cmd/compile: wire up Bswap/ReverseBytes intrinsics for loong64

Micro-benchmark results on Loongson 3A5000 and 3A6000:

goos: linux
goarch: loong64
pkg: math/bits
cpu: Loongson-3A6000 @ 2500.00MHz
               |  bench.old   |              bench.new               |
               |    sec/op    |    sec/op     vs base                |
ReverseBytes     2.0020n ± 0%   0.4040n ± 0%  -79.82% (p=0.000 n=20)
ReverseBytes16   0.8866n ± 1%   0.8007n ± 0%   -9.69% (p=0.000 n=20)
ReverseBytes32   1.2195n ± 0%   0.8007n ± 0%  -34.34% (p=0.000 n=20)
ReverseBytes64   2.0705n ± 0%   0.8008n ± 0%  -61.32% (p=0.000 n=20)
geomean           1.455n        0.6749n       -53.62%

goos: linux
goarch: loong64
pkg: math/bits
cpu: Loongson-3A5000 @ 2500.00MHz
               |  bench.old   |              bench.new               |
               |    sec/op    |    sec/op     vs base                |
ReverseBytes     2.8040n ± 0%   0.5205n ± 0%  -81.44% (p=0.000 n=20)
ReverseBytes16   0.7066n ± 0%   0.8011n ± 0%  +13.37% (p=0.000 n=20)
ReverseBytes32   1.5500n ± 0%   0.8010n ± 0%  -48.32% (p=0.000 n=20)
ReverseBytes64   2.7665n ± 0%   0.8010n ± 0%  -71.05% (p=0.000 n=20)
geomean           1.707n        0.7192n       -57.87%

Updates #59120

This patch is a copy of CL 483357.
Co-authored-by: WANG Xuerui <git@xen0n.name>

Change-Id: If355354cd031533df91991fcc3392e5a6c314295
Reviewed-on: https://go-review.googlesource.com/c/go/+/624576
Reviewed-by: David Chase <drchase@google.com>
Reviewed-by: abner chenc <chenguoqi@loongson.cn>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Carlos Amedee <carlos@golang.org>

src/cmd/compile/internal/loong64/ssa.go

@@ -487,6 +487,9 @@ func ssaGenValue(s *ssagen.State, v *ssa.Value) {
 		ssa.OpLOONG64CLZV,
 		ssa.OpLOONG64SQRTD,
 		ssa.OpLOONG64SQRTF,
+		ssa.OpLOONG64REVB2H,
+		ssa.OpLOONG64REVB2W,
+		ssa.OpLOONG64REVBV,
 		ssa.OpLOONG64ABSD:
 		p := s.Prog(v.Op.Asm())
 		p.From.Type = obj.TYPE_REG

src/cmd/compile/internal/ssa/_gen/LOONG64.rules

@@ -147,6 +147,7 @@
 
 (BitLen64 <t> x) => (NEGV <t> (SUBVconst <t> [64] (CLZV <t> x)))
 (BitLen32 <t> x) => (NEGV <t> (SUBVconst <t> [32] (CLZW <t> x)))
+(Bswap(16|32|64) ...) => (REVB(2H|2W|V) ...)
 
 // math package intrinsics
 (Sqrt ...) => (SQRTD ...)

src/cmd/compile/internal/ssa/_gen/LOONG64Ops.go

@@ -202,6 +202,10 @@ func init() {
 		{name: "CLZW", argLength: 1, reg: gp11, asm: "CLZW"}, // Count leading (high order) zeroes (returns 0-32)
 		{name: "CLZV", argLength: 1, reg: gp11, asm: "CLZV"}, // Count leading (high order) zeroes (returns 0-64)
 
+		{name: "REVB2H", argLength: 1, reg: gp11, asm: "REVB2H"}, // Swap bytes: 0x11223344 -> 0x22114433 (sign extends to 64 bits)
+		{name: "REVB2W", argLength: 1, reg: gp11, asm: "REVB2W"}, // Swap bytes: 0x1122334455667788 -> 0x4433221188776655
+		{name: "REVBV", argLength: 1, reg: gp11, asm: "REVBV"},   // Swap bytes: 0x1122334455667788 -> 0x8877665544332211
+
 		{name: "FMINF", argLength: 2, reg: fp21, resultNotInArgs: true, asm: "FMINF", commutative: true, typ: "Float32"}, // min(arg0, arg1), float32
 		{name: "FMIND", argLength: 2, reg: fp21, resultNotInArgs: true, asm: "FMIND", commutative: true, typ: "Float64"}, // min(arg0, arg1), float64
 		{name: "FMAXF", argLength: 2, reg: fp21, resultNotInArgs: true, asm: "FMAXF", commutative: true, typ: "Float32"}, // max(arg0, arg1), float32

src/cmd/compile/internal/ssagen/intrinsics.go

@@ -183,7 +183,7 @@ func initIntrinsics(cfg *intrinsicBuildConfig) {
 		},
 		all...)
 
