From c147589d79a48ceca14ea9f86a793e132e66e1de Mon Sep 17 00:00:00 2001 From: Arlie Davis Date: Thu, 17 Sep 2015 15:19:24 -0700 Subject: mesa: Reduce libGL.so binary size by about 15% Ok, here's v2 of the change, with the suggested edits. From 5f393faa058f453408dfc640eecae3fe6335dfed Mon Sep 17 00:00:00 2001 From: Arlie Davis 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) --- src/mapi/glapi/gen/gl_gentable.py | 57 ++++++++++++++++++++++++++++----------- 1 file changed, 41 insertions(+), 16 deletions(-) diff --git a/src/mapi/glapi/gen/gl_gentable.py b/src/mapi/glapi/gen/gl_gentable.py index 1b3eb72470..7cd475aa2b 100644 --- a/src/mapi/glapi/gen/gl_gentable.py +++ b/src/mapi/glapi/gen/gl_gentable.py @@ -113,6 +113,9 @@ __glapi_gentable_set_remaining_noop(struct _glapi_table *disp) { dispatch[i] = p.v; } +""" + +footer = """ struct _glapi_table * _glapi_create_table_from_handle(void *handle, const char *symbol_prefix) { struct _glapi_table *disp = calloc(_glapi_get_dispatch_table_size(), sizeof(_glapi_proc)); @@ -123,27 +126,28 @@ _glapi_create_table_from_handle(void *handle, const char *symbol_prefix) { if(symbol_prefix == NULL) symbol_prefix = ""; -""" -footer = """ - __glapi_gentable_set_remaining_noop(disp); - - return disp; -} -""" + /* Note: This code relies on _glapi_table_func_names being sorted by the + * entry point index of each function. + */ + for (int func_index = 0; func_index < GLAPI_TABLE_COUNT; ++func_index) { + const char *name = _glapi_table_func_names[func_index]; + void ** procp = &((void **)disp)[func_index]; -body_template = """ - if(!disp->%(name)s) { - void ** procp = (void **) &disp->%(name)s; - snprintf(symboln, sizeof(symboln), "%%s%(entry_point)s", symbol_prefix); + snprintf(symboln, sizeof(symboln), \"%s%s\", symbol_prefix, name); #ifdef _WIN32 *procp = GetProcAddress(handle, symboln); #else *procp = dlsym(handle, symboln); #endif } + __glapi_gentable_set_remaining_noop(disp); + + return disp; +} """ + class PrintCode(gl_XML.gl_print_base): def __init__(self): @@ -180,12 +184,33 @@ class PrintCode(gl_XML.gl_print_base): def printBody(self, api): - for f in api.functionIterateByOffset(): - for entry_point in f.entry_points: - vars = { 'entry_point' : entry_point, - 'name' : f.name } - print body_template % vars + # Determine how many functions have a defined offset. + func_count = 0 + for f in api.functions_by_name.itervalues(): + if f.offset != -1: + func_count += 1 + + # Build the mapping from offset to function name. + funcnames = [None] * func_count + for f in api.functions_by_name.itervalues(): + if f.offset != -1: + if not (funcnames[f.offset] is None): + raise Exception("Function table has more than one function with same offset (offset %d, func %s)" % (f.offset, f.name)) + funcnames[f.offset] = f.name + + # Check that the table has no gaps. We expect a function at every offset, + # and the code which generates the table relies on this. + for i in xrange(0, func_count): + if funcnames[i] is None: + raise Exception("Function table has no function at offset %d" % (i)) + + print "#define GLAPI_TABLE_COUNT %d" % func_count + print "static const char * const _glapi_table_func_names[GLAPI_TABLE_COUNT] = {" + for i in xrange(0, func_count): + print " /* %5d */ \"%s\"," % (i, funcnames[i]) + print "};" + return -- cgit v1.2.3