MIPS: Improve Lsa/Dlsa implementations.

src/mips/macro-assembler-mips.cc

Index: src/mips/macro-assembler-mips.cc
diff --git a/src/mips/macro-assembler-mips.cc b/src/mips/macro-assembler-mips.cc
index 326e757f6180de273d55b3efd74faec556700cef..3022f43a16916ecab9290895fc1783619da9c7ef 100644
--- a/src/mips/macro-assembler-mips.cc
+++ b/src/mips/macro-assembler-mips.cc
@@ -1148,8 +1148,9 @@ void MacroAssembler::Pref(int32_t hint, const MemOperand& rs) {
 
 void MacroAssembler::Lsa(Register rd, Register rt, Register rs, uint8_t sa,
                          Register scratch) {
+  DCHECK(sa >= 1 && sa <= 31);
   if (IsMipsArchVariant(kMips32r6) && sa <= 4) {
-    lsa(rd, rt, rs, sa);
+    lsa(rd, rt, rs, sa - 1);
   } else {
     Register tmp = rd.is(rt) ? scratch : rd;
     DCHECK(!tmp.is(rt));