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[PATCH 1/2] Fix LTO bootstrap documentation

From: Andi Kleen <>

BUILD_CONFIG=bootstrap-lto does not work currently and causes build
failures.  Remove a reference to that in the install documentation and instead
document a working method using BOOT_CFLAGS.

Bootstrapped on x86-64 together with the -fwhopr=jobserver patchkit

v2: Fix grammar/texinfo based on feedback

Ok to commit?

2010-08-17  Andi Kleen	<>

	* doc/install.texi (Building a native compiler): Remove
	reference to broken BUILD_CONFIG=bootstrap-lto.
	Document working method instead.
 gcc/doc/install.texi |   12 +++++++-----
 1 files changed, 7 insertions(+), 5 deletions(-)

diff --git a/gcc/doc/install.texi b/gcc/doc/install.texi
index fc9b988..e98675d 100644
--- a/gcc/doc/install.texi
+++ b/gcc/doc/install.texi
@@ -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.
 @code{BOOT_CFLAGS} does not apply to bootstrapped target libraries.
 Since these are always compiled with the compiler currently being
 bootstrapped, you can use @code{CFLAGS_FOR_TARGET} to modify their
@@ -2155,11 +2162,6 @@ Removes any @option{-O}-started option from @code{BOOT_CFLAGS}, and adds
 @item @samp{bootstrap-O3}
 Analogous to @code{bootstrap-O1}.
-@item @samp{bootstrap-lto}
-Enables Link-Time Optimization for host tools during bootstrapping.
-@samp{BUILD_CONFIG=bootstrap-lto} is equivalent to adding
-@option{-flto} to @samp{BOOT_CFLAGS}.
 @item @samp{bootstrap-debug}
 Verifies that the compiler generates the same executable code, whether
 or not it is asked to emit debug information.  To this end, this

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