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From: "lmakhlis at bmc dot com" <gcc-bugzilla@gcc.gnu.org> To: gcc-bugs@gcc.gnu.org Subject: [Bug tree-optimization/28940] New: Overzealous CSE with static array access Date: Sat, 02 Sep 2006 21:14:00 -0000 [thread overview] Message-ID: <bug-28940-10833@http.gcc.gnu.org/bugzilla/> (raw) char a[10], b[10]; int f1(int i) { return a[i+1] + b[i+1]; } With -O1 and higher, gcc performs CSE on i+1: addl $1, %edi movslq %edi,%rdi movsbl a(%rdi),%eax movsbl b(%rdi),%edx addl %edx, %eax ret This doesn't happen with the equivalent return (&a[0])[i+1] + (&b[0])[i+1]; or return *(a + i + 1) + *(b + i + 1); which both compile to movslq %edi,%rdi movsbl a+1(%rdi),%eax movsbl b+1(%rdi),%edx addl %edx, %eax ret -- Summary: Overzealous CSE with static array access Product: gcc Version: 4.1.1 Status: UNCONFIRMED Severity: minor Priority: P3 Component: tree-optimization AssignedTo: unassigned at gcc dot gnu dot org ReportedBy: lmakhlis at bmc dot com GCC build triplet: x86_64-redhat-linux GCC host triplet: x86_64-redhat-linux GCC target triplet: x86_64-redhat-linux http://gcc.gnu.org/bugzilla/show_bug.cgi?id=28940
next reply other threads:[~2006-09-02 21:14 UTC|newest] Thread overview: 20+ messages / expand[flat|nested] mbox.gz Atom feed top 2006-09-02 21:14 lmakhlis at bmc dot com [this message] 2006-09-02 21:29 ` [Bug rtl-optimization/28940] [4.1/4.2 Regression] address selection does not work correctly pinskia at gcc dot gnu dot org 2006-09-07 1:16 ` mmitchel at gcc dot gnu dot org 2006-09-07 8:11 ` bonzini at gnu dot org 2006-09-07 8:15 ` bonzini at gnu dot org 2006-09-09 5:48 ` [Bug rtl-optimization/28940] [4.0/4.1/4.2 " pinskia at gcc dot gnu dot org 2006-09-09 13:02 ` bonzini at gnu dot org 2006-09-09 13:03 ` bonzini at gnu dot org 2006-10-11 12:23 ` [Bug c/28940] " rguenth at gcc dot gnu dot org 2006-10-11 12:30 ` rguenth at gcc dot gnu dot org 2006-10-11 12:47 ` bonzini at gnu dot org 2006-10-11 12:53 ` rguenth at gcc dot gnu dot org 2006-10-11 13:05 ` paolo dot bonzini at lu dot unisi dot ch 2007-01-15 20:21 ` [Bug rtl-optimization/28940] " pinskia at gcc dot gnu dot org 2007-02-14 9:19 ` mmitchel at gcc dot gnu dot org 2007-07-05 10:37 ` bonzini at gnu dot org 2007-07-05 10:43 ` ebotcazou at gcc dot gnu dot org 2007-07-05 10:46 ` paolo dot bonzini at lu dot unisi dot ch 2007-11-03 7:53 ` ebotcazou at gcc dot gnu dot org 2007-11-03 7:54 ` ebotcazou at gcc dot gnu dot org
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