[Bug tree-optimization/116166] risc-v (last) insn-emit-nn.c build takes hours

[rguenth at gcc dot gnu.org via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=116166

--- Comment #17 from Richard Biener <rguenth at gcc dot gnu.org> ---
(In reply to Richard Biener from comment #16)
> So with --param logical-op-non-short-circuit=1 (and my patch) the
> insn-emit-96.cc testcase as attached compiles in 100s and
> 
>  dominator optimization             :   5.62 (  6%)   0.05 (  1%)   5.56 ( 
> 5%)  3015k (  0%)
>  backwards jump threading           :  27.60 ( 27%)   0.02 (  0%)  27.63 (
> 26%)  6783k (  1%)
> 
> The reproducing run with unpatched tree still runs since 27 minutes,
> the patched tree still runs since 12 minutes.

My unpatched reproducing run finished in 2623s:

 dominator optimization             :2537.62 ( 97%)   0.16 (  4%)2538.50 ( 97%)
   17M (  3%)
 backwards jump threading           :  34.21 (  1%)   0.13 (  3%)  34.39 (  1%)
   39M (  6%)

and the patched finished in 2599s, not much of an improvement:

 dominator optimization             :2514.61 ( 97%)   0.13 (  3%)2515.28 ( 97%)
   17M (  3%)
 backwards jump threading           :  33.05 (  1%)   0.08 (  2%)  33.18 (  1%)
   39M (  6%)


Note the testcase can be reduced to maybe_code_for_pred_indexed_load which
takes 10 minutes to compile.