[Interpreter] Only materialize output register if in a different equivalence set.

We only need to materialize the existing output register for a given
register transfer if it is in a different equivalence set, otherwise we
already have the value we want in the output register.

BUG=v8:4280

Change-Id: Ic4966590ac10445180aff353940d2c93e6a818aa
Reviewed-on: https://chromium-review.googlesource.com/493168Reviewed-by: Mythri Alle <mythria@chromium.org>
Commit-Queue: Ross McIlroy <rmcilroy@chromium.org>
Cr-Commit-Position: refs/heads/master@{#45051}

src/interpreter/bytecode-register-optimizer.cc

@@ -318,6 +318,15 @@ void BytecodeRegisterOptimizer::AddToEquivalenceSet(
 
 void BytecodeRegisterOptimizer::RegisterTransfer(RegisterInfo* input_info,
                                                  RegisterInfo* output_info) {
+  bool output_is_observable =
+      RegisterIsObservable(output_info->register_value());
+  bool in_same_equivalence_set =
+      output_info->IsInSameEquivalenceSet(input_info);
+  if (in_same_equivalence_set &&
+      (!output_is_observable || output_info->materialized())) {
+    return;  // Nothing more to do.
+  }
+
   // Materialize an alternate in the equivalence set that
   // |output_info| is leaving.
   if (output_info->materialized()) {
@@ -325,12 +334,10 @@ void BytecodeRegisterOptimizer::RegisterTransfer(RegisterInfo* input_info,
   }
 
   // Add |output_info| to new equivalence set.
-  if (!output_info->IsInSameEquivalenceSet(input_info)) {
+  if (!in_same_equivalence_set) {
     AddToEquivalenceSet(input_info, output_info);
   }
 
-  bool output_is_observable =
-      RegisterIsObservable(output_info->register_value());
   if (output_is_observable) {
     // Force store to be emitted when register is observable.
     output_info->set_materialized(false);

test/cctest/interpreter/bytecode_expectations/ClassDeclarations.golden

@@ -118,7 +118,7 @@ snippet: "
 "
 frame size: 10
 parameter count: 1
-bytecode array length: 116
+bytecode array length: 114
 bytecodes: [
                 B(CreateFunctionContext), U8(2),
                 B(PushContext), R(3),
@@ -158,7 +158,6 @@ bytecodes: [
                 B(JumpIfFalse), U8(7),
                 B(CallRuntime), U16(Runtime::kThrowStaticPrototypeError), R(0), U8(0),
                 B(CreateClosure), U8(5), U8(4), U8(2),
-                B(Star), R(8),
                 B(StaDataPropertyInLiteral), R(6), R(7), U8(3), U8(7),
                 B(CallRuntime), U16(Runtime::kInstallClassNameAccessorWithCheck), R(4), U8(1),
                 B(CallRuntime), U16(Runtime::kToFastProperties), R(4), U8(1),

test/cctest/interpreter/bytecode_expectations/CompoundExpressions.golden

@@ -58,9 +58,9 @@ bytecodes: [
   /*   30 E> */ B(StackCheck),
   /*   42 S> */ B(CreateObjectLiteral), U8(0), U8(2), U8(1), R(1),
                 B(Mov), R(1), R(0),
-  /*   54 S> */ B(LdaNamedProperty), R(0), U8(1), U8(3),
+  /*   54 S> */ B(LdaNamedProperty), R(1), U8(1), U8(3),
                 B(MulSmi), I8(2), U8(5),
-  /*   61 E> */ B(StaNamedPropertySloppy), R(0), U8(1), U8(6),
+  /*   61 E> */ B(StaNamedPropertySloppy), R(1), U8(1), U8(6),
                 B(LdaUndefined),
   /*   67 S> */ B(Return),
 ]
@@ -84,9 +84,9 @@ bytecodes: [
                 B(Mov), R(1), R(0),
   /*   52 S> */ B(LdaSmi), I8(1),
                 B(Star), R(2),
-                B(LdaKeyedProperty), R(0), U8(3),
+                B(LdaKeyedProperty), R(1), U8(3),
                 B(BitwiseXorSmi), I8(2), U8(5),
-  /*   57 E> */ B(StaKeyedPropertySloppy), R(0), R(2), U8(6),
+  /*   57 E> */ B(StaKeyedPropertySloppy), R(1), R(2), U8(6),
                 B(LdaUndefined),
   /*   63 S> */ B(Return),
 ]

