x86: Update memcpy/memset inline strategies for Ice Lake
Simply memcpy and memset inline strategies to avoid branches for
-mtune=icelake:
1. With MOVE_RATIO and CLEAR_RATIO == 17, GCC will use integer/vector
load and store for up to 16 * 16 (256) bytes when the data size is
fixed and known.
2. Inline only if data size is known to be <= 256.
a. Use "rep movsb/stosb" with simple code sequence if the data size
is a constant.
b. Use loop if data size is not a constant.
3. Use memcpy/memset libray function if data size is unknown or > 256.
On Ice Lake processor with -march=native -Ofast -flto,
* config/i386/i386-expand.c (expand_set_or_cpymem_via_rep):
For TARGET_PREFER_KNOWN_REP_MOVSB_STOSB, don't convert QImode
to SImode.
(decide_alg): For TARGET_PREFER_KNOWN_REP_MOVSB_STOSB, use
"rep movsb/stosb" only for known sizes.
* config/i386/i386-options.c (processor_cost_table): Use Ice
Lake cost for Cannon Lake, Ice Lake, Tiger Lake, Sapphire
Rapids and Alder Lake.
* config/i386/i386.h (TARGET_PREFER_KNOWN_REP_MOVSB_STOSB): New.
* config/i386/x86-tune-costs.h (icelake_memcpy): New.
(icelake_memset): Likewise.
(icelake_cost): Likewise.
* config/i386/x86-tune.def (X86_TUNE_PREFER_KNOWN_REP_MOVSB_STOSB):
New.