TABLE OF CONTENTS Conditional execution is important to alter the control flow from the default sequential execution. The MIPS architecture provides several instructions to facilitate conditional execution. We have already seen some of these instructions including the unconditional and conditional branch instructions. In addition, procedure invocation and return also alter control flow. We briefly introduced some of these instructions in previous chapters. This chapter gives a complete discussion of these instructions.
The target address of these flow-altering instructions can be specified either directly in the instruction or indirectly via a register. In previous chapters, we used direct specification for jumps and procedure calls. However, we used indirect specification to return from a procedure. Most jumps and procedure calls use the direct specification. However, sometimes it is useful to specify the target address indirectly via a register. We discuss such indirect jumps and procedure calls toward the end of the chapter. We conclude the chapter with a summary.
Modern high-level languages provide a variety of decision structures. These structures include selection structures such as if-then-else and iterative structures such as while and for loops. Assembly language, being a low-level language, does not provide these structures directly. However, assembly language provides several basic instructions that could be used to construct these high-level language selection and iteration structures. For example, the following code
li $t2,50loop: addu $t0,$t0,$t1 sub ...
