[cleanup] Refactor CSignature helper

The implementation can be greatly simplified by using variadic
templates.

R=mstarzinger@chromium.org

Change-Id: I8dbeea3d570bf0fac83109f334c48dbe39aaa853
Reviewed-on: https://chromium-review.googlesource.com/859785
Commit-Queue: Clemens Hammacher <clemensh@chromium.org>
Reviewed-by: Michael Starzinger <mstarzinger@chromium.org>
Cr-Commit-Position: refs/heads/master@{#50611}

test/cctest/compiler/c-signature.h

@@ -28,18 +28,16 @@ namespace compiler {
   V(int*, MachineType::Pointer())
 
 template <typename T>
-inline MachineType MachineTypeForC() {
-  while (false) {
-    // All other types T must be assignable to Object*
-    *(static_cast<Object* volatile*>(0)) = static_cast<T>(0);
-  }
+inline constexpr MachineType MachineTypeForC() {
+  static_assert(std::is_convertible<T, Object*>::value,
+                "all non-specialized types must be convertible to Object*");
   return MachineType::AnyTagged();
 }
 
-#define DECLARE_TEMPLATE_SPECIALIZATION(ctype, mtype) \
-  template <>                                         \
-  inline MachineType MachineTypeForC<ctype>() {       \
-    return mtype;                                     \
+#define DECLARE_TEMPLATE_SPECIALIZATION(ctype, mtype)     \
+  template <>                                             \
+  inline MachineType constexpr MachineTypeForC<ctype>() { \
+    return mtype;                                         \
   }
 FOREACH_CTYPE_MACHINE_TYPE_MAPPING(DECLARE_TEMPLATE_SPECIALIZATION)
 #undef DECLARE_TEMPLATE_SPECIALIZATION
@@ -51,21 +49,13 @@ class CSignature : public MachineSignature {
       : MachineSignature(return_count, parameter_count, reps) {}
 
  public:
-  template <typename P1 = void, typename P2 = void, typename P3 = void,
-            typename P4 = void, typename P5 = void>
+  template <typename... Params>
   static void VerifyParams(MachineSignature* sig) {
-    // Verifies the C signature against the machine types. Maximum {5} params.
-    CHECK_LT(sig->parameter_count(), 6u);
-    const int kMax = 5;
-    MachineType params[] = {MachineTypeForC<P1>(), MachineTypeForC<P2>(),
-                            MachineTypeForC<P3>(), MachineTypeForC<P4>(),
-                            MachineTypeForC<P5>()};
-    for (int p = kMax - 1; p >= 0; p--) {
-      if (p < static_cast<int>(sig->parameter_count())) {
-        CHECK_EQ(sig->GetParam(p), params[p]);
-      } else {
-        CHECK_EQ(MachineType::None(), params[p]);
-      }
+    // Verifies the C signature against the machine types.
+    std::array<MachineType, sizeof...(Params)> params{
+        MachineTypeForC<Params>()...};
+    for (size_t p = 0; p < params.size(); ++p) {
+      CHECK_EQ(sig->GetParam(p), params[p]);
     }
   }
 
@@ -73,96 +63,59 @@ class CSignature : public MachineSignature {
     return reinterpret_cast<CSignature*>(msig);
   }
 