test/cctest/interpreter/bytecode_expectations/CountOperators.golden

@@ -102,11 +102,11 @@ bytecodes: [
   /*   30 E> */ B(StackCheck),
   /*   42 S> */ B(CreateObjectLiteral), U8(0), U8(2), U8(1), R(1),
                 B(Mov), R(1), R(0),
-  /*   54 S> */ B(LdaNamedProperty), R(0), U8(1), U8(3),
+  /*   54 S> */ B(LdaNamedProperty), R(1), U8(1), U8(3),
                 B(ToNumber), R(2), U8(7),
                 B(Ldar), R(2),
                 B(Inc), U8(7),
-  /*   66 E> */ B(StaNamedPropertySloppy), R(0), U8(1), U8(5),
+  /*   66 E> */ B(StaNamedPropertySloppy), R(1), U8(1), U8(5),
                 B(Ldar), R(2),
   /*   70 S> */ B(Return),
 ]
@@ -128,9 +128,9 @@ bytecodes: [
   /*   30 E> */ B(StackCheck),
   /*   42 S> */ B(CreateObjectLiteral), U8(0), U8(2), U8(1), R(1),
                 B(Mov), R(1), R(0),
-  /*   54 S> */ B(LdaNamedProperty), R(0), U8(1), U8(3),
+  /*   54 S> */ B(LdaNamedProperty), R(1), U8(1), U8(3),
                 B(Dec), U8(7),
-  /*   65 E> */ B(StaNamedPropertySloppy), R(0), U8(1), U8(5),
+  /*   65 E> */ B(StaNamedPropertySloppy), R(1), U8(1), U8(5),
   /*   70 S> */ B(Return),
 ]
 constant pool: [
@@ -154,11 +154,11 @@ bytecodes: [
   /*   60 S> */ B(CreateObjectLiteral), U8(1), U8(2), U8(1), R(2),
                 B(Mov), R(2), R(1),
   /*   72 S> */ B(Ldar), R(0),
-  /*   81 E> */ B(LdaKeyedProperty), R(1), U8(3),
+  /*   81 E> */ B(LdaKeyedProperty), R(2), U8(3),
                 B(ToNumber), R(4), U8(7),
                 B(Ldar), R(4),
                 B(Dec), U8(7),
-  /*   86 E> */ B(StaKeyedPropertySloppy), R(1), R(0), U8(5),
+  /*   86 E> */ B(StaKeyedPropertySloppy), R(2), R(0), U8(5),
                 B(Ldar), R(4),
   /*   90 S> */ B(Return),
 ]
@@ -183,9 +183,9 @@ bytecodes: [
   /*   60 S> */ B(CreateObjectLiteral), U8(1), U8(2), U8(1), R(2),
                 B(Mov), R(2), R(1),
   /*   72 S> */ B(Ldar), R(0),
-  /*   83 E> */ B(LdaKeyedProperty), R(1), U8(3),
+  /*   83 E> */ B(LdaKeyedProperty), R(2), U8(3),
                 B(Inc), U8(7),
-  /*   87 E> */ B(StaKeyedPropertySloppy), R(1), R(0), U8(5),
+  /*   87 E> */ B(StaKeyedPropertySloppy), R(2), R(0), U8(5),
   /*   90 S> */ B(Return),
 ]
 constant pool: [

test/cctest/interpreter/bytecode_expectations/Delete.golden

@@ -17,7 +17,7 @@ bytecodes: [
   /*   42 S> */ B(CreateObjectLiteral), U8(0), U8(2), U8(1), R(1),
                 B(Mov), R(1), R(0),
   /*   56 S> */ B(LdaConstant), U8(1),
-                B(DeletePropertySloppy), R(0),
+                B(DeletePropertySloppy), R(1),
   /*   75 S> */ B(Return),
 ]
 constant pool: [
@@ -39,7 +39,7 @@ bytecodes: [
   /*   56 S> */ B(CreateObjectLiteral), U8(0), U8(2), U8(1), R(1),
                 B(Mov), R(1), R(0),
   /*   70 S> */ B(LdaConstant), U8(1),
-                B(DeletePropertyStrict), R(0),
+                B(DeletePropertyStrict), R(1),
   /*   89 S> */ B(Return),
 ]
 constant pool: [
@@ -61,7 +61,7 @@ bytecodes: [
   /*   42 S> */ B(CreateObjectLiteral), U8(0), U8(2), U8(1), R(1),
                 B(Mov), R(1), R(0),
   /*   56 S> */ B(LdaSmi), I8(2),
-                B(DeletePropertySloppy), R(0),
+                B(DeletePropertySloppy), R(1),
   /*   76 S> */ B(Return),
 ]
 constant pool: [

