Re: [PATCH] On x86 allow if-conversion of more than one insn as long as there is at most one cmov (PR tree-optimization/79390)

[Jeff Law <law@redhat.com>]

On 04/01/2017 06:20 AM, Jakub Jelinek wrote:
> Hi!
>
> As discussed in the PR, in the following testcase we don't if-convert
> with the generic (and many other) tuning, because we default to
> --param max-rtl-if-conversion-insns=1 in most of the tunings.
> The problem we have is with multiple cmov instructions, but in the
> testcase there is just one cmov and the other insn is turned into a SSE
> max insn, which is fine.
>
> This patch stops artificially lowering that param, and for one_if_conv_insn
> tuning it instead rejects the if-conversion if the resulting sequence has
> multiple cmov instructions.  The hook is passed if_info too, so it can
> in the future do better heuristics based on predictability of the edges,
> how far the uses of the cmov result are (I assume cmov major problem is
> latency, right?) etc.
>
> Bootstrapped/regtested on x86_64-linux and i686-linux, ok for trunk?
>
> 2017-04-01  Jakub Jelinek  <jakub@redhat.com>
>
> 	PR tree-optimization/79390
> 	* target.h (struct noce_if_info): Declare.
> 	* targhooks.h (default_noce_conversion_profitable_p): Declare.
> 	* target.def (noce_conversion_profitable_p): New target hook.
> 	* ifcvt.h (struct noce_if_info): New type, moved from ...
> 	* ifcvt.c (struct noce_if_info): ... here.
> 	(noce_conversion_profitable_p): Renamed to ...
> 	(default_noce_conversion_profitable_p): ... this.  No longer
> 	static nor inline.
> 	(noce_try_store_flag_constants, noce_try_addcc,
> 	noce_try_store_flag_mask, noce_try_cmove, noce_try_cmove_arith,
> 	noce_convert_multiple_sets): Use targetm.noce_conversion_profitable_p
> 	instead of noce_conversion_profitable_p.
> 	* config/i386/i386.c: Include ifcvt.h.
> 	(ix86_option_override_internal): Don't override
> 	PARAM_MAX_RTL_IF_CONVERSION_INSNS default.
> 	(ix86_noce_conversion_profitable_p): New function.
> 	(TARGET_NOCE_CONVERSION_PROFITABLE_P): Redefine.
> 	* config/i386/x86-tune.def (X86_TUNE_ONE_IF_CONV_INSN): Adjust comment.
> 	* doc/tm.texi.in (TARGET_NOCE_CONVERSION_PROFITABLE_P): Add.
> 	* doc/tm.texi: Regenerated.
>
> 	* gcc.target/i386/pr79390.c: New test.
> 	* gcc.dg/ifcvt-4.c: Use -mtune-ctrl=^one_if_conv_insn for i?86/x86_64.
OK.
jeff