Conditional clobbering

[Joern Rennecke]

Quoting "Paulo J. Matos" <pocmatos@gmail.com>:
> I have a situation in writing a specific condition on an md file.
> I have an insn with 2 alternatives and then I use which_alternative to
> generate the assembler code but if which_alternative == 1 I am
> clobbering a register. How can I tell gcc that if it matches 1, a
> given register is clobbered?

You use a clobber with a matching constraint for alternative 1 and X for
other alternatives.  Make sure the patten is not named.