kumquat-buildroot/toolchain/gcc/4.2.0/904-flatten-switch-stmt-00.patch
2007-06-25 09:44:12 +00:00

154 lines
4.0 KiB
Diff

Hi,
The attached patch makes sure that we create smaller object code for
simple switch statements. We just make sure to flatten the switch
statement into an if-else chain, basically.
This fixes a size-regression as compared to gcc-3.4, as can be seen
below.
2007-04-15 Bernhard Fischer <..>
* stmt.c (expand_case): Do not create a complex binary tree when
optimizing for size but rather use the simple ordered list.
(emit_case_nodes): do not emit jumps to the default_label when
optimizing for size.
Not regtested so far.
Comments?
Attached is the test switch.c mentioned below.
$ 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
gcc-$i -DCHAIN -Os -o switch-CHAIN-$i.o -c switch.c ;done
$ 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
gcc-$i -UCHAIN -Os -o switch-$i.o -c switch.c ;done
$ size switch-*.o
text data bss dec hex filename
169 0 0 169 a9 switch-2.95.o
115 0 0 115 73 switch-3.3.o
103 0 0 103 67 switch-3.4.o
124 0 0 124 7c switch-4.0.o
124 0 0 124 7c switch-4.1.o
124 0 0 124 7c switch-4.2.orig-HEAD.o
95 0 0 95 5f switch-4.3-HEAD.o
124 0 0 124 7c switch-4.3.orig-HEAD.o
166 0 0 166 a6 switch-CHAIN-2.95.o
111 0 0 111 6f switch-CHAIN-3.3.o
95 0 0 95 5f switch-CHAIN-3.4.o
95 0 0 95 5f switch-CHAIN-4.0.o
95 0 0 95 5f switch-CHAIN-4.1.o
95 0 0 95 5f switch-CHAIN-4.2.orig-HEAD.o
95 0 0 95 5f switch-CHAIN-4.3-HEAD.o
95 0 0 95 5f switch-CHAIN-4.3.orig-HEAD.o
Content-Type: text/x-diff; charset=us-ascii
Content-Disposition: attachment; filename="gcc-4.3.gcc-flatten-switch-stmt.00.diff"
Index: gcc-4.2.0/gcc/stmt.c
===================================================================
--- gcc-4.2.0.orig/gcc/stmt.c (revision 123843)
+++ gcc-4.2.0/gcc/stmt.c (working copy)
@@ -2517,7 +2517,11 @@ expand_case (tree exp)
use_cost_table
= (TREE_CODE (orig_type) != ENUMERAL_TYPE
&& estimate_case_costs (case_list));
- balance_case_nodes (&case_list, NULL);
+ /* When optimizing for size, we want a straight list to avoid
+ jumps as much as possible. This basically creates an if-else
+ chain. */
+ if (!optimize_size)
+ balance_case_nodes (&case_list, NULL);
emit_case_nodes (index, case_list, default_label, index_type);
emit_jump (default_label);
}
@@ -3075,6 +3079,7 @@ emit_case_nodes (rtx index, case_node_pt
{
if (!node_has_low_bound (node, index_type))
{
+ if (!optimize_size) /* don't jl to the .default_label. */
emit_cmp_and_jump_insns (index,
convert_modes
(mode, imode,
Content-Type: text/x-csrc; charset=us-ascii
Content-Disposition: attachment; filename="switch.c"
int
commutative_tree_code (int code)
{
#define CASE(val, ret) case val:/* __asm__("# val="#val ",ret="#ret);*/ return ret;
#ifndef CHAIN
switch (code)
{
# if 1
CASE(1,3)
CASE(3,2)
CASE(5,8)
CASE(7,1)
CASE(33,4)
CASE(44,9)
CASE(55,10)
CASE(66,-1)
CASE(77,99)
CASE(666,0)
# else
case 1:
return 3;
case 3:
return 2;
case 5:
return 8;
case 7:
return 1;
case 33:
return 4;
case 44:
return 9;
case 55:
return 10;
case 66:
return -1;
case 77:
return 99;
case 666:
return 0;
# endif
default:
break;
}
return 4711;
#else
if (code == 1)
return 3;
else if (code == 3)
return 2;
else if (code == 5)
return 8;
else if (code == 7)
return 1;
else if (code == 33)
return 4;
else if (code == 44)
return 9;
else if (code == 55)
return 10;
else if (code == 66)
return -1;
else if (code == 77)
return 99;
else if (code == 666)
return 0;
else
return 4711;
#endif
}
--AhhlLboLdkugWU4S--