cmd/compile, runtime: intrinsify atomic And8 and Or8 on s390x
Intrinsify these functions to match other platforms. Update the
sequence of instructions used in the assembly implementations to
match the intrinsics.
Also, add a micro benchmark so we can more easily measure the
performance of these two functions:
name old time/op new time/op delta
And8-8 5.33ns ± 7% 2.55ns ± 8% -52.12% (p=0.000 n=20+20)
And8Parallel-8 7.39ns ± 5% 3.74ns ± 4% -49.34% (p=0.000 n=20+20)
Or8-8 4.84ns ±15% 2.64ns ±11% -45.50% (p=0.000 n=20+20)
Or8Parallel-8 7.27ns ± 3% 3.84ns ± 4% -47.10% (p=0.000 n=19+20)
By using a 'rotate then xor selected bits' instruction combined with
either a 'load and and' or a 'load and or' instruction we can
implement And8 and Or8 with far fewer instructions. Replacing
'compare and swap' with atomic instructions may also improve
performance when there is contention.
Change-Id: I28bb8032052b73ae8ccdf6e4c612d2877085fa01
Reviewed-on: https://go-review.googlesource.com/c/go/+/204277
Run-TryBot: Michael Munday <mike.munday@ibm.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
diff --git a/src/cmd/compile/internal/gc/ssa.go b/src/cmd/compile/internal/gc/ssa.go
index bff038b..fa4fd05 100644
--- a/src/cmd/compile/internal/gc/ssa.go
+++ b/src/cmd/compile/internal/gc/ssa.go
@@ -3490,13 +3490,13 @@
s.vars[&memVar] = s.newValue3(ssa.OpAtomicAnd8, types.TypeMem, args[0], args[1], s.mem())
return nil
},
- sys.AMD64, sys.ARM64, sys.MIPS, sys.PPC64)
+ sys.AMD64, sys.ARM64, sys.MIPS, sys.PPC64, sys.S390X)
addF("runtime/internal/atomic", "Or8",
func(s *state, n *Node, args []*ssa.Value) *ssa.Value {
s.vars[&memVar] = s.newValue3(ssa.OpAtomicOr8, types.TypeMem, args[0], args[1], s.mem())
return nil
},
- sys.AMD64, sys.ARM64, sys.MIPS, sys.PPC64)
+ sys.AMD64, sys.ARM64, sys.MIPS, sys.PPC64, sys.S390X)
alias("runtime/internal/atomic", "Loadint64", "runtime/internal/atomic", "Load64", all...)
alias("runtime/internal/atomic", "Xaddint64", "runtime/internal/atomic", "Xadd64", all...)
diff --git a/src/cmd/compile/internal/s390x/ssa.go b/src/cmd/compile/internal/s390x/ssa.go
index 885c14b..f1725bd 100644
--- a/src/cmd/compile/internal/s390x/ssa.go
+++ b/src/cmd/compile/internal/s390x/ssa.go
@@ -173,6 +173,21 @@
if r != r1 {
p.Reg = r1
}
+ case ssa.OpS390XRXSBG:
+ r1 := v.Reg()
+ if r1 != v.Args[0].Reg() {
+ v.Fatalf("input[0] and output not in same register %s", v.LongString())
+ }
+ r2 := v.Args[1].Reg()
+ i := v.Aux.(s390x.RotateParams)
+ p := s.Prog(v.Op.Asm())
+ p.From = obj.Addr{Type: obj.TYPE_CONST, Offset: int64(i.Start)}
+ p.RestArgs = []obj.Addr{
+ {Type: obj.TYPE_CONST, Offset: int64(i.End)},
+ {Type: obj.TYPE_CONST, Offset: int64(i.Amount)},
+ {Type: obj.TYPE_REG, Reg: r2},
+ }
+ p.To = obj.Addr{Type: obj.TYPE_REG, Reg: r1}
case ssa.OpS390XADD, ssa.OpS390XADDW,
ssa.OpS390XSUB, ssa.OpS390XSUBW,
ssa.OpS390XAND, ssa.OpS390XANDW,
@@ -736,6 +751,25 @@
p.To.Type = obj.TYPE_MEM
p.To.Reg = v.Args[0].Reg()
gc.AddAux(&p.To, v)
+ case ssa.OpS390XLANfloor, ssa.OpS390XLAOfloor:
+ r := v.Args[0].Reg() // clobbered, assumed R1 in comments
+
+ // Round ptr down to nearest multiple of 4.
+ // ANDW $~3, R1
+ ptr := s.Prog(s390x.AANDW)
+ ptr.From.Type = obj.TYPE_CONST
+ ptr.From.Offset = 0xfffffffc
+ ptr.To.Type = obj.TYPE_REG
+ ptr.To.Reg = r
+
+ // Redirect output of LA(N|O) into R1 since it is clobbered anyway.
