Fix ABI on Win32.

We can't simply use the C calling convention, as the D(MD)
ABI is callee-pop, and this is hardcoded in naked functions
with stack parameters.

The \1 "trick" is normally used to avoid prefixes added by
LLVM; on the 3.2 release, a patch is needed to make it work
for the @<n> stdcall suffixes as well.

gen/abi-x86.cpp

@@ -36,8 +36,6 @@ struct X86TargetABI : TargetABI
             return llvm::CallingConv::C;
         case LINKd:
         case LINKdefault:
-            return global.params.targetTriple.isOSWindows() ?
-                llvm::CallingConv::C : llvm::CallingConv::X86_StdCall;
         case LINKpascal:
         case LINKwindows:
             return llvm::CallingConv::X86_StdCall;
@@ -46,6 +44,30 @@ struct X86TargetABI : TargetABI
         }
     }
 
+    std::string mangleForLLVM(llvm::StringRef name, LINK l)
+    {
+        switch (l)
+        {
+        case LINKc:
+        case LINKcpp:
+        case LINKintrinsic:
+        case LINKpascal:
+        case LINKwindows:
+            return name;
+        case LINKd:
+        case LINKdefault:
+            if (global.params.targetTriple.isOSWindows())
+            {
+                // Prepend a 0x1 byte to keep LLVM from adding the usual
+                // "@<paramsize>" stdcall suffix.
+                return ("\1_" + name).str();
+            }
+            return name;
+        default:
+            llvm_unreachable("Unhandled D linkage type.");
+        }
+    }
+
     bool returnInArg(TypeFunction* tf)
     {
 #if DMDV2

gen/abi.h

@@ -60,7 +60,15 @@ struct TargetABI
 
     /// Returns the LLVM calling convention to be used for the given D linkage
     /// type on the target.
-    virtual llvm::CallingConv::ID callingConv(enum LINK l) = 0;
+    virtual llvm::CallingConv::ID callingConv(LINK l) = 0;
+
+    /// Applies any rewrites that might be required to accurately reproduce the
+    /// passed function name on LLVM given a specific calling convention.
+    ///
+    /// Using this function at a stage where the name could be user-visible is
+    /// almost certainly a mistake; it is intended to e.g. prepend '\1' where
+    /// disabling the LLVM-internal name mangling/postprocessing is required.
+    virtual std::string mangleForLLVM(llvm::StringRef name, LINK l) { return name; }
 
     /// Called if a new function type is resolved
     virtual void newFunctionType(TypeFunction* tf) {}

gen/functions.cpp

@@ -741,48 +741,52 @@ void DtoDeclareFunction(FuncDeclaration* fdecl)
         fdecl->ir.irFunc = new IrFunction(fdecl);
     }
 
-    // mangled name
-    const char* mangled_name;
-    if (fdecl->llvmInternal == LLVMintrinsic)
-        mangled_name = fdecl->intrinsicName.c_str();
-    else
-        mangled_name = fdecl->mangle();
-
     LLFunction* vafunc = 0;
     if (fdecl->isVaIntrinsic())
         vafunc = DtoDeclareVaFunction(fdecl);
 
+    // calling convention
+    LINK link = f->linkage;
+    if (vafunc || fdecl->llvmInternal == LLVMintrinsic
+#if DMDV2
+        // DMD treats _Dmain as having C calling convention and this has been
+        // hardcoded into druntime, even if the frontend type has D linkage.
+        // See Bugzilla issue 9028.
+        || fdecl->isMain()
+#endif
+    )
+    {
+        link = LINKc;
+    }
+
+    // mangled name
+    std::string mangledName;
+    if (fdecl->llvmInternal == LLVMintrinsic)
+        mangledName = fdecl->intrinsicName;
+    else
+        mangledName = fdecl->mangle();
+    mangledName = gABI->mangleForLLVM(mangledName, link);
+
     // construct function
     LLFunctionType* functype = DtoFunctionType(fdecl);
-    LLFunction* func = vafunc ? vafunc : gIR->module->getFunction(mangled_name);
+    LLFunction* func = vafunc ? vafunc : gIR->module->getFunction(mangledName);
     if (!func) {
         if(fdecl->llvmInternal == LLVMinline_ir)
             func = DtoInlineIRFunction(fdecl);
         else
-            func = LLFunction::Create(functype, DtoLinkage(fdecl), mangled_name, gIR->module);
+            func = LLFunction::Create(functype, DtoLinkage(fdecl), mangledName, gIR->module);
     } else if (func->getFunctionType() != functype) {
         error(fdecl->loc, "Function type does not match previously declared function with the same mangled name: %s", fdecl->mangle());
     }
 
+    func->setCallingConv(gABI->callingConv(link));
+
     if (Logger::enabled())
         Logger::cout() << "func = " << *func << std::endl;
 
     // add func to IRFunc
     fdecl->ir.irFunc->func = func;
 
-    // calling convention
-    if (!vafunc && fdecl->llvmInternal != LLVMintrinsic
-#if DMDV2
-        // DMD treats _Dmain as having C calling convention and this has been
-        // hardcoded into druntime, even if the frontend type has D linkage.
-        // See Bugzilla issue 9028.
-        && !fdecl->isMain()
-#endif
-        )
-        func->setCallingConv(gABI->callingConv(f->linkage));
-    else // fall back to C, it should be the right thing to do
-        func->setCallingConv(llvm::CallingConv::C);
-
     // parameter attributes
     if (!fdecl->isIntrinsic()) {
         set_param_attrs(f, func, fdecl);

gen/module.cpp

@@ -74,15 +74,18 @@ static llvm::Function* build_module_function(const std::string &name, const std:
 
     std::vector<LLType*> argsTy;
     LLFunctionType* fnTy = LLFunctionType::get(LLType::getVoidTy(gIR->context()),argsTy,false);
-    assert(gIR->module->getFunction(name) == NULL);
+
-    llvm::Function* fn = llvm::Function::Create(fnTy, llvm::GlobalValue::InternalLinkage, name, gIR->module);
+    std::string const symbolName = gABI->mangleForLLVM(name, LINKd);
+    assert(gIR->module->getFunction(symbolName) == NULL);
+    llvm::Function* fn = llvm::Function::Create(fnTy,
+        llvm::GlobalValue::InternalLinkage, symbolName, gIR->module);
     fn->setCallingConv(gABI->callingConv(LINKd));
 
     llvm::BasicBlock* bb = llvm::BasicBlock::Create(gIR->context(), "entry", fn);
     IRBuilder<> builder(bb);
 
     // debug info
-    DtoDwarfSubProgramInternal(name.c_str(), name.c_str());
+    DtoDwarfSubProgramInternal(name.c_str(), symbolName.c_str());
 
     // Call ctor's
     typedef std::list<FuncDeclaration*>::const_iterator FuncIterator;