mesa: Reduce libGL.so binary size by about 15%11.1

Ok, here's v2 of the change, with the suggested edits.

From 5f393faa058f453408dfc640eecae3fe6335dfed Mon Sep 17 00:00:00 2001
From: Arlie Davis <arlied@google.com>
Date: Tue, 15 Sep 2015 09:58:34 -0700
Subject: [PATCH] This patch significantly reduces the size of the libGL.so
 binary. It does not change the (externally visible) behavior of libGL.so at
 all.

gl_gentable.py generates a function, _glapi_create_table_from_handle.
This function allocates a large dispatch table, consisting of 1300 or so
function pointers, and fills this dispatch table by doing symbol lookups
on a given shared library.  Previously, gl_gentable.py would generate a
single, very large _glapi_create_table_from_handle function, with a short
cluster of lines for each entry point (function).  The idiom it generates
was a NULL check, a call to snprintf, a call to dlsym / GetProcAddress,
and then a store into the dispatch table.  Since this function processes
a large number of entry points, this code is duplicated many times over.

We can encode the same information much more compactly, by using a lookup
table.  The previous total size of _glapi_create_table_from_handle on x64
was 125848 bytes.  By using a lookup table, the size of
_glapi_create_table_from_handle (and the related lookup tables) is reduced
to 10840 bytes.  In other words, this enormous function is reduced by 91%.
The size of the entire libGL.so binary (measured when stripped) itself drops
by 15%.

So the purpose of this change is to reduce the binary size, which frees up
disk space, memory, etc.

(cherry picked from commit 2a2c8fa7d480d83dac73b0e4e89c79a3777309b6)

0 files changed, 0 insertions, 0 deletions