[x86 PATCH] Avoid andn and generate shorter not;and with -Oz.

[Roger Sayle]

The x86 instruction encoding for SImode andn is longer than the
equivalent notl/andl sequence when the source for the not operand
is the same register as the destination.  This patch adds post_reload
splitters to i386.md to avoid "-mbmi" (which enables andn) increasing
code size with "-Oz".

One minor subtlety with this patch is that the splitter for
*andn_si_ccno swaps the order of operands (match_dup 2 and match_dup 3)
as memory operands need to appear first in the *test<mode>_1 patterns.

This patch has been tested on x86_64-pc-linux-gnu with make bootstrap
and make -k check, both with and without --target_board=unix{-m32},
with no new failures [and like the previous patch on CSiBE].
Ok for mainline?


2022-04-13  Roger Sayle  <roger@nextmovesoftware.com>

gcc/ChangeLog
	* config/i386/i386.md (define_split):  Split *andsi_1 and
	*andn_si_ccno after reload with -Oz.

gcc/testsuite/ChangeLog
	* gcc.target/i386/bmi-and-3.c: New test case.


Thanks in advance,
Roger
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