[wasm] ReturnCall Implementation (interpreter)

Implement the ReturnCall functionality for the interpreter.

Note that some tests have had to be deferred to the implementation
of ReturnCall for TurboFan.

Bug: v8:7431
Change-Id: I091528e72f9113ddf1929bd1a5650b490bc8cc0c
Reviewed-on: https://chromium-review.googlesource.com/c/1467343Reviewed-by: Andreas Haas <ahaas@chromium.org>
Reviewed-by: Clemens Hammacher <clemensh@chromium.org>
Commit-Queue: Francis McCabe <fgm@chromium.org>
Cr-Commit-Position: refs/heads/master@{#59803}

src/wasm/wasm-interpreter.cc

@@ -1354,17 +1354,24 @@ class ThreadImpl {
     CommitPc(pc);
   }
 
+  // Check if there is room for a function's activation.
+  void EnsureStackSpaceForCall(InterpreterCode* code) {
+    EnsureStackSpace(code->side_table->max_stack_height_ +
+                     code->locals.type_list.size());
+    DCHECK_GE(StackHeight(), code->function->sig->parameter_count());
+  }
+
   // Push a frame with arguments already on the stack.
   void PushFrame(InterpreterCode* code) {
     DCHECK_NOT_NULL(code);
     DCHECK_NOT_NULL(code->side_table);
-    EnsureStackSpace(code->side_table->max_stack_height_ +
-                     code->locals.type_list.size());
+    EnsureStackSpaceForCall(code);
 
     ++num_interpreted_calls_;
     size_t arity = code->function->sig->parameter_count();
     // The parameters will overlap the arguments already on the stack.
     DCHECK_GE(StackHeight(), arity);
+
     frames_.push_back({code, 0, StackHeight() - arity});
     frames_.back().pc = InitLocals(code);
     TRACE("  => PushFrame #%zu (#%u @%zu)\n", frames_.size() - 1,
@@ -1484,6 +1491,41 @@ class ThreadImpl {
     return true;
   }
 
