[Async CC] Put bindings after formal arguments.

Bindings will always be supplied by the first partial apply, so they
will only be added to the async context when its full layout is known.
If they are earlier in the layout, subsequent partial applies will put
their arguments into the wrong position because they will not be privy
to the space requirements of the bindings.

Author: nate-chandler

lib/IRGen/GenCall.cpp

@@ -168,15 +168,6 @@ AsyncContextLayout irgen::getAsyncContextLayout(
   }
 
   //   ArgTypes formalArguments...;
-  auto bindings = NecessaryBindings::forAsyncFunctionInvocation(
-      IGF.IGM, originalType, substitutionMap);
-  if (!bindings.empty()) {
-    auto bindingsSize = bindings.getBufferSize(IGF.IGM);
-    auto &bindingsTI = IGF.IGM.getOpaqueStorageTypeInfo(
-        bindingsSize, IGF.IGM.getPointerAlignment());
-    valTypes.push_back(SILType());
-    typeInfos.push_back(&bindingsTI);
-  }
   for (auto parameter : parameters) {
     SILType ty = IGF.IGM.silConv.getSILType(
         parameter, substitutedType, IGF.IGM.getMaximalTypeExpansionContext());
@@ -191,6 +182,15 @@ AsyncContextLayout irgen::getAsyncContextLayout(
     typeInfos.push_back(&ti);
     paramInfos.push_back({ty, parameter.getConvention()});
   }
+  auto bindings = NecessaryBindings::forAsyncFunctionInvocation(
+      IGF.IGM, originalType, substitutionMap);
+  if (!bindings.empty()) {
+    auto bindingsSize = bindings.getBufferSize(IGF.IGM);
+    auto &bindingsTI = IGF.IGM.getOpaqueStorageTypeInfo(
+        bindingsSize, IGF.IGM.getPointerAlignment());
+    valTypes.push_back(SILType());
+    typeInfos.push_back(&bindingsTI);
+  }
 
   Optional<AsyncContextLayout::TrailingWitnessInfo> trailingWitnessInfo;
   if (originalType->getRepresentation() ==

lib/IRGen/GenCall.h

@@ -131,27 +131,27 @@ namespace irgen {
     unsigned getIndexAfterLocalContext() {
       return getIndexAfterDirectReturns() + (hasLocalContext() ? 1 : 0);
     }
+    unsigned getFirstArgumentIndex() { return getIndexAfterLocalContext(); }
+    unsigned getIndexAfterArguments() {
+      return getFirstArgumentIndex() + getArgumentCount();
+    }
     unsigned getBindingsIndex() {
       assert(hasBindings());
-      return getIndexAfterLocalContext();
+      return getIndexAfterArguments();
     }
     unsigned getIndexAfterBindings() {
-      return getIndexAfterLocalContext() + (hasBindings() ? 1 : 0);
-    }
-    unsigned getFirstArgumentIndex() { return getIndexAfterBindings(); }
-    unsigned getIndexAfterArguments() {
-      return getFirstArgumentIndex() + getArgumentCount();
+      return getIndexAfterArguments() + (hasBindings() ? 1 : 0);
     }
     unsigned getSelfMetadataIndex() {
       assert(hasTrailingWitnesses());
-      return getIndexAfterArguments();
+      return getIndexAfterBindings();
     }
     unsigned getSelfWitnessTableIndex() {
       assert(hasTrailingWitnesses());
-      return getIndexAfterArguments() + 1;
+      return getIndexAfterBindings() + 1;
     }
     unsigned getIndexAfterTrailingWitnesses() {
-      return getIndexAfterArguments() + (hasTrailingWitnesses() ? 2 : 0);
+      return getIndexAfterBindings() + (hasTrailingWitnesses() ? 2 : 0);
     }
 
   public: