[PATCH] nvptx: Add support for PTX's cnot instruction.

[Roger Sayle]

Happy New Year for 2022.  This is a simple patch, now that the
nvptx backend has transitioned to STORE_FLAG_VALUE=1, that adds
support for NVidia's cnot instruction, that implements C/C++
style logical negation.

Previously, the simple function:

int foo(int x) { return !x; }

on nvptx-none with -O2 would generate:

        mov.u32 %r24, %ar0;
        setp.eq.u32     %r28, %r24, 0;
        selp.u32        %value, 1, 0, %r28;

with this patch, GCC now generates:

        mov.u32 %r24, %ar0;
        cnot.b32        %value, %r24;


This patch has been tested on nvptx-none hosted on x86_64-pc-linux-gnu
(including newlib) with a make and make -k check with no new failures.
Ok for mainline?


2022-01-06  Roger Sayle  <roger@nextmovesoftware.com>

gcc/ChangeLog
	* config/nvptx/nvptx.md (*cnot<mode>2): New define_insn.

gcc/testsuite/ChangeLog
	* gcc.target/nvptx/cnot-1.c: New test case.


Thanks in advance,
Roger
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