Use IndirectByvalRewrite for non-POD args and extern(C++) on Posix (#2728)

Fixing one aspect of issue #2702; not tackling the different destruction
rules yet.

gen/abi-aarch64.cpp

@@ -32,10 +32,10 @@ struct AArch64TargetABI : TargetABI {
     if (!isPOD(rt))
       return true;
 
-    return passByVal(rt);
+    return passByVal(tf, rt);
   }
 
-  bool passByVal(Type *t) override {
+  bool passByVal(TypeFunction *, Type *t) override {
     t = t->toBasetype();
     return t->ty == Tsarray ||
            (t->ty == Tstruct && t->size() > 16 && !isHFA((TypeStruct *)t));

gen/abi-arm.cpp

@@ -42,7 +42,7 @@ struct ArmTargetABI : TargetABI {
              !isHFA((TypeStruct *)rt)));
   }
 
-  bool passByVal(Type *t) override {
+  bool passByVal(TypeFunction *, Type *t) override {
     // AAPCS does not use an indirect arg to pass aggregates, however
     // clang uses byval for types > 64-bytes, then llvm backend
     // converts back to non-byval.  Without this special handling the

gen/abi-mips64.cpp

@@ -42,7 +42,7 @@ struct MIPS64TargetABI : TargetABI {
     return (rt->ty == Tstruct || rt->ty == Tsarray);
   }
 
-  bool passByVal(Type *t) override {
+  bool passByVal(TypeFunction *, Type *t) override {
     TY ty = t->toBasetype()->ty;
     return ty == Tstruct || ty == Tsarray;
   }

gen/abi-nvptx.cpp

@@ -24,7 +24,7 @@ struct NVPTXTargetABI : TargetABI {
     else
         return llvm::CallingConv::PTX_Device;
   }
-  bool passByVal(Type *t) override {
+  bool passByVal(TypeFunction *, Type *t) override {
     t = t->toBasetype();
     return ((t->ty == Tsarray || t->ty == Tstruct) && t->size() > 64);
   }

gen/abi-ppc.cpp

@@ -49,7 +49,7 @@ struct PPCTargetABI : TargetABI {
     return rt->ty == Tsarray || rt->ty == Tstruct;
   }
 
-  bool passByVal(Type *t) override {
+  bool passByVal(TypeFunction *, Type *t) override {
     // On ppc, aggregates are always passed as an indirect value.
     // On ppc64, they are always passed by value. However, clang
     // used byval for type > 64 bytes.

gen/abi-ppc64le.cpp

@@ -38,10 +38,10 @@ struct PPC64LETargetABI : TargetABI {
     if (!isPOD(rt))
       return true;
 
-    return passByVal(rt);
+    return passByVal(tf, rt);
   }
 
-  bool passByVal(Type *t) override {
+  bool passByVal(TypeFunction *, Type *t) override {
     t = t->toBasetype();
     return t->ty == Tsarray || (t->ty == Tstruct && t->size() > 16 &&
                                 !isHFA((TypeStruct *)t, nullptr, 8));

gen/abi-spirv.cpp

@@ -24,7 +24,7 @@ struct SPIRVTargetABI : TargetABI {
     else
       return llvm::CallingConv::SPIR_FUNC;
   }
-  bool passByVal(Type *t) override {
+  bool passByVal(TypeFunction *, Type *t) override {
     t = t->toBasetype();
     return ((t->ty == Tsarray || t->ty == Tstruct) && t->size() > 64);
   }

gen/abi-win64.cpp

@@ -117,7 +117,7 @@ public:
     return passPointerToHiddenCopy(rt, /*isReturnValue=*/true, tf->linkage);
   }
 
-  bool passByVal(Type *t) override {
+  bool passByVal(TypeFunction *, Type *) override {
     // LLVM's byval attribute is not compatible with the Win64 ABI
     return false;
   }

gen/abi-x86-64.cpp

@@ -217,15 +217,16 @@ struct ImplicitByvalRewrite : ABIRewrite {
 struct X86_64TargetABI : TargetABI {
   X86_64_C_struct_rewrite struct_rewrite;
   ImplicitByvalRewrite byvalRewrite;
+  IndirectByvalRewrite indirectByvalRewrite;
 
   bool returnInArg(TypeFunction *tf) override;
 
