[wasm] Remove type from LocalIndexImmediate

The immediate itself is just the index, and the local type can easily be
looked up in every environment where the immediate is used. Hence remove
that field.

R=thibaudm@chromium.org

Bug: v8:10576
Change-Id: If3176fa4880a75bdc475ec61dea60e08001220f5
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2266532
Commit-Queue: Clemens Backes <clemensb@chromium.org>
Reviewed-by: Thibaud Michaud <thibaudm@chromium.org>
Cr-Commit-Position: refs/heads/master@{#68544}

src/wasm/baseline/liftoff-compiler.cc

@@ -1609,18 +1609,17 @@ class LiftoffCompiler {
   void LocalGet(FullDecoder* decoder, Value* result,
                 const LocalIndexImmediate<validate>& imm) {
     auto& slot = __ cache_state()->stack_state[imm.index];
-    DCHECK_EQ(slot.type(), imm.type);
     switch (slot.loc()) {
       case kRegister:
         __ PushRegister(slot.type(), slot.reg());
         break;
       case kIntConst:
-        __ PushConstant(imm.type, slot.i32_const());
+        __ PushConstant(slot.type(), slot.i32_const());
         break;
       case kStack: {
-        auto rc = reg_class_for(imm.type);
+        auto rc = reg_class_for(slot.type());
         LiftoffRegister reg = __ GetUnusedRegister(rc, {});
-        __ Fill(reg, slot.offset(), imm.type);
+        __ Fill(reg, slot.offset(), slot.type());
         __ PushRegister(slot.type(), reg);
         break;
       }

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

@@ -260,7 +260,6 @@ ValueType read_value_type(Decoder* decoder, const byte* pc,
 template <Decoder::ValidateFlag validate>
 struct LocalIndexImmediate {
   uint32_t index;
-  ValueType type = kWasmStmt;
   uint32_t length;
 
   inline LocalIndexImmediate(Decoder* decoder, const byte* pc) {
@@ -1137,7 +1136,6 @@ class WasmDecoder : public Decoder {
       errorf(pc + 1, "invalid local index: %u", imm.index);
       return false;
     }
-    imm.type = this->local_type(imm.index);
     return true;
   }
 
@@ -2601,7 +2599,7 @@ class WasmFullDecoder : public WasmDecoder<validate> {
       case kExprLocalGet: {
         LocalIndexImmediate<validate> imm(this, this->pc_);
         if (!this->Validate(this->pc_, imm)) break;
-        Value* value = Push(imm.type);
+        Value* value = Push(this->local_type(imm.index));
         CALL_INTERFACE_IF_REACHABLE(LocalGet, value, imm);
         len = 1 + imm.length;
         break;