IRGen: Fix the computation of the number of type metadata pointers for distributed thunks under opaque pointer IR

When using opaque pointers we can no longer depend on the LLVM IR type
to perform the computation. Instead compute the number while we are
building a signature.

Author: aschwaighofer

lib/IRGen/GenDistributed.cpp

@@ -681,14 +681,17 @@ void DistributedAccessor::emit() {
     // We need this to determine the expected number of witness tables
     // to load from the buffer provided by the caller.
     llvm::SmallVector<llvm::Type *, 4> targetGenericArguments;
-    expandPolymorphicSignature(IGM, targetTy, targetGenericArguments);
+    auto numDirectGenericArgs =
+        expandPolymorphicSignature(IGM, targetTy, targetGenericArguments);
 
     // Generic arguments associated with the distributed thunk directly
     // e.g. `distributed func echo<T, U>(...)`
-    auto numDirectGenericArgs =
-        llvm::count_if(targetGenericArguments, [&](const llvm::Type *type) {
-          return type == IGM.TypeMetadataPtrTy;
-        });
+    assert(
+        !IGM.getLLVMContext().supportsTypedPointers() ||
+        numDirectGenericArgs ==
+            llvm::count_if(targetGenericArguments, [&](const llvm::Type *type) {
+              return type == IGM.TypeMetadataPtrTy;
+            }));
 
     auto expectedWitnessTables =
         targetGenericArguments.size() - numDirectGenericArgs;

lib/IRGen/GenProto.cpp

@@ -3456,12 +3456,15 @@ void irgen::bindGenericRequirement(IRGenFunction &IGF,
 namespace {
   /// A class for expanding a polymorphic signature.
   class ExpandPolymorphicSignature : public PolymorphicConvention {
+    unsigned numTypeMetadataPtrs = 0;
+
   public:
     ExpandPolymorphicSignature(IRGenModule &IGM, CanSILFunctionType fn)
       : PolymorphicConvention(IGM, fn) {}
 
-    void expand(SmallVectorImpl<llvm::Type *> &out,
-                SmallVectorImpl<PolymorphicSignatureExpandedTypeSource> *reqs) {
+    unsigned
+    expand(SmallVectorImpl<llvm::Type *> &out,
+           SmallVectorImpl<PolymorphicSignatureExpandedTypeSource> *reqs) {
       auto outStartSize = out.size();
       (void)outStartSize;
       for (auto &source : getSources())
@@ -3472,9 +3475,13 @@ namespace {
           reqs->push_back(reqt);
         out.push_back(reqt.Protocol ? IGM.WitnessTablePtrTy
                                     : IGM.TypeMetadataPtrTy);
+
+        if (!reqt.Protocol)
+          ++numTypeMetadataPtrs;
       });
       assert((!reqs || reqs->size() == (out.size() - outStartSize)) &&
              "missing type source for type");
+      return numTypeMetadataPtrs;
     }
 
   private:
@@ -3488,6 +3495,7 @@ namespace {
       case MetadataSource::Kind::GenericLValueMetadata:
         if (reqs)
           reqs->push_back(source);
+        ++numTypeMetadataPtrs;
         return out.push_back(IGM.TypeMetadataPtrTy);
       case MetadataSource::Kind::SelfMetadata:
       case MetadataSource::Kind::SelfWitnessTable:
@@ -3501,11 +3509,11 @@ namespace {
 } // end anonymous namespace
 
 /// Given a generic signature, add the argument types required in order to call it.
-void irgen::expandPolymorphicSignature(
+unsigned irgen::expandPolymorphicSignature(
     IRGenModule &IGM, CanSILFunctionType polyFn,
     SmallVectorImpl<llvm::Type *> &out,
     SmallVectorImpl<PolymorphicSignatureExpandedTypeSource> *outReqs) {
-  ExpandPolymorphicSignature(IGM, polyFn).expand(out, outReqs);
+  return ExpandPolymorphicSignature(IGM, polyFn).expand(out, outReqs);
 }
 
 void irgen::expandTrailingWitnessSignature(IRGenModule &IGM,

lib/IRGen/GenProto.h

@@ -101,7 +101,8 @@ namespace irgen {
 
   /// Add the witness parameters necessary for calling a function with
   /// the given generics clause.
-  void expandPolymorphicSignature(
+  /// Returns the number of type metadata pointers added to `types`.
+  unsigned expandPolymorphicSignature(
       IRGenModule &IGM, CanSILFunctionType type,
       SmallVectorImpl<llvm::Type *> &types,
       SmallVectorImpl<PolymorphicSignatureExpandedTypeSource> *outReqs =