test/cctest/interpreter/bytecode_expectations/ForOf.golden

@@ -50,8 +50,8 @@ bytecodes: [
                 B(Star), R(13),
                 B(Ldar), R(closure),
                 B(CreateCatchContext), R(13), U8(5), U8(6),
-                B(Star), R(12),
                 B(PushContext), R(8),
+                B(Star), R(12),
                 B(LdaSmi), I8(2),
                 B(TestEqualStrict), R(4), U8(15),
                 B(JumpIfFalse), U8(6),
@@ -191,8 +191,8 @@ bytecodes: [
                 B(Star), R(14),
                 B(Ldar), R(closure),
                 B(CreateCatchContext), R(14), U8(5), U8(6),
-                B(Star), R(13),
                 B(PushContext), R(9),
+                B(Star), R(13),
                 B(LdaSmi), I8(2),
                 B(TestEqualStrict), R(5), U8(14),
                 B(JumpIfFalse), U8(6),
@@ -345,8 +345,8 @@ bytecodes: [
                 B(Star), R(13),
                 B(Ldar), R(closure),
                 B(CreateCatchContext), R(13), U8(5), U8(6),
-                B(Star), R(12),
                 B(PushContext), R(8),
+                B(Star), R(12),
                 B(LdaSmi), I8(2),
                 B(TestEqualStrict), R(4), U8(17),
                 B(JumpIfFalse), U8(6),
@@ -489,8 +489,8 @@ bytecodes: [
                 B(Star), R(12),
                 B(Ldar), R(closure),
                 B(CreateCatchContext), R(12), U8(7), U8(8),
-                B(Star), R(11),
                 B(PushContext), R(7),
+                B(Star), R(11),
                 B(LdaSmi), I8(2),
                 B(TestEqualStrict), R(3), U8(20),
                 B(JumpIfFalse), U8(6),

test/cctest/interpreter/bytecode_expectations/ForOfLoop.golden

@@ -60,8 +60,8 @@ bytecodes: [
                 B(Star), R(15),
                 B(Ldar), R(closure),
   /*   49 E> */ B(CreateCatchContext), R(15), U8(4), U8(5),
-                B(Star), R(14),
                 B(PushContext), R(10),
+                B(Star), R(14),
                 B(LdaSmi), I8(2),
                 B(TestEqualStrict), R(6), U8(14),
                 B(JumpIfFalse), U8(6),
@@ -238,8 +238,8 @@ bytecodes: [
                 B(Star), R(14),
                 B(Ldar), R(closure),
                 B(CreateCatchContext), R(14), U8(8), U8(9),
-                B(Star), R(13),
                 B(PushContext), R(9),
+                B(Star), R(13),
                 B(LdaSmi), I8(2),
                 B(TestEqualStrict), R(3), U8(18),
                 B(JumpIfFalse), U8(6),
@@ -395,8 +395,8 @@ bytecodes: [
                 B(Star), R(13),
                 B(Ldar), R(closure),
                 B(CreateCatchContext), R(13), U8(6), U8(7),
-                B(Star), R(12),
                 B(PushContext), R(8),
+                B(Star), R(12),
                 B(LdaSmi), I8(2),
                 B(TestEqualStrict), R(4), U8(17),
                 B(JumpIfFalse), U8(6),
@@ -563,8 +563,8 @@ bytecodes: [
                 B(Star), R(18),
                 B(Ldar), R(closure),
   /*   58 E> */ B(CreateCatchContext), R(18), U8(7), U8(8),
-                B(Star), R(17),
                 B(PushContext), R(13),
+                B(Star), R(17),
                 B(LdaSmi), I8(2),
                 B(TestEqualStrict), R(9), U8(21),
                 B(JumpIfFalse), U8(6),
@@ -791,8 +791,8 @@ bytecodes: [
                 B(Star), R(13),
                 B(Ldar), R(closure),
                 B(CreateCatchContext), R(13), U8(7), U8(8),
-                B(Star), R(12),
                 B(PushContext), R(2),
+                B(Star), R(12),
                 B(LdaContextSlot), R(1), U8(10), U8(0),
                 B(Star), R(13),
                 B(LdaSmi), I8(2),
@@ -1133,8 +1133,8 @@ bytecodes: [
                 B(Star), R(12),
                 B(Ldar), R(closure),
                 B(CreateCatchContext), R(12), U8(6), U8(7),
-                B(Star), R(11),
                 B(PushContext), R(2),
+                B(Star), R(11),
                 B(LdaContextSlot), R(1), U8(10), U8(0),
                 B(Star), R(12),
                 B(LdaSmi), I8(2),

