Delegating yield does not re-box result objects

Delegating yield (yield*) should just pass on the iterator results it
receives instead of re-boxing them.

R=rossberg@chromium.org
TEST=mjsunit/harmony/generators-iteration
BUG=

Review URL: https://codereview.chromium.org/16695006

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@15113 ce2b1a6d-e550-0410-aec6-3dcde31c8c00

src/arm/full-codegen-arm.cc

@@ -2044,9 +2044,11 @@ void FullCodeGenerator::VisitYield(Yield* expr) {
       __ push(r0);                                       // exception
       __ jmp(&l_call);
 
-      // try { received = yield result.value }
+      // try { received = %yield result }
+      // Shuffle the received result above a try handler and yield it without
+      // re-boxing.
       __ bind(&l_try);
-      EmitCreateIteratorResult(false);                   // pop and box to r0
+      __ pop(r0);                                        // result
       __ PushTryHandler(StackHandler::CATCH, expr->index());
       const int handler_size = StackHandlerConstants::kSize;
       __ push(r0);                                       // result
@@ -2075,16 +2077,9 @@ void FullCodeGenerator::VisitYield(Yield* expr) {
       CallIC(ic);
       __ ldr(cp, MemOperand(fp, StandardFrameConstants::kContextOffset));
 
-      // val = result.value; if (!result.done) goto l_try;
+      // if (!result.done) goto l_try;
       __ bind(&l_loop);
-      // result.value
       __ push(r0);                                       // save result
-      __ LoadRoot(r2, Heap::kvalue_stringRootIndex);     // "value"
-      Handle<Code> value_ic = isolate()->builtins()->LoadIC_Initialize();
-      CallIC(value_ic);                                  // result.value in r0
-      __ pop(r1);                                        // result
-      __ push(r0);                                       // result.value
-      __ mov(r0, r1);                                    // result
       __ LoadRoot(r2, Heap::kdone_stringRootIndex);      // "done"
       Handle<Code> done_ic = isolate()->builtins()->LoadIC_Initialize();
       CallIC(done_ic);                                   // result.done in r0
@@ -2094,7 +2089,10 @@ void FullCodeGenerator::VisitYield(Yield* expr) {
       __ b(eq, &l_try);
 
       // result.value
-      __ pop(r0);                                        // result.value
+      __ pop(r0);                                        // result
+      __ LoadRoot(r2, Heap::kvalue_stringRootIndex);     // "value"
+      Handle<Code> value_ic = isolate()->builtins()->LoadIC_Initialize();
+      CallIC(value_ic);                                  // result.value in r0
       context()->DropAndPlug(2, r0);                     // drop iter and g
       break;
     }

src/ia32/full-codegen-ia32.cc

@@ -2003,9 +2003,11 @@ void FullCodeGenerator::VisitYield(Yield* expr) {
       __ push(eax);                                      // exception
       __ jmp(&l_call);
 
-      // try { received = yield result.value }
+      // try { received = %yield result }
+      // Shuffle the received result above a try handler and yield it without
+      // re-boxing.
       __ bind(&l_try);
-      EmitCreateIteratorResult(false);                    // pop and box to eax
+      __ pop(eax);                                       // result
       __ PushTryHandler(StackHandler::CATCH, expr->index());
       const int handler_size = StackHandlerConstants::kSize;
       __ push(eax);                                      // result
@@ -2034,17 +2036,10 @@ void FullCodeGenerator::VisitYield(Yield* expr) {
       __ mov(esi, Operand(ebp, StandardFrameConstants::kContextOffset));
       __ Drop(1);  // The key is still on the stack; drop it.
 
