrap(&I), ErrorType::NoType,
+                                 &TR.analyzer, nullptr, wrap(&BuilderZ));
+            } else {
+              EmitFailure("CannotDeduceType", I.getDebugLoc(), &I, ss.str());
+            }
+            return;
           }
-          return;
         }
-      }
 
       Value *diff = nullptr;
       if (!EnzymeRuntimeActivityCheck && CustomErrorHandler && constantval) {