On 8/9/19 2:38 PM, Martin Liška wrote:
> On 8/9/19 10:19 AM, Richard Biener wrote:
>> OK with that. I still think that making -flto use a jobserver if detected
>> (but _not_ use the number of CPU cores by default) makes
>> sense as an independent change.
>
> In order to address that, I'm suggesting following patch that I've been
> testing.
>
> Martin
>
Hm, I take back the config changes.
Martin
>From 1f9c9f74a84ec3ca930bbc9525ef2185200e0ce8 Mon Sep 17 00:00:00 2001
From: Martin Liska <mli...@suse.cz>
Date: Fri, 9 Aug 2019 14:03:11 +0200
Subject: [PATCH] Automatically detect GNU jobserver with -flto.
gcc/ChangeLog:
2019-08-09 Martin Liska <mli...@suse.cz>
* doc/invoke.texi: Document automatic detection of jobserver.
* lto-wrapper.c (run_gcc): Detect jobserver always.
---
gcc/doc/invoke.texi | 3 ++-
gcc/lto-wrapper.c | 2 +-
2 files changed, 3 insertions(+), 2 deletions(-)
diff --git a/gcc/doc/invoke.texi b/gcc/doc/invoke.texi
index 5b6b824bdd3..0000d358e48 100644
--- a/gcc/doc/invoke.texi
+++ b/gcc/doc/invoke.texi
@@ -10422,7 +10422,8 @@ job server mode to determine the number of parallel jobs. This
is useful when the Makefile calling GCC is already executing in parallel.
You must prepend a @samp{+} to the command recipe in the parent Makefile
for this to work. This option likely only works if @env{MAKE} is
-GNU make.
+GNU make. Even without the option value, GCC tries to automatically
+detect a running GNU make's job server.
Use @option{-flto=auto} to use GNU make's job server, if available,
or otherwise fall back to autodetection of the number of CPU threads
diff --git a/gcc/lto-wrapper.c b/gcc/lto-wrapper.c
index 84f59cf1a1f..339c379d972 100644
--- a/gcc/lto-wrapper.c
+++ b/gcc/lto-wrapper.c
@@ -1427,7 +1427,7 @@ run_gcc (unsigned argc, char *argv[])
auto_parallel = 0;
parallel = 0;
}
- else if (!jobserver && auto_parallel)
+ else if (!jobserver)
jobserver = jobserver_active_p ();
if (linker_output)
--
2.22.0
