From 6f83cb2905e2cbf6b7822bc714ae1cd4481e3193 Mon Sep 17 00:00:00 2001
From: David Nadlinger <code@klickverbot.at>
Date: Wed, 16 Sep 2015 18:37:48 +0200
Subject: [PATCH] x86: Only skip empty structs on OS X

---
 gen/abi-x86.cpp   | 25 +++++++++++++++++++++++++
 gen/functions.cpp | 11 -----------
 2 files changed, 25 insertions(+), 11 deletions(-)

diff --git a/gen/abi-x86.cpp b/gen/abi-x86.cpp
index 1e07392e49..b0c282fc21 100644
--- a/gen/abi-x86.cpp
+++ b/gen/abi-x86.cpp
@@ -215,6 +215,31 @@ struct X86TargetABI : TargetABI
             // IMPLICIT PARAMETERS
 
             // EXPLICIT PARAMETERS
+
+            // Clang does not pass empty structs, while it seems that GCC does,
+            // at least on Linux x86.
+            if (isOSX)
+            {
+                size_t i = 0;
+                while (i < fty.args.size())
+                {
+                    Type *type = fty.args[i]->type->toBasetype();
+                    if (type->ty == Tstruct)
+                    {
+                        // Do not pass empty structs at all for C++ ABI compatibility.
+                        // Tests with clang reveal that more complex "empty" types, for
+                        // example a struct containing an empty struct, are not
+                        // optimized in the same way.
+                        StructDeclaration *sd = static_cast<TypeStruct *>(type)->sym;
+                        if (sd->fields.empty())
+                        {
+                            fty.args.erase(fty.args.begin() + i);
+                            continue;
+                        }
+                    }
+                    ++i;
+                }
+            }
         }
     }
 };
diff --git a/gen/functions.cpp b/gen/functions.cpp
index f385f30e97..dc1998ad99 100644
--- a/gen/functions.cpp
+++ b/gen/functions.cpp
@@ -164,17 +164,6 @@ llvm::FunctionType* DtoFunctionType(Type* type, IrFuncTy &irFty, Type* thistype,
         }
         else if (!passPointer)
         {
-            if (loweredDType->toBasetype()->ty == Tstruct)
-            {
-                // Do not pass empty structs at all for C++ ABI compatibility.
-                // Tests with clang reveal that more complex "empty" types, for
-                // example a struct containing an empty struct, are not
-                // optimized in the same way.
-                StructDeclaration *sd =
-                    static_cast<TypeStruct*>(loweredDType->toBasetype())->sym;
-                if (sd->fields.empty()) continue;
-            }
-
             if (abi->passByVal(loweredDType))
             {
                 attrBuilder.add(LDC_ATTRIBUTE(ByVal));