[mips] Fix code generation bug in handling of immediates

src/compiler/mips64/instruction-selector-mips64.cc

 // Copyright 2014 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "src/base/adapters.h"
 #include "src/base/bits.h"
 #include "src/compiler/instruction-selector-impl.h"
 #include "src/compiler/node-matchers.h"
 #include "src/compiler/node-properties.h"
 
@@ skipping 251 matching lines @@
   Int32BinopMatcher m(node);
   InstructionOperand inputs[4];
   size_t input_count = 0;
   InstructionOperand outputs[2];
   size_t output_count = 0;
 
   if (TryMatchImmediate(selector, &opcode, m.right().node(), &input_count,
                         &inputs[1])) {
     inputs[0] = g.UseRegister(m.left().node());
     input_count++;
-  }
-  if (has_reverse_opcode &&
-      TryMatchImmediate(selector, &reverse_opcode, m.left().node(),
-                        &input_count, &inputs[1])) {
+  } else if (has_reverse_opcode &&
+             TryMatchImmediate(selector, &reverse_opcode, m.left().node(),
+                               &input_count, &inputs[1])) {
     inputs[0] = g.UseRegister(m.right().node());
     opcode = reverse_opcode;
     input_count++;
   } else {
     inputs[input_count++] = g.UseRegister(m.left().node());
     inputs[input_count++] = g.UseOperand(m.right().node(), opcode);
   }
 
   if (cont->IsBranch()) {
     inputs[input_count++] = g.Label(cont->true_block());
@@ skipping 2355 matching lines @@
   } else {
     DCHECK(kArchVariant == kMips64r2);
     return MachineOperatorBuilder::AlignmentRequirements::
         NoUnalignedAccessSupport();
   }
 }
 
 }  // namespace compiler
 }  // namespace internal
 }  // namespace v8