+  // Returns true if the tail call was successful, false if the stack check
+  // failed.
+  bool DoReturnCall(Decoder* decoder, InterpreterCode* target, pc_t* pc,
+                    pc_t* limit) V8_WARN_UNUSED_RESULT {
+    DCHECK_NOT_NULL(target);
+    DCHECK_NOT_NULL(target->side_table);
+    EnsureStackSpaceForCall(target);
+
+    ++num_interpreted_calls_;
+
+    Frame* top = &frames_.back();
+
+    // Drop everything except current parameters.
+    WasmValue* sp_dest = stack_.get() + top->sp;
+    size_t arity = target->function->sig->parameter_count();
+
+    DoStackTransfer(sp_dest, arity);
+
+    *limit = target->end - target->start;
+    decoder->Reset(target->start, target->end);
+
+    // Rebuild current frame to look like a call to callee.
+    top->code = target;
+    top->pc = 0;
+    top->sp = StackHeight() - arity;
+    top->pc = InitLocals(target);
+
+    *pc = top->pc;
+
+    TRACE("  => ReturnCall #%zu (#%u @%zu)\n", frames_.size() - 1,
+          target->function->func_index, top->pc);
+
+    return true;
+  }
+
   // Copies {arity} values on the top of the stack down the stack to {dest},
   // dropping the values in-between.
   void DoStackTransfer(WasmValue* dest, size_t arity) {
@@ -2540,8 +2582,7 @@ class ThreadImpl {
             switch (result.type) {
               case ExternalCallResult::INTERNAL:
                 // The import is a function of this instance. Call it directly.
-                target = result.interpreter_code;
-                DCHECK(!target->function->imported);
+                DCHECK(!result.interpreter_code->function->imported);
                 break;
               case ExternalCallResult::INVALID_FUNC:
               case ExternalCallResult::SIGNATURE_MISMATCH:
@@ -2565,6 +2606,7 @@ class ThreadImpl {
           PAUSE_IF_BREAK_FLAG(AfterCall);
           continue;  // Do not bump pc.
         } break;
+
         case kExprCallIndirect: {
           CallIndirectImmediate<Decoder::kNoValidate> imm(&decoder,
                                                           code->at(pc));
@@ -2597,6 +2639,117 @@ class ThreadImpl {
               continue;  // Do not bump pc.
           }
         } break;
+
+        case kExprReturnCall: {
+          CallFunctionImmediate<Decoder::kNoValidate> imm(&decoder,
+                                                          code->at(pc));
+          InterpreterCode* target = codemap()->GetCode(imm.index);
+          if (target->function->imported) {
+            CommitPc(pc);
+            ExternalCallResult result =
+                CallImportedFunction(target->function->func_index);
+            switch (result.type) {
+              case ExternalCallResult::INTERNAL:
+                // Cannot import internal functions
+                UNREACHABLE();
+              case ExternalCallResult::INVALID_FUNC:
+              case ExternalCallResult::SIGNATURE_MISMATCH:
+                // Direct calls are checked statically.
+                UNREACHABLE();
+              case ExternalCallResult::EXTERNAL_RETURNED:
+                len = 1 + imm.length;
+                break;
+              case ExternalCallResult::EXTERNAL_UNWOUND:
+                return;
+              case ExternalCallResult::EXTERNAL_CAUGHT:
+                ReloadFromFrameOnException(&decoder, &code, &pc, &limit);
+                continue;
+            }
+            if (result.type != ExternalCallResult::INTERNAL) {
+              size_t arity = code->function->sig->return_count();
+              if (!DoReturn(&decoder, &code, &pc, &limit, arity)) return;
+              PAUSE_IF_BREAK_FLAG(AfterReturn);
+              continue;
+            }
