X64: Convert smis to holding 32 bits of payload.

src/x64/stub-cache-x64.cc

Index: src/x64/stub-cache-x64.cc
diff --git a/src/x64/stub-cache-x64.cc b/src/x64/stub-cache-x64.cc
index 0994230073cba9ff05367bbd028908bae0e50cb1..58a3e0f6a2f4466f5ed21eb376e3842d20518882 100644
--- a/src/x64/stub-cache-x64.cc
+++ b/src/x64/stub-cache-x64.cc
@@ -47,19 +47,24 @@ static void ProbeTable(MacroAssembler* masm,
                        StubCache::Table table,
                        Register name,
                        Register offset) {
-  // The offset register must hold a *positive* smi.
+  ASSERT_EQ(8, kPointerSize);
+  ASSERT_EQ(16, sizeof(StubCache::Entry));
+  // The offset register holds the entry offset times four (due to masking
+  // and shifting optimizations).
   ExternalReference key_offset(SCTableReference::keyReference(table));
   Label miss;
 
   __ movq(kScratchRegister, key_offset);
-  SmiIndex index = masm->SmiToIndex(offset, offset, kPointerSizeLog2);
   // Check that the key in the entry matches the name.
-  __ cmpl(name, Operand(kScratchRegister, index.reg, index.scale, 0));
+  // Multiply entry offset by 16 to get the entry address. Since the
+  // offset register already holds the entry offset times four, multiply
+  // by a further four.
+  __ cmpl(name, Operand(kScratchRegister, offset, times_4, 0));
   __ j(not_equal, &miss);
   // Get the code entry from the cache.
   // Use key_offset + kPointerSize, rather than loading value_offset.
   __ movq(kScratchRegister,
-          Operand(kScratchRegister, index.reg, index.scale, kPointerSize));
+          Operand(kScratchRegister, offset, times_4, kPointerSize));
   // Check that the flags match what we're looking for.
   __ movl(offset, FieldOperand(kScratchRegister, Code::kFlagsOffset));
   __ and_(offset, Immediate(~Code::kFlagsNotUsedInLookup));