-  bool passByVal(Type *t) override;
+  bool passByVal(TypeFunction *tf, Type *t) override;
 
   void rewriteFunctionType(IrFuncTy &fty) override;
   void rewriteVarargs(IrFuncTy &fty, std::vector<IrFuncTyArg *> &args) override;
   void rewriteArgument(IrFuncTy &fty, IrFuncTyArg &arg) override;
-  void rewriteArgument(IrFuncTyArg &arg, RegCount &regCount);
+  void rewriteArgument(IrFuncTy &fty, IrFuncTyArg &arg, RegCount &regCount);
 
   LLValue *prepareVaStart(DLValue *ap) override;
 
@@ -252,11 +253,15 @@ bool X86_64TargetABI::returnInArg(TypeFunction *tf) {
     return false;
   }
 
-  Type *rt = tf->next;
-  return passByVal(rt);
+  Type *rt = tf->next->toBasetype();
+  return dmd_abi::passByVal(rt);
 }
 
-bool X86_64TargetABI::passByVal(Type *t) {
+bool X86_64TargetABI::passByVal(TypeFunction *tf, Type *t) {
+  // indirectly by-value for extern(C++) functions and non-POD args
+  if (tf->linkage == LINKcpp && !isPOD(t))
+    return false;
+
   return dmd_abi::passByVal(t->toBasetype());
 }
 
@@ -264,10 +269,21 @@ void X86_64TargetABI::rewriteArgument(IrFuncTy &fty, IrFuncTyArg &arg) {
   llvm_unreachable("Please use the other overload explicitly.");
 }
 
-void X86_64TargetABI::rewriteArgument(IrFuncTyArg &arg, RegCount &regCount) {
+void X86_64TargetABI::rewriteArgument(IrFuncTy &fty, IrFuncTyArg &arg,
+                                      RegCount &regCount) {
   LLType *originalLType = arg.ltype;
   Type *t = arg.type->toBasetype();
 
+  // indirectly by-value for extern(C++) functions and non-POD args
+  if (fty.type->linkage == LINKcpp && !isPOD(t)) {
+    indirectByvalRewrite.applyTo(arg);
+    if (regCount.int_regs > 0) {
+      regCount.int_regs--;
+    }
+
+    return;
+  }
+
   LLType *abiTy = getAbiType(t);
   if (abiTy && !LLTypeMemoryLayout::typesAreEquivalent(abiTy, originalLType)) {
     IF_LOG {
@@ -280,11 +296,12 @@ void X86_64TargetABI::rewriteArgument(IrFuncTyArg &arg, RegCount &regCount) {
   }
 
   if (regCount.trySubtract(arg) == RegCount::ArgumentWouldFitInPartially) {
-    // pass LL structs implicitly ByVal, otherwise LLVM passes
-    // them partially in registers, partially in memory
+    // pass the LL struct with byval attribute to prevent LLVM from passing it
+    // partially in registers, partially in memory
     assert(originalLType->isStructTy());
-    IF_LOG Logger::cout() << "Passing implicitly ByVal: " << arg.type->toChars()
-                          << " (" << *originalLType << ")\n";
+    IF_LOG Logger::cout() << "Passing byval to prevent register/memory mix: "
+                          << arg.type->toChars() << " (" << *originalLType
+                          << ")\n";
     byvalRewrite.applyTo(arg);
   }
 }
@@ -298,7 +315,7 @@ void X86_64TargetABI::rewriteFunctionType(IrFuncTy &fty) {
     Logger::println("x86-64 ABI: Transforming return type");
     LOG_SCOPE;
     RegCount dummy;
-    rewriteArgument(*fty.ret, dummy);
+    rewriteArgument(fty, *fty.ret, dummy);
   }
 
   // IMPLICIT PARAMETERS
@@ -336,7 +353,7 @@ void X86_64TargetABI::rewriteFunctionType(IrFuncTy &fty) {
       continue;
     }
 
-    rewriteArgument(arg, regCount);
+    rewriteArgument(fty, arg, regCount);
   }
 
