Enable -Wimplicit-fallthrough.

Falling through switch cases on a clang build must now annotate the fallthrough
with the FALLTHROUGH_INTENDED macro.
Bug: 17731372

Change-Id: I836451cd5f96b01d1ababdbf9eef677fe8fa8324
diff --git a/compiler/dex/quick/x86/int_x86.cc b/compiler/dex/quick/x86/int_x86.cc
index 5177176..07034cb 100755
--- a/compiler/dex/quick/x86/int_x86.cc
+++ b/compiler/dex/quick/x86/int_x86.cc
@@ -2930,25 +2930,25 @@
       break;
     case Instruction::ADD_INT_2ADDR:
       is_two_addr = true;
-      // Fallthrough
+      FALLTHROUGH_INTENDED;
     case Instruction::ADD_INT:
       op = kOpAdd;
       break;
     case Instruction::SUB_INT_2ADDR:
       is_two_addr = true;
-      // Fallthrough
+      FALLTHROUGH_INTENDED;
     case Instruction::SUB_INT:
       op = kOpSub;
       break;
     case Instruction::MUL_INT_2ADDR:
       is_two_addr = true;
-      // Fallthrough
+      FALLTHROUGH_INTENDED;
     case Instruction::MUL_INT:
       op = kOpMul;
       break;
     case Instruction::DIV_INT_2ADDR:
       is_two_addr = true;
-      // Fallthrough
+      FALLTHROUGH_INTENDED;
     case Instruction::DIV_INT:
       op = kOpDiv;
       is_div_rem = true;
@@ -2956,46 +2956,46 @@
     /* NOTE: returns in kArg1 */
     case Instruction::REM_INT_2ADDR:
       is_two_addr = true;
-      // Fallthrough
+      FALLTHROUGH_INTENDED;
     case Instruction::REM_INT:
       op = kOpRem;
       is_div_rem = true;
       break;
     case Instruction::AND_INT_2ADDR:
       is_two_addr = true;
-      // Fallthrough
+      FALLTHROUGH_INTENDED;
     case Instruction::AND_INT:
       op = kOpAnd;
       break;
     case Instruction::OR_INT_2ADDR:
       is_two_addr = true;
-      // Fallthrough
+      FALLTHROUGH_INTENDED;
     case Instruction::OR_INT:
       op = kOpOr;
       break;
     case Instruction::XOR_INT_2ADDR:
       is_two_addr = true;
-      // Fallthrough
+      FALLTHROUGH_INTENDED;
     case Instruction::XOR_INT:
       op = kOpXor;
       break;
     case Instruction::SHL_INT_2ADDR:
       is_two_addr = true;
-      // Fallthrough
+      FALLTHROUGH_INTENDED;
     case Instruction::SHL_INT:
       shift_op = true;
       op = kOpLsl;
       break;
     case Instruction::SHR_INT_2ADDR:
       is_two_addr = true;
-      // Fallthrough
+      FALLTHROUGH_INTENDED;
     case Instruction::SHR_INT:
       shift_op = true;
       op = kOpAsr;
       break;
     case Instruction::USHR_INT_2ADDR:
       is_two_addr = true;
-      // Fallthrough
+      FALLTHROUGH_INTENDED;
     case Instruction::USHR_INT:
       shift_op = true;
       op = kOpLsr;
@@ -3245,19 +3245,19 @@
   switch (opcode) {
     case Instruction::SHL_LONG_2ADDR:
       is_two_addr = true;
-      // Fallthrough
+      FALLTHROUGH_INTENDED;
     case Instruction::SHL_LONG:
       op = kOpLsl;
       break;
     case Instruction::SHR_LONG_2ADDR:
       is_two_addr = true;
-      // Fallthrough
+      FALLTHROUGH_INTENDED;
     case Instruction::SHR_LONG:
       op = kOpAsr;
       break;
     case Instruction::USHR_LONG_2ADDR:
       is_two_addr = true;
-      // Fallthrough
+      FALLTHROUGH_INTENDED;
     case Instruction::USHR_LONG:
       op = kOpLsr;
       break;
diff --git a/compiler/dex/quick/x86/utility_x86.cc b/compiler/dex/quick/x86/utility_x86.cc
index 6898b50..8d5dabc 100644
--- a/compiler/dex/quick/x86/utility_x86.cc
+++ b/compiler/dex/quick/x86/utility_x86.cc
@@ -657,7 +657,8 @@
         CHECK_EQ(is_array, false);
         CHECK_EQ(r_dest.IsFloat(), false);
         break;
-      }  // else fall-through to k32 case
+      }
+      FALLTHROUGH_INTENDED;  // else fall-through to k32 case
     case k32:
     case kSingle:
     case kReference:  // TODO: update for reference decompression on 64-bit targets.
@@ -791,7 +792,7 @@
   switch (size) {
     case k64:
       consider_non_temporal = true;
-      // Fall through!
+      FALLTHROUGH_INTENDED;
     case kDouble:
       if (r_src.IsFloat()) {
         opcode = is_array ? kX86MovsdAR : kX86MovsdMR;
@@ -810,7 +811,8 @@
         CHECK_EQ(r_src.IsFloat(), false);
         consider_non_temporal = true;
         break;
-      }  // else fall-through to k32 case
+      }
+      FALLTHROUGH_INTENDED;  // else fall-through to k32 case
     case k32:
     case kSingle:
     case kReference: