Robert P. J. DAY says:
According to Mike Frysinger, this patch was removed from Gentoo in the
2.3.x series and didn't seem to cause any adverse effects. So toss it
from the patch directories for glibc 2.5 and up.
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
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
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
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)
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
63 + balance_case_nodes (&case_list, NULL);
64 emit_case_nodes (index, case_list, default_label, index_type);
65 emit_jump (default_label);
67 @@ -3075,6 +3079,7 @@ emit_case_nodes (rtx index, case_node_pt
69 if (!node_has_low_bound (node, index_type))
71 + if (!optimize_size) /* don't jl to the .default_label. */
72 emit_cmp_and_jump_insns (index,
77 Content-Type: text/x-csrc; charset=us-ascii
78 Content-Disposition: attachment; filename="switch.c"
81 commutative_tree_code (int code)
83 #define CASE(val, ret) case val:/* __asm__("# val="#val ",ret="#ret);*/ return ret;
144 else if (code == 666)