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openwrt-xburst/toolchain/gcc/patches/4.2.4/904-flatten-switch-stmt-00.patch
kaloz 54a1da8d7c gcc 4.2.4 support
git-svn-id: svn://svn.openwrt.org/openwrt/trunk@11310 3c298f89-4303-0410-b956-a3cf2f4a3e73
2008-05-31 18:45:07 +00:00

75 lines
2.9 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-4.2.3/gcc/stmt.c
===================================================================
--- gcc-4.2.3.orig/gcc/stmt.c 2007-09-01 17:28:30.000000000 +0200
+++ gcc-4.2.3/gcc/stmt.c 2008-05-21 13:45:59.137288494 +0200
@@ -2511,7 +2511,11 @@
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);
}
@@ -3069,6 +3073,7 @@
{
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,