[wasm-simd] Clean up unused simd shift immediates

SIMD shifts was changed to use register in https://crrev.com/c/1722198
so all this code to deal with shift immediates can be removed.

SimdOp was also removed from the interface, so now Liftoff does not need
to implement it.

Bug: v8:9810
Change-Id: I845e28b4f5712ff188d68beea7121eebddebdd9e
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1913506Reviewed-by: Bill Budge <bbudge@chromium.org>
Commit-Queue: Zhi An Ng <zhin@chromium.org>
Cr-Commit-Position: refs/heads/master@{#64944}

src/wasm/baseline/liftoff-compiler.cc

@@ -2031,11 +2031,6 @@ class LiftoffCompiler {
                   const Vector<Value> inputs, Value* result) {
     unsupported(decoder, kSimd, "simd");
   }
-  void SimdShiftOp(FullDecoder* decoder, WasmOpcode opcode,
-                   const SimdShiftImmediate<validate>& imm, const Value& input,
-                   Value* result) {
-    unsupported(decoder, kSimd, "simd");
-  }
   void Simd8x16ShuffleOp(FullDecoder* decoder,
                          const Simd8x16ShuffleImmediate<validate>& imm,
                          const Value& input0, const Value& input1,

src/wasm/function-body-decoder-impl.h

@@ -486,17 +486,6 @@ struct SimdLaneImmediate {
   }
 };
 
-// Immediate for SIMD shift operations.
-template <Decoder::ValidateFlag validate>
-struct SimdShiftImmediate {
-  uint8_t shift;
-  uint32_t length = 1;
-
-  inline SimdShiftImmediate(Decoder* decoder, const byte* pc) {
-    shift = decoder->read_u8<validate>(pc + 2, "shift");
-  }
-};
-
 // Immediate for SIMD S8x16 shuffle operations.
 template <Decoder::ValidateFlag validate>
 struct Simd8x16ShuffleImmediate {
@@ -1098,42 +1087,6 @@ class WasmDecoder : public Decoder {
     }
   }
 
-  inline bool Validate(const byte* pc, WasmOpcode opcode,
-                       SimdShiftImmediate<validate>& imm) {
-    uint8_t max_shift = 0;
-    switch (opcode) {
-      case kExprI64x2Shl:
-      case kExprI64x2ShrS:
-      case kExprI64x2ShrU:
-        max_shift = 64;
-        break;
-      case kExprI32x4Shl:
-      case kExprI32x4ShrS:
-      case kExprI32x4ShrU:
-        max_shift = 32;
-        break;
-      case kExprI16x8Shl:
-      case kExprI16x8ShrS:
-      case kExprI16x8ShrU:
-        max_shift = 16;
-        break;
-      case kExprI8x16Shl:
-      case kExprI8x16ShrS:
-      case kExprI8x16ShrU:
-        max_shift = 8;
-        break;
-      default:
-        UNREACHABLE();
-        break;
-    }
-    if (!VALIDATE(imm.shift >= 0 && imm.shift < max_shift)) {
-      error(pc_ + 2, "invalid shift amount");
-      return false;
-    } else {
-      return true;
-    }
-  }
-
   inline bool Validate(const byte* pc,
                        Simd8x16ShuffleImmediate<validate>& imm) {
     uint8_t max_lane = 0;