test/cctest/interpreter/bytecode_expectations/Generators.golden

@@ -448,8 +448,8 @@ bytecodes: [
                 B(Star), R(12),
                 B(Ldar), R(closure),
                 B(CreateCatchContext), R(12), U8(7), U8(8),
-                B(Star), R(11),
                 B(PushContext), R(2),
+                B(Star), R(11),
                 B(LdaContextSlot), R(1), U8(9), U8(0),
                 B(Star), R(12),
                 B(LdaSmi), I8(2),

test/cctest/interpreter/bytecode_expectations/LetVariable.golden

@@ -53,7 +53,7 @@ snippet: "
 "
 frame size: 3
 parameter count: 1
-bytecode array length: 29
+bytecode array length: 26
 bytecodes: [
                 B(LdaTheHole),
                 B(Star), R(0),
@@ -65,7 +65,6 @@ bytecodes: [
                 B(LdaConstant), U8(0),
                 B(Star), R(2),
   /*   45 E> */ B(CallRuntime), U16(Runtime::kThrowReferenceError), R(2), U8(1),
-                B(Mov), R(1), R(0),
                 B(Mov), R(1), R(0),
                 B(LdaUndefined),
   /*   52 S> */ B(Return),

test/cctest/interpreter/bytecode_expectations/ObjectLiterals.golden

@@ -281,9 +281,9 @@ handlers: [
 snippet: "
   var a = 'test'; return { [a]: 1 };
 "
-frame size: 4
+frame size: 3
 parameter count: 1
-bytecode array length: 24
+bytecode array length: 22
 bytecodes: [
   /*   30 E> */ B(StackCheck),
   /*   42 S> */ B(LdaConstant), U8(0),
@@ -291,7 +291,6 @@ bytecodes: [
   /*   50 S> */ B(CreateObjectLiteral), U8(1), U8(2), U8(67), R(1),
   /*   60 E> */ B(ToName), R(2),
                 B(LdaSmi), I8(1),
-                B(Star), R(3),
                 B(StaDataPropertyInLiteral), R(1), R(2), U8(0), U8(3),
                 B(Ldar), R(1),
   /*   69 S> */ B(Return),
@@ -307,9 +306,9 @@ handlers: [
 snippet: "
   var a = 'test'; return { val: a, [a]: 1 };
 "
-frame size: 4
+frame size: 3
 parameter count: 1
-bytecode array length: 28
+bytecode array length: 26
 bytecodes: [
   /*   30 E> */ B(StackCheck),
   /*   42 S> */ B(LdaConstant), U8(0),
@@ -318,7 +317,6 @@ bytecodes: [
   /*   64 E> */ B(StaNamedOwnProperty), R(1), U8(2), U8(3),
   /*   68 E> */ B(ToName), R(2),
                 B(LdaSmi), I8(1),
-                B(Star), R(3),
                 B(StaDataPropertyInLiteral), R(1), R(2), U8(0), U8(5),
                 B(Ldar), R(1),
   /*   77 S> */ B(Return),
@@ -345,9 +343,9 @@ bytecodes: [
   /*   50 S> */ B(CreateObjectLiteral), U8(1), U8(3), U8(67), R(1),
   /*   60 E> */ B(ToName), R(2),
                 B(LdaSmi), I8(1),
-                B(Star), R(3),
                 B(StaDataPropertyInLiteral), R(1), R(2), U8(0), U8(4),
                 B(CreateObjectLiteral), U8(1), U8(2), U8(67), R(4),
+                B(Star), R(3),
                 B(Mov), R(1), R(2),
                 B(Mov), R(4), R(3),
                 B(CallRuntime), U16(Runtime::kInternalSetPrototype), R(2), U8(2),
@@ -375,8 +373,8 @@ bytecodes: [
   /*   50 S> */ B(CreateObjectLiteral), U8(1), U8(4), U8(67), R(1),
   /*   60 E> */ B(ToName), R(2),
                 B(LdaConstant), U8(2),
-                B(Star), R(3),
                 B(StaDataPropertyInLiteral), R(1), R(2), U8(0), U8(5),
+                B(Star), R(3),
                 B(LdaConstant), U8(3),
                 B(Star), R(3),
                 B(CreateClosure), U8(4), U8(2), U8(2),