Improvements in lithium code generation. Recognizing if some operands are constants, we can often s…

src/ia32/lithium-ia32.cc

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 2273 matching lines @@
 
     if (instr->value()->representation().IsDouble()) {
       LOperand* object = UseRegisterAtStart(instr->elements());
       LOperand* val = NULL;
       if (CpuFeatures::IsSafeForSnapshot(SSE2)) {
         val = UseRegisterAtStart(instr->value());
       } else if (!instr->IsConstantHoleStore()) {
         val = UseX87TopOfStack(instr->value());
       }
       LOperand* key = UseRegisterOrConstantAtStart(instr->key());
-
       return new(zone()) LStoreKeyed(object, key, val);
     } else {
       ASSERT(instr->value()->representation().IsTagged());
       bool needs_write_barrier = instr->NeedsWriteBarrier();
 
       LOperand* obj = UseRegister(instr->elements());
-      LOperand* val = needs_write_barrier
-          ? UseTempRegister(instr->value())
-          : UseRegisterAtStart(instr->value());
-      LOperand* key = needs_write_barrier
-          ? UseTempRegister(instr->key())
-          : UseRegisterOrConstantAtStart(instr->key());
+      LOperand* val;
+      LOperand* key;
+      if (needs_write_barrier) {
+        val = UseTempRegister(instr->value());
+        key = UseTempRegister(instr->key());
+      } else {
+        val = UseRegisterOrConstantAtStart(instr->value());
+        key = UseRegisterOrConstantAtStart(instr->key());
+      }
       return new(zone()) LStoreKeyed(obj, key, val);
     }
   }
 
   ElementsKind elements_kind = instr->elements_kind();
   ASSERT(
       (instr->value()->representation().IsInteger32() &&
        (elements_kind != EXTERNAL_FLOAT_ELEMENTS) &&
        (elements_kind != EXTERNAL_DOUBLE_ELEMENTS)) ||
       (instr->value()->representation().IsDouble() &&
@@ skipping 79 matching lines @@
   if (needs_write_barrier) {
     obj = instr->is_in_object()
         ? UseRegister(instr->object())
         : UseTempRegister(instr->object());
   } else {
     obj = needs_write_barrier_for_map
         ? UseRegister(instr->object())
         : UseRegisterAtStart(instr->object());
   }
 
-  LOperand* val = needs_write_barrier
-      ? UseTempRegister(instr->value())
-      : UseRegister(instr->value());
+  LOperand* val = NULL;
+  if (needs_write_barrier) {
+    val = UseTempRegister(instr->value());
+  } else if (instr->value()->IsConstant()) {
+    // If it's tagged, it might still be in new space
+    HConstant* constant_value = HConstant::cast(instr->value());
+    if (constant_value->HasInteger32Value() ||
+        constant_value->HasDoubleValue() ||
+        constant_value->ImmortalImmovable()) {
+      val = UseRegisterOrConstant(instr->value());
+    }
+  }
+
+  if (val == NULL) {
+    val = UseRegister(instr->value());

[danno, 2013/04/18 15:37:54]

Can't you just move this to the else of the above clause?

[mvstanton, 2013/04/19 16:53:28]

I reworked this to be less awkward, I think.

+  }
 
   // We only need a scratch register if we have a write barrier or we
   // have a store into the properties array (not in-object-property).
   LOperand* temp = (!instr->is_in_object() || needs_write_barrier ||
       needs_write_barrier_for_map) ? TempRegister() : NULL;
 
   // We need a temporary register for write barrier of the map field.
   LOperand* temp_map = needs_write_barrier_for_map ? TempRegister() : NULL;
 
   return new(zone()) LStoreNamedField(obj, val, temp, temp_map);
@@ skipping 146 matching lines @@
   // There are no real uses of the arguments object.
   // arguments.length and element access are supported directly on
   // stack arguments, and any real arguments object use causes a bailout.
   // So this value is never used.
   return NULL;
 }
 
 
 LInstruction* LChunkBuilder::DoAccessArgumentsAt(HAccessArgumentsAt* instr) {
   LOperand* args = UseRegister(instr->arguments());
-  LOperand* length = UseTempRegister(instr->length());
-  LOperand* index = Use(instr->index());
+  LOperand* length;
+  LOperand* index;
+  if (instr->length()->IsConstant() && instr->index()->IsConstant()) {
+    length = UseRegisterOrConstant(instr->length());
+    index = UseOrConstant(instr->index());
+  } else {
+    length = UseTempRegister(instr->length());
+    index = Use(instr->index());
+  }
   return DefineAsRegister(new(zone()) LAccessArgumentsAt(args, length, index));
 }
 
 
 LInstruction* LChunkBuilder::DoToFastProperties(HToFastProperties* instr) {
   LOperand* object = UseFixed(instr->value(), eax);
   LToFastProperties* result = new(zone()) LToFastProperties(object);
   return MarkAsCall(DefineFixed(result, eax), instr);
 }
 
@@ skipping 137 matching lines @@
 LInstruction* LChunkBuilder::DoLoadFieldByIndex(HLoadFieldByIndex* instr) {
   LOperand* object = UseRegister(instr->object());
   LOperand* index = UseTempRegister(instr->index());
   return DefineSameAsFirst(new(zone()) LLoadFieldByIndex(object, index));
 }
 
 
 } }  // namespace v8::internal
 
 #endif  // V8_TARGET_ARCH_IA32