patches/gcc/4.3.0/250-flatten-switch-stmt-00.patch
author "Yann E. MORIN" <yann.morin.1998@anciens.enib.fr>
Mon Jul 28 21:08:01 2008 +0000 (2008-07-28)
changeset 746 b150d6f590fc
parent 552 patches/gcc/4.3.0/250-904-flatten-switch-stmt-00.patch@4edbcdb17e3d
permissions -rw-r--r--
Third go at renaming patches to contain neither the package name nor the package version.
     1 Original patch from gentoo: gentoo/src/patchsets/gcc/4.3.0/gentoo/18_all_904-flatten-switch-stmt-00.patch
     2 http://gcc.gnu.org/ml/gcc-patches/2007-04/msg00927.html
     3 
     4 Hi,
     5 
     6 The attached patch makes sure that we create smaller object code for
     7 simple switch statements. We just make sure to flatten the switch
     8 statement into an if-else chain, basically.
     9 
    10 This fixes a size-regression as compared to gcc-3.4, as can be seen
    11 below.
    12 
    13 2007-04-15  Bernhard Fischer  <..>
    14 
    15 	* stmt.c (expand_case): Do not create a complex binary tree when
    16 	optimizing for size but rather use the simple ordered list.
    17 	(emit_case_nodes): do not emit jumps to the default_label when
    18 	optimizing for size.
    19 
    20 Not regtested so far.
    21 Comments?
    22 
    23 Attached is the test switch.c mentioned below.
    24 
    25 $ for i in 2.95 3.3 3.4 4.0 4.1 4.2.orig-HEAD 4.3.orig-HEAD 4.3-HEAD;do
    26 gcc-$i  -DCHAIN -Os -o switch-CHAIN-$i.o -c switch.c ;done
    27 $ for i in 2.95 3.3 3.4 4.0 4.1 4.2.orig-HEAD 4.3.orig-HEAD 4.3-HEAD;do
    28 gcc-$i  -UCHAIN -Os -o switch-$i.o -c switch.c ;done
    29 
    30 $ size switch-*.o
    31    text	   data	    bss	    dec	    hex	filename
    32     169	      0	      0	    169	     a9	switch-2.95.o
    33     115	      0	      0	    115	     73	switch-3.3.o
    34     103	      0	      0	    103	     67	switch-3.4.o
    35     124	      0	      0	    124	     7c	switch-4.0.o
    36     124	      0	      0	    124	     7c	switch-4.1.o
    37     124	      0	      0	    124	     7c	switch-4.2.orig-HEAD.o
    38      95	      0	      0	     95	     5f	switch-4.3-HEAD.o
    39     124	      0	      0	    124	     7c	switch-4.3.orig-HEAD.o
    40     166	      0	      0	    166	     a6	switch-CHAIN-2.95.o
    41     111	      0	      0	    111	     6f	switch-CHAIN-3.3.o
    42      95	      0	      0	     95	     5f	switch-CHAIN-3.4.o
    43      95	      0	      0	     95	     5f	switch-CHAIN-4.0.o
    44      95	      0	      0	     95	     5f	switch-CHAIN-4.1.o
    45      95	      0	      0	     95	     5f	switch-CHAIN-4.2.orig-HEAD.o
    46      95	      0	      0	     95	     5f	switch-CHAIN-4.3-HEAD.o
    47      95	      0	      0	     95	     5f	switch-CHAIN-4.3.orig-HEAD.o
    48 
    49 
    50 Content-Type: text/x-diff; charset=us-ascii
    51 Content-Disposition: attachment; filename="gcc-4.3.gcc-flatten-switch-stmt.00.diff"
    52 
    53 diff -durN gcc-4.3.0.orig/gcc/stmt.c gcc-4.3.0/gcc/stmt.c
    54 --- gcc-4.3.0.orig/gcc/stmt.c	2007-12-04 22:55:32.000000000 +0100
    55 +++ gcc-4.3.0/gcc/stmt.c	2008-06-10 14:44:33.000000000 +0200
    56 @@ -2508,7 +2508,11 @@
    57  	  use_cost_table
    58  	    = (TREE_CODE (orig_type) != ENUMERAL_TYPE
    59  	       && estimate_case_costs (case_list));
    60 -	  balance_case_nodes (&case_list, NULL);
    61 +	  /* When optimizing for size, we want a straight list to avoid
    62 +	     jumps as much as possible. This basically creates an if-else
    63 +	     chain.  */
    64 +	  if (!optimize_size)
    65 +	    balance_case_nodes (&case_list, NULL);
    66  	  emit_case_nodes (index, case_list, default_label, index_type);
    67  	  emit_jump (default_label);
    68  	}
    69 @@ -3066,6 +3070,7 @@
    70  	    {
    71  	      if (!node_has_low_bound (node, index_type))
    72  		{
    73 +		  if (!optimize_size) /* don't jl to the .default_label. */
    74  		  emit_cmp_and_jump_insns (index,
    75  					   convert_modes
    76  					   (mode, imode,