Bad generation of jmp r/m32 with offset

[Joseph Kain <joseph at 3dfx dot com>]

Title: Bad generation of jmp r/m32 with offset

gcc version 2.95.2 19991024 (release)
RedHat 6.1 Linux 2.2.12 Pentium III
Built like this
        gcc -v --save-temps -o jump jump.c proc.S 2> output    

The output from the above is included in plain text below.  Attached
are jump.c and proc.S, and jump.i.  This a small sample program that
causes the bug. 

Here is a description of the bug.  gcc 2.95.2 produces the wrong asm for
the dispatch function.  The dispatch function looks like this:
        void
        dispatch (int *i)
        {      
          /* Pop frame pointer */
          asm ( "pop %ebp");
          asm ( "jmp %0"
                : /* no outputs */
                : "m" (info.context->procs.test)
                );
        }

The generated asm looks like this:
        .globl dispatch
                .type    dispatch,@function
        dispatch:
                pushl %ebp
                movl %esp,%ebp
        #APP
                pop %ebp
        #NO_APP
                movl info+4,%eax
        #APP
                jmp 4(%eax)
        #NO_APP
        .L2:
                leave
                ret
        .Lfe1:

With GNU as version 2.9.1 (BFD 2.9.1.0.24) the following warning is issued for
the jump instruction.
        Warning: warning: missing prefix `*' in absolute indirect address,
        maybe misassembled!
However it correctly assembles the jump as
        FF6004  (JMP r/m32)

GNU as version 2.9.5 (BFD 2.9.5.0.22) issues no warning but instead assembles
the jump incorectly as:
        FF6804  (JMP FAR mem)

Although it is the behavior of the assembler that has changed I
believe this is a bug in gcc as it is emiting the wrong assembly.  If the
jump instruction is changed from
                jmp 4(%eax)
to
                jmp *4(%eax)

Then no warning is issued from as 2.9.1 and both assemblers generate
the correct binary code.

Joseph Kain

gcc version/invocation information follows:

cat output
Reading specs from /usr/lib/gcc-lib/i386-redhat-linux/2.95.2/specs
gcc version 2.95.2 19991024 (release)
 /usr/lib/gcc-lib/i386-redhat-linux/2.95.2/cpp -lang-c -v -D__GNUC__=2 -D__GNUC_MINOR__=95 -D__ELF__ -Dunix -D__i386__ -Dlinux -D__ELF__ -D__unix__ -D__i386__ -D__linux__ -D__unix -D__linux -Asystem(posix) -Acpu(i386) -Amachine(i386) -Di386 -D__i386 -D__i386__ jump.c jump.i

GNU CPP version 2.95.2 19991024 (release) (i386 Linux/ELF)
#include "..." search starts here:
#include <...> search starts here:
 /usr/local/include
 /usr/lib/gcc-lib/i386-redhat-linux/2.95.2/include
 /usr/include
End of search list.
The following default directories have been omitted from the search path:
 /usr/lib/gcc-lib/i386-redhat-linux/2.95.2/../../../../include/g++-3
 /usr/lib/gcc-lib/i386-redhat-linux/2.95.2/../../../../i386-redhat-linux/includeEnd of omitted list.
 /usr/lib/gcc-lib/i386-redhat-linux/2.95.2/cc1 jump.i -quiet -dumpbase jump.c -version -o jump.s
GNU C version 2.95.2 19991024 (release) (i386-redhat-linux) compiled by GNU C version 2.95.2 19991024 (release).
 as -V -Qy -o jump.o jump.s
GNU assembler version 2.9.5 (i386-redhat-linux) using BFD version 2.9.5.0.22
 /usr/lib/gcc-lib/i386-redhat-linux/2.95.2/cpp -lang-asm -v -$ -D__ELF__ -Dunix -D__i386__ -Dlinux -D__ELF__ -D__unix__ -D__i386__ -D__linux__ -D__unix -D__linux -Asystem(posix) -D__ASSEMBLER__ -Acpu(i386) -Amachine(i386) -Di386 -D__i386 -D__i386__ proc.S proc.s

GNU CPP version 2.95.2 19991024 (release) (i386 Linux/ELF)
#include "..." search starts here:
#include <...> search starts here:
 /usr/local/include
 /usr/lib/gcc-lib/i386-redhat-linux/2.95.2/include
 /usr/include
End of search list.
The following default directories have been omitted from the search path:
 /usr/lib/gcc-lib/i386-redhat-linux/2.95.2/../../../../include/g++-3
 /usr/lib/gcc-lib/i386-redhat-linux/2.95.2/../../../../i386-redhat-linux/includeEnd of omitted list.
 as -V -Qy -o proc.o proc.s
GNU assembler version 2.9.5 (i386-redhat-linux) using BFD version 2.9.5.0.22
 /usr/lib/gcc-lib/i386-redhat-linux/2.95.2/collect2 -m elf_i386 -dynamic-linker /lib/ld-linux.so.2 -o jump /usr/lib/crt1.o /usr/lib/crti.o /usr/lib/gcc-lib/i386-redhat-linux/2.95.2/crtbegin.o -L/usr/lib/gcc-lib/i386-redhat-linux/2.95.2 jump.o proc.o -lgcc -lc -lgcc /usr/lib/gcc-lib/i386-redhat-linux/2.95.2/crtend.o /usr/lib/crtn.o

<<bugreport.tar.bz2>>

bugreport.tar.bz2