install.texi (Specific, [...]): Document need to bootstrap with -mips3.

	* doc/install.texi (Specific, mips-sgi-irix6): Document need to
	bootstrap with -mips3.

From-SVN: r53565

diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index b57b910e271f161ebd5233acd52ba5af30303f7d..5bef9fc39c467bc00924cb3feae1465e61007f6b 100644 (file)
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,3 +1,8 @@
+2002-05-17  Rainer Orth  <ro@TechFak.Uni-Bielefeld.DE>
+
+       * doc/install.texi (Specific, mips-sgi-irix6): Document need to
+       bootstrap with -mips3.
+
 2002-05-17  David S. Miller  <davem@redhat.com>
 
        PR c/6689, PR optimization/6615

diff --git a/gcc/doc/install.texi b/gcc/doc/install.texi
index d97a98eb8f6286b490fdde7e8e5719a61558e1c3..77577f771b5232562142afcc17400591a280c6e3 100644 (file)
--- a/gcc/doc/install.texi
+++ b/gcc/doc/install.texi
@@ -3179,6 +3179,27 @@ then your version of @command{cc} uses the O32 or N64 ABI by default.  You
 should set the environment variable @env{CC} to @samp{cc -n32}
 before configuring GCC@.
 
+If you want the resulting @command{gcc} to run on old 32-bit systems
+with the MIPS R4400 CPU, you need to ensure that only code for the mips3
+instruction set architecture (ISA) is generated.  While GCC 3.x does
+this correctly, both GCC 2.95 and SGI's MIPSpro @command{cc} may change
+the ISA depending on the machine where GCC is built.  Using one of them
+as the bootstrap compiler may result in mips4 code, which won't run at
+all on mips3-only systems.  For the test program above, you should see:
+
+@example
+test.o: ELF N32 MSB mips-3 @dots{}
+@end example
+
+If you get:
+
+@example
+test.o: ELF N32 MSB mips-4 @dots{}
+@end example
+
+instead, you should set the environment variable @env{CC} to @samp{cc
+-n32 -mips3} or @samp{gcc -mips3} respectively before configuring GCC@.
+
 GCC on IRIX 6 is usually built to support both the N32 and N64 ABIs.  If
 you build GCC on a system that doesn't have the N64 libraries installed,
 you need to configure with @option{--disable-multilib} so GCC doesn't