   // regCount (fty.tag) is now in the state after all implicit & formal args,
@@ -351,7 +368,7 @@ void X86_64TargetABI::rewriteVarargs(IrFuncTy &fty,
 
   for (auto arg : args) {
     if (!arg->byref) { // don't rewrite ByVal arguments
-      rewriteArgument(*arg, regCount);
+      rewriteArgument(fty, *arg, regCount);
     }
   }
 }

gen/abi-x86.cpp

@@ -24,6 +24,7 @@ struct X86TargetABI : TargetABI {
   const bool isMSVC;
   bool returnStructsInRegs;
   IntegerRewrite integerRewrite;
+  IndirectByvalRewrite indirectByvalRewrite;
 
   X86TargetABI()
       : isOSX(global.params.targetTriple->isMacOSX()),
@@ -118,7 +119,11 @@ struct X86TargetABI : TargetABI {
     return !canRewriteAsInt(rt);
   }
 
-  bool passByVal(Type *t) override {
+  bool passByVal(TypeFunction *tf, Type *t) override {
+    // indirectly by-value for extern(C++) functions and non-POD args on Posix
+    if (!isMSVC && tf->linkage == LINKcpp && !isPOD(t))
+      return false;
+
     // pass all structs and static arrays with the LLVM byval attribute
     return DtoIsInMemoryOnly(t);
   }
@@ -182,6 +187,13 @@ struct X86TargetABI : TargetABI {
 
       // all other arguments are passed on the stack, don't rewrite
     }
+    // extern(C++) on Posix: non-POD args are passed indirectly by-value
+    else if (!isMSVC && fty.type->linkage == LINKcpp) {
+      for (auto arg : fty.args) {
+        if (!arg->byref && !isPOD(arg->type))
+          indirectByvalRewrite.applyTo(*arg);
+      }
+    }
 
     workaroundIssue1356(fty.args);
 

gen/abi.cpp

@@ -310,7 +310,9 @@ struct UnknownTargetABI : TargetABI {
     return (rt->ty == Tstruct || rt->ty == Tsarray);
   }
 
-  bool passByVal(Type *t) override { return t->toBasetype()->ty == Tstruct; }
+  bool passByVal(TypeFunction *, Type *t) override {
+    return t->toBasetype()->ty == Tstruct;
+  }
 
   void rewriteFunctionType(IrFuncTy &) override {
     // why?
@@ -361,7 +363,7 @@ struct IntrinsicABI : TargetABI {
 
   bool returnInArg(TypeFunction *tf) override { return false; }
 
-  bool passByVal(Type *t) override { return false; }
+  bool passByVal(TypeFunction *, Type *t) override { return false; }
 
   bool reverseExplicitParams(TypeFunction *) override { return false; }
 

gen/abi.h

@@ -137,7 +137,7 @@ struct TargetABI {
   /// parameter.
   /// The LL caller needs to pass a pointer to the original argument (the memcpy
   /// source).
-  virtual bool passByVal(Type *t) = 0;
+  virtual bool passByVal(TypeFunction *tf, Type *t) = 0;
 
   /// Returns true if the 'this' argument is to be passed before the 'sret'
   /// argument.

gen/functions.cpp

@@ -170,7 +170,7 @@ llvm::FunctionType *DtoFunctionType(Type *type, IrFuncTy &irFty, Type *thistype,
       // ref/out
       attrs.addDereferenceable(loweredDType->size());
     } else {
-      if (abi->passByVal(loweredDType)) {
+      if (abi->passByVal(f, loweredDType)) {
         // LLVM ByVal parameters are pointers to a copy in the function
         // parameters stack. The caller needs to provide a pointer to the
         // original argument.

gen/tocall.cpp

@@ -129,7 +129,7 @@ static void addExplicitArguments(std::vector<LLValue *> &args, AttrSet &attrs,
   std::vector<IrFuncTyArg *> optionalIrArgs;
   for (size_t i = formalDArgCount; i < explicitDArgCount; i++) {
     Type *argType = argexps[i]->type;
-    bool passByVal = gABI->passByVal(argType);
+    bool passByVal = gABI->passByVal(irFty.type, argType);
 
     AttrBuilder initialAttrs;
     if (passByVal) {

tests/d2/dmd-testsuite

@@ -1 +1 @@
-Subproject commit a0f157abcc2d2779aa44cd9d6dec84aa56950d81
+Subproject commit b0b28297a8befba66640c7b4462ecdc12c40c318