[wasm] Introduce EmitVarInt and EmitWithVarInt

src/wasm/wasm-module-builder.cc

Index: src/wasm/wasm-module-builder.cc
diff --git a/src/wasm/wasm-module-builder.cc b/src/wasm/wasm-module-builder.cc
index 6458e06797ef0e67170aede5e1744e28c203ac7c..5ebe8662ee4605cbfa9ec3f2ae9c95e1b40da0e1 100644
--- a/src/wasm/wasm-module-builder.cc
+++ b/src/wasm/wasm-module-builder.cc
@@ -62,13 +62,20 @@ WasmFunctionBuilder::WasmFunctionBuilder(WasmModuleBuilder* builder)
       direct_calls_(builder->zone()),
       asm_offsets_(builder->zone(), 8) {}
 
+void WasmFunctionBuilder::EmitVarInt(int32_t val) {
+  byte buffer[5];
+  byte* ptr = buffer;
+  LEBHelper::write_i32v(&ptr, val);
+  DCHECK_GE(5, ptr - buffer);
+  body_.insert(body_.end(), buffer, ptr);
+}
+
 void WasmFunctionBuilder::EmitVarUint(uint32_t val) {
-  byte buffer[8];
+  byte buffer[5];
   byte* ptr = buffer;
   LEBHelper::write_u32v(&ptr, val);
-  for (byte* p = buffer; p < ptr; p++) {
-    body_.push_back(*p);
-  }
+  DCHECK_GE(5, ptr - buffer);
+  body_.insert(body_.end(), buffer, ptr);
 }
 
 void WasmFunctionBuilder::SetSignature(FunctionSig* sig) {
@@ -116,6 +123,11 @@ void WasmFunctionBuilder::EmitWithU8U8(WasmOpcode opcode, const byte imm1,
   body_.push_back(imm2);
 }
 
+void WasmFunctionBuilder::EmitWithVarInt(WasmOpcode opcode, int32_t immediate) {
+  body_.push_back(static_cast<byte>(opcode));
+  EmitVarInt(immediate);
+}
+
 void WasmFunctionBuilder::EmitWithVarUint(WasmOpcode opcode,
                                           uint32_t immediate) {
   body_.push_back(static_cast<byte>(opcode));
@@ -123,13 +135,7 @@ void WasmFunctionBuilder::EmitWithVarUint(WasmOpcode opcode,
 }
 
 void WasmFunctionBuilder::EmitI32Const(int32_t value) {
-  if (-64 <= value && value <= 63) {
-    EmitWithU8(kExprI32Const, static_cast<byte>(value & 0x7F));
-  } else {
-    // TODO(titzer): variable-length signed and unsigned i32 constants.
-    byte code[] = {WASM_I32V_5(value)};
-    EmitCode(code, sizeof(code));
-  }
+  EmitWithVarInt(kExprI32Const, value);
 }
 
 void WasmFunctionBuilder::EmitDirectCallIndex(uint32_t index) {