MIPS: Array index computation dehoisting.

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 2486 matching lines @@
 
 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.
   __ sll(scratch, key, kPointerSizeLog2);  // Key indexes words.
   __ addu(scratch, elements, scratch);
-  __ lw(result, FieldMemOperand(scratch, FixedArray::kHeaderSize));
+  uint32_t offset = FixedArray::kHeaderSize +
+                    (instr->additional_index() << kPointerSizeLog2);
+  __ lw(result, FieldMemOperand(scratch, offset));
 
   // Check for the hole value.
   if (instr->hydrogen()->RequiresHoleCheck()) {
     __ LoadRoot(scratch, Heap::kTheHoleValueRootIndex);
     DeoptimizeIf(eq, instr->environment(), result, Operand(scratch));
   }
 }
 
 
 void LCodeGen::DoLoadKeyedFastDoubleElement(
@@ skipping 10 matching lines @@
   if (key_is_constant) {
     constant_key = ToInteger32(LConstantOperand::cast(instr->key()));
     if (constant_key & 0xF0000000) {
       Abort("array index constant value too big.");
     }
   } else {
     key = ToRegister(instr->key());
   }
 
   if (key_is_constant) {
-    __ Addu(elements, elements, Operand(constant_key * (1 << shift_size) +
-            FixedDoubleArray::kHeaderSize - kHeapObjectTag));
+    __ Addu(elements, elements,
+        Operand(((constant_key + instr->additional_index()) << shift_size) +
+                FixedDoubleArray::kHeaderSize - kHeapObjectTag));
   } else {
     __ sll(scratch, key, shift_size);
     __ Addu(elements, elements, Operand(scratch));
     __ Addu(elements, elements,
-            Operand(FixedDoubleArray::kHeaderSize - kHeapObjectTag));
+            Operand((FixedDoubleArray::kHeaderSize - kHeapObjectTag) +
+                    (instr->additional_index() << shift_size)));
   }
 
   if (instr->hydrogen()->RequiresHoleCheck()) {
     __ lw(scratch, MemOperand(elements, sizeof(kHoleNanLower32)));
     DeoptimizeIf(eq, instr->environment(), scratch, Operand(kHoleNanUpper32));
   }
 
   __ ldc1(result, MemOperand(elements));
 }
 
 
 void LCodeGen::DoLoadKeyedSpecializedArrayElement(
     LLoadKeyedSpecializedArrayElement* instr) {
   Register external_pointer = ToRegister(instr->external_pointer());
   Register key = no_reg;
   ElementsKind elements_kind = instr->elements_kind();
   bool key_is_constant = instr->key()->IsConstantOperand();
   int constant_key = 0;
   if (key_is_constant) {
     constant_key = ToInteger32(LConstantOperand::cast(instr->key()));
     if (constant_key & 0xF0000000) {
       Abort("array index constant value too big.");
     }
   } else {
     key = ToRegister(instr->key());
   }
   int shift_size = ElementsKindToShiftSize(elements_kind);
+  int additional_offset = instr->additional_index() << shift_size;
 
   if (elements_kind == EXTERNAL_FLOAT_ELEMENTS ||
       elements_kind == EXTERNAL_DOUBLE_ELEMENTS) {
     FPURegister result = ToDoubleRegister(instr->result());
     if (key_is_constant) {
-      __ Addu(scratch0(), external_pointer, constant_key * (1 << shift_size));
+      __ Addu(scratch0(), external_pointer, constant_key << shift_size);
     } else {
       __ sll(scratch0(), key, shift_size);
       __ Addu(scratch0(), scratch0(), external_pointer);
     }
 
     if (elements_kind == EXTERNAL_FLOAT_ELEMENTS) {
-      __ lwc1(result, MemOperand(scratch0()));
+      __ lwc1(result, MemOperand(scratch0(), additional_offset));
       __ cvt_d_s(result, result);
     } else  {  // i.e. elements_kind == EXTERNAL_DOUBLE_ELEMENTS
-      __ ldc1(result, MemOperand(scratch0()));
+      __ ldc1(result, MemOperand(scratch0(), additional_offset));
     }
   } else {
     Register result = ToRegister(instr->result());
     Register scratch = scratch0();
+    if (instr->additional_index() != 0 && !key_is_constant) {
+      __ Addu(scratch, key, instr->additional_index());
+    }
     MemOperand mem_operand(zero_reg);
     if (key_is_constant) {
       mem_operand = MemOperand(external_pointer,
-                               constant_key * (1 << shift_size));
+                               (constant_key << shift_size) + additional_offset);

[Massi, 2012/05/24 09:01:31]

Nit: the line exceeds 80 chars.