+ // LA(N|O) Rx, R1, 0(R1)
+ op := s.Prog(v.Op.Asm())
+ op.From.Type = obj.TYPE_REG
+ op.From.Reg = v.Args[1].Reg()
+ op.Reg = r
+ op.To.Type = obj.TYPE_MEM
+ op.To.Reg = r
case ssa.OpS390XLAA, ssa.OpS390XLAAG:
p := s.Prog(v.Op.Asm())
p.Reg = v.Reg0()
diff --git a/src/cmd/compile/internal/ssa/gen/S390X.rules b/src/cmd/compile/internal/ssa/gen/S390X.rules
index 3635aeb..989b20e 100644
--- a/src/cmd/compile/internal/ssa/gen/S390X.rules
+++ b/src/cmd/compile/internal/ssa/gen/S390X.rules
@@ -167,6 +167,36 @@
(AtomicCompareAndSwap32 ptr old new_ mem) -> (LoweredAtomicCas32 ptr old new_ mem)
(AtomicCompareAndSwap64 ptr old new_ mem) -> (LoweredAtomicCas64 ptr old new_ mem)
+// Atomic and: *(*uint8)(ptr) &= val
+//
+// Round pointer down to nearest word boundary and pad value with ones before
+// applying atomic AND operation to target word.
+//
+// *(*uint32)(ptr &^ 3) &= rotateleft(uint32(val) | 0xffffff00, ((3 << 3) ^ ((ptr & 3) << 3))
+//
+(AtomicAnd8 ptr val mem)
+ -> (LANfloor
+ ptr
+ (RLL <typ.UInt32>
+ (ORWconst <typ.UInt32> val [-1<<8])
+ (RXSBG <typ.UInt32> {s390x.NewRotateParams(59, 60, 3)} (MOVDconst [3<<3]) ptr))
+ mem)
+
+// Atomic or: *(*uint8)(ptr) |= val
+//
+// Round pointer down to nearest word boundary and pad value with zeros before
+// applying atomic OR operation to target word.
+//
+// *(*uint32)(ptr &^ 3) |= uint32(val) << ((3 << 3) ^ ((ptr & 3) << 3))
+//
+(AtomicOr8 ptr val mem)
+ -> (LAOfloor
+ ptr
+ (SLW <typ.UInt32>
+ (MOVBZreg <typ.UInt32> val)
+ (RXSBG <typ.UInt32> {s390x.NewRotateParams(59, 60, 3)} (MOVDconst [3<<3]) ptr))
+ mem)
+
// Lowering extension
// Note: we always extend to 64 bits even though some ops don't need that many result bits.
(SignExt8to(16|32|64) x) -> (MOVBreg x)
diff --git a/src/cmd/compile/internal/ssa/gen/S390XOps.go b/src/cmd/compile/internal/ssa/gen/S390XOps.go
index dc9d328..6517957 100644
--- a/src/cmd/compile/internal/ssa/gen/S390XOps.go
+++ b/src/cmd/compile/internal/ssa/gen/S390XOps.go
@@ -170,6 +170,7 @@
gpstoreidx = regInfo{inputs: []regMask{ptrsp, ptrsp, gpsp, 0}}
gpstorebr = regInfo{inputs: []regMask{ptrsp, gpsp, 0}}
gpstorelaa = regInfo{inputs: []regMask{ptrspsb, gpsp, 0}, outputs: gponly}
+ gpstorelab = regInfo{inputs: []regMask{r1, gpsp, 0}, clobbers: r1}
gpmvc = regInfo{inputs: []regMask{ptrsp, ptrsp, 0}}
@@ -347,6 +348,27 @@
{name: "RLLGconst", argLength: 1, reg: gp11, asm: "RLLG", aux: "Int8"}, // arg0 rotate left auxint, rotate amount 0-63
{name: "RLLconst", argLength: 1, reg: gp11, asm: "RLL", aux: "Int8"}, // arg0 rotate left auxint, rotate amount 0-31
+ // Rotate then (and|or|xor|insert) selected bits instructions.
+ //
+ // Aux is an s390x.RotateParams struct containing Start, End and rotation
+ // Amount fields.
+ //
+ // arg1 is rotated left by the rotation amount then the bits from the start
+ // bit to the end bit (inclusive) are combined with arg0 using the logical
+ // operation specified. Bit indices are specified from left to right - the
+ // MSB is 0 and the LSB is 63.
