Behaviour of i386 add instruction changes based on operand

[Ian Lance Taylor]

Assemble this i386 source:

	add $1, 0(%edx)
	add $128, 0(%edx)

I get this:

foo.s: Assembler messages:
foo.s:2: Error: no instruction mnemonic suffix given and no register operands; can't size instruction

The instructions do generate different opcodes (0x80 vs. 0x83).  When
adding a constant to memory, if the operand is a sign extended 8-bit
value, we default to addl.  If the operand is something else, we have
no default.  That seems inconsistent.  Is this a bug or a feature?

Ian