     } else {
-      __ sll(scratch, key, shift_size);
+      if (instr->additional_index() == 0) {
+        __ sll(scratch, key, shift_size);
+      } else {
+        __ sll(scratch, scratch, shift_size);
+      }
       __ Addu(scratch, scratch, external_pointer);
       mem_operand = MemOperand(scratch);
     }
     switch (elements_kind) {
       case EXTERNAL_BYTE_ELEMENTS:
         __ lb(result, mem_operand);
         break;
       case EXTERNAL_PIXEL_ELEMENTS:
       case EXTERNAL_UNSIGNED_BYTE_ELEMENTS:
         __ lbu(result, mem_operand);
@@ skipping 897 matching lines @@
   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) * kPointerSize + FixedArray::kHeaderSize;
+        (ToInteger32(const_operand) + instr->additional_index()) * kPointerSize
+        + FixedArray::kHeaderSize;
     __ sw(value, FieldMemOperand(elements, offset));
   } 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));
   }
 
   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,
@@ skipping 22 matching lines @@
   if (key_is_constant) {
     constant_key = ToInteger32(LConstantOperand::cast(instr->key()));
     if (constant_key & 0xF0000000) {
       Abort("array index constant value too big.");
     }
   } else {
     key = ToRegister(instr->key());
   }
   int shift_size = ElementsKindToShiftSize(FAST_DOUBLE_ELEMENTS);
   if (key_is_constant) {
-    __ Addu(scratch, elements, Operand(constant_key * (1 << shift_size) +
+    __ Addu(scratch, elements, Operand((constant_key << shift_size) +
             FixedDoubleArray::kHeaderSize - kHeapObjectTag));
   } else {
     __ sll(scratch, key, shift_size);
     __ Addu(scratch, elements, Operand(scratch));
     __ Addu(scratch, scratch,
             Operand(FixedDoubleArray::kHeaderSize - kHeapObjectTag));
   }
 
   if (instr->NeedsCanonicalization()) {
     Label is_nan;
     // Check for NaN. All NaNs must be canonicalized.
     __ BranchF(NULL, &is_nan, eq, value, value);
     __ Branch(&not_nan);
 
     // Only load canonical NaN if the comparison above set the overflow.
     __ bind(&is_nan);
     __ Move(value, FixedDoubleArray::canonical_not_the_hole_nan_as_double());
   }
 
   __ bind(&not_nan);
-  __ sdc1(value, MemOperand(scratch));
+  __ sdc1(value, MemOperand(scratch, instr->additional_index() << shift_size));
 }
 
 
 void LCodeGen::DoStoreKeyedSpecializedArrayElement(
     LStoreKeyedSpecializedArrayElement* instr) {
 
   Register external_pointer = ToRegister(instr->external_pointer());
   Register key = no_reg;
   ElementsKind elements_kind = instr->elements_kind();
   bool key_is_constant = instr->key()->IsConstantOperand();
   int constant_key = 0;
   if (key_is_constant) {
     constant_key = ToInteger32(LConstantOperand::cast(instr->key()));
     if (constant_key & 0xF0000000) {
       Abort("array index constant value too big.");
     }
   } else {
     key = ToRegister(instr->key());
   }
   int shift_size = ElementsKindToShiftSize(elements_kind);
+  int additional_offset = instr->additional_index() << shift_size;
 
   if (elements_kind == EXTERNAL_FLOAT_ELEMENTS ||
       elements_kind == EXTERNAL_DOUBLE_ELEMENTS) {
     FPURegister value(ToDoubleRegister(instr->value()));
     if (key_is_constant) {
-      __ Addu(scratch0(), external_pointer, constant_key * (1 << shift_size));
+      __ Addu(scratch0(), external_pointer, constant_key << shift_size);
     } else {
       __ sll(scratch0(), key, shift_size);
       __ Addu(scratch0(), scratch0(), external_pointer);
     }
 
     if (elements_kind == EXTERNAL_FLOAT_ELEMENTS) {
       __ cvt_s_d(double_scratch0(), value);
-      __ swc1(double_scratch0(), MemOperand(scratch0()));
+      __ swc1(double_scratch0(), MemOperand(scratch0(), additional_offset));
     } else {  // i.e. elements_kind == EXTERNAL_DOUBLE_ELEMENTS
-      __ sdc1(value, MemOperand(scratch0()));
+      __ sdc1(value, MemOperand(scratch0(), additional_offset));
     }
   } else {
     Register value(ToRegister(instr->value()));
+    Register scratch = scratch0();
+    if (instr->additional_index() != 0 && !key_is_constant) {
+      __ Addu(scratch0(), key, instr->additional_index());

[Massi, 2012/05/24 09:01:31]

You moved the declaration "Register scratch = scratch0();" just before this
block but you still use "scratch0()" in the Addu: wouldn't it be cleaner using
"scratch"?

[palfia, 2012/05/24 16:16:33]

Yes, it is much cleaner.

+    }
     MemOperand mem_operand(zero_reg);
-    Register scratch = scratch0();
     if (key_is_constant) {
       mem_operand = MemOperand(external_pointer,
-                               constant_key * (1 << shift_size));
+                               ((constant_key + instr->additional_index())
+                                   << shift_size));
     } else {
-      __ sll(scratch, key, shift_size);
+      if (instr->additional_index() == 0) {
+        __ sll(scratch, key, shift_size);
+      } else {
+        __ sll(scratch, scratch, shift_size);
+      }
       __ Addu(scratch, scratch, external_pointer);
       mem_operand = MemOperand(scratch);
     }
     switch (elements_kind) {
       case EXTERNAL_PIXEL_ELEMENTS:
       case EXTERNAL_BYTE_ELEMENTS:
       case EXTERNAL_UNSIGNED_BYTE_ELEMENTS:
         __ sb(value, mem_operand);
         break;
       case EXTERNAL_SHORT_ELEMENTS:
@@ skipping 1495 matching lines @@
   __ Subu(scratch, result, scratch);
   __ lw(result, FieldMemOperand(scratch,
                                 FixedArray::kHeaderSize - kPointerSize));
   __ bind(&done);
 }
 
 
 #undef __
 
 } }  // namespace v8::internal