+          }
+          // Execute an internal return call with found function.
+          if (!DoReturnCall(&decoder, target, &pc, &limit)) return;
+          code = target;
+          PAUSE_IF_BREAK_FLAG(AfterCall);
+          continue;  // do not bump pc.
+        } break;
+
+        case kExprReturnCallIndirect: {
+          CallIndirectImmediate<Decoder::kNoValidate> imm(&decoder,
+                                                          code->at(pc));
+          uint32_t entry_index = Pop().to<uint32_t>();
+          // Assume only one table for now.
+          DCHECK_LE(module()->tables.size(), 1u);
+          CommitPc(pc);  // TODO(wasm): Be more disciplined about committing PC.
+
+          // TODO(wasm): Calling functions needs some refactoring to avoid
+          // multi-exit code like this.
+          ExternalCallResult result =
+              CallIndirectFunction(0, entry_index, imm.sig_index);
+          switch (result.type) {
+            case ExternalCallResult::INTERNAL: {
+              InterpreterCode* target = result.interpreter_code;
+
+              if (target->function->imported) {
+                CommitPc(pc);
+                ExternalCallResult result =
+                    CallImportedFunction(target->function->func_index);
+                switch (result.type) {
+                  case ExternalCallResult::INTERNAL:
+                    // Cannot import internal functions
+                    UNREACHABLE();
+                  case ExternalCallResult::INVALID_FUNC:
+                  case ExternalCallResult::SIGNATURE_MISMATCH:
+                    // Direct calls are checked statically.
+                    UNREACHABLE();
+                  case ExternalCallResult::EXTERNAL_RETURNED:
+                    len = 1 + imm.length;
+                    break;
+                  case ExternalCallResult::EXTERNAL_UNWOUND:
+                    return;
+                  case ExternalCallResult::EXTERNAL_CAUGHT:
+                    ReloadFromFrameOnException(&decoder, &code, &pc, &limit);
+                    continue;
+                }
+                size_t arity = code->function->sig->return_count();
+                if (!DoReturn(&decoder, &code, &pc, &limit, arity)) return;
+                PAUSE_IF_BREAK_FLAG(AfterReturn);
+                continue;
+              }
+
+              // The import is a function of this instance. Call it directly.
+              if (!DoReturnCall(&decoder, result.interpreter_code, &pc, &limit))
+                return;
+              code = result.interpreter_code;
+              PAUSE_IF_BREAK_FLAG(AfterCall);
+              continue;  // do not bump pc.
+            }
+            case ExternalCallResult::INVALID_FUNC:
+              return DoTrap(kTrapFuncInvalid, pc);
+            case ExternalCallResult::SIGNATURE_MISMATCH:
+              return DoTrap(kTrapFuncSigMismatch, pc);
+            case ExternalCallResult::EXTERNAL_RETURNED: {
+              len = 1 + imm.length;
+
+              size_t arity = code->function->sig->return_count();
+              if (!DoReturn(&decoder, &code, &pc, &limit, arity)) return;
+              PAUSE_IF_BREAK_FLAG(AfterCall);
+              break;
+            }
+            case ExternalCallResult::EXTERNAL_UNWOUND:
+              return;
+
+            case ExternalCallResult::EXTERNAL_CAUGHT:
+              ReloadFromFrameOnException(&decoder, &code, &pc, &limit);
+              break;
+          }
+        } break;
+
         case kExprGetGlobal: {
           GlobalIndexImmediate<Decoder::kNoValidate> imm(&decoder,
                                                          code->at(pc));