+  template <typename... ParamMachineTypes>
   static CSignature* New(Zone* zone, MachineType ret,
-                         MachineType p1 = MachineType::None(),
-                         MachineType p2 = MachineType::None(),
-                         MachineType p3 = MachineType::None(),
-                         MachineType p4 = MachineType::None(),
-                         MachineType p5 = MachineType::None()) {
-    MachineType* buffer = zone->NewArray<MachineType>(6);
-    int pos = 0;
+                         ParamMachineTypes... params) {
+    constexpr size_t param_count = sizeof...(params);
+    std::array<MachineType, param_count> param_arr{params...};
+    const size_t buffer_size =
+        param_count + (ret == MachineType::None() ? 0 : 1);
+    MachineType* buffer = zone->NewArray<MachineType>(buffer_size);
+    size_t pos = 0;
     size_t return_count = 0;
     if (ret != MachineType::None()) {
       buffer[pos++] = ret;
       return_count++;
     }
-    buffer[pos++] = p1;
-    buffer[pos++] = p2;
-    buffer[pos++] = p3;
-    buffer[pos++] = p4;
-    buffer[pos++] = p5;
-    size_t param_count = 5;
-    if (p5 == MachineType::None()) param_count--;
-    if (p4 == MachineType::None()) param_count--;
-    if (p3 == MachineType::None()) param_count--;
-    if (p2 == MachineType::None()) param_count--;
-    if (p1 == MachineType::None()) param_count--;
-    for (size_t i = 0; i < param_count; i++) {
-      // Check that there are no MachineType::None()'s in the middle of
-      // parameters.
-      CHECK_NE(MachineType::None(), buffer[return_count + i]);
+    for (MachineType p : param_arr) {
+      // Check that there are no MachineType::None()'s in the parameters.
+      CHECK_NE(MachineType::None(), p);
+      buffer[pos++] = p;
     }
+    DCHECK_EQ(buffer_size, pos);
     return new (zone) CSignature(return_count, param_count, buffer);
   }
 };
 
-
-template <typename Ret, uint16_t kParamCount>
-class CSignatureOf : public CSignature {
- protected:
-  MachineType storage_[1 + kParamCount];
-
-  CSignatureOf()
-      : CSignature(MachineTypeForC<Ret>() != MachineType::None() ? 1 : 0,
-                   kParamCount, reinterpret_cast<MachineType*>(&storage_)) {
-    if (return_count_ == 1) storage_[0] = MachineTypeForC<Ret>();
-  }
-  void Set(int index, MachineType type) {
-    CHECK_LE(0, index);
-    CHECK_LT(index, kParamCount);
-    reps_[return_count_ + index] = type;
-  }
-};
-
 // Helper classes for instantiating Signature objects to be callable from C.
-template <typename Ret>
-class CSignature0 : public CSignatureOf<Ret, 0> {
- public:
-  CSignature0() : CSignatureOf<Ret, 0>() {}
-};
-
-template <typename Ret, typename P1>
-class CSignature1 : public CSignatureOf<Ret, 1> {
+template <typename Ret, typename... Params>
+class CSignatureOf : public CSignature {
  public:
-  CSignature1() : CSignatureOf<Ret, 1>() {
-    this->Set(0, MachineTypeForC<P1>());
+  CSignatureOf() : CSignature(kReturnCount, kParamCount, storage_) {
+    constexpr std::array<MachineType, kParamCount> param_types{
+        MachineTypeForC<Params>()...};
+    if (kReturnCount == 1) storage_[0] = MachineTypeForC<Ret>();
+    static_assert(
+        std::is_same<decltype(*reps_), decltype(*param_types.data())>::value,
+        "type mismatch, cannot memcpy");
+    memcpy(storage_ + kReturnCount, param_types.data(),
+           sizeof(*storage_) * kParamCount);
   }
-};
 
-template <typename Ret, typename P1, typename P2>
-class CSignature2 : public CSignatureOf<Ret, 2> {
- public:
-  CSignature2() : CSignatureOf<Ret, 2>() {
-    this->Set(0, MachineTypeForC<P1>());
-    this->Set(1, MachineTypeForC<P2>());
-  }
-};
+ private:
+  static constexpr size_t kReturnCount =
+      MachineTypeForC<Ret>() == MachineType::None() ? 0 : 1;
+  static constexpr size_t kParamCount = sizeof...(Params);
 
-template <typename Ret, typename P1, typename P2, typename P3>
-class CSignature3 : public CSignatureOf<Ret, 3> {
- public:
-  CSignature3() : CSignatureOf<Ret, 3>() {
-    this->Set(0, MachineTypeForC<P1>());
-    this->Set(1, MachineTypeForC<P2>());
-    this->Set(2, MachineTypeForC<P3>());
-  }
+  MachineType storage_[kReturnCount + kParamCount];
 };
 
