Fix shadowed variable in faiss/impl/simd_result_handlers.h (#3960)

Summary:
Pull Request resolved: #3960

Our upcoming compiler upgrade will require us not to have shadowed variables. Such variables have a _high_ bug rate and reduce readability, so we would like to avoid them even if the compiler was not forcing us to do so.

This codemod attempts to fix an instance of a shadowed variable. Please review with care: if it's failed the result will be a silent bug.

**What's a shadowed variable?**

Shadowed variables are variables in an inner scope with the same name as another variable in an outer scope. Having the same name for both variables might be semantically correct, but it can make the code confusing to read! It can also hide subtle bugs.

This diff fixes such an issue by renaming the variable.

 - If you approve of this diff, please use the "Accept & Ship" button :-)

Reviewed By: meyering

Differential Revision: D64398709

fbshipit-source-id: b10e44b40aa1d3e21aeb5112eb93fb63d64d4118

faiss/impl/simd_result_handlers.h

@@ -368,10 +368,10 @@ struct HeapHandler : ResultHandlerCompare<C, with_id_map> {
                 auto real_idx = this->adjust_id(b, j);
                 lt_mask -= 1 << j;
                 if (this->sel->is_member(real_idx)) {
-                    T dis = d32tab[j];
-                    if (C::cmp(heap_dis[0], dis)) {
+                    T dis_2 = d32tab[j];
+                    if (C::cmp(heap_dis[0], dis_2)) {
                         heap_replace_top<C>(
-                                k, heap_dis, heap_ids, dis, real_idx);
+                                k, heap_dis, heap_ids, dis_2, real_idx);
                     }
                 }
             }
@@ -380,10 +380,10 @@ struct HeapHandler : ResultHandlerCompare<C, with_id_map> {
                 // find first non-zero
                 int j = __builtin_ctz(lt_mask);
                 lt_mask -= 1 << j;
-                T dis = d32tab[j];
-                if (C::cmp(heap_dis[0], dis)) {
+                T dis_2 = d32tab[j];
+                if (C::cmp(heap_dis[0], dis_2)) {
                     int64_t idx = this->adjust_id(b, j);
-                    heap_replace_top<C>(k, heap_dis, heap_ids, dis, idx);
+                    heap_replace_top<C>(k, heap_dis, heap_ids, dis_2, idx);
                 }
             }
         }
@@ -480,17 +480,17 @@ struct ReservoirHandler : ResultHandlerCompare<C, with_id_map> {
                 auto real_idx = this->adjust_id(b, j);
                 lt_mask -= 1 << j;
                 if (this->sel->is_member(real_idx)) {
-                    T dis = d32tab[j];
-                    res.add(dis, real_idx);
+                    T dis_2 = d32tab[j];
+                    res.add(dis_2, real_idx);
                 }
             }
         } else {
             while (lt_mask) {
                 // find first non-zero
                 int j = __builtin_ctz(lt_mask);
                 lt_mask -= 1 << j;
-                T dis = d32tab[j];
-                res.add(dis, this->adjust_id(b, j));
+                T dis_2 = d32tab[j];
+                res.add(dis_2, this->adjust_id(b, j));
             }
         }
     }
@@ -719,10 +719,10 @@ void dispatch_SIMDResultHandler_fixedCW(
         Types... args) {
     if (auto resh = dynamic_cast<SingleResultHandler<C, W>*>(&res)) {
         consumer.template f<SingleResultHandler<C, W>>(*resh, args...);
-    } else if (auto resh = dynamic_cast<HeapHandler<C, W>*>(&res)) {
-        consumer.template f<HeapHandler<C, W>>(*resh, args...);
-    } else if (auto resh = dynamic_cast<ReservoirHandler<C, W>*>(&res)) {
-        consumer.template f<ReservoirHandler<C, W>>(*resh, args...);
+    } else if (auto resh_2 = dynamic_cast<HeapHandler<C, W>*>(&res)) {
+        consumer.template f<HeapHandler<C, W>>(*resh_2, args...);
+    } else if (auto resh_2 = dynamic_cast<ReservoirHandler<C, W>*>(&res)) {
+        consumer.template f<ReservoirHandler<C, W>>(*resh_2, args...);
     } else { // generic handler -- will not be inlined
         FAISS_THROW_IF_NOT_FMT(
                 simd_result_handlers_accept_virtual,
@@ -752,8 +752,8 @@ void dispatch_SIMDResultHandler(
     if (res.sizeof_ids == 0) {
         if (auto resh = dynamic_cast<StoreResultHandler*>(&res)) {
             consumer.template f<StoreResultHandler>(*resh, args...);
-        } else if (auto resh = dynamic_cast<DummyResultHandler*>(&res)) {
-            consumer.template f<DummyResultHandler>(*resh, args...);
+        } else if (auto resh_2 = dynamic_cast<DummyResultHandler*>(&res)) {
+            consumer.template f<DummyResultHandler>(*resh_2, args...);
         } else { // generic path
             FAISS_THROW_IF_NOT_FMT(
                     simd_result_handlers_accept_virtual,