ADD vs. ADDI, vasm vs. Asmone

koobo · 14 August 2022, 08:47

While investigating the differences in resulting binaries by vasm and AsmOne I noticed that with input

Code:

   ADD.W #10,D0

AsmOne gives:

Code:

   0640000A   ADDI.W #10,D0

vasm gives:

Code:

   D07C000A   ADD.W #10,D0

This, for me, is a bit surprising, I didn't think that there could be such overlaps in the instructions. The instruction format documentation describes these in detail. The documentation for ADD mentions "ADDI and ADDQ are used when the source is immediate data. Most assemblers automatically make this distinction."

alexh · 14 August 2022, 10:03

http://eab.abime.net/showthread.php?t=94176

Thomas Richter · 14 August 2022, 10:38

Well, here two instructions fall together. ADDI is "add immediate to some complex addressing mode, including data registers", whereas ADD is "add some complex addressing mode to data register" or "add data register to some complex addressing mode". In some cases, the two opcodes just fall together, as you see.

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14 August 2022, 08:47	#1
koobo Registered User Join Date: Sep 2019 Location: Finland Posts: 363	ADD vs. ADDI, vasm vs. Asmone While investigating the differences in resulting binaries by vasm and AsmOne I noticed that with input Code: ADD.W #10,D0 AsmOne gives: Code: 0640000A ADDI.W #10,D0 vasm gives: Code: D07C000A ADD.W #10,D0 This, for me, is a bit surprising, I didn't think that there could be such overlaps in the instructions. The instruction format documentation describes these in detail. The documentation for ADD mentions "ADDI and ADDQ are used when the source is immediate data. Most assemblers automatically make this distinction."

14 August 2022, 10:03	#2
alexh Thalion Webshrine Join Date: Jan 2004 Location: Oxford Posts: 14,354	http://eab.abime.net/showthread.php?t=94176

14 August 2022, 10:38	#3
Thomas Richter Registered User Join Date: Jan 2019 Location: Germany Posts: 3,233	Well, here two instructions fall together. ADDI is "add immediate to some complex addressing mode, including data registers", whereas ADD is "add some complex addressing mode to data register" or "add data register to some complex addressing mode". In some cases, the two opcodes just fall together, as you see.

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