From: alexandre.rames@arm.com <alexandre.rames@arm.com@ce2b1a6d-e550-0410-aec6-3dcde31c8c00>
Date: Tue, 18 Feb 2014 15:14:23 +0000 (+0000)
Subject: A64: Minor code generation improvement: only load the object map if needed.
X-Git-Tag: upstream/4.7.83~10640
X-Git-Url: http://review.tizen.org/git/?a=commitdiff_plain;h=d54305e12afa4aa5a73cac46b9d28d74662bf455;p=platform%2Fupstream%2Fv8.git

A64: Minor code generation improvement: only load the object map if needed.

R=ulan@chromium.org

Review URL: https://codereview.chromium.org/170503004

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@19456 ce2b1a6d-e550-0410-aec6-3dcde31c8c00
---

diff --git a/src/a64/stub-cache-a64.cc b/src/a64/stub-cache-a64.cc
index 3cf2a29..57c03e8 100644
--- a/src/a64/stub-cache-a64.cc
+++ b/src/a64/stub-cache-a64.cc
@@ -888,9 +888,13 @@ Register StubCompiler::CheckPrototypes(Handle<HeapType> type,
       reg = holder_reg;  // From now on the object will be in holder_reg.
       __ Ldr(reg, FieldMemOperand(scratch1, Map::kPrototypeOffset));
     } else {
-      Register map_reg = scratch1;
-      // TODO(jbramley): Skip this load when we don't need the map.
-      __ Ldr(map_reg, FieldMemOperand(reg, HeapObject::kMapOffset));
+      bool need_map = (depth != 1 || check == CHECK_ALL_MAPS) ||
+                      heap()->InNewSpace(*prototype);
+      Register map_reg = NoReg;
+      if (need_map) {
+        map_reg = scratch1;
+        __ Ldr(map_reg, FieldMemOperand(reg, HeapObject::kMapOffset));
+      }
 
       if (depth != 1 || check == CHECK_ALL_MAPS) {
         __ CheckMap(map_reg, current_map, miss, DONT_DO_SMI_CHECK);