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

src/compiler/machine-operator.h

 // Copyright 2013 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.
 
 #ifndef V8_COMPILER_MACHINE_OPERATOR_H_
 #define V8_COMPILER_MACHINE_OPERATOR_H_
 
 #include "src/base/flags.h"
 #include "src/machine-type.h"
 
@@ skipping 103 matching lines @@
     kUint32DivIsSafe = 1u << 14,
     kWord32ShiftIsSafe = 1u << 15,
     kWord32Ctz = 1u << 16,
     kWord64Ctz = 1u << 17,
     kWord32Popcnt = 1u << 18,
     kWord64Popcnt = 1u << 19,
     kWord32ReverseBits = 1u << 20,
     kWord64ReverseBits = 1u << 21,
     kFloat32Neg = 1u << 22,
     kFloat64Neg = 1u << 23,
+    kWord16ReverseBytes = 1u << 24,
+    kWord32ReverseBytes = 1u << 25,
+    kWord64ReverseBytes = 1u << 26,
     kAllOptionalOps =
         kFloat32Max | kFloat32Min | kFloat64Max | kFloat64Min |
         kFloat32RoundDown | kFloat64RoundDown | kFloat32RoundUp |
         kFloat64RoundUp | kFloat32RoundTruncate | kFloat64RoundTruncate |
         kFloat64RoundTiesAway | kFloat32RoundTiesEven | kFloat64RoundTiesEven |
         kWord32Ctz | kWord64Ctz | kWord32Popcnt | kWord64Popcnt |
-        kWord32ReverseBits | kWord64ReverseBits | kFloat32Neg | kFloat64Neg
+        kWord32ReverseBits | kWord64ReverseBits | kFloat32Neg | kFloat64Neg |
+        kWord16ReverseBytes | kWord32ReverseBytes | kWord64ReverseBytes
   };
   typedef base::Flags<Flag, unsigned> Flags;
 
   class AlignmentRequirements {
    public:
     enum UnalignedAccessSupport { kNoSupport, kSomeSupport, kFullSupport };
 
     bool IsUnalignedLoadSupported(const MachineType& machineType,
                                   uint8_t alignment) const {
       return IsUnalignedSupported(unalignedLoadSupportedTypes_, machineType,
@@ skipping 69 matching lines @@
   const Operator* Word32Shr();
   const Operator* Word32Sar();
   const Operator* Word32Ror();
   const Operator* Word32Equal();
   const Operator* Word32Clz();
   const OptionalOperator Word32Ctz();
   const OptionalOperator Word32Popcnt();
   const OptionalOperator Word64Popcnt();
   const OptionalOperator Word32ReverseBits();
   const OptionalOperator Word64ReverseBits();
+  const OptionalOperator Word16ReverseBytes();
+  const OptionalOperator Word32ReverseBytes();
+  const OptionalOperator Word64ReverseBytes();
   bool Word32ShiftIsSafe() const { return flags_ & kWord32ShiftIsSafe; }
 
   const Operator* Word64And();
   const Operator* Word64Or();
   const Operator* Word64Xor();
   const Operator* Word64Shl();
   const Operator* Word64Shr();
   const Operator* Word64Sar();
   const Operator* Word64Ror();
   const Operator* Word64Clz();
@@ skipping 383 matching lines @@
   const Operator* CheckedLoad(CheckedLoadRepresentation);
   // checked-store heap, index, length, value
   const Operator* CheckedStore(CheckedStoreRepresentation);
 
   // atomic-load [base + index]
   const Operator* AtomicLoad(LoadRepresentation rep);
   // atomic-store [base + index], value
   const Operator* AtomicStore(MachineRepresentation rep);
 
   // Target machine word-size assumed by this builder.
+  bool Is16() const { return word() == MachineRepresentation::kWord16; }

[ahaas, 2016/07/27 01:31:15]

The introduction of Is16() worries me. Is a word size of 16 actually supported
in V8? At several places in the code there is the assumption that "Is32() ==
(!Is64())". It seems that the introduction of Is16() violates this assumption.

[john.yan, 2016/07/27 18:18:19]

Ok, I agree. Word16ReverseBytes Opcode is now removed.

   bool Is32() const { return word() == MachineRepresentation::kWord32; }
   bool Is64() const { return word() == MachineRepresentation::kWord64; }
   MachineRepresentation word() const { return word_; }
 
   bool UnalignedLoadSupported(const MachineType& machineType,
                               uint8_t alignment) {
     return alignment_requirements_.IsUnalignedLoadSupported(machineType,
                                                             alignment);
   }
 
   bool UnalignedStoreSupported(const MachineType& machineType,
                                uint8_t alignment) {
     return alignment_requirements_.IsUnalignedStoreSupported(machineType,
                                                              alignment);
   }
 
+  bool ReverseBytesSupported(const MachineType& machineType) {

[ahaas, 2016/07/27 01:31:15]

Why is the machineType passed in if it is not used?

[john.yan, 2016/07/27 18:18:19]

Thanks for pointing out. This is my mistake.

+    if (Is16())
+      return Word16ReverseBytes().IsSupported();
+    else if (Is32())
+      return Word32ReverseBytes().IsSupported();
+    else if (Is64())
+      return Word64ReverseBytes().IsSupported();
+    else
+      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) \
   V(Word, And)            \
   V(Word, Or)             \
   V(Word, Xor)            \
   V(Word, Shl)            \
   V(Word, Shr)            \
   V(Word, Sar)            \
   V(Word, Ror)            \
@@ skipping 28 matching lines @@
 };
 
 
 DEFINE_OPERATORS_FOR_FLAGS(MachineOperatorBuilder::Flags)
 
 }  // namespace compiler
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_COMPILER_MACHINE_OPERATOR_H_