+ //
+ // Examples:
+ // | aux |
+ // | instruction | start | end | amount | arg0 | arg1 | result |
+ // +-------------+-------+-----+--------+-----------------------+-----------------------+-----------------------+
+ // | RXSBG (XOR) | 0 | 1 | 0 | 0xffff_ffff_ffff_ffff | 0xffff_ffff_ffff_ffff | 0x3fff_ffff_ffff_ffff |
+ // | RXSBG (XOR) | 62 | 63 | 0 | 0xffff_ffff_ffff_ffff | 0xffff_ffff_ffff_ffff | 0xffff_ffff_ffff_fffc |
+ // | RXSBG (XOR) | 0 | 47 | 16 | 0xffff_ffff_ffff_ffff | 0x0000_0000_0000_ffff | 0xffff_ffff_0000_ffff |
+ // +-------------+-------+-----+--------+-----------------------+-----------------------+-----------------------+
+ //
+ {name: "RXSBG", argLength: 2, reg: gp21, asm: "RXSBG", resultInArg0: true, aux: "ArchSpecific", clobberFlags: true}, // rotate then xor selected bits
+
// unary ops
{name: "NEG", argLength: 1, reg: gp11, asm: "NEG", clobberFlags: true}, // -arg0
{name: "NEGW", argLength: 1, reg: gp11, asm: "NEGW", clobberFlags: true}, // -arg0
@@ -509,6 +531,12 @@
{name: "AddTupleFirst32", argLength: 2}, // arg1=tuple <x,y>. Returns <x+arg0,y>.
{name: "AddTupleFirst64", argLength: 2}, // arg1=tuple <x,y>. Returns <x+arg0,y>.
+ // Atomic bitwise operations.
+ // Note: 'floor' operations round the pointer down to the nearest word boundary
+ // which reflects how they are used in the runtime.
+ {name: "LAOfloor", argLength: 3, reg: gpstorelab, asm: "LAO", typ: "Mem", clobberFlags: true, hasSideEffects: true}, // *(floor(arg0, 4)) |= arg1. arg2 = mem.
+ {name: "LANfloor", argLength: 3, reg: gpstorelab, asm: "LAN", typ: "Mem", clobberFlags: true, hasSideEffects: true}, // *(floor(arg0, 4)) &= arg1. arg2 = mem.
+
// Compare and swap.
// arg0 = pointer, arg1 = old value, arg2 = new value, arg3 = memory.
// if *(arg0+auxint+aux) == arg1 {
diff --git a/src/cmd/compile/internal/ssa/opGen.go b/src/cmd/compile/internal/ssa/opGen.go
index 047a2a5..a5951dd 100644
--- a/src/cmd/compile/internal/ssa/opGen.go
+++ b/src/cmd/compile/internal/ssa/opGen.go
@@ -1982,6 +1982,7 @@
OpS390XRLL
OpS390XRLLGconst
OpS390XRLLconst
+ OpS390XRXSBG
OpS390XNEG
OpS390XNEGW
OpS390XNOT
@@ -2081,6 +2082,8 @@
OpS390XLAAG
OpS390XAddTupleFirst32
OpS390XAddTupleFirst64
+ OpS390XLAOfloor
+ OpS390XLANfloor
OpS390XLoweredAtomicCas32
OpS390XLoweredAtomicCas64
OpS390XLoweredAtomicExchange32
@@ -26502,6 +26505,23 @@
},
},
{
+ name: "RXSBG",
+ auxType: auxArchSpecific,
+ argLen: 2,
+ resultInArg0: true,
+ clobberFlags: true,
+ asm: s390x.ARXSBG,
+ reg: regInfo{
+ inputs: []inputInfo{
+ {0, 23551}, // R0 R1 R2 R3 R4 R5 R6 R7 R8 R9 R11 R12 R14
+ {1, 23551}, // R0 R1 R2 R3 R4 R5 R6 R7 R8 R9 R11 R12 R14
+ },
+ outputs: []outputInfo{
+ {0, 23551}, // R0 R1 R2 R3 R4 R5 R6 R7 R8 R9 R11 R12 R14
+ },
+ },
+ },
+ {
name: "NEG",
argLen: 1,
clobberFlags: true,
@@ -27843,6 +27863,34 @@
reg: regInfo{},
},
{
+ name: "LAOfloor",
+ argLen: 3,
+ clobberFlags: true,
+ hasSideEffects: true,
+ asm: s390x.ALAO,
+ reg: regInfo{
+ inputs: []inputInfo{
+ {0, 2}, // R1
+ {1, 56319}, // R0 R1 R2 R3 R4 R5 R6 R7 R8 R9 R11 R12 R14 SP
+ },
+ clobbers: 2, // R1
+ },
+ },
+ {
+ name: "LANfloor",
+ argLen: 3,
+ clobberFlags: true,
+ hasSideEffects: true,
+ asm: s390x.ALAN,
+ reg: regInfo{
+ inputs: []inputInfo{
+ {0, 2}, // R1
+ {1, 56319}, // R0 R1 R2 R3 R4 R5 R6 R7 R8 R9 R11 R12 R14 SP
+ },
+ clobbers: 2, // R1
+ },
+ },
+ {
name: "LoweredAtomicCas32",
auxType: auxSymOff,
argLen: 4,
diff --git a/src/cmd/compile/internal/ssa/rewriteS390X.go b/src/cmd/compile/internal/ssa/rewriteS390X.go
index 5c3be61..c85ffde 100644
--- a/src/cmd/compile/internal/ssa/rewriteS390X.go