MIPS: Use the Lsa() macro/r6 instruction in existing code.

src/ic/mips/stub-cache-mips.cc

Index: src/ic/mips/stub-cache-mips.cc
diff --git a/src/ic/mips/stub-cache-mips.cc b/src/ic/mips/stub-cache-mips.cc
index 1a9897e8f35000c4c44d2d48a17224f3f1b067d1..039763c4cfda34feb83735188e264b40dda4aa6a 100644
--- a/src/ic/mips/stub-cache-mips.cc
+++ b/src/ic/mips/stub-cache-mips.cc
@@ -42,13 +42,11 @@ static void ProbeTable(Isolate* isolate, MacroAssembler* masm,
   scratch = no_reg;
 
   // Multiply by 3 because there are 3 fields per entry (name, code, map).
-  __ sll(offset_scratch, offset, 1);
-  __ Addu(offset_scratch, offset_scratch, offset);
+  __ Lsa(offset_scratch, offset, offset, 1);
 
   // Calculate the base address of the entry.
   __ li(base_addr, Operand(key_offset));
-  __ sll(at, offset_scratch, kPointerSizeLog2);
-  __ Addu(base_addr, base_addr, at);
+  __ Lsa(base_addr, base_addr, offset_scratch, kPointerSizeLog2);
 
   // Check that the key in the entry matches the name.
   __ lw(at, MemOperand(base_addr, 0));