bpf: make use of the bswap{16,32,64} V4 BPF instruction

This patch makes the BPF backend to use the new V4 bswap{16,32,64}
instructions in order to implement the __builtin_bswap{16,32,64}
built-ins.  It also adds support for -mcpu=v4 and -m[no]bswap
command-line options.  Tests and doc updates are includes.

Tested in bpf-unknown-none.

gcc/ChangeLog

	PR target/110786
	* config/bpf/bpf.opt (mcpu): Add ISA_V4 and make it the default.
	(mbswap): New option.
	* config/bpf/bpf-opts.h (enum bpf_isa_version): New value ISA_V4.
	* config/bpf/bpf.cc (bpf_option_override): Set bpf_has_bswap.
	* config/bpf/bpf.md: Use bswap instructions if available for
	bswap* insn, and fix constraint.
	* doc/invoke.texi (eBPF Options): Document -mcpu=v4 and -mbswap.

gcc/testsuite/ChangeLog

	PR target/110786
	* gcc.target/bpf/bswap-1.c: Pass -mcpu=v3 to build test.
	* gcc.target/bpf/bswap-2.c: New test.

1 files changed, 10 insertions, 1 deletions

diff --git a/gcc/doc/invoke.texi b/gcc/doc/invoke.texi
index efd356e..a977a34 100644
--- a/gcc/doc/invoke.texi
+++ b/gcc/doc/invoke.texi
@@ -24707,10 +24707,14 @@ Enable 32-bit jump instructions. Enabled for CPU v3 and above.
 @item -malu32
 Enable 32-bit ALU instructions. Enabled for CPU v3 and above.
 
+@opindex mbswap
+@item -mbswap
+Enable byte swap instructions.  Enabled for CPU v4 and above.
+
 @opindex mcpu
 @item -mcpu=@var{version}
 This specifies which version of the eBPF ISA to target. Newer versions
-may not be supported by all kernels. The default is @samp{v3}.
+may not be supported by all kernels. The default is @samp{v4}.
 
 Supported values for @var{version} are:
 
@@ -24728,6 +24732,11 @@ All features of v2, plus:
 @item 32-bit ALU operations, as in @option{-malu32}
 @end itemize
 
+@item v4
+All features of v3, plus:
+@itemize @minus
+@item Byte swap instructions, as in @option{-mbswap}
+@end itemize
 @end table
 
 @opindex mco-re