feat: 添加跳转指令支持及条件语句编译实现

src/Compiler/StmtCompiler.cpp

@@ -37,6 +37,117 @@ namespace Fig
         }
         return Result<void, Error>();
     }
+
+    Result<void, Error> Compiler::CompileBlockStmt(BlockStmt *blockStmt)
+    {
+        for (Stmt *stmt : blockStmt->nodes)
+        {
+            const auto &result = CompileStmt(stmt);
+            if (!result)
+            {
+                return result;
+            }
+        }
+        return {};
+    }
+
+    Result<void, Error> Compiler::CompileIfStmt(IfStmt *stmt)
+    {
+        /*
+            if cond1
+            {
+            }
+            else if cond2   #1
+            {
+            }
+            else if cond3   #2
+            {
+            }
+            else            #3
+            {
+            }
+            quit #4
+
+            Bytecode:
+                JmpIfFalse cond1 #1
+                ; consequent内容
+                ; ...
+                ; if条件为true, 跳过所有 else/elseif
+
+                Jmp #4
+
+                ; #1
+                JmpIfFalse cond2 #2
+                ; consequent
+
+                Jmp #4
+
+                ; #2
+                JmpIfFalse cond3 #3
+                ; consequent
+
+                Jmp #4
+
+                ; #3
+                ; 没有一次执行分支
+                ; else部分
+                ; ...
+
+                #4
+
+        */
+        std::vector<int> exitJumps; // 所有分支都要跳到最后，收集所有jump最后回填
+        const auto      &condResult = CompileExpr(stmt->cond);
+        if (!condResult)
+        {
+            return std::unexpected(condResult.error());
+        }
+        std::uint8_t condReg    = *condResult;
+        int          jumpToNext = EmitJump(OpCode::JmpIfFalse, condReg);
+        FreeReg(condReg);
+
+        const auto &blockResult = CompileStmt(stmt->consequent);
+        if (!blockResult)
+        {
+            return blockResult;
+        }
+
+        exitJumps.push_back(EmitJump(OpCode::Jmp)); // 执行完if直接跳到出口
+        PatchJump(jumpToNext);                      // 回填，跳到下一个else/elseif
+
+        for (auto *elif : stmt->elifs)
+        {
+            const auto &elifCondResult = CompileExpr(elif->cond);
+            if (!elifCondResult)
+                return std::unexpected(elifCondResult.error());
+            std::uint8_t elifCondReg = *elifCondResult;
+
+            jumpToNext = EmitJump(OpCode::JmpIfFalse, elifCondReg);
+            FreeReg(elifCondReg);
+
+            const auto &blockResult = CompileStmt(elif->consequent);
+            if (!blockResult)
+            {
+                return blockResult;
+            }
+            exitJumps.push_back(EmitJump(OpCode::Jmp)); // 执行完else if，跳到出口
+            PatchJump(jumpToNext);                      // 跳到下一个分支
+        }
+
+        if (stmt->alternate)
+        {
+            const auto &result = CompileStmt(stmt->alternate);
+            if (!result)
+            {
+                return result;
+            }
+        }
+        for (int exitIndex : exitJumps)
+        {
+            PatchJump(exitIndex); // 回填所有跳转出口的指令
+        }
+        return {};
+    }
     Result<void, Error> Compiler::CompileStmt(Stmt *stmt) // 编译语句
     {
         if (stmt->type == AstType::ExprStmt)
@@ -48,11 +159,20 @@ namespace Fig
             {
                 return std::unexpected(result.error());
             }
+            FreeReg(*result);
         }
         else if (stmt->type == AstType::VarDecl)
         {
             return CompileVarDecl(static_cast<VarDecl *>(stmt));
         }
+        else if (stmt->type == AstType::BlockStmt)
+        {
+            return CompileBlockStmt(static_cast<BlockStmt *>(stmt));
+        }
+        else if (stmt->type == AstType::IfStmt)
+        {
+            return CompileIfStmt(static_cast<IfStmt *>(stmt));
+        }
         return Result<void, Error>();
     }
 }; // namespace Fig