cmd/compile: wire up math/bits.TrailingZeros 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                |
TrailingZeros     1.7240n ± 0%   0.8120n ± 0%  -52.90% (p=0.000 n=20)
TrailingZeros8    1.0530n ± 0%   0.8015n ± 0%  -23.88% (p=0.000 n=20)
TrailingZeros16    2.072n ± 0%    1.015n ± 0%  -51.01% (p=0.000 n=20)
TrailingZeros32   1.7160n ± 0%   0.8122n ± 0%  -52.67% (p=0.000 n=20)
TrailingZeros64   2.0060n ± 0%   0.8125n ± 0%  -59.50% (p=0.000 n=20)
geomean            1.669n        0.8470n       -49.25%

goos: linux
goarch: loong64
pkg: math/bits
cpu: Loongson-3A5000 @ 2500.00MHz
                |  bench.old   |              bench.new               |
                |    sec/op    |    sec/op     vs base                |
TrailingZeros     2.6275n ± 0%   0.9120n ± 0%  -65.29% (p=0.000 n=20)
TrailingZeros8     1.451n ± 0%    1.163n ± 0%  -19.85% (p=0.000 n=20)
TrailingZeros16    3.069n ± 0%    1.201n ± 0%  -60.87% (p=0.000 n=20)
TrailingZeros32   2.9060n ± 0%   0.9115n ± 0%  -68.63% (p=0.000 n=20)
TrailingZeros64   2.6305n ± 0%   0.9115n ± 0%  -65.35% (p=0.000 n=20)
geomean            2.456n         1.011n       -58.83%

This patch is a copy of CL 479498.
Co-authored-by: WANG Xuerui <git@xen0n.name>

Change-Id: I1a5b2114a844dc0d02c8e68f41ce2443ac3b5fda
Reviewed-on: https://go-review.googlesource.com/c/go/+/624356
Reviewed-by: abner chenc <chenguoqi@loongson.cn>
Reviewed-by: David Chase <drchase@google.com>
Reviewed-by: Cherry Mui <cherryyz@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Keith Randall <khr@google.com>

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

@@ -512,6 +512,8 @@ func ssaGenValue(s *ssagen.State, v *ssa.Value) {
 		ssa.OpLOONG64NEGD,
 		ssa.OpLOONG64CLZW,
 		ssa.OpLOONG64CLZV,
+		ssa.OpLOONG64CTZW,
+		ssa.OpLOONG64CTZV,
 		ssa.OpLOONG64SQRTD,
 		ssa.OpLOONG64SQRTF,
 		ssa.OpLOONG64REVB2H,

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

@@ -152,6 +152,8 @@
 (BitRev16 <t> x) => (REVB2H (BITREV4B <t> x))
 (BitRev32 ...) => (BITREVW ...)
 (BitRev64 ...) => (BITREVV ...)
+(Ctz(32|64)NonZero ...) => (Ctz(32|64) ...)
+(Ctz(32|64) ...) => (CTZ(W|V) ...)
 
 (PopCount64 <t> x) => (MOVVfpgp <t> (VPCNT64 <typ.Float64> (MOVVgpfp <typ.Float64> x)))
 (PopCount32 <t> x) => (MOVWfpgp <t> (VPCNT32 <typ.Float32> (MOVWgpfp <typ.Float32> x)))

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

@@ -174,6 +174,8 @@ 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: "CTZW", argLength: 1, reg: gp11, asm: "CTZW"}, // Count trailing (low order) zeroes (returns 0-32)
+		{name: "CTZV", argLength: 1, reg: gp11, asm: "CTZV"}, // Count trailing (low 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

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

@@ -811,7 +811,7 @@ func initIntrinsics(cfg *intrinsicBuildConfig) {
 		func(s *state, n *ir.CallExpr, args []*ssa.Value) *ssa.Value {
 			return s.newValue1(ssa.OpCtz64, types.Types[types.TINT], args[0])
 		},
-		sys.AMD64, sys.ARM64, sys.ARM, sys.S390X, sys.MIPS, sys.PPC64, sys.Wasm)
+		sys.AMD64, sys.ARM64, sys.ARM, sys.Loong64, sys.S390X, sys.MIPS, sys.PPC64, sys.Wasm)
 	addF("math/bits", "TrailingZeros64",
 		func(s *state, n *ir.CallExpr, args []*ssa.Value) *ssa.Value {
 			lo := s.newValue1(ssa.OpInt64Lo, types.Types[types.TUINT32], args[0])
@@ -823,7 +823,7 @@ func initIntrinsics(cfg *intrinsicBuildConfig) {
 		func(s *state, n *ir.CallExpr, args []*ssa.Value) *ssa.Value {
 			return s.newValue1(ssa.OpCtz32, types.Types[types.TINT], args[0])
 		},
-		sys.AMD64, sys.I386, sys.ARM64, sys.ARM, sys.S390X, sys.MIPS, sys.PPC64, sys.Wasm)
+		sys.AMD64, sys.I386, sys.ARM64, sys.ARM, sys.Loong64, sys.S390X, sys.MIPS, sys.PPC64, sys.Wasm)
 	addF("math/bits", "TrailingZeros16",
 		func(s *state, n *ir.CallExpr, args []*ssa.Value) *ssa.Value {
 			x := s.newValue1(ssa.OpZeroExt16to32, types.Types[types.TUINT32], args[0])
@@ -844,7 +844,7 @@ func initIntrinsics(cfg *intrinsicBuildConfig) {
 			y := s.newValue2(ssa.OpOr64, types.Types[types.TUINT64], x, c)
 			return s.newValue1(ssa.OpCtz64, types.Types[types.TINT], y)
 		},
-		sys.S390X, sys.PPC64)
+		sys.Loong64, sys.S390X, sys.PPC64)
 	addF("math/bits", "TrailingZeros8",
 		func(s *state, n *ir.CallExpr, args []*ssa.Value) *ssa.Value {
 			x := s.newValue1(ssa.OpZeroExt8to32, types.Types[types.TUINT32], args[0])
@@ -865,7 +865,7 @@ func initIntrinsics(cfg *intrinsicBuildConfig) {
 			y := s.newValue2(ssa.OpOr64, types.Types[types.TUINT64], x, c)
 			return s.newValue1(ssa.OpCtz64, types.Types[types.TINT], y)
 		},
-		sys.S390X)
+		sys.Loong64, sys.S390X)
 	alias("math/bits", "ReverseBytes64", "internal/runtime/sys", "Bswap64", all...)
 	alias("math/bits", "ReverseBytes32", "internal/runtime/sys", "Bswap32", all...)
 	addF("math/bits", "ReverseBytes16",

