This is the mail archive of the
mailing list for the GCC project.
Re: How to find out register information at the beginning of a basic block?
- From: "Vladimir N. Makarov" <vmakarov at redhat dot com>
- To: "H.J. Lu" <hjl dot tools at gmail dot com>
- Cc: GCC Development <gcc at gcc dot gnu dot org>
- Date: Mon, 31 May 2010 23:09:59 -0400
- Subject: Re: How to find out register information at the beginning of a basic block?
- References: <AANLkTikiXdsulo-u7fCJyz0ZAUu9wa4S32ZR1HZY2Igs@mail.gmail.com> <AANLkTilXTAnHxsK9oyCDDI8GTWXFofmkJVwL-lHcvlDB@mail.gmail.com> <4C040E9A.firstname.lastname@example.org> <AANLkTinPTCUY7Vxt8Zyr-IIJCsYU-ljbh6y1jJM3Kq3z@mail.gmail.com>
On 05/31/2010 08:17 PM, H.J. Lu wrote:
On Mon, May 31, 2010 at 12:31 PM, Vladimir Makarov<email@example.com> wrote:If you mean what part of hard register lives, then as I know there is no
such infrastructure code. As I remember Ken Zadeck tried to implement
something analogous in the old RA. You could try to find this code in
H.J. Lu wrote:My impression is hard_regno_nregs tells me that number of
I am working on generating vzeroupper to avoid AVX->SSE transition
I have generated vzeroupper on function return as well as function
call. I am working on a backend pass to eliminate those vzeroupper
instructions when I can prove that the upper 128bits of AVX registers
are dead at the point where vzeroupper is added. To do that, I need
to find out if a register is live at the beginning of a basic block as
as its size. I thought dataflow might give me such info. But I couldn't
find a way to access such information. Does anyone have any pointers?
DF_LR_IN (bb) returns bitmap of livings prseudo regnos.
DF_LIVE_IN (bb) takes availability info into account.
Size of hard registers is defined by hard_regno_nregs.
hard registers given machine mode occupy. It doesn't tell me
the live size of a hard register at the beginning of a basic
block. How do I get this information?