Re: optimization/4085: PPC -fPIC code generation problem

Re: optimization/4085: PPC -fPIC code generation problem

[dje]

Synopsis: PPC -fPIC code generation problem

Responsible-Changed-From-To: unassigned->dje
Responsible-Changed-By: dje
Responsible-Changed-When: Fri Dec 28 10:37:12 2001
Responsible-Changed-Why:
    PowerPC codegen
State-Changed-From-To: open->closed
State-Changed-By: dje
State-Changed-When: Fri Dec 28 10:37:12 2001
State-Changed-Why:
    I believe this bug is fixed.  If it is not, please re-open
    a PR and let me know.

http://gcc.gnu.org/cgi-bin/gnatsweb.pl?cmd=view%20audit-trail&database=gcc&pr=4085

optimization/4085: PPC -fPIC code generation problem

[green]

>Number:         4085
>Category:       optimization
>Synopsis:       PPC -fPIC code generation problem
>Confidential:   no
>Severity:       serious
>Priority:       medium
>Responsible:    unassigned
>State:          open
>Class:          wrong-code
>Submitter-Id:   net
>Arrival-Date:   Wed Aug 22 14:46:01 PDT 2001
>Closed-Date:
>Last-Modified:
>Originator:     
>Release:        3.1 20010811 (experimental)
>Organization:
>Environment:
System: Linux peach.cygnus.co.uk 2.2.17pre20-ben3 #2 Wed Sep 6 01:14:01 CEST 2000 ppc unknown
Architecture: ppc

	
host: powerpc-unknown-linux-gnu
build: powerpc-unknown-linux-gnu
target: powerpc-unknown-linux-gnu
configured with: /peach/green/net/trunk/gcc/configure --prefix=/peach/green/net/trunk/i --enable-threads --enable-language=c,c++,java --enable-languages=c,c++,java --disable-multilibs --disable-multilib : (reconfigured)  : (reconfigured)  : (reconfigured)  : (reconfigured) 
>Description:
The following (admittedly bogus) code does not link on ppc Linux.
$ gcc -O2 -fPIC -o ppcbug ppcbug.c
/tmp/ccCbVD67.o(.rodata+0x10): undefined reference to `.L23'
/tmp/ccCbVD67.o(.rodata+0x14): undefined reference to `.L23'
/tmp/ccCbVD67.o(.rodata+0x18): undefined reference to `.L23'
/tmp/ccCbVD67.o(.rodata+0x1c): undefined reference to `.L23'
/tmp/ccCbVD67.o(.rodata+0x20): undefined reference to `.L22'
collect2: ld returned 1 exit status

It looks like gcc is creating a jump table for the switch.  It's
realizing that it can optimize away all cases except for default, but
references to the deleted code are left arount in the jump table.

#include <stdio.h>

int main (int argc, char *argv[])
{
  char *foo; 
  switch (argc) 
    {
    case 1:
      foo = "one";
    case 2:
      foo = "two";
    case 3:
      foo = "three";
    case 4:
      foo = "four";
    case 5:
      foo = "five";
    default:
      foo = "default";
    }
  puts (foo);
  return 0;
}


>How-To-Repeat:
	Try compiling the code above with "-O2 -fPIC".
>Fix:
	
>Release-Note:
>Audit-Trail:
>Unformatted: