[FE training-materials-updates] Toolchains: make -march, -mtune and -mcpu explanations a little more correct

[Michael Opdenacker]

Repository : git://git.free-electrons.com/training-materials.git
On branch  : master
Link       : http://git.free-electrons.com/training-materials/commit/?id=f164ca31e012b1ee983e8d218df75b31d71424dd

>---------------------------------------------------------------

commit f164ca31e012b1ee983e8d218df75b31d71424dd
Author: Michael Opdenacker <michael.opdenacker at free-electrons.com>
Date:   Tue Jun 13 06:32:44 2017 +0200

    Toolchains: make -march, -mtune and -mcpu explanations a little more correct
    
    - The primary options are -march and -mtune, not -march and -mcpu
    - -mcpu can be used as a shortcut, guessing the instruction set from
      the cpu name.
    
    Signed-off-by: Michael Opdenacker <michael.opdenacker at free-electrons.com>


>---------------------------------------------------------------

f164ca31e012b1ee983e8d218df75b31d71424dd
 .../sysdev-toolchains-options/sysdev-toolchains-options.tex | 13 ++++++++-----
 1 file changed, 8 insertions(+), 5 deletions(-)

diff --git a/slides/sysdev-toolchains-options/sysdev-toolchains-options.tex b/slides/sysdev-toolchains-options/sysdev-toolchains-options.tex
index 65675d5..57fe638 100644
--- a/slides/sysdev-toolchains-options/sysdev-toolchains-options.tex
+++ b/slides/sysdev-toolchains-options/sysdev-toolchains-options.tex
@@ -48,16 +48,19 @@
   \begin{itemize}
   \item A set of cross-compiling tools is specific to a CPU architecture (ARM,
     x86, MIPS, PowerPC)
-  \item However, with the \code{-march=}, \code{-mcpu=},
-    \code{-mtune=} options, one can select more precisely the
-    target CPU type
+  \item However, gcc offers further options:
     \begin{itemize}
-    \item For example, \code{-march=armv7 -mcpu=cortex-a8}
+    \item \code{-march} allows to select a specific target instruction set
+    \item \code{-tune} allows to optimize code for a specific CPU
+    \item For example: \code{-march=armv7 -mtune=cortex-a8}
+    \item \code{-mcpu=cortex-a8} can be used instead to allow gcc to infer the target
+      instruction set (\code{-march=armv7}) and cpu optimizations (\code{-mtune=cortex-a8})
+    \item \url{https://gcc.gnu.org/onlinedocs/gcc/ARM-Options.html}
     \end{itemize}
   \item At the toolchain compilation time, values can be chosen. They are used:
     \begin{itemize}
     \item As the default values for the cross-compiling tools, when no
-      other \code{-march}, \code{-mcpu}, \code{-mtune} options are
+      other \code{-march}, \code{-mtune}, \code{-mcpu} options are
       passed
     \item To compile the C library
     \end{itemize}