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Re: nvptx offloading patches [3/n], RFD
- From: Ilya Verbin <iverbin at gmail dot com>
- To: Jakub Jelinek <jakub at redhat dot com>
- Cc: Richard Biener <richard dot guenther at gmail dot com>, Jan Hubicka <hubicka at ucw dot cz>, Bernd Schmidt <bernds at codesourcery dot com>, Thomas Schwinge <thomas at codesourcery dot com>, gcc-patches at gcc dot gnu dot org
- Date: Tue, 17 Feb 2015 16:32:06 +0300
- Subject: Re: nvptx offloading patches [3/n], RFD
- Authentication-results: sourceware.org; auth=none
- References: <5454CAB9 dot 3040907 at codesourcery dot com> <20150204113817 dot GO1746 at tucnak dot redhat dot com> <CAFiYyc11FF2EeOQzqVmQu=q9-Uh-YCN0e38jUn-jmhD9gUrWsw at mail dot gmail dot com> <20150216210812 dot GO1746 at tucnak dot redhat dot com>
On Mon, Feb 16, 2015 at 22:08:12 +0100, Jakub Jelinek wrote:
> Anyway, the question is if for offloading we use wpa stage at all these days
> or not at all, if there is a way for ACCEL_COMPILER to differentiate
> somehow between LTO sections written by the host compiler and LTO sections
> perhaps created by the offloading compiler when trying to LTO the thing (if
> it does it at all). Because obviously the host compiler written LTO
> (in .gnu.offload_lto_*) would need the machine modes translated, while
> LTO streamed already by the ACCEL_COMPILER (if any) generally would already
> use the offloading target machine modes and therefore should be treated as
> native lto (.gnu.lto_*).
Currently both intelmic and nvptx offloading compilers are executed in
non-partitioned LTO mode. I don't know whether we need to support WHOPR
(WPA+LTRANS) mode. Maybe it would be useful for programs with large number of
target regions? But I think this is not needed for GCC 5.
>
> If we don't try to write .gnu.offload_lto_* again, I think following patch
> with additionally not calling lto_write_mode_table for !lto_stream_offload_p
> and not calling lto_input_mode_table for !ACCEL_COMPILER - instead build
> a single shared identity table - might actually work.
>
> Thoughts on this?
Probably the ACCEL_COMPILER in WPA mode (flag_wpa) can read .gnu.offload_lto_*
sections and produce temporary partitions with .gnu.lto_* sections. And the
ACCEL_COMPILER in LTRANS mode (flag_ltrans) will read .gnu.lto_* sections?
-- Ilya