MIPS:[turbofan] Use Ins, Dins to clear bits instead of And with inverted immediate.

src/compiler/mips/instruction-selector-mips.cc

Index: src/compiler/mips/instruction-selector-mips.cc
diff --git a/src/compiler/mips/instruction-selector-mips.cc b/src/compiler/mips/instruction-selector-mips.cc
index 80079c2ef663fc4b1c8ec1e32010c0fa963301a9..53a01d77e229083c2eff6eb525240955b93e20e2 100644
--- a/src/compiler/mips/instruction-selector-mips.cc
+++ b/src/compiler/mips/instruction-selector-mips.cc
@@ -284,6 +284,18 @@ void InstructionSelector::VisitWord32And(Node* node) {
       // Other cases fall through to the normal And operation.
     }
   }
+  if (m.right().HasValue()) {
+    uint32_t mask = m.right().Value();
+    uint32_t shift = base::bits::CountPopulation32(~mask);
+    uint32_t msb = base::bits::CountLeadingZeros32(~mask);
+    if (shift != 0 && shift != 32 && msb + shift == 32) {
+      // Insert zeros for (x >> K) << K => x & ~(2^K - 1) expression reduction
+      // and remove constant loading of invereted mask.

[paul.l..., 2015/12/01 17:49:34]

nit: spelling of inverted.

+      Emit(kMipsIns, g.DefineSameAsFirst(node), g.UseRegister(m.left().node()),
+           g.TempImmediate(0), g.TempImmediate(shift));
+      return;
+    }
+  }
   VisitBinop(this, node, kMipsAnd);
 }