From c8cfb0cea88fec22f5aa0582fe846b46baf77eb1 Mon Sep 17 00:00:00 2001
From: Thomas G. Lockhart
Date: Sun, 1 Mar 1998 08:16:16 +0000
Subject: SGML source for new documentation.

---
 doc/src/sgml/compiler.sgml | 73 ++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 73 insertions(+)
 create mode 100644 doc/src/sgml/compiler.sgml

(limited to 'doc/src/sgml/compiler.sgml')

diff --git a/doc/src/sgml/compiler.sgml b/doc/src/sgml/compiler.sgml
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+<Chapter>
+<DocInfo>
+<AuthorGroup>
+<Author>
+<FirstName>Brian</FirstName>
+<Surname>Gallew</Surname>
+</Author>
+</AuthorGroup>
+<Date>Transcribed 1998-02-12</Date>
+</DocInfo>
+
+<Title>GCC Default Optimizations</Title>
+
+<Para>
+<Note>
+<Para>
+Contributed by <ULink url="mailto:geek+@cmu.edu">Brian Gallew</ULink>
+</Para>
+</Note>
+
+<Para>
+Configuring gcc to use certain flags by default is a simple matter of
+editing the 
+<FileName>/usr/local/lib/gcc-lib/<Replaceable>platform</Replaceable>/<Replaceable>version</Replaceable>/specs</FileName>
+file.
+The format of this file pretty simple.  The file is broken into
+sections, each of which is three lines long.  The first line is
+"*<Replaceable>section_name</Replaceable>:" (e.g. "*asm:").
+The second line is a list of flags,
+and the third line is blank.
+
+<Para>
+The easiest change to make is to append
+the desired default flags to the list in the appropriate section.  As
+an example, let's suppose that I have linux running on a '486 with gcc
+2.7.2 installed in the default location.  In the file
+/usr/local/lib/gcc-lib/i486-linux/2.7.2/specs, 13 lines down I find
+the following section:
+<ProgramListing>
+- ----------SECTION----------
+*cc1:
+
+
+- ----------SECTION----------
+</ProgramListing>
+As you can see, there aren't any default flags.  If I always wanted
+compiles of C code to use "-m486 -fomit-frame-pointer", I would
+change it to look like:
+<ProgramListing>
+- ----------SECTION----------
+*cc1:
+- -m486 -fomit-frame-pointer
+
+- ----------SECTION----------
+</ProgramListing>
+If I wanted to be able to generate 386 code for another, older linux
+box lying around, I'd have to make it look like this:
+<ProgramListing>
+- ----------SECTION----------
+*cc1:
+%{!m386:-m486} -fomit-frame-pointer
+
+- ----------SECTION----------
+</ProgramListing>
+This will always omit frame pointers, any will build 486-optimized
+code unless -m386 is specified on the command line.
+
+<Para>
+You can actually do quite a lot of customization with the specs file.
+Always remember, however, that these changes are global, and affect
+all users of the system.
+
+</Chapter>
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