[wasm] Move definition of FunctionSig to a common place

We were re-definining the FunctionSig typedef in several places. This
CL moves it to value-type.h, since it's a signature over ValueType.

R=titzer@chromium.org

Bug: v8:8238
Change-Id: Id5e8a55c7e0f98d61235e32a5e6cd12e04d26947
Reviewed-on: https://chromium-review.googlesource.com/c/1278387
Commit-Queue: Clemens Hammacher <clemensh@chromium.org>
Reviewed-by: Ben Titzer <titzer@chromium.org>
Cr-Commit-Position: refs/heads/master@{#56597}

src/wasm/signature-map.h

@@ -15,8 +15,6 @@ namespace internal {
 
 namespace wasm {
 
-using FunctionSig = Signature<ValueType>;
-
 // A signature map canonicalizes signatures into a range of indices so that
 // two different {FunctionSig} instances with the same contents map to the
 // same index.

src/wasm/value-type.h

@@ -10,6 +10,10 @@
 
 namespace v8 {
 namespace internal {
+
+template <typename T>
+class Signature;
+
 namespace wasm {
 
 enum ValueType : uint8_t {
@@ -25,6 +29,8 @@ enum ValueType : uint8_t {
   kWasmVar,
 };
 
+using FunctionSig = Signature<ValueType>;
+
 inline size_t hash_value(ValueType type) { return static_cast<size_t>(type); }
 
 // TODO(clemensh): Compute memtype and size from ValueType once we have c++14

src/wasm/wasm-import-wrapper-cache-inl.h

@@ -16,8 +16,6 @@ namespace v8 {
 namespace internal {
 namespace wasm {
 
-using FunctionSig = Signature<ValueType>;
-
 // Implements a cache for import wrappers.
 class WasmImportWrapperCache {
  public:

src/wasm/wasm-objects.h

@@ -29,7 +29,6 @@ struct WasmModule;
 class SignatureMap;
 class WireBytesRef;
 class WasmInterpreter;
-using FunctionSig = Signature<ValueType>;
 struct WasmFeatures;
 }  // namespace wasm
 

src/wasm/wasm-opcodes.h

@@ -13,12 +13,8 @@
 namespace v8 {
 namespace internal {
 
-template <typename T>
-class Signature;
-
 namespace wasm {
 
-using FunctionSig = Signature<ValueType>;
 std::ostream& operator<<(std::ostream& os, const FunctionSig& function);
 bool IsJSCompatibleSignature(const FunctionSig* sig);
 

test/common/wasm/test-signatures.h

@@ -6,14 +6,13 @@
 #define TEST_SIGNATURES_H
 
 #include "src/signature.h"
+#include "src/wasm/value-type.h"
 #include "src/wasm/wasm-opcodes.h"
 
 namespace v8 {
 namespace internal {
 namespace wasm {
 
-typedef Signature<ValueType> FunctionSig;
-
 // A helper class with many useful signatures in order to simplify tests.
 class TestSignatures {
  public: