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Re: [PATCH 1/2] Fix LTO bootstrap documentation

From: Diego Novillo <dnovillo at google dot com>
To: Andi Kleen <andi at firstfloor dot org>
Cc: gcc-patches at gcc dot gnu dot org, Andi Kleen <ak at linux dot intel dot com>
Date: Tue, 31 Aug 2010 08:24:47 -0400
Subject: Re: [PATCH 1/2] Fix LTO bootstrap documentation
References: <1283250838-13800-1-git-send-email-andi@firstfloor.org>

On 10-08-31 06:33 , Andi Kleen wrote:

@@ -2108,6 +2108,13 @@ to work around this, by choosing @code{BOOT_CFLAGS} to avoid the parts
  of the stage1 compiler that were miscompiled, or by using @samp{make
  bootstrap4} to increase the number of stages of bootstrap.

+You can also use @code{BOOT_CFLAGS} to force an LTO bootstrap with
+@samp{BOOT_CFLAGS='-O2 -fwhopr=jobserver -fuse-linker-plugin -frandom-seed=1'}.
+Configure the compiler with @samp{--enable-stage1-languages=c,lto}. This
+will only work with the @command{gold} linker and if linker plugins are
+correctly configured.  The @option{-frandom-seed=1} is needed to avoid
+bootstrap comparison failures.

Could you add an explanation on why frandom-seed avoids the comparison failures? It's not immediately obvious.

OK with that change.

Diego.

Follow-Ups:
- Re: [PATCH 1/2] Fix LTO bootstrap documentation
  - From: Paolo Bonzini

References:
- [PATCH 1/2] Fix LTO bootstrap documentation
  - From: Andi Kleen

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