MIPS: Fixing performance regression in issue 1787.

src/mips/code-stubs-mips.cc

Index: src/mips/code-stubs-mips.cc
diff --git a/src/mips/code-stubs-mips.cc b/src/mips/code-stubs-mips.cc
index 85e929d39acd7f6c7ac98c89679cbeed04863c3e..16461ec7d7f6726efeddad9587ceab9bc5f36d18 100644
--- a/src/mips/code-stubs-mips.cc
+++ b/src/mips/code-stubs-mips.cc
@@ -7112,6 +7112,11 @@ void StringDictionaryLookupStub::GeneratePositiveLookup(MacroAssembler* masm,
                                                         Register name,
                                                         Register scratch1,
                                                         Register scratch2) {
+  ASSERT(!elements.is(scratch1));
+  ASSERT(!elements.is(scratch2));
+  ASSERT(!name.is(scratch1));
+  ASSERT(!name.is(scratch2));
+
   // Assert that name contains a string.
   if (FLAG_debug_code) __ AbortIfNotString(name);