Avoid using a register for constant external array indices.

src/x64/lithium-codegen-x64.cc

 // Copyright 2011 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 2328 matching lines @@
                                key,
                                times_pointer_size,
                                FixedArray::kHeaderSize));
 
   // Check for the hole value.
   __ CompareRoot(result, Heap::kTheHoleValueRootIndex);
   DeoptimizeIf(equal, instr->environment());
 }
 
 
+Operand LCodeGen::BuildExternalArrayOperand(LOperand* external_pointer,
+                                            LOperand* key,
+                                            ExternalArrayType array_type) {
+  Register external_pointer_reg = ToRegister(external_pointer);
+  ScaleFactor scale_factor = times_1;
+  int element_size = 1;
+  switch (array_type) {
+    case kExternalByteArray:
+    case kExternalUnsignedByteArray:
+    case kExternalPixelArray:
+      scale_factor = times_1;
+      element_size = 1;
+      break;
+    case kExternalShortArray:
+    case kExternalUnsignedShortArray:
+      scale_factor = times_2;
+      element_size = 2;
+      break;
+    case kExternalIntArray:
+    case kExternalUnsignedIntArray:
+    case kExternalFloatArray:
+      scale_factor = times_4;
+      element_size = 4;
+      break;
+    case kExternalDoubleArray:
+      scale_factor = times_8;
+      element_size = 8;
+      break;
+  }
+  int constant_value = 0;
+  Register key_reg;
+  bool key_is_constant = key->IsConstantOperand();
+  if (key_is_constant) {
+    constant_value = ToInteger32(LConstantOperand::cast(key));
+    if (constant_value & 0xF0000000) {
+      Abort("array index constant value too big");
+    }
+  } else {
+    key_reg = ToRegister(key);
+  }
+  if (key_is_constant)

[fschneider, 2011/04/29 09:13:47]

Please always add { } for multiline if-statements.

Here you can move the returns into the if-statment above.

[Jakob Kummerow, 2011/04/29 10:04:16]

OK, I'll remember that.
Good idea, that makes the whole thing easier. Done.

+    return Operand(external_pointer_reg, constant_value * element_size);
+  return Operand(external_pointer_reg, key_reg, scale_factor, 0);
+}
+
+
 void LCodeGen::DoLoadKeyedSpecializedArrayElement(
     LLoadKeyedSpecializedArrayElement* instr) {
-  Register external_pointer = ToRegister(instr->external_pointer());
-  Register key = ToRegister(instr->key());
   ExternalArrayType array_type = instr->array_type();
+  Operand operand(BuildExternalArrayOperand(instr->external_pointer(),
+                                            instr->key(), array_type));
   if (array_type == kExternalFloatArray) {
     XMMRegister result(ToDoubleRegister(instr->result()));
-    __ movss(result, Operand(external_pointer, key, times_4, 0));
+    __ movss(result, operand);
     __ cvtss2sd(result, result);
   } else if (array_type == kExternalDoubleArray) {
-    __ movsd(ToDoubleRegister(instr->result()),
-             Operand(external_pointer, key, times_8, 0));
+    __ movsd(ToDoubleRegister(instr->result()), operand);
   } else {
     Register result(ToRegister(instr->result()));
     switch (array_type) {
       case kExternalByteArray:
-        __ movsxbq(result, Operand(external_pointer, key, times_1, 0));
+        __ movsxbq(result, operand);
         break;
       case kExternalUnsignedByteArray:
       case kExternalPixelArray:
-        __ movzxbq(result, Operand(external_pointer, key, times_1, 0));
+        __ movzxbq(result, operand);
         break;
       case kExternalShortArray:
-        __ movsxwq(result, Operand(external_pointer, key, times_2, 0));
+        __ movsxwq(result, operand);
         break;
       case kExternalUnsignedShortArray:
-        __ movzxwq(result, Operand(external_pointer, key, times_2, 0));
+        __ movzxwq(result, operand);
         break;
       case kExternalIntArray:
-        __ movsxlq(result, Operand(external_pointer, key, times_4, 0));
+        __ movsxlq(result, operand);
         break;
       case kExternalUnsignedIntArray:
-        __ movl(result, Operand(external_pointer, key, times_4, 0));
+        __ movl(result, operand);
         __ testl(result, result);
         // TODO(danno): we could be more clever here, perhaps having a special
         // version of the stub that detects if the overflow case actually
         // happens, and generate code that returns a double rather than int.
         DeoptimizeIf(negative, instr->environment());
         break;
       case kExternalFloatArray:
       case kExternalDoubleArray:
         UNREACHABLE();
         break;
@@ skipping 640 matching lines @@
   __ Move(rcx, instr->hydrogen()->name());
   Handle<Code> ic = instr->strict_mode()
       ? isolate()->builtins()->StoreIC_Initialize_Strict()
       : isolate()->builtins()->StoreIC_Initialize();
   CallCode(ic, RelocInfo::CODE_TARGET, instr);
 }
 
 
 void LCodeGen::DoStoreKeyedSpecializedArrayElement(
     LStoreKeyedSpecializedArrayElement* instr) {
-  Register external_pointer = ToRegister(instr->external_pointer());
-  Register key = ToRegister(instr->key());
   ExternalArrayType array_type = instr->array_type();
+  Operand operand(BuildExternalArrayOperand(instr->external_pointer(),
+                                            instr->key(), array_type));
   if (array_type == kExternalFloatArray) {
     XMMRegister value(ToDoubleRegister(instr->value()));
     __ cvtsd2ss(value, value);
-    __ movss(Operand(external_pointer, key, times_4, 0), value);
+    __ movss(operand, value);
   } else if (array_type == kExternalDoubleArray) {
-    __ movsd(Operand(external_pointer, key, times_8, 0),
-             ToDoubleRegister(instr->value()));
+    __ movsd(operand, ToDoubleRegister(instr->value()));
   } else {
     Register value(ToRegister(instr->value()));
     switch (array_type) {
       case kExternalPixelArray:
         {  // Clamp the value to [0..255].
           NearLabel done;
           __ testl(value, Immediate(0xFFFFFF00));
           __ j(zero, &done);
           __ setcc(negative, value);  // 1 if negative, 0 if positive.
           __ decb(value);  // 0 if negative, 255 if positive.
           __ bind(&done);
-          __ movb(Operand(external_pointer, key, times_1, 0), value);
+          __ movb(operand, value);
         }
         break;
       case kExternalByteArray:
       case kExternalUnsignedByteArray:
-        __ movb(Operand(external_pointer, key, times_1, 0), value);
+        __ movb(operand, value);
         break;
       case kExternalShortArray:
       case kExternalUnsignedShortArray:
-        __ movw(Operand(external_pointer, key, times_2, 0), value);
+        __ movw(operand, value);
         break;
       case kExternalIntArray:
       case kExternalUnsignedIntArray:
-        __ movl(Operand(external_pointer, key, times_4, 0), value);
+        __ movl(operand, value);
         break;
       case kExternalFloatArray:
       case kExternalDoubleArray:
         UNREACHABLE();
         break;
     }
   }
 }
 
 
@@ skipping 962 matching lines @@
   RegisterEnvironmentForDeoptimization(environment);
   ASSERT(osr_pc_offset_ == -1);
   osr_pc_offset_ = masm()->pc_offset();
 }
 
 #undef __
 
 } }  // namespace v8::internal
 
 #endif  // V8_TARGET_ARCH_X64