| Original patch from: ../4.3.2/160-flatten-switch-stmt-00.patch |
| |
| -= BEGIN original header =- |
| Original patch from gentoo: gentoo/src/patchsets/gcc/4.3.1/gentoo/18_all_904-flatten-switch-stmt-00.patch |
| http://gcc.gnu.org/ml/gcc-patches/2007-04/msg00927.html |
| |
| 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" |
| |
| -= END original header =- |
| |
| diff -durN gcc-4.3.3.orig/gcc/stmt.c gcc-4.3.3/gcc/stmt.c |
| --- gcc-4.3.3.orig/gcc/stmt.c 2008-05-09 20:12:13.000000000 +0200 |
| +++ gcc-4.3.3/gcc/stmt.c 2009-01-27 22:19:28.000000000 +0100 |
| @@ -2509,7 +2509,11 @@ |
| 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); |
| } |
| @@ -3067,6 +3071,7 @@ |
| { |
| 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, |