Panasonic MN1030 user manual Optimization of branches, BRA label, Label JMP label, Label JSR label

Chapter 4 Optimization

Table 4-8 Substituted Instructions For Out-Of Range Conditional Branch Instructions

Source Instruction	Candidate instruction 1	Candidate instruction 2	Candidate instruction 3
BLT LABEL	BRA LABEL	BGE *+5	BGE *+7
		JMP LABEL	JMP LABEL
BGT LABEL	BGT LABEL	BLE *+5	BLE *+7
		JMP LABEL	JMP LABEL
BGE LABEL	BGE LABEL	BLT *+5	BLT *+7
		JMP LABEL	JMP LABEL
BLE LABEL	BLE LABEL	BGT * +5	BGT *+7
		JMP LABEL	JMP LABEL
BCS LABEL	BCS LABEL	BCC *+5	BCC *+7
		JMP LABEL	JMP LABEL
BHI LABEL	BHI LABEL	BLS *+5	BLS *+7
		JMP LABEL	JMP LABEL
BCC LABEL	BCC LABEL	BCS *+5	BCS *+7
		JMP LABEL	JMP LABEL
BLS LABEL	BLS LABEL	BHI *+5	BHI *+7
		JMP LABEL	JMP LABEL
BEQ LABEL	BEQ LABEL	BNE *+5	BNE *+7
		JMP LABEL	JMP LABEL
BNE LABEL	BNE LABEL	BEQ *+5	BEQ *+7
		JMP LABEL	JMP LABEL
BVC LABEL	BVC LABEL	BVS *+6	BVS *+8
		JMP LABEL	JMP LABEL
BVS LABEL	BVS LABEL	BVC *+6	BVC *+8
		JMP LABEL	JMP LABEL
BNC LABEL	BNC LABEL	BNS *+6	BNS *+8
		JMP LABEL	JMP LABEL
BNS LABEL	BNS LABEL	BNC *+6	BNC *+8
		JMP LABEL	JMP LABEL

Optimization of branches

For unconditional branch instructions, a JMP label instruction is replaced by a BRA label instruction if the jump target is within the range available for the shorter, relative branch instruction BRA. Similarly, a CALL label, CALLS label, or JSR label instruction is replaced by the shorter version with a 16-bit displacement (d16,PC) instead of the one with the 32-bit displacement (d32,PC).

The following table shows the possibilities for optimizing the unconditional branch instructions and the subroutine call instructions.

Table 4-9 Optimization of branches

Source Instruction	First Candidate		Second Candidate	Third Candidate
BRA label	BRA	label	JMP label	JMP label
JMP label	BRA	label	JMP label	JMP label
CALL label	CALL label		CALL label
CALLS label	CALLS label		CALLS label
JSR label	JSR	label	JSR label

52 Usage Example