[Bug optimization/11832] New: Optimization of common code in switch statements

[Bug optimization/11832] New: Optimization of common code in switch statements

[alga at rgai dot hu]

PLEASE REPLY TO gcc-bugzilla@gcc.gnu.org ONLY, *NOT* gcc-bugs@gcc.gnu.org.

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=11832

           Summary: Optimization of common code in switch statements
           Product: gcc
           Version: 3.4
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: optimization
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: alga at rgai dot hu
                CC: gcc-bugs at gcc dot gnu dot org
 GCC build triplet: i686-pc-linux-gnu
  GCC host triplet: i686-pc-linux-gnu
GCC target triplet: arm-unknown-elf

If a C switch statement contains common code among certain case branches,
GCC isn't able to combine the common code.
Reorganization of the switch may solve this problem.

--- c example ---
int a, b, e;
unsigned char *c;
void foo()
{
  int d = 13;
  b = -1;   
  switch (e) {
    case 1:
      b++; c[b] = (unsigned char)d;
      break;
    case 2:
      b++; c[b] = (unsigned char)d;
      b++; c[b] = (unsigned char)d;
      break;
    case 3:
      b++; c[b] = (unsigned char)d;
      b++; c[b] = (unsigned char)d;
      b++; c[b] = (unsigned char)d;
      break;
    default:
      a = 1;
      b++; c[b] = (unsigned char)d;
      b++; c[b] = (unsigned char)d;
      b++; c[b] = (unsigned char)d;
      b++; c[b] = (unsigned char)d;
  }
}

--- arm code ---
foo:
 stmfd sp!, {r4, lr}
 ldr r3, .L10
 ldr r2, [r3, #0]
 ldr lr, .L10+4
 mvn r3, #0
 cmp r2, #2
 str r3, [lr, #0]
 mov r4, #13
 beq .L4
 bgt .L7
 cmp r2, #1
 beq .L3
 b .L6
.L7:
 cmp r2, #3
 beq .L5
 b .L6
.L3:
 ldr r3, .L10+8
 ldr r2, [r3, #0]
 mov r3, #0
 str r3, [lr, #0]
 strb r4, [r2, #0]
 ldmfd sp!, {r4, pc}
.L4:
 ldr r1, .L10+8
 ldr r2, [r1, #0]
 mov r3, #0
 str r3, [lr, #0]
 strb r4, [r2, #0]
 ldr r3, [lr, #0]
 ldr r2, [r1, #0]
 b .L8
.L5:
 ldr r2, .L10+8
 ldr r1, [r2, #0]
 mov r3, #0
 str r3, [lr, #0]
 strb r4, [r1, #0]
 ldr r3, [lr, #0]
 ldr r1, [r2, #0]
 add r3, r3, #1
 str r3, [lr, #0]
 strb r4, [r1, r3]
 ldr r3, [lr, #0]
 ldr r2, [r2, #0]
.L8:
 add r3, r3, #1
.L9:
 str r3, [lr, #0]
 strb r4, [r2, r3]
 ldmfd sp!, {r4, pc}
.L6:
 ldr r0, .L10+8
 ldr r2, [lr, #0]
 ldr ip, [r0, #0]
 ldr r3, .L10+12
 mov r1, #1
 add r2, r2, #1
 str r2, [lr, #0]
 str r1, [r3, #0]
 strb r4, [ip, r2]
 ldr r3, [lr, #0]
 ldr r2, [r0, #0]
 add r3, r3, r1
 str r3, [lr, #0]
 strb r4, [r2, r3]
 ldr r3, [lr, #0]
 ldr r2, [r0, #0]
 add r3, r3, r1
 str r3, [lr, #0]
 strb r4, [r2, r3]
 ldr r3, [lr, #0]
 ldr r2, [r0, #0]
 add r3, r3, r1
 b .L9

[Bug optimization/11832] Optimization of common code in switch statements

[pinskia at physics dot uc dot edu]

PLEASE REPLY TO gcc-bugzilla@gcc.gnu.org ONLY, *NOT* gcc-bugs@gcc.gnu.org.

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=11832


pinskia at physics dot uc dot edu changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Severity|normal                      |enhancement
             Status|UNCONFIRMED                 |NEW
     Ever Confirmed|                            |1
           Keywords|                            |pessimizes-code
   Last reconfirmed|0000-00-00 00:00:00         |2003-08-06 12:50:48
               date|                            |


------- Additional Comments From pinskia at physics dot uc dot edu  2003-08-06 12:50 -------
I can confirm this on htem mainline (20030806).

[Bug optimization/11832] Optimization of common code in switch statements

[dhazeghi at yahoo dot com]

PLEASE REPLY TO gcc-bugzilla@gcc.gnu.org ONLY, *NOT* gcc-bugs@gcc.gnu.org.

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=11832


dhazeghi at yahoo dot com changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
  GCC build triplet|i686-pc-linux-gnu           |
   GCC host triplet|i686-pc-linux-gnu           |
   Target Milestone|3.4                         |---