[wasm] Introduce Encoder::GetLocal and Encoder::SetLocal utilities.

R=bradnelson@chromium.org,aseemgarg@chromium.org
BUG=

Review URL: https://codereview.chromium.org/1895013002

Cr-Commit-Position: refs/heads/master@{#35598}

src/wasm/asm-wasm-builder.cc

@@ -510,30 +510,28 @@ class AsmWasmBuilderImpl : public AstVisitor {
   void VisitVariableProxy(VariableProxy* expr) {
     if (in_function_) {
       Variable* var = expr->var();
+      LocalType var_type = TypeOf(expr);
       if (is_set_op_) {
+        is_set_op_ = false;
         if (var->IsContextSlot()) {
-          current_function_builder_->Emit(kExprStoreGlobal);
+          return current_function_builder_->EmitWithVarInt(
+              kExprStoreGlobal, LookupOrInsertGlobal(var, var_type));
         } else {
-          current_function_builder_->Emit(kExprSetLocal);
+          return current_function_builder_->EmitSetLocal(
+              LookupOrInsertLocal(var, var_type));
         }
-        is_set_op_ = false;
       } else {
         if (VisitStdlibConstant(var)) {
           return;
         }
         if (var->IsContextSlot()) {
-          current_function_builder_->Emit(kExprLoadGlobal);
+          return current_function_builder_->EmitWithVarInt(
+              kExprLoadGlobal, LookupOrInsertGlobal(var, var_type));
         } else {
-          current_function_builder_->Emit(kExprGetLocal);
+          return current_function_builder_->EmitGetLocal(
+              LookupOrInsertLocal(var, var_type));
         }
       }
-      LocalType var_type = TypeOf(expr);
-      DCHECK_NE(kAstStmt, var_type);
-      if (var->IsContextSlot()) {
-        AddLeb128(LookupOrInsertGlobal(var, var_type), false);
-      } else {
-        AddLeb128(LookupOrInsertLocal(var, var_type), true);
-      }
     }
   }
 
@@ -1387,19 +1385,6 @@ class AsmWasmBuilderImpl : public AstVisitor {
     }
   }
 
-  void AddLeb128(uint32_t index, bool is_local) {
-    std::vector<uint8_t> index_vec = UnsignedLEB128From(index);
-    if (is_local) {
-      uint32_t pos_of_index[1] = {0};
-      current_function_builder_->EmitCode(
-          &index_vec[0], static_cast<uint32_t>(index_vec.size()), pos_of_index,
-          1);
-    } else {
-      current_function_builder_->EmitCode(
-          &index_vec[0], static_cast<uint32_t>(index_vec.size()));
-    }
-  }
-
   void VisitCompareOperation(CompareOperation* expr) {
     switch (expr->op()) {
       BINOP_CASE(Token::EQ, Eq, NON_SIGNED_BINOP, false);

src/wasm/encoder.cc

@@ -150,6 +150,15 @@ void WasmFunctionBuilder::EmitCode(const byte* code, uint32_t code_size) {
   EmitCode(code, code_size, nullptr, 0);
 }
 
+void WasmFunctionBuilder::EmitGetLocal(uint32_t local_index) {
+  local_indices_.push_back(static_cast<uint32_t>(body_.size() + 1));
+  EmitWithVarInt(kExprGetLocal, local_index);
+}
+
+void WasmFunctionBuilder::EmitSetLocal(uint32_t local_index) {
+  local_indices_.push_back(static_cast<uint32_t>(body_.size() + 1));
+  EmitWithVarInt(kExprSetLocal, local_index);
+}
 
 void WasmFunctionBuilder::EmitCode(const byte* code, uint32_t code_size,
                                    const uint32_t* local_indices,

src/wasm/encoder.h

@@ -54,6 +54,8 @@ class WasmFunctionBuilder : public ZoneObject {
   void EmitCode(const byte* code, uint32_t code_size,
                 const uint32_t* local_indices, uint32_t indices_size);
   void Emit(WasmOpcode opcode);
+  void EmitGetLocal(uint32_t index);
+  void EmitSetLocal(uint32_t index);
   void EmitWithU8(WasmOpcode opcode, const byte immediate);
   void EmitWithU8U8(WasmOpcode opcode, const byte imm1, const byte imm2);
   void EmitWithVarInt(WasmOpcode opcode, uint32_t immediate);