Re: What does %P1 mean in gcc inline assembly?

On Sat, Mar 05, 2016 at 11:37:21AM +0800, 张云 wrote:

On Mar 4, 2016, at 11:59 PM, Dave Tian <dave.jing.tian@gmail.com> wrote:

This ‘P’ is used to make gcc happy and work. Without ‘P’, this inline would be interpreted as: leal $-512(%esp), %eax With ‘P’, this inline is the thing we really want: leal -512(%esp), %eax

Eventually, my gcc 4.9.2 does not compile with ‘P’ is missing. I am not sure if this is still the case for newer gcc (5/6). But you get the point.

-daveti

Thank you for your detailed answer !

By the way， If someone have the problems alike, I suggest them to write some inline assembly and check the compiler’s assembly output.

Didn't get different outputs here, do you have updates? -- Adam Lee http://adam8157.info