Daniel Jacobowitz wrote:
>
> On Wed, Aug 15, 2001 at 09:53:20AM +1000, Simon Gee wrote:
> > >
> > > .set noreorder
> > > .set noat
> > > move $1,$31 # save current return address
> > > jal _mcount
> > > subu $sp,$sp,8 # _mcount pops 2 words from stack
> > > .set reorder
> > > .set at
> > >
> >
> > Given this assembler sequence, which is produced by:
> >
> > /* Output assembler code to FILE to increment profiler label # LABELNO
> > for profiling a function entry. */
> >
> > #define FUNCTION_PROFILER(FILE, LABELNO) \
> > { \
> > if (TARGET_MIPS16) \
> > sorry ("mips16 function profiling"); \
> > fprintf (FILE, "\t.set\tnoreorder\n"); \
> > fprintf (FILE, "\t.set\tnoat\n"); \
> > fprintf (FILE, "\tmove\t%s,%s\t\t# save current return address\n", \
> > reg_names[GP_REG_FIRST + 1], reg_names[GP_REG_FIRST + 31]); \
> > fprintf (FILE, "\tjal\t_mcount\n"); \
> > fprintf (FILE, \
> > "\t%s\t%s,%s,%d\t\t# _mcount pops 2 words from stack\n", \
> > TARGET_64BIT ? "dsubu" : "subu", \
> > reg_names[STACK_POINTER_REGNUM], \
> > reg_names[STACK_POINTER_REGNUM], \
> > Pmode == DImode ? 16 : 8); \
> > fprintf (FILE, "\t.set\treorder\n"); \
> > fprintf (FILE, "\t.set\tat\n"); \
> > }
> >
> > in mips.h, wouldn't the positioning of "subu $sp,$sp,8" imply that it was
> > intended to be within "jal"'s delay slot (the expansion of jal is really
> > annoying!) ? This being the case, the stack adjustment may have had to have
> > been made before the call to _mcount is made.
>
> *sigh* Yes, I think the adjustment was meant to be made before the
> call. Perhaps binutils should warn about things in the "delay slot" of a
> macro?
>
It is a reasonable warning if we are in "noreorder" state. Programmers tend
to make assumptions about the delay slot after they do "set .noreorder".
Jun
