[IRGen] Use ABI notion of function parameter flags to compute ‘has parameter flags’ bit.

There are some cases where the AST’s notion of what constitutes function parameter flags
differ from the ABI notion. Specifically, these are @escaping and @autoclosure, which
are both modeled as types in the ABI. Teach IRGen to look at the ABI’s version of
function parameter flags when determining whether to pass parameter flags
to swift_getFunctionType([0-3])?.

Without this fix, we would end up with mismatches between the function types
built by IRGen and those built from mangled names. Part of
rdar://problem/37551850.

Author: DougGregor

lib/IRGen/MetadataRequest.cpp

@@ -924,9 +924,17 @@ namespace {
       auto params = type.getParams();
       auto numParams = params.size();
 
+      // Retrieve the ABI parameter flags from the type-level parameter
+      // flags.
+      auto getABIParameterFlags = [](ParameterTypeFlags flags) {
+        return ParameterFlags()
+                 .withValueOwnership(flags.getValueOwnership())
+                 .withVariadic(flags.isVariadic());
+      };
+
       bool hasFlags = false;
       for (auto param : params) {
-        if (!param.getParameterFlags().isNone()) {
+        if (!getABIParameterFlags(param.getParameterFlags()).isNone()) {
           hasFlags = true;
           break;
         }
@@ -969,11 +977,7 @@ namespace {
               auto param = params[index];
               auto flags = param.getParameterFlags();
 
-              auto parameterFlags =
-                  ParameterFlags()
-                      .withValueOwnership(flags.getValueOwnership())
-                      .withVariadic(flags.isVariadic());
-
+              auto parameterFlags = getABIParameterFlags(flags);
               processor(index, getFunctionParameterRef(param), parameterFlags);
             }
           };

test/IRGen/function_metadata.swift

@@ -51,4 +51,8 @@ func test_arch() {
   // CHECK: store %swift.type* @"$ss4Int8VN", %swift.type** [[T:%.*]], align [[ALIGN:(4|8)]]
   // CHECK: call %swift.type* @swift_getFunctionTypeMetadata([[WORD]] 100663300, %swift.type** {{%.*}}, i32* getelementptr inbounds ([4 x i32], [4 x i32]* @parameter-flags.{{.*}}, i32 0, i32 0), %swift.type* getelementptr inbounds (%swift.full_type, %swift.full_type* @"$sytN", i32 0, i32 1))
   arch({(x: inout Int, y: Double, z: String, w: Int8) -> () in })
+
+  // CHECK-LABEL: define{{( protected)?}} linkonce_odr hidden swiftcc %swift.metadata_response @"$syyyccMa"
+  // CHECK: call %swift.type* @swift_getFunctionTypeMetadata1(i64 67108865
+  arch({(x: @escaping () -> ()) -> () in })
 }