Implement basic array prefetching hints in Hydrogen.

src/ia32/lithium-codegen-ia32.cc

Index: src/ia32/lithium-codegen-ia32.cc
===================================================================
--- src/ia32/lithium-codegen-ia32.cc	(revision 13123)
+++ src/ia32/lithium-codegen-ia32.cc	(working copy)
@@ -2849,6 +2849,14 @@
         break;
     }
   }
+
+  if (instr->prefetch_distance() != NULL) {
+    InsertArrayPrefetch(
+        operand,
+        instr->prefetch_distance(),
+        elements_kind,
+        ToRegister(instr->temp()));
+  }
 }
 
 
@@ -2876,20 +2884,30 @@
       FixedDoubleArray::kHeaderSize - kHeapObjectTag,
       instr->additional_index());
   __ movdbl(result, double_load_operand);
+
+  if (instr->prefetch_distance() != NULL) {
+    InsertArrayPrefetch(
+        double_load_operand,
+        instr->prefetch_distance(),
+        FAST_DOUBLE_ELEMENTS,
+        ToRegister(instr->temp()));
+  }
 }
 
 
 void LCodeGen::DoLoadKeyedFixedArray(LLoadKeyed* instr) {
   Register result = ToRegister(instr->result());
 
+  Operand load_operand = BuildFastArrayOperand(
+      instr->elements(),
+      instr->key(),
+      instr->hydrogen()->key()->representation(),
+      FAST_ELEMENTS,
+      FixedArray::kHeaderSize - kHeapObjectTag,
+      instr->additional_index());
+
   // Load the result.
-  __ mov(result,
-         BuildFastArrayOperand(instr->elements(),
-                               instr->key(),
-                               instr->hydrogen()->key()->representation(),
-                               FAST_ELEMENTS,
-                               FixedArray::kHeaderSize - kHeapObjectTag,
-                               instr->additional_index()));
+  __ mov(result, load_operand);
 
   // Check for the hole value.
   if (instr->hydrogen()->RequiresHoleCheck()) {
@@ -2901,6 +2919,14 @@
       DeoptimizeIf(equal, instr->environment());
     }
   }
+
+  if (instr->prefetch_distance() != NULL) {
+    InsertArrayPrefetch(
+        load_operand,
+        instr->prefetch_distance(),
+        FAST_ELEMENTS,
+        ToRegister(instr->temp()));
+  }
 }
 
 
@@ -2915,6 +2941,26 @@
 }
 
 
+void LCodeGen::InsertArrayPrefetch(
+    const Operand& operand,
+    LOperand* prefetch_distance,
+    ElementsKind elements_kind,
+    Register scratch) {
+  __ lea(scratch, operand);
+  int shift_size = ElementsKindToShiftSize(elements_kind);
+  if (prefetch_distance->IsConstantOperand()) {
+    __ prefetch(Operand(scratch,
+        ToInteger32(LConstantOperand::cast(prefetch_distance)) << shift_size),
+        1);
+  } else {
+    ASSERT(prefetch_distance->IsRegister());
+    ScaleFactor scale_factor = static_cast<ScaleFactor>(shift_size);
+    __ prefetch(
+        Operand(scratch, ToRegister(prefetch_distance), scale_factor, 0), 1);
+  }
+}
+
+
 Operand LCodeGen::BuildFastArrayOperand(
     LOperand* elements_pointer,
     LOperand* key,