crosstool-ng: patches/gcc/4.2.0/260-flatten-switch-stmt-00.patch@88020b2c3246

     1 Hi,

     3 The attached patch makes sure that we create smaller object code for

     4 simple switch statements. We just make sure to flatten the switch

     5 statement into an if-else chain, basically.

     7 This fixes a size-regression as compared to gcc-3.4, as can be seen

     8 below.

    10 2007-04-15  Bernhard Fischer  <..>

    12 	* stmt.c (expand_case): Do not create a complex binary tree when

    13 	optimizing for size but rather use the simple ordered list.

    14 	(emit_case_nodes): do not emit jumps to the default_label when

    15 	optimizing for size.

    17 Not regtested so far.

    18 Comments?

    20 Attached is the test switch.c mentioned below.

    22 $ 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

    23 gcc-$i  -DCHAIN -Os -o switch-CHAIN-$i.o -c switch.c ;done

    24 $ 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

    25 gcc-$i  -UCHAIN -Os -o switch-$i.o -c switch.c ;done

    27 $ size switch-*.o

    28    text	   data	    bss	    dec	    hex	filename

    29     169	      0	      0	    169	     a9	switch-2.95.o

    30     115	      0	      0	    115	     73	switch-3.3.o

    31     103	      0	      0	    103	     67	switch-3.4.o

    32     124	      0	      0	    124	     7c	switch-4.0.o

    33     124	      0	      0	    124	     7c	switch-4.1.o

    34     124	      0	      0	    124	     7c	switch-4.2.orig-HEAD.o

    35      95	      0	      0	     95	     5f	switch-4.3-HEAD.o

    36     124	      0	      0	    124	     7c	switch-4.3.orig-HEAD.o

    37     166	      0	      0	    166	     a6	switch-CHAIN-2.95.o

    38     111	      0	      0	    111	     6f	switch-CHAIN-3.3.o

    39      95	      0	      0	     95	     5f	switch-CHAIN-3.4.o

    40      95	      0	      0	     95	     5f	switch-CHAIN-4.0.o

    41      95	      0	      0	     95	     5f	switch-CHAIN-4.1.o

    42      95	      0	      0	     95	     5f	switch-CHAIN-4.2.orig-HEAD.o

    43      95	      0	      0	     95	     5f	switch-CHAIN-4.3-HEAD.o

    44      95	      0	      0	     95	     5f	switch-CHAIN-4.3.orig-HEAD.o

    47 Content-Type: text/x-diff; charset=us-ascii

    48 Content-Disposition: attachment; filename="gcc-4.3.gcc-flatten-switch-stmt.00.diff"

    50 Index: gcc-4.2.0/gcc/stmt.c

    51 ===================================================================

    52 --- gcc-4.2.0.orig/gcc/stmt.c	(revision 123843)

    53 +++ gcc-4.2.0/gcc/stmt.c	(working copy)

    54 @@ -2517,7 +2517,11 @@ expand_case (tree exp)

    55  	  use_cost_table

    56  	    = (TREE_CODE (orig_type) != ENUMERAL_TYPE

    57  	       && estimate_case_costs (case_list));

    58 -	  balance_case_nodes (&case_list, NULL);

    59 +	  /* When optimizing for size, we want a straight list to avoid

    60 +	     jumps as much as possible. This basically creates an if-else

    61 +	     chain.  */

    62 +	  if (!optimize_size)

    63 +	    balance_case_nodes (&case_list, NULL);

    64  	  emit_case_nodes (index, case_list, default_label, index_type);

    65  	  emit_jump (default_label);

    66  	}

    67 @@ -3075,6 +3079,7 @@ emit_case_nodes (rtx index, case_node_pt

    68  	    {

    69  	      if (!node_has_low_bound (node, index_type))

    70  		{

    71 +		  if (!optimize_size) /* don't jl to the .default_label. */

    72  		  emit_cmp_and_jump_insns (index,

    73  					   convert_modes

    74  					   (mode, imode,

    77 Content-Type: text/x-csrc; charset=us-ascii

    78 Content-Disposition: attachment; filename="switch.c"

    80 int

    81 commutative_tree_code (int code)

    82 {

    83 #define CASE(val, ret) case val:/* __asm__("# val="#val ",ret="#ret);*/ return ret;

    84 #ifndef CHAIN

    85   switch (code)

    86     {

    87 # if 1

    88   CASE(1,3)

    89   CASE(3,2)

    90   CASE(5,8)

    91   CASE(7,1)

    92   CASE(33,4)

    93   CASE(44,9)

    94   CASE(55,10)

    95   CASE(66,-1)

    96   CASE(77,99)

    97   CASE(666,0)

    98 # else

    99     case 1:

   100       return 3;

   101     case 3:

   102       return 2;

   103     case 5:

   104       return 8;

   105     case 7:

   106       return 1;

   107     case 33:

   108       return 4;

   109     case 44:

   110       return 9;

   111     case 55:

   112       return 10;

   113     case 66:

   114       return -1;

   115     case 77:

   116       return 99;

   117     case 666:

   118       return 0;

   119 # endif

   120     default:

   121       break;

   122     }

   123   return 4711;

   125 #else

   126    if (code == 1)

   127 	return 3;

   128   else if (code == 3)

   129 	return 2;

   130   else if (code == 5)

   131 	return 8;

   132   else if (code == 7)

   133 	return 1;

   134   else if (code == 33)

   135 	return 4;

   136   else if (code == 44)

   137 	return 9;

   138   else if (code == 55)

   139 	return 10;

   140   else if (code == 66)

   141 	return -1;

   142   else if (code == 77)

   143 	return 99;

   144   else if (code == 666)

   145 	return 0;

   146   else

   147 	return 4711;

   148 #endif

   149 }

   152 --AhhlLboLdkugWU4S--

author	"Yann E. MORIN" <yann.morin.1998@anciens.enib.fr>
	Tue Jan 12 19:24:03 2010 +0100 (2010-01-12)
changeset 1761	88020b2c3246
parent 251	b23a09443f72
permissions	-rw-r--r--