> I was fiddling around with the loop unrolling pass and noticed a check 
> in decide_unroll_* functions (in the patch). The comment on top of this 
> check says
> "/* If we were not asked to unroll this loop, just return back silently. 
>   */"
> However the check returns when loop->unroll == 0 rather than 1.
> The check was added in r255106 where the ChangeLog suggests that the 
> actual intention was probably to check the value 1 and not 0.

No, this is intended, 0 is the default value of the field, not 1.  And note 
that decide_unroll_constant_iterations, decide_unroll_runtime_iterations and 
decide_unroll_stupid *cannot* be called with loop->unroll == 1 because of this 
check in decide_unrolling:

      if (loop->unroll == 1)
          if (dump_file)
            fprintf (dump_file,
                     ";; Not unrolling loop, user didn't want it unrolled\n");

> Tested on aarch64-none-elf with one new regression:
> FAIL: gcc.dg/pr40209.c (test for excess errors)
> This fails because the changes cause the loop to unroll 3 times using 
> unroll_stupid and that shows up as excess error due -fopt-info. This 
> option was added in r202077 but I am not sure why this particular test 
> was chosen for it.

That's a regression, there should be no unrolling.

Eric Botcazou

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