Array index computation dehoisting.

src/arm/lithium-codegen-arm.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 2730 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.
   __ add(scratch, elements, Operand(key, LSL, kPointerSizeLog2));
-  __ ldr(result, FieldMemOperand(scratch, FixedArray::kHeaderSize));
+  __ ldr(result,

[Jakob Kummerow, 2012/05/15 15:53:23]

Formatting proposal:

  uint32_t offset = FixedArray::kHeaderSize +
                    (instr->additional_index() << kPointerSizeLog2);
  __ ldr(result, FieldMemOperand(scratch, offset));

+         FieldMemOperand(scratch,
+                         FixedArray::kHeaderSize
+                             + (instr->additional_index()
+                                 << kPointerSizeLog2)));
 
   // Check for the hole value.
   if (instr->hydrogen()->RequiresHoleCheck()) {
     __ LoadRoot(scratch, Heap::kTheHoleValueRootIndex);
     __ cmp(result, scratch);
     DeoptimizeIf(eq, instr->environment());
   }
 }
 
 
@@ skipping 11 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());
   }
 
   Operand operand = key_is_constant
-      ? Operand(constant_key * (1 << shift_size) +
+      ? Operand(((constant_key + instr->additional_index()) << shift_size) +
                 FixedDoubleArray::kHeaderSize - kHeapObjectTag)
       : Operand(key, LSL, shift_size);
   __ add(elements, elements, operand);
   if (!key_is_constant) {
     __ add(elements, elements,
-           Operand(FixedDoubleArray::kHeaderSize - kHeapObjectTag));
+           Operand((FixedDoubleArray::kHeaderSize - kHeapObjectTag)
+                   + (instr->additional_index() << shift_size)));

[Jakob Kummerow, 2012/05/15 15:53:23]

nit: for consistency, the operator goes at the end of the last line.

   }
 
   __ ldr(scratch, MemOperand(elements, sizeof(kHoleNanLower32)));
   __ cmp(scratch, Operand(kHoleNanUpper32));
   DeoptimizeIf(eq, instr->environment());
 
   __ vldr(result, elements, 0);
 }
 
 
 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) {
     CpuFeatures::Scope scope(VFP3);
     DwVfpRegister result = ToDoubleRegister(instr->result());
     Operand operand = key_is_constant
         ? Operand(constant_key * (1 << shift_size))
         : Operand(key, LSL, shift_size);
     __ add(scratch0(), external_pointer, operand);
     if (elements_kind == EXTERNAL_FLOAT_ELEMENTS) {
-      __ vldr(result.low(), scratch0(), 0);
+      __ vldr(result.low(), scratch0(), additional_offset);
       __ vcvt_f64_f32(result, result.low());
     } else  {  // i.e. elements_kind == EXTERNAL_DOUBLE_ELEMENTS
-      __ vldr(result, scratch0(), 0);
+      __ vldr(result, scratch0(), additional_offset);
     }
   } else {
     Register result = ToRegister(instr->result());
+    if (instr->additional_index() != 0 && !key_is_constant) {
+      __ add(scratch0(), key, Operand(instr->additional_index()));
+    }
     MemOperand mem_operand(key_is_constant
-        ? MemOperand(external_pointer, constant_key * (1 << shift_size))
-        : MemOperand(external_pointer, key, LSL, shift_size));
+        ? MemOperand(external_pointer,
+                     constant_key * (1 << shift_size) + additional_offset)

[Jakob Kummerow, 2012/05/15 15:53:23]

nit: drop the "* (1". Just "(constant_key << shift_size)". It's cleaner.