-      // val = result.value; if (!result.done) goto l_try;
+      // if (!result.done) goto l_try;
       __ bind(&l_loop);
-      // result.value
       __ push(eax);                                      // save result
       __ mov(edx, eax);                                  // result
-      __ mov(ecx, isolate()->factory()->value_string());  // "value"
-      Handle<Code> value_ic = isolate()->builtins()->LoadIC_Initialize();
-      CallIC(value_ic);                                  // result.value in eax
-      __ pop(ebx);                                       // result
-      __ push(eax);                                      // result.value
-      __ mov(edx, ebx);                                  // result
       __ mov(ecx, isolate()->factory()->done_string());  // "done"
       Handle<Code> done_ic = isolate()->builtins()->LoadIC_Initialize();
       CallIC(done_ic);                                   // result.done in eax
@@ -2054,7 +2049,10 @@ void FullCodeGenerator::VisitYield(Yield* expr) {
       __ j(zero, &l_try);
 
       // result.value
-      __ pop(eax);                                       // result.value
+      __ pop(edx);                                       // result
+      __ mov(ecx, isolate()->factory()->value_string());  // "value"
+      Handle<Code> value_ic = isolate()->builtins()->LoadIC_Initialize();
+      CallIC(value_ic);                                  // result.value in eax
       context()->DropAndPlug(2, eax);                    // drop iter and g
       break;
     }

src/x64/full-codegen-x64.cc

@@ -2026,9 +2026,11 @@ void FullCodeGenerator::VisitYield(Yield* expr) {
       __ push(rax);                                      // exception
       __ jmp(&l_call);
 
-      // try { received = yield result.value }
+      // try { received = %yield result }
+      // Shuffle the received result above a try handler and yield it without
+      // re-boxing.
       __ bind(&l_try);
-      EmitCreateIteratorResult(false);                    // pop and box to rax
+      __ pop(rax);                                       // result
       __ PushTryHandler(StackHandler::CATCH, expr->index());
       const int handler_size = StackHandlerConstants::kSize;
       __ push(rax);                                      // result
@@ -2057,16 +2059,9 @@ void FullCodeGenerator::VisitYield(Yield* expr) {
       __ movq(rsi, Operand(rbp, StandardFrameConstants::kContextOffset));
       __ Drop(1);  // The key is still on the stack; drop it.
 
-      // val = result.value; if (!result.done) goto l_try;
+      // if (!result.done) goto l_try;
       __ bind(&l_loop);
-      // result.value
       __ push(rax);                                      // save result
-      __ LoadRoot(rcx, Heap::kvalue_stringRootIndex);    // "value"
-      Handle<Code> value_ic = isolate()->builtins()->LoadIC_Initialize();
-      CallIC(value_ic);                                  // result.value in rax
-      __ pop(rbx);                                       // result
-      __ push(rax);                                      // result.value
-      __ movq(rax, rbx);                                 // result
       __ LoadRoot(rcx, Heap::kdone_stringRootIndex);     // "done"
       Handle<Code> done_ic = isolate()->builtins()->LoadIC_Initialize();
       CallIC(done_ic);                                   // result.done in rax
@@ -2076,7 +2071,10 @@ void FullCodeGenerator::VisitYield(Yield* expr) {
       __ j(zero, &l_try);
 
       // result.value
-      __ pop(rax);                                       // result.value
+      __ pop(rax);                                       // result
+      __ LoadRoot(rcx, Heap::kvalue_stringRootIndex);    // "value"
+      Handle<Code> value_ic = isolate()->builtins()->LoadIC_Initialize();
+      CallIC(value_ic);                                  // result.value in rax
       context()->DropAndPlug(2, rax);                    // drop iter and g
       break;
     }

test/mjsunit/harmony/generators-iteration.js

@@ -346,6 +346,36 @@ TestGenerator(
     "foo",
     [3, undefined]);
 
+// Test that yield* re-yields received results without re-boxing.
+function TestDelegatingYield() {
+  function results(results) {
+    var i = 0;
+    function next() {
+      return results[i++];
+    }
+    return { next: next }
+  }
+  function* yield_results(expected) {
+    return yield* results(expected);
+  }
+  function collect_results(iter) {
+    var ret = [];
+    var result;
+    do {
+      result = iter.next();
+      ret.push(result);
+    } while (!result.done);
+    return ret;
+  }
+  // We have to put a full result for the end, because the return will re-box.
+  var expected = [{value: 1}, 13, "foo", {value: 34, done: true}];
+
+  // Sanity check.
+  assertEquals(expected, collect_results(results(expected)));
+  assertEquals(expected, collect_results(yield_results(expected)));
+}
+TestDelegatingYield();
+
 function TestTryCatch(instantiate) {
   function* g() { yield 1; try { yield 2; } catch (e) { yield e; } yield 3; }
   function Sentinel() {}