Data processing system and method for executing block call and block return instructions

A method of controlling an execution flow for running a program in a data processing system, comprising:

• when a first block call instruction in the program is read while a level status of the execution flow has an initial value:
• storing a return address of the first block call instruction in a control register;
• incrementing a value of the level status;
• and
• redirecting the execution flow to a target address indicated by the first block call instruction;
• when a block return instruction corresponding to the first block call instruction in the program is read while the value of the level status is not equal to the initial value, decrementing the value of the level status;
• after decrementing the value of the level status, if the value of the level status is equal to the initial value of the level status, redirecting the execution flow to the return address of the first block call instruction;
• and
• when a level-status-dependent non-function call control transfer instruction is read while the value of the level status is not equal to the initial value of the level status, resetting the value of the level status to the initial value of the level status and redirecting the execution flow to a target address indicated by the level-status-dependent non-function call control transfer instruction.

A data processing system, comprising:

• a control register configured to store a level status of an execution flow for running a program of the data processing system and at least one return address;
• a program counter configured to hold a current address of the execution flow;
• and
• a controller configured to control operations of the data processing system;
• wherein:
• when the controller reads a first block call instruction in the program while a level status of the execution flow has an initial value, the controller stores a return address of the first block call instruction in the control register, increments a value of the level status, and redirects the execution flow to a target address indicated by the first block call instruction;
• when the controller reads a block return instruction corresponding to the first block call instruction in the program while the value of the level status is not equal to the initial value, the controller decrements the value of the level status;
• after the controller decrements the value of the level status, if the value of the level status is equal to the initial value of the level status, the controller redirects the execution flow to the return address of the first block call instruction stored in the control register;
• and
• when the controller reads a function call control transfer instruction while the value of the level status is not equal to the initial value of the level status, the controller resets the value of the level status to the initial value, replacing a return address of the function call control transfer instruction with a return address of a previous block call instruction, and redirects the execution flow to a target address indicated by the function call control transfer instruction.