[compiler] [wasm] Introduce Word32/64ReverseBytes as TF Optional Opcode

src/compiler/machine-operator.h

Index: src/compiler/machine-operator.h
diff --git a/src/compiler/machine-operator.h b/src/compiler/machine-operator.h
index e9045d114499ef3e45b9dba8e439105ecfe4a688..b8aa9600cb37def13eecf3c23739f5dd2c32933e 100644
--- a/src/compiler/machine-operator.h
+++ b/src/compiler/machine-operator.h
@@ -121,13 +121,16 @@ class MachineOperatorBuilder final : public ZoneObject {
     kWord64ReverseBits = 1u << 21,
     kFloat32Neg = 1u << 22,
     kFloat64Neg = 1u << 23,
-    kAllOptionalOps =
-        kFloat32Max | kFloat32Min | kFloat64Max | kFloat64Min |
-        kFloat32RoundDown | kFloat64RoundDown | kFloat32RoundUp |
-        kFloat64RoundUp | kFloat32RoundTruncate | kFloat64RoundTruncate |
-        kFloat64RoundTiesAway | kFloat32RoundTiesEven | kFloat64RoundTiesEven |
-        kWord32Ctz | kWord64Ctz | kWord32Popcnt | kWord64Popcnt |
-        kWord32ReverseBits | kWord64ReverseBits | kFloat32Neg | kFloat64Neg
+    kWord32ReverseBytes = 1u << 24,
+    kWord64ReverseBytes = 1u << 25,
+    kAllOptionalOps = kFloat32Max | kFloat32Min | kFloat64Max | kFloat64Min |
+                      kFloat32RoundDown | kFloat64RoundDown | kFloat32RoundUp |
+                      kFloat64RoundUp | kFloat32RoundTruncate |
+                      kFloat64RoundTruncate | kFloat64RoundTiesAway |
+                      kFloat32RoundTiesEven | kFloat64RoundTiesEven |
+                      kWord32Ctz | kWord64Ctz | kWord32Popcnt | kWord64Popcnt |
+                      kWord32ReverseBits | kWord64ReverseBits | kFloat32Neg |
+                      kFloat64Neg | kWord32ReverseBytes | kWord64ReverseBytes
   };
   typedef base::Flags<Flag, unsigned> Flags;
 
@@ -217,6 +220,8 @@ class MachineOperatorBuilder final : public ZoneObject {
   const OptionalOperator Word64Popcnt();
   const OptionalOperator Word32ReverseBits();
   const OptionalOperator Word64ReverseBits();
+  const OptionalOperator Word32ReverseBytes();
+  const OptionalOperator Word64ReverseBytes();
   bool Word32ShiftIsSafe() const { return flags_ & kWord32ShiftIsSafe; }
 
   const Operator* Word64And();
@@ -636,6 +641,18 @@ class MachineOperatorBuilder final : public ZoneObject {
                                                              alignment);
   }
 
+  bool ReverseBytesSupported(size_t size_in_bytes) {

[ahaas, 2016/07/28 14:12:59]

Could this function not just be a helper function in wasm-compiler.cc?

[john.yan, 2016/07/28 18:03:50]

Sure.

+    switch (size_in_bytes) {
+      case 4:
+        return Word32ReverseBytes().IsSupported();
+      case 8:
+        return Word64ReverseBytes().IsSupported();
+      default:
+        break;

[ahaas, 2016/07/28 14:12:59]

Do you expect that the default case is ever reached? If not, then I would
suggest you put an UNREACHABLE() there.

[john.yan, 2016/07/28 18:03:50]

No, I expect it to return false (unsupported).

+    }
+    return false;
+  }
+
 // Pseudo operators that translate to 32/64-bit operators depending on the
 // word-size of the target machine assumed by this builder.
 #define PSEUDO_OP_LIST(V) \