-typedef CSignature2<int32_t, int32_t, int32_t> CSignature_i_ii;
-typedef CSignature2<uint32_t, uint32_t, uint32_t> CSignature_u_uu;
-typedef CSignature2<float, float, float> CSignature_f_ff;
-typedef CSignature2<double, double, double> CSignature_d_dd;
-typedef CSignature2<Object*, Object*, Object*> CSignature_o_oo;
+typedef CSignatureOf<int32_t, int32_t, int32_t> CSignature_i_ii;
+typedef CSignatureOf<uint32_t, uint32_t, uint32_t> CSignature_u_uu;
+typedef CSignatureOf<float, float, float> CSignature_f_ff;
+typedef CSignatureOf<double, double, double> CSignature_d_dd;
+typedef CSignatureOf<Object*, Object*, Object*> CSignature_o_oo;
+
 }  // namespace compiler
 }  // namespace internal
 }  // namespace v8

test/cctest/compiler/graph-builder-tester.h

@@ -50,16 +50,12 @@ class GraphBuilderTester : public HandleAndZoneScope,
                            public GraphAndBuilders,
                            public CallHelper<ReturnType> {
  public:
-  explicit GraphBuilderTester(MachineType p0 = MachineType::None(),
-                              MachineType p1 = MachineType::None(),
-                              MachineType p2 = MachineType::None(),
-                              MachineType p3 = MachineType::None(),
-                              MachineType p4 = MachineType::None())
+  template <typename... ParamMachTypes>
+  explicit GraphBuilderTester(ParamMachTypes... p)
       : GraphAndBuilders(main_zone()),
         CallHelper<ReturnType>(
             main_isolate(),
-            CSignature::New(main_zone(), MachineTypeForC<ReturnType>(), p0, p1,
-                            p2, p3, p4)),
+            CSignature::New(main_zone(), MachineTypeForC<ReturnType>(), p...)),
         effect_(nullptr),
         return_(nullptr),
         parameters_(main_zone()->template NewArray<Node*>(parameter_count())) {
@@ -192,37 +188,10 @@ class GraphBuilderTester : public HandleAndZoneScope,
     return NewNode(simplified()->StoreElement(access), object, index, value);
   }
 
-  Node* NewNode(const Operator* op) {
-    return MakeNode(op, 0, static_cast<Node**>(nullptr));
-  }
-
-  Node* NewNode(const Operator* op, Node* n1) { return MakeNode(op, 1, &n1); }
-
-  Node* NewNode(const Operator* op, Node* n1, Node* n2) {
-    Node* buffer[] = {n1, n2};
-    return MakeNode(op, arraysize(buffer), buffer);
-  }
-
-  Node* NewNode(const Operator* op, Node* n1, Node* n2, Node* n3) {
-    Node* buffer[] = {n1, n2, n3};
-    return MakeNode(op, arraysize(buffer), buffer);
-  }
-
-  Node* NewNode(const Operator* op, Node* n1, Node* n2, Node* n3, Node* n4) {
-    Node* buffer[] = {n1, n2, n3, n4};
-    return MakeNode(op, arraysize(buffer), buffer);
-  }
-
-  Node* NewNode(const Operator* op, Node* n1, Node* n2, Node* n3, Node* n4,
-                Node* n5) {
-    Node* buffer[] = {n1, n2, n3, n4, n5};
-    return MakeNode(op, arraysize(buffer), buffer);
-  }
-
-  Node* NewNode(const Operator* op, Node* n1, Node* n2, Node* n3, Node* n4,
-                Node* n5, Node* n6) {
-    Node* nodes[] = {n1, n2, n3, n4, n5, n6};
-    return MakeNode(op, arraysize(nodes), nodes);
+  template <typename... NodePtrs>
+  Node* NewNode(const Operator* op, NodePtrs... n) {
+    std::array<Node*, sizeof...(n)> inputs{n...};
+    return MakeNode(op, inputs.size(), inputs.data());
   }
 