-	brev_arch := []sys.ArchFamily{sys.AMD64, sys.I386, sys.ARM64, sys.ARM, sys.S390X}
+	brev_arch := []sys.ArchFamily{sys.AMD64, sys.I386, sys.ARM64, sys.ARM, sys.Loong64, sys.S390X}
 	if cfg.goppc64 >= 10 {
 		// Use only on Power10 as the new byte reverse instructions that Power10 provide
 		// make it worthwhile as an intrinsic
@@ -804,6 +804,11 @@ func initIntrinsics(cfg *intrinsicBuildConfig) {
 		sys.S390X)
 	alias("math/bits", "ReverseBytes64", "internal/runtime/sys", "Bswap64", all...)
 	alias("math/bits", "ReverseBytes32", "internal/runtime/sys", "Bswap32", all...)
+	addF("math/bits", "ReverseBytes16",
+		func(s *state, n *ir.CallExpr, args []*ssa.Value) *ssa.Value {
+			return s.newValue1(ssa.OpBswap16, types.Types[types.TUINT16], args[0])
+		},
+		sys.Loong64)
 	// ReverseBytes inlines correctly, no need to intrinsify it.
 	// Nothing special is needed for targets where ReverseBytes16 lowers to a rotate
 	// On Power10, 16-bit rotate is not available so use BRH instruction

src/cmd/compile/internal/ssagen/intrinsics_test.go

@@ -390,6 +390,8 @@ var wantIntrinsics = map[testIntrinsicKey]struct{}{
 	{"loong64", "internal/runtime/math", "Add64"}:              struct{}{},
 	{"loong64", "internal/runtime/math", "Mul64"}:              struct{}{},
 	{"loong64", "internal/runtime/math", "MulUintptr"}:         struct{}{},
+	{"loong64", "internal/runtime/sys", "Bswap32"}:             struct{}{},
+	{"loong64", "internal/runtime/sys", "Bswap64"}:             struct{}{},
 	{"loong64", "internal/runtime/sys", "GetCallerPC"}:         struct{}{},
 	{"loong64", "internal/runtime/sys", "GetCallerSP"}:         struct{}{},
 	{"loong64", "internal/runtime/sys", "GetClosurePtr"}:       struct{}{},
@@ -411,6 +413,9 @@ var wantIntrinsics = map[testIntrinsicKey]struct{}{
 	{"loong64", "math/bits", "RotateLeft"}:                     struct{}{},
 	{"loong64", "math/bits", "RotateLeft32"}:                   struct{}{},
 	{"loong64", "math/bits", "RotateLeft64"}:                   struct{}{},
+	{"loong64", "math/bits", "ReverseBytes16"}:                 struct{}{},
+	{"loong64", "math/bits", "ReverseBytes32"}:                 struct{}{},
+	{"loong64", "math/bits", "ReverseBytes64"}:                 struct{}{},
 	{"loong64", "math/bits", "Sub"}:                            struct{}{},
 	{"loong64", "math/bits", "Sub64"}:                          struct{}{},
 	{"loong64", "runtime", "KeepAlive"}:                        struct{}{},

test/codegen/mathbits.go

@@ -208,6 +208,7 @@ func ReverseBytes(n uint) uint {
 	// 386:"BSWAPL"
 	// s390x:"MOVDBR"
 	// arm64:"REV"
+	// loong64:"REVBV"
 	return bits.ReverseBytes(n)
 }
 
@@ -217,6 +218,7 @@ func ReverseBytes64(n uint64) uint64 {
 	// s390x:"MOVDBR"
 	// arm64:"REV"
 	// ppc64x/power10: "BRD"
+	// loong64:"REVBV"
 	return bits.ReverseBytes64(n)
 }
 
@@ -225,6 +227,7 @@ func ReverseBytes32(n uint32) uint32 {
 	// 386:"BSWAPL"
 	// s390x:"MOVWBR"
 	// arm64:"REVW"
+	// loong64:"REVB2W"
 	// ppc64x/power10: "BRW"
 	return bits.ReverseBytes32(n)
 }
@@ -235,6 +238,7 @@ func ReverseBytes16(n uint16) uint16 {
 	// arm/5:"SLL","SRL","ORR"
 	// arm/6:"REV16"
 	// arm/7:"REV16"
+	// loong64:"REVB2H"
 	// ppc64x/power10: "BRH"
 	return bits.ReverseBytes16(n)
 }