[cxx-interop] [nfc] Don't emit a cast if the cast is a no-op.

Author: zoecarver

lib/Sema/CSApply.cpp

@@ -204,10 +204,16 @@ synthesizeDependentTypeThunkParamForwarding(AbstractFunctionDecl *afd, void *con
     paramRefExpr->setType(param->getType());
 
     auto specParamTy = specializedFuncDecl->getParameters()->get(paramIndex)->getType();
-    auto cast = ForcedCheckedCastExpr::createImplicit(
-        ctx, paramRefExpr, specParamTy);
 
-    forwardingParams.push_back(Argument(SourceLoc(), Identifier(), cast));
+    Expr *argExpr = nullptr;
+    if (specParamTy->isEqual(paramRefExpr->getType())) {
+      argExpr = paramRefExpr;
+    } else {
+      argExpr = ForcedCheckedCastExpr::createImplicit(ctx, paramRefExpr,
+                                                      specParamTy);
+    }
+
+    forwardingParams.push_back(Argument(SourceLoc(), Identifier(), argExpr));
     paramIndex++;
   }
 
@@ -220,10 +226,16 @@ synthesizeDependentTypeThunkParamForwarding(AbstractFunctionDecl *afd, void *con
   specializedFuncCallExpr->setType(specializedFuncDecl->getResultInterfaceType());
   specializedFuncCallExpr->setThrows(false);
 
-  auto cast = ForcedCheckedCastExpr::createImplicit(
-      ctx, specializedFuncCallExpr, thunkDecl->getResultInterfaceType());
+  Expr *resultExpr = nullptr;
+  if (specializedFuncCallExpr->getType()->isEqual(thunkDecl->getResultInterfaceType())) {
+    resultExpr = specializedFuncCallExpr;
+  } else {
+    resultExpr = ForcedCheckedCastExpr::createImplicit(
+        ctx, specializedFuncCallExpr, thunkDecl->getResultInterfaceType());
+  }
 
-  auto returnStmt = new (ctx) ReturnStmt(SourceLoc(), cast, /*implicit=*/true);
+  auto returnStmt = new (ctx)
+      ReturnStmt(SourceLoc(), resultExpr, /*implicit=*/true);
   auto body = BraceStmt::create(ctx, SourceLoc(), {returnStmt}, SourceLoc(),
                                 /*implicit=*/true);
   return {body, /*isTypeChecked=*/true};

test/Interop/Cxx/templates/dependent-types-silgen.swift

@@ -27,14 +27,9 @@ import DependentTypes
 // CHECK-LABEL: sil [transparent] [serialized] [ossa] @$sSC27dependantReturnTypeInfferedyyps5Int64VF : $@convention(thin) (Int64) -> @out Any
 // CHECK: bb0(%0 : $*Any, %1 : $Int64):
 // CHECK:   [[SPEC_OUT:%.*]] = alloc_stack $__CxxTemplateInst1MIxE
-// CHECK:   [[TMP_INT:%.*]] = alloc_stack $Int64
-// CHECK:   store %1 to [trivial] [[TMP_INT]] : $*Int64
-// CHECK:   [[TMP_INT_CASTED:%.*]] = alloc_stack $Int64
-// CHECK:   unconditional_checked_cast_addr Int64 in [[TMP_INT]] : $*Int64 to Int64 in [[TMP_INT_CASTED]] : $*Int64
 
-// CHECK:   [[ARG:%.*]] = load [trivial] [[TMP_INT_CASTED]] : $*Int64
 // CHECK:   [[FN:%.*]] = function_ref @{{_Z27dependantReturnTypeInfferedIxE1MIT_ES1_|\?\?\$dependantReturnTypeInffered@_J@@YA\?AU\?\$M@_J@@_J@Z}} : $@convention(c) (Int64) -> __CxxTemplateInst1MIxE
-// CHECK:   [[OUT:%.*]] = apply [[FN]]([[ARG]]) : $@convention(c) (Int64) -> __CxxTemplateInst1MIxE
+// CHECK:   [[OUT:%.*]] = apply [[FN]](%1) : $@convention(c) (Int64) -> __CxxTemplateInst1MIxE
 
 // CHECK:   store [[OUT]] to [trivial] [[SPEC_OUT]] : $*__CxxTemplateInst1MIxE
 // CHECK:   unconditional_checked_cast_addr __CxxTemplateInst1MIxE in [[SPEC_OUT]] : $*__CxxTemplateInst1MIxE to Any in %0 : $*Any