test/cctest/wasm/test-run-wasm-interpreter.cc

@@ -143,6 +143,118 @@ TEST(Run_Wasm_nested_ifs_i) {
   CHECK_EQ(14, r.Call(0, 0));
 }
 
+// Repeated from test-run-wasm.cc to avoid poluting header files.
+template <typename T>
+static T factorial(T v) {
+  T expected = 1;
+  for (T i = v; i > 1; i--) {
+    expected *= i;
+  }
+  return expected;
+}
+
+// Basic test of return call in interpreter. Good old factorial.
+TEST(Run_Wasm_returnCallFactorial) {
+  EXPERIMENTAL_FLAG_SCOPE(return_call);
+  // Run in bounded amount of stack - 8kb.
+  FlagScope<int32_t> stack_size(&v8::internal::FLAG_stack_size, 8);
+
+  WasmRunner<int32_t, int32_t> r(ExecutionTier::kInterpreter);
+
+  WasmFunctionCompiler& fact_fn = r.NewFunction<int32_t, int32_t>("fact");
+  WasmFunctionCompiler& fact_aux_fn =
+      r.NewFunction<int32_t, int32_t, int32_t>("fact_aux");
+
+  BUILD(r, WASM_CALL_FUNCTION(fact_fn.function_index(), WASM_GET_LOCAL(0)));
+
+  BUILD(fact_fn, WASM_RETURN_CALL_FUNCTION(fact_aux_fn.function_index(),
+                                           WASM_GET_LOCAL(0), WASM_I32V(1)));
+
+  BUILD(fact_aux_fn,
+        WASM_IF_ELSE_I(
+            WASM_I32_EQ(WASM_I32V(1), WASM_GET_LOCAL(0)), WASM_GET_LOCAL(1),
+            WASM_RETURN_CALL_FUNCTION(
+                fact_aux_fn.function_index(),
+                WASM_I32_SUB(WASM_GET_LOCAL(0), WASM_I32V(1)),
+                WASM_I32_MUL(WASM_GET_LOCAL(0), WASM_GET_LOCAL(1)))));
+
+  // Runs out of stack space without using return call.
+  int test_values[] = {1, 2, 5, 10, 20, 20000};
+
+  for (int v : test_values) {
+    int32_t found = r.Call(v);
+    CHECK_EQ(factorial(v), found);
+  }
+}
+
+TEST(Run_Wasm_returnCallFactorial64) {
+  EXPERIMENTAL_FLAG_SCOPE(return_call);
+
+  int32_t test_values[] = {1, 2, 5, 10, 20};
+  WasmRunner<int64_t, int32_t> r(ExecutionTier::kInterpreter);
+
+  WasmFunctionCompiler& fact_fn = r.NewFunction<int64_t, int32_t>("fact");
+  WasmFunctionCompiler& fact_aux_fn =
+      r.NewFunction<int64_t, int32_t, int64_t>("fact_aux");
+  BUILD(r, WASM_CALL_FUNCTION(fact_fn.function_index(), WASM_GET_LOCAL(0)));
+
+  BUILD(fact_fn, WASM_RETURN_CALL_FUNCTION(fact_aux_fn.function_index(),
+                                           WASM_GET_LOCAL(0), WASM_I64V(1)));
+
+  BUILD(fact_aux_fn,
+        WASM_IF_ELSE_L(
+            WASM_I32_EQ(WASM_I32V(1), WASM_GET_LOCAL(0)), WASM_GET_LOCAL(1),
+            WASM_RETURN_CALL_FUNCTION(
+                fact_aux_fn.function_index(),
+                WASM_I32_SUB(WASM_GET_LOCAL(0), WASM_I32V(1)),
+                WASM_I64_MUL(WASM_I64_SCONVERT_I32(WASM_GET_LOCAL(0)),
+                             WASM_GET_LOCAL(1)))));
+
+  for (int32_t v : test_values) {
+    CHECK_EQ(factorial<int64_t>(v), r.Call(v));
+  }
+}
+
+TEST(Run_Wasm_tailCallIndirectFactorial) {
+  EXPERIMENTAL_FLAG_SCOPE(return_call);
+
+  TestSignatures sigs;
+
+  WasmRunner<int32_t, int32_t> r(ExecutionTier::kInterpreter);
+
+  WasmFunctionCompiler& fact_fn = r.NewFunction(sigs.i_i(), "fact");
+
+  WasmFunctionCompiler& fact_aux_fn = r.NewFunction(sigs.i_ii(), "fact_aux");
+  fact_aux_fn.SetSigIndex(0);
+
+  r.builder().AddSignature(sigs.i_ii());
+
+  // Function table.
+  uint16_t indirect_function_table[] = {
+      static_cast<uint16_t>(fact_aux_fn.function_index())};
+
+  r.builder().AddIndirectFunctionTable(indirect_function_table,
+                                       arraysize(indirect_function_table));
+  r.builder().PopulateIndirectFunctionTable();
+
+  BUILD(r, WASM_CALL_FUNCTION(fact_fn.function_index(), WASM_GET_LOCAL(0)));
+
+  BUILD(fact_fn, WASM_RETURN_CALL_INDIRECT(0, WASM_I32V(0), WASM_GET_LOCAL(0),
+                                           WASM_I32V(1)));
+
+  BUILD(fact_aux_fn,
+        WASM_IF_ELSE_I(
+            WASM_I32_EQ(WASM_I32V(1), WASM_GET_LOCAL(0)), WASM_GET_LOCAL(1),
+            WASM_RETURN_CALL_INDIRECT(
+                0, WASM_I32V(0), WASM_I32_SUB(WASM_GET_LOCAL(0), WASM_I32V(1)),
+                WASM_I32_MUL(WASM_GET_LOCAL(0), WASM_GET_LOCAL(1)))));
+
+  int32_t test_values[] = {1, 2, 5, 10, 20};
+
+  for (int32_t v : test_values) {
+    CHECK_EQ(factorial(v), r.Call(v));
+  }
+}
 // Make tests more robust by not hard-coding offsets of various operations.
 // The {Find} method finds the offsets for the given bytecodes, returning
 // the offsets in an array.

test/mjsunit/wasm/wasm-module-builder.js

@@ -204,6 +204,8 @@ let kExprBrTable = 0x0e;
 let kExprReturn = 0x0f;
 let kExprCallFunction = 0x10;
 let kExprCallIndirect = 0x11;
+let kExprReturnCall = 0x12;
+let kExprReturnCallIndirect = 0x13;
 let kExprDrop = 0x1a;
 let kExprSelect = 0x1b;
 let kExprGetLocal = 0x20;