MIPS: Improve constant element index access code generation

src/mips/lithium-codegen-mips.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 2507 matching lines @@
   __ subu(length, length, index);
   __ Addu(length, length, Operand(1));
   __ sll(length, length, kPointerSizeLog2);
   __ Addu(at, arguments, Operand(length));
   __ lw(result, MemOperand(at, 0));
 }
 
 
 void LCodeGen::DoLoadKeyedFastElement(LLoadKeyedFastElement* instr) {
   Register elements = ToRegister(instr->elements());
-  Register key = EmitLoadRegister(instr->key(), scratch0());
   Register result = ToRegister(instr->result());
   Register scratch = scratch0();
 
-  // Load the result.
-  if (instr->hydrogen()->key()->representation().IsTagged()) {
-    __ sll(scratch, key, kPointerSizeLog2 - kSmiTagSize);
-    __ addu(scratch, elements, scratch);
+  if (instr->key()->IsConstantOperand()) {
+    LConstantOperand* const_operand = LConstantOperand::cast(instr->key());
+    int offset =
+        (ToInteger32(const_operand) + instr->additional_index()) * kPointerSize
+        + FixedArray::kHeaderSize;
+    __ lw(result, FieldMemOperand(elements, offset));
   } else {
-    __ sll(scratch, key, kPointerSizeLog2);
-    __ addu(scratch, elements, scratch);
+    Register key = EmitLoadRegister(instr->key(), scratch);
+    // Even though the HLoadKeyedFastElement instruction forces the input
+    // representation for the key to be an integer, the input gets replaced
+    // during bound check elimination with the index argument to the bounds
+    // check, which can be tagged, so that case must be handled here, too.
+    if (instr->hydrogen()->key()->representation().IsTagged()) {
+      __ sll(scratch, key, kPointerSizeLog2 - kSmiTagSize);
+      __ addu(scratch, elements, scratch);
+    } else {
+      __ sll(scratch, key, kPointerSizeLog2);
+      __ addu(scratch, elements, scratch);
+    }
+    uint32_t offset = FixedArray::kHeaderSize +
+        (instr->additional_index() << kPointerSizeLog2);
+    __ lw(result, FieldMemOperand(scratch, offset));
   }
-  uint32_t offset = FixedArray::kHeaderSize +
-                    (instr->additional_index() << kPointerSizeLog2);
-  __ lw(result, FieldMemOperand(scratch, offset));
 
   // Check for the hole value.
   if (instr->hydrogen()->RequiresHoleCheck()) {
     if (IsFastSmiElementsKind(instr->hydrogen()->elements_kind())) {
       __ And(scratch, result, Operand(kSmiTagMask));
       DeoptimizeIf(ne, instr->environment(), scratch, Operand(zero_reg));
     } else {
       __ LoadRoot(scratch, Heap::kTheHoleValueRootIndex);
       DeoptimizeIf(eq, instr->environment(), result, Operand(scratch));
     }
@@ skipping 1025 matching lines @@
   // Name is always in a2.
   __ li(a2, Operand(instr->name()));
   Handle<Code> ic = (instr->strict_mode_flag() == kStrictMode)
       ? isolate()->builtins()->StoreIC_Initialize_Strict()
       : isolate()->builtins()->StoreIC_Initialize();
   CallCode(ic, RelocInfo::CODE_TARGET, instr);
 }
 
 
 void LCodeGen::DoBoundsCheck(LBoundsCheck* instr) {
-  DeoptimizeIf(hs,
-               instr->environment(),
-               ToRegister(instr->index()),
-               Operand(ToRegister(instr->length())));
+  if (instr->index()->IsConstantOperand()) {
+    int constant_index =
+        ToInteger32(LConstantOperand::cast(instr->index()));
+    if (instr->hydrogen()->length()->representation().IsTagged()) {
+      __ li(at, Operand(Smi::FromInt(constant_index)));
+    } else {
+      __ li(at, Operand(constant_index));
+    }
+    DeoptimizeIf(hs,
+                 instr->environment(),
+                 at,
+                 Operand(ToRegister(instr->length())));
+  } else {
+    DeoptimizeIf(hs,
+                 instr->environment(),
+                 ToRegister(instr->index()),
+                 Operand(ToRegister(instr->length())));
+  }
 }
 
 
 void LCodeGen::DoStoreKeyedFastElement(LStoreKeyedFastElement* instr) {
   Register value = ToRegister(instr->value());
   Register elements = ToRegister(instr->object());
   Register key = instr->key()->IsRegister() ? ToRegister(instr->key()) : no_reg;
   Register scratch = scratch0();
 
   // Do the store.
   if (instr->key()->IsConstantOperand()) {
     ASSERT(!instr->hydrogen()->NeedsWriteBarrier());
     LConstantOperand* const_operand = LConstantOperand::cast(instr->key());
     int offset =
         (ToInteger32(const_operand) + instr->additional_index()) * kPointerSize
         + FixedArray::kHeaderSize;
     __ sw(value, FieldMemOperand(elements, offset));
   } else {
+    // Even though the HLoadKeyedFastElement instruction forces the input
+    // representation for the key to be an integer, the input gets replaced
+    // during bound check elimination with the index argument to the bounds
+    // check, which can be tagged, so that case must be handled here, too.
     if (instr->hydrogen()->key()->representation().IsTagged()) {
       __ sll(scratch, key, kPointerSizeLog2 - kSmiTagSize);
       __ addu(scratch, elements, scratch);
     } else {
       __ sll(scratch, key, kPointerSizeLog2);
       __ addu(scratch, elements, scratch);
     }
-    if (instr->additional_index() != 0) {
-      __ Addu(scratch,
-              scratch,
-              instr->additional_index() << kPointerSizeLog2);
-    }
-    __ sw(value, FieldMemOperand(scratch, FixedArray::kHeaderSize));
+    uint32_t offset = FixedArray::kHeaderSize +
+        (instr->additional_index() << kPointerSizeLog2);
+    __ sw(value, FieldMemOperand(scratch, offset));
   }
 
   if (instr->hydrogen()->NeedsWriteBarrier()) {
     HType type = instr->hydrogen()->value()->type();
     SmiCheck check_needed =
         type.IsHeapObject() ? OMIT_SMI_CHECK : INLINE_SMI_CHECK;
     // Compute address of modified element and store it into key register.
     __ Addu(key, scratch, Operand(FixedArray::kHeaderSize - kHeapObjectTag));
     __ RecordWrite(elements,
                    key,
@@ skipping 1606 matching lines @@
   __ Subu(scratch, result, scratch);
   __ lw(result, FieldMemOperand(scratch,
                                 FixedArray::kHeaderSize - kPointerSize));
   __ bind(&done);
 }
 
 
 #undef __
 
 } }  // namespace v8::internal