On Fri, 2021-04-09 at 17:09 -0400, Michael Meissner wrote:
> Fix logic error in 32-bit trampolines, PR target/98952.
>
> The test in the PowerPC 32-bit trampoline support is backwards. It aborts
> if the trampoline size is greater than the expected size. It should abort
> when the trampoline size is less than the expected size.
>
> I verified this by creating a 32-bit trampoline program and manually
> changing the size of the trampoline to be 48 instead of 40. The program
> aborted with the larger size. I updated this code and ran the test again
> and it passed.
>
> I did a bootstrap build on a big endian power8 system that supports both
> 32-bit and 64-bit executables, and there were no regressions. Can I check
> this patch into the trunk?
>
> libgcc/
> 2021-04-09 Michael Meissner <meiss...@linux.ibm.com>
>
> PR target/98952
> * config/rs6000/tramp.S (__trampoline_setup): Fix trampoline size
> comparison in 32-bit.
> ---
> libgcc/config/rs6000/tramp.S | 3 +--
> 1 file changed, 1 insertion(+), 2 deletions(-)
>
> diff --git a/libgcc/config/rs6000/tramp.S b/libgcc/config/rs6000/tramp.S
> index 4236a82b402..6b61d892da6 100644
> --- a/libgcc/config/rs6000/tramp.S
> +++ b/libgcc/config/rs6000/tramp.S
> @@ -64,8 +64,7 @@ FUNC_START(__trampoline_setup)
> mflr r11
> addi r7,r11,trampoline_initial-4-.LCF0 /* trampoline address -4 */
>
> - li r8,trampoline_size /* verify that the trampoline is big
> enough */
> - cmpw cr1,r8,r4
> + cmpwi cr1,r4,trampoline_size /* verify that the trampoline is big
> enough */
Hmm, I spent several minutes trying to determine how cmpw behaves
differently than cmpwi before noticing you also swapped the
order of the r4,r8 operands.
That seems OK.
A statement in the description indicating that you used a cmpwi instead
of a cmpw since you were in the neighborhood would help call that out.
The #elif _CALL_ELF == 2 portion of tramp.S (line 159 or so) has a
similar compare stanza with respect to the order of operands on the
compare. Will this also have a backwards greater-than less-than issue?
li r8,trampoline_size /* verify that the trampoline is big
enough */
cmpw cr1,r8,r4
srwi r4,r4,3 /* # doublewords to move */
addi r9,r3,-8 /* adjust pointer for stdu */
mtctr r4
blt cr1,.Labort
thanks
-Will
> srwi r4,r4,2 /* # words to move */
> addi r9,r3,-4 /* adjust pointer for lwzu */
> mtctr r4
> --
> 2.22.0
>
>