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

@@ -408,6 +408,9 @@ var wantIntrinsics = map[testIntrinsicKey]struct{}{
 	{"loong64", "internal/runtime/sys", "Len64"}:               struct{}{},
 	{"loong64", "internal/runtime/sys", "Len8"}:                struct{}{},
 	{"loong64", "internal/runtime/sys", "OnesCount64"}:         struct{}{},
+	{"loong64", "internal/runtime/sys", "TrailingZeros32"}:     struct{}{},
+	{"loong64", "internal/runtime/sys", "TrailingZeros64"}:     struct{}{},
+	{"loong64", "internal/runtime/sys", "TrailingZeros8"}:      struct{}{},
 	{"loong64", "math", "Abs"}:                                 struct{}{},
 	{"loong64", "math", "Copysign"}:                            struct{}{},
 	{"loong64", "math", "FMA"}:                                 struct{}{},
@@ -436,6 +439,10 @@ var wantIntrinsics = map[testIntrinsicKey]struct{}{
 	{"loong64", "math/bits", "ReverseBytes16"}:                 struct{}{},
 	{"loong64", "math/bits", "ReverseBytes32"}:                 struct{}{},
 	{"loong64", "math/bits", "ReverseBytes64"}:                 struct{}{},
+	{"loong64", "math/bits", "TrailingZeros16"}:                struct{}{},
+	{"loong64", "math/bits", "TrailingZeros32"}:                struct{}{},
+	{"loong64", "math/bits", "TrailingZeros64"}:                struct{}{},
+	{"loong64", "math/bits", "TrailingZeros8"}:                 struct{}{},
 	{"loong64", "math/bits", "Sub"}:                            struct{}{},
 	{"loong64", "math/bits", "Sub64"}:                          struct{}{},
 	{"loong64", "runtime", "KeepAlive"}:                        struct{}{},

test/codegen/mathbits.go

@@ -361,6 +361,7 @@ func TrailingZeros(n uint) int {
 	// 386:"BSFL"
 	// arm:"CLZ"
 	// arm64:"RBIT","CLZ"
+	// loong64:"CTZV"
 	// s390x:"FLOGR"
 	// ppc64x/power8:"ANDN","POPCNTD"
 	// ppc64x/power9: "CNTTZD"
@@ -373,6 +374,7 @@ func TrailingZeros64(n uint64) int {
 	// amd64/v3:"TZCNTQ"
 	// 386:"BSFL"
 	// arm64:"RBIT","CLZ"
+	// loong64:"CTZV"
 	// s390x:"FLOGR"
 	// ppc64x/power8:"ANDN","POPCNTD"
 	// ppc64x/power9: "CNTTZD"
@@ -392,6 +394,7 @@ func TrailingZeros32(n uint32) int {
 	// 386:"BSFL"
 	// arm:"CLZ"
 	// arm64:"RBITW","CLZW"
+	// loong64:"CTZW"
 	// s390x:"FLOGR","MOVWZ"
 	// ppc64x/power8:"ANDN","POPCNTW"
 	// ppc64x/power9: "CNTTZW"
@@ -404,6 +407,7 @@ func TrailingZeros16(n uint16) int {
 	// 386:"BSFL\t"
 	// arm:"ORR\t\\$65536","CLZ",-"MOVHU\tR"
 	// arm64:"ORR\t\\$65536","RBITW","CLZW",-"MOVHU\tR",-"RBIT\t",-"CLZ\t"
+	// loong64:"CTZV"
 	// s390x:"FLOGR","OR\t\\$65536"
 	// ppc64x/power8:"POPCNTD","ORIS\\t\\$1"
 	// ppc64x/power9:"CNTTZD","ORIS\\t\\$1"
@@ -416,6 +420,7 @@ func TrailingZeros8(n uint8) int {
 	// 386:"BSFL"
 	// arm:"ORR\t\\$256","CLZ",-"MOVBU\tR"
 	// arm64:"ORR\t\\$256","RBITW","CLZW",-"MOVBU\tR",-"RBIT\t",-"CLZ\t"
+	// loong64:"CTZV"
 	// s390x:"FLOGR","OR\t\\$256"
 	// wasm:"I64Ctz"
 	return bits.TrailingZeros8(n)