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From: gertom@rgai.hu To: gcc-gnats@gcc.gnu.org Subject: middle-end/9707: Unnecessary range test in switches with less than 4 cases Date: Fri, 14 Feb 2003 16:46:00 -0000 [thread overview] Message-ID: <20030214164315.26069.qmail@sources.redhat.com> (raw) [-- Warning: decoded text below may be mangled, UTF-8 assumed --] [-- Attachment #1: Type: text/plain, Size: 2604 bytes --] >Number: 9707 >Category: middle-end >Synopsis: Unnecessary range test in switches with less than 4 cases >Confidential: no >Severity: non-critical >Priority: medium >Responsible: unassigned >State: open >Class: pessimizes-code >Submitter-Id: net >Arrival-Date: Fri Feb 14 16:46:00 UTC 2003 >Closed-Date: >Last-Modified: >Originator: Tamás Gergely >Release: gcc version 3.3 20030210 (prerelease) >Organization: >Environment: BUILD & HOST: Linux 2.4.20 i686 unknown TARGET: arm-unknown-elf >Description: When a switch has less than 4 cases gcc tests for the middle-case-value and makes an additional less-greater check instead of immediately evaluating the other case-values. If there are more case branches in the switch, this kind of checking would speed up the search of the corresponding case branch (but those switches are solved with jump-tables anyway). But for only a few case branches, the direct equality checks would be better. >How-To-Repeat: arm-elf-gcc -S -g0 -Os -o 01_3d.s ./01_3d.i //01_3d.i # 1 "01_3d.c" # 1 "<built-in>" # 1 "<command line>" # 1 "01_3d.c" unsigned int g; int main () { int r; switch (r) { case 1: g=11; break; case 2: g=12; break; case 3: g=13; break; default: g=20; break; } return 0; } >Fix: >Release-Note: >Audit-Trail: >Unformatted: ----gnatsweb-attachment---- Content-Type: application/x-gzip; name="switch.tar.gz" Content-Transfer-Encoding: base64 Content-Disposition: attachment; filename="switch.tar.gz" H4sIAAgbTT4AA+2YXW/aMBSGuQ0S/+GIbhJIJPMHHyus06RedBfTdjHtappQSA6Z1SRmjlPWTfvv s01KUb+lCaZKfi6Iffwex8GcFwyhc55GorVPCCVkPCYtQgidjIb2Suhwc7WMOG+RyZhxRobcxikl bNQCstdVNdSVjhVAK0OlZXG/Ls4xOcR6DswRUOgS9yFIup22675Z1CLXoSjfbiOJLIq4TCEXJW6j 12l1WYmsxBREqSGbddr2WsSihF6/0/7daYMbUTPbqtZCJ9+hp/rgRgCSuEKg001nS3ZC6ew6tlAY n892EtgdCeyhBH5HAr8nIcVlXOf6dgYjd2b8sS8Kda1KsArT/99b+yQ2e1jt+R4P1j8ldmxT/3w0 Zq7++dDX/yEIoqXIMdip5SDS+FPba5ybog6YbWa5XMR5YEvaKS5X6DoDeLmsy0QLaeI2YAomeAex yio4ATKAlakJNMbhOksVF2ibTuR68xIxxWa8rrCax6UsLwtZm1Yzi1Mb5zk3BZaJSqOCKr5AwFwU oow1ppGRJMUqUHwAR2yjV9BMvZTKLEPmMqvRDBXyAn8EihkltdKF6UUfjm0r06b1encueiPB9hdG RM2ijHS6q+U3tNxKKJluwiVuwsxlHttoniqXaVTNfQJl3oUj+8CVVk7/1U1NvjXjq2RgnsxNbO1v Z4/sJC6ylioNMtuqxK+rXYrCq62zTh5kAxgOgLutFSmWOuienZ5OoXf28UsfeMSBEcIJowR6ZgcV 5mgMtN99JqbmeTKu7ueFTMVS4J6+CB71/yHd/v4jfGz0bDwh3v8Pgff/a/9/2PVvy7zhe5475gCT Frjfezx2/ieTUeP/lE+YO/8z7v3/ILyXa9DSGOsKY3vafWG8uwgxX4ZZkkD4GcKMQPipglBCc1aE 6BU5wL9GHo/H4/F4PB6Px+PxeDwej8fj+Rf+AoRk6ToAKAAA
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