Hi Kyrill, the patched gcc generates correct asm for me for the test
case. (I'll then build the whole system to see if other it-block
related bugs are gone too.)
One short question, the newly generated RTL for
x = x | <cond> (a)
will be
orr %0, %1, #1; it <cond>; mov%D2\\t%0, %1 (b)
The cond in (a) should be the reverse of cond in(b), right?
Thanks for your quick fix.
Han
On Thu, Jan 21, 2016 at 9:51 AM, Kyrill Tkachov
<kyrylo.tkac...@foss.arm.com> wrote:
> Hi all,
>
> In this wrong-code PR the pattern for performing
> x = x | <cond> for -mrestrict-it is buggy and ends up writing 1 to the
> result register rather than orring it.
>
> The offending pattern is *thumb2_ior_scc_strict_it.
> My proposed solution is to rewrite it as a splitter, remove the
> alternative for the case where operands[1] and 0 are the same reg
> that emits the bogus:
> it <cond>; mov<cond>%0, #1; it <cond>; orr<cond> %0, %1
>
> to emit the RTL equivalent to:
> orr %0, %1, #1; it <cond>; mov%D2\\t%0, %1
> while marking operand 0 as an earlyclobber operand so that it doesn't
> get assigned the same register as operand 1.
>
> This way we avoid the wrong-code, make the sequence better (by eliminating
> the move of #1 into a register
> and relaxing the constraints from 'l' to 'r' since only the register move
> has to be conditional).
> and still stay within the rules for arm_restrict_it.
>
> Bootstrapped and tested on arm-none-linux-gnueabihf configured
> --with-arch=armv8-a and --with-mode=thumb.
>
> Ok for trunk, GCC 5 and 4.9?
>
> Han, can you please try this out to see if it solves the problem on your end
> as well?
>
> Thanks,
> Kyrill
>
> 2016-01-21 Kyrylo Tkachov <kyrylo.tkac...@arm.com>
>
> PR target/69403
> * config/arm/thumb2.md (*thumb2_ior_scc_strict_it): Convert to
> define_insn_and_split. Ensure operands[1] and operands[0] do not
> get assigned the same register.
>
> 2016-01-21 Kyrylo Tkachov <kyrylo.tkac...@arm.com>
>
> PR target/69403
> * gcc.c-torture/execute/pr69403.c: New test.
--
Han Shen | Software Engineer | shen...@google.com | +1-650-440-3330
