Re: [RFA] Handle sh-elf-gcc scheduling code into a prologue when no debug info present

Elena Zannoni
2004-02-16T15:47:02Z

Fred Fish writes:
> For the following test case:
>
> sub1 ()
> {
> printf ("In sub1\n");
> }
>
> sub2 ()
> {
> printf ("In sub2\n");
> }
>
> main ()
> {
> sub1 ();
> sub2 ();
> }
>

Is this in our testsuite? (it looks familiar) If not could it be added?

> sh-elf-gcc with -O2 will schedule the code to call sub1 into the
> prologue of main. If the code is compiled WITHOUT debug info, the
> prologue scanner in gdb will not stop when it sees the jsr and will
> eventually return a pc somewhere after the jsr. For example:
>
> (gdb) br main
> Breakpoint 1 at 0x1162
> (gdb) x/8i main
> 0x1158 : mov.l r14,@-r15
> 0x115a <main+2>: mov.l 0x116c <main+20>,r0 ! 0x1120
> 0x115c <main+4>: sts.l pr,@-r15
> 0x115e <main+6>: jsr @r0
> 0x1160 <main+8>: mov r15,r14
> * 0x1162 <main+10>: mov.l 0x1170 <main+24>,r1 ! 0x113c
> 0x1164 <main+12>: mov r14,r15
> 0x1166 <main+14>: lds.l @r15+,pr
>
> Note that the breakpoint on main() gets set well after the jsr. When
> you set breakpoints at sub1 and sub2 and run the program, you get:
>
> (gdb) run
> Starting program: /links1/build/sourceware/gdb/T-sh-elf/gdb/g
> Breakpoint 2, 0x00001128 in sub1 ()
> (gdb) c
> Continuing.
> In sub1
> Breakpoint 1, 0x00001162 in main ()
> (gdb) c
> Continuing.
> Breakpoint 3, 0x00001144 in sub2 ()
> (gdb) c
> Continuing.
> In sub2
> Program exited with code 012.
>
> which is very confusing because it appears that sub1 is called before main!
>
> With the attached patch, the prologue scanner returns the pc of the
> jsr instruction, allowing the breakpoint at main to be hit before the
> breakpoint at sub1:
>

OK.