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.

4 files changed, 23 insertions, 7 deletions

diff --git a/gcc/config/bpf/bpf-opts.h b/gcc/config/bpf/bpf-opts.h
index 92db01e..e0be591 100644
--- a/gcc/config/bpf/bpf-opts.h
+++ b/gcc/config/bpf/bpf-opts.h
@@ -58,6 +58,7 @@ enum bpf_isa_version
   ISA_V1,
   ISA_V2,
   ISA_V3,
+  ISA_V4
 };
 
 enum bpf_asm_dialect
diff --git a/gcc/config/bpf/bpf.cc b/gcc/config/bpf/bpf.cc
index 1d39368..6bc7154 100644
--- a/gcc/config/bpf/bpf.cc
+++ b/gcc/config/bpf/bpf.cc
@@ -253,6 +253,9 @@ bpf_option_override (void)
   if (bpf_has_jmp32 == -1)
     bpf_has_jmp32 = (bpf_isa >= ISA_V3);
 
+  if (bpf_has_bswap == -1)
+    bpf_has_bswap = (bpf_isa >= ISA_V4);
+
   /* Disable -fstack-protector as it is not supported in BPF.  */
   if (flag_stack_protect)
     {
diff --git a/gcc/config/bpf/bpf.md b/gcc/config/bpf/bpf.md
index 80220f2..81e2268 100644
--- a/gcc/config/bpf/bpf.md
+++ b/gcc/config/bpf/bpf.md
@@ -60,7 +60,7 @@
 ;; Instruction classes.
 ;; alu		64-bit arithmetic.
 ;; alu32	32-bit arithmetic.
-;; end		endianness conversion instructions.
+;; end		endianness conversion or byte swap instructions.
 ;; ld		load instructions.
 ;; lddx		load 64-bit immediate instruction.
 ;; ldx		generic load instructions.
@@ -354,20 +354,25 @@
   "{rsh<msuffix>\t%0,%2|%w0 >>= %w2}"
   [(set_attr "type" "<mtype>")])
 
-;;;; Endianness conversion
+;;;; Byte swapping
 
 (define_mode_iterator BSM [HI SI DI])
 (define_mode_attr endmode [(HI "16") (SI "32") (DI "64")])
 
 (define_insn "bswap<BSM:mode>2"
   [(set (match_operand:BSM 0 "register_operand"            "=r")
-        (bswap:BSM (match_operand:BSM 1 "register_operand" " r")))]
+        (bswap:BSM (match_operand:BSM 1 "register_operand" " 0")))]
   ""
 {
-  if (TARGET_BIG_ENDIAN)
-    return "{endle\t%0, <endmode>|%0 = le<endmode> %0}";
+  if (bpf_has_bswap)
+    return "{bswap\t%0, <endmode>|%0 = bswap<endmode> %1}";
   else
-    return "{endbe\t%0, <endmode>|%0 = be<endmode> %0}";
+    {
+      if (TARGET_BIG_ENDIAN)
+        return "{endle\t%0, <endmode>|%0 = le<endmode> %1}";
+      else
+        return "{endbe\t%0, <endmode>|%0 = be<endmode> %1}";
+    }
 }
   [(set_attr "type" "end")])
 
diff --git a/gcc/config/bpf/bpf.opt b/gcc/config/bpf/bpf.opt
index ff805f9..1e4dcc8 100644
--- a/gcc/config/bpf/bpf.opt
+++ b/gcc/config/bpf/bpf.opt
@@ -146,8 +146,12 @@ mjmp32
 Target Var(bpf_has_jmp32) Init(-1)
 Enable 32-bit jump instructions.
 
+mbswap
+Target Var(bpf_has_bswap) Init(-1)
+Enable byte swap instructions.
+
 mcpu=
-Target RejectNegative Joined Var(bpf_isa) Enum(bpf_isa) Init(ISA_V3)
+Target RejectNegative Joined Var(bpf_isa) Enum(bpf_isa) Init(ISA_V4)
 
 Enum
 Name(bpf_isa) Type(enum bpf_isa_version)
@@ -161,6 +165,9 @@ Enum(bpf_isa) String(v2) Value(ISA_V2)
 EnumValue
 Enum(bpf_isa) String(v3) Value(ISA_V3)
 
+EnumValue
+Enum(bpf_isa) String(v4) Value(ISA_V4)
+
 masm=
 Target RejectNegative Joined Var(asm_dialect) Enum(asm_dialect) Init(ASM_NORMAL)
 Use given assembler dialect.