+        : (instr->additional_index() == 0
+           ? MemOperand(external_pointer, key, LSL, shift_size)
+           : MemOperand(external_pointer, scratch0(), LSL, shift_size)));
     switch (elements_kind) {
       case EXTERNAL_BYTE_ELEMENTS:
         __ ldrsb(result, mem_operand);
         break;
       case EXTERNAL_PIXEL_ELEMENTS:
       case EXTERNAL_UNSIGNED_BYTE_ELEMENTS:
         __ ldrb(result, mem_operand);
         break;
       case EXTERNAL_SHORT_ELEMENTS:
         __ ldrsh(result, mem_operand);
@@ skipping 877 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;

[Jakob Kummerow, 2012/05/15 15:53:23]

nit: looks like "* kPointerSize" might just fit onto the line before, which
would make more sense.

     __ str(value, FieldMemOperand(elements, offset));
   } else {
     __ add(scratch, elements, Operand(key, LSL, kPointerSizeLog2));
+    if (instr->additional_index() != 0) {
+      __ add(scratch,
+             scratch,
+             Operand(instr->additional_index() << kPointerSizeLog2));
+    }
     __ str(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.
     __ add(key, scratch, Operand(FixedArray::kHeaderSize - kHeapObjectTag));
     __ RecordWrite(elements,
@@ skipping 39 matching lines @@
 
   if (instr->NeedsCanonicalization()) {
     // Check for NaN. All NaNs must be canonicalized.
     __ VFPCompareAndSetFlags(value, value);
     // Only load canonical NaN if the comparison above set the overflow.
     __ Vmov(value,
             FixedDoubleArray::canonical_not_the_hole_nan_as_double(),
             vs);
   }
 
-  __ vstr(value, scratch, 0);
+  __ vstr(value, 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) {
     CpuFeatures::Scope scope(VFP3);
     DwVfpRegister value(ToDoubleRegister(instr->value()));
     Operand operand(key_is_constant ? Operand(constant_key * (1 << shift_size))
                                     : Operand(key, LSL, shift_size));
     __ add(scratch0(), external_pointer, operand);
     if (elements_kind == EXTERNAL_FLOAT_ELEMENTS) {
       __ vcvt_f32_f64(double_scratch0().low(), value);
-      __ vstr(double_scratch0().low(), scratch0(), 0);
+      __ vstr(double_scratch0().low(), scratch0(), additional_offset);
     } else {  // i.e. elements_kind == EXTERNAL_DOUBLE_ELEMENTS
-      __ vstr(value, scratch0(), 0);
+      __ vstr(value, scratch0(), additional_offset);
     }
   } else {
     Register value(ToRegister(instr->value()));
+    if (instr->additional_index() != 0 && !key_is_constant) {
+      __ add(scratch0(), key, Operand(instr->additional_index()));
+    }
     MemOperand mem_operand(key_is_constant
-        ? MemOperand(external_pointer, constant_key * (1 << shift_size))
-        : MemOperand(external_pointer, key, LSL, shift_size));
+        ? MemOperand(external_pointer,
+                     (constant_key + instr->additional_index())
+                         * (1 << shift_size))
+        : (instr->additional_index() == 0
+           ? MemOperand(external_pointer, key, LSL, shift_size)

[Jakob Kummerow, 2012/05/15 15:53:23]

nit: 4 space indent please.

+           : MemOperand(external_pointer, scratch0(), LSL, shift_size)));
     switch (elements_kind) {
       case EXTERNAL_PIXEL_ELEMENTS:
       case EXTERNAL_BYTE_ELEMENTS:
       case EXTERNAL_UNSIGNED_BYTE_ELEMENTS:
         __ strb(value, mem_operand);
         break;
       case EXTERNAL_SHORT_ELEMENTS:
       case EXTERNAL_UNSIGNED_SHORT_ELEMENTS:
         __ strh(value, mem_operand);
         break;
@@ skipping 1465 matching lines @@
   __ sub(scratch, result, Operand(index, LSL, kPointerSizeLog2 - kSmiTagSize));
   __ ldr(result, FieldMemOperand(scratch,
                                  FixedArray::kHeaderSize - kPointerSize));
   __ bind(&done);
 }
 
 
 #undef __
 
 } }  // namespace v8::internal