[Interpreter] i32.sub (WebAssembly#7259)

Building on top of WebAssembly#7227, i32.sub is implemented and tested.

Author: ashleynh

src/interpreter/interpreter.cpp

@@ -94,6 +94,9 @@ struct ExpressionInterpreter : OverriddenVisitor<ExpressionInterpreter, Flow> {
     if (curr->op == AddInt32) {
       push(lhs.add(rhs));
       return {};
+    } else if (curr->op == SubInt32) {
+      push(lhs.sub(rhs));
+      return {};
     }
     WASM_UNREACHABLE("TODO");
   }

test/gtest/interpreter.cpp

@@ -25,7 +25,7 @@
 
 using namespace wasm;
 
-TEST(InterpreterTest, Add) {
+TEST(InterpreterTest, AddI32) {
   Module wasm;
   IRBuilder builder(wasm);
 
@@ -41,3 +41,20 @@ TEST(InterpreterTest, Add) {
 
   EXPECT_EQ(results, expected);
 }
+
+TEST(InterpreterTest, SubI32) {
+  Module wasm;
+  IRBuilder builder(wasm);
+
+  ASSERT_FALSE(builder.makeConst(Literal(uint32_t(1))).getErr());
+  ASSERT_FALSE(builder.makeConst(Literal(uint32_t(2))).getErr());
+  ASSERT_FALSE(builder.makeBinary(SubInt32).getErr());
+
+  auto expr = builder.build();
+  ASSERT_FALSE(expr.getErr());
+
+  auto results = Interpreter{}.run(*expr);
+  std::vector<Literal> expected{Literal(uint32_t(-1))};
+
+  EXPECT_EQ(results, expected);
+}