   Node* NewNode(const Operator* op, int value_input_count,

test/cctest/compiler/test-run-machops.cc

@@ -3524,8 +3524,10 @@ TEST(RunWord32EqualAndWord32ShrP) {
 
 TEST(RunDeadNodes) {
   for (int i = 0; true; i++) {
-    RawMachineAssemblerTester<int32_t> m(i == 5 ? MachineType::Int32()
-                                                : MachineType::None());
+    RawMachineAssemblerTester<int32_t> m_v;
+    RawMachineAssemblerTester<int32_t> m_i(MachineType::Int32());
+    RawMachineAssemblerTester<int32_t>& m = i == 5 ? m_i : m_v;
+
     int constant = 0x55 + i;
     switch (i) {
       case 0:
@@ -6736,7 +6738,7 @@ TEST(RunComputedCodeObject) {
 
   // TODO(titzer): all this descriptor hackery is just to call the above
   // functions as code objects instead of direct addresses.
-  CSignature0<int32_t> sig;
+  CSignatureOf<int32_t> sig;
   CallDescriptor* c = Linkage::GetSimplifiedCDescriptor(r.zone(), &sig);
   LinkageLocation ret[] = {c->GetReturnLocation(0)};
   Signature<LinkageLocation> loc(1, 0, ret);

test/cctest/compiler/test-run-native-calls.cc

@@ -446,7 +446,7 @@ class Computer {
       inner = CompileGraph("Compute", desc, &graph, raw.Export());
     }
 
-    CSignature0<int32_t> csig;
+    CSignatureOf<int32_t> csig;
     ArgsBuffer<CType> io(num_params, seed);
 
     {
@@ -583,7 +583,7 @@ static void CopyTwentyInt32(CallDescriptor* desc) {
     inner = CompileGraph("CopyTwentyInt32", desc, &graph, raw.Export());
   }
 
-  CSignature0<int32_t> csig;
+  CSignatureOf<int32_t> csig;
   Handle<Code> wrapper = Handle<Code>::null();
   {
     // Loads parameters from the input buffer and calls the above code.
@@ -1076,7 +1076,7 @@ void MixedParamTest(int start) {
       char bytes[kDoubleSize];
       V8_ALIGNED(8) char output[kDoubleSize];
       int expected_size = 0;
-      CSignature0<int32_t> csig;
+      CSignatureOf<int32_t> csig;
       {
         // Wrap the select code with a callable function that passes constants.
         Zone zone(&allocator, ZONE_NAME);

test/cctest/test-run-wasm-relocation-arm.cc

@@ -40,7 +40,7 @@ TEST(WasmRelocationArmContextReference) {
   Handle<Code> code =
       isolate->factory()->NewCode(desc, Code::STUB, Handle<Code>());
 
-  compiler::CSignature0<int32_t> csig;
+  compiler::CSignatureOf<int32_t> csig;
   compiler::CodeRunner<int32_t> runnable(isolate, code, &csig);
   int32_t ret_value = runnable.Call();
   CHECK_EQ(ret_value, imm);

test/cctest/test-run-wasm-relocation-arm64.cc

@@ -45,7 +45,7 @@ TEST(WasmRelocationArm64ContextReference) {
   Handle<Code> code =
       isolate->factory()->NewCode(desc, Code::STUB, Handle<Code>());
 
-  compiler::CSignature0<int64_t> csig;
+  compiler::CSignatureOf<int64_t> csig;
   compiler::CodeRunner<int64_t> runnable(isolate, code, &csig);
   int64_t ret_value = runnable.Call();
   CHECK_EQ(ret_value, imm);

test/cctest/test-run-wasm-relocation-ia32.cc

@@ -40,7 +40,7 @@ TEST(WasmRelocationIa32ContextReference) {
   __ nop();
   __ ret(0);
 
-  compiler::CSignature0<int32_t> csig;
+  compiler::CSignatureOf<int32_t> csig;
   CodeDesc desc;
   assm.GetCode(isolate, &desc);
   Handle<Code> code =

test/cctest/test-run-wasm-relocation-x64.cc

@@ -43,7 +43,7 @@ TEST(WasmRelocationX64ContextReference) {
       isolate->factory()->NewCode(desc, Code::STUB, Handle<Code>());
   USE(code);
 
-  CSignature0<int64_t> csig;
+  CSignatureOf<int64_t> csig;
   CodeRunner<int64_t> runnable(isolate, code, &csig);
   int64_t ret_value = runnable.Call();
   CHECK_EQ(ret_value, imm);