Re: [PATCH] tree-optimization/111294 - backwards threader PHI costing

[Jeff Law <jeffreyalaw@gmail.com>]

On 9/14/23 07:23, Richard Biener via Gcc-patches wrote:
> This revives an earlier patch since the problematic code applying
> extra costs to PHIs in copied blocks we couldn't make any sense of
> prevents a required threading in this case.  Instead of coming up
> with an artificial other costing the following simply removes the
> bits.
> 
> As with all threading changes this requires a plethora of testsuite
> adjustments, but only the last three are unfortunate as is the
> libgomp team.c adjustment which is required to avoid a bogus -Werror
> diagnostic during bootstrap.
> 
> Bootstrapped and tested on x86_64-unknown-linux-gnu.
> 
> Any objections?
> 
> Thanks,
> Richard.
> 
> 	PR tree-optimization/111294
> gcc/
> 	* tree-ssa-threadbackward.cc (back_threader_profitability::m_name):
> 	Remove
> 	(back_threader::find_paths_to_names): Adjust.
> 	(back_threader::maybe_thread_block): Likewise.
> 	(back_threader_profitability::possibly_profitable_path_p): Remove
> 	code applying extra costs to copies PHIs.
> 
> libgomp/
> 	* team.c (gomp_team_start): Guard gomp_alloca to avoid false
> 	positive alloc-size diagnostic.
> 
> gcc/testsuite/
> 	* gcc.dg/tree-ssa/pr111294.c: New test.
> 	* gcc.dg/tree-ssa/phi_on_compare-4.c: Adjust.
> 	* gcc.dg/tree-ssa/pr59597.c: Likewise.
> 	* gcc.dg/tree-ssa/pr61839_2.c: Likewise.
> 	* gcc.dg/tree-ssa/ssa-sink-18.c: Likewise.
> 	* g++.dg/warn/Wstringop-overflow-4.C: XFAIL subtest on ilp32.
> 	* gcc.dg/uninit-pred-9_b.c: XFAIL subtest everywhere.
> 	* gcc.dg/vect/vect-117.c: Make scan for not Invalid sum
> 	conditional on lp64.
No objections. IIRC this was all to deal with a code explosion problem 
seen on sparc.  As long as tree-ssa/pr69196-1.c hasn't gone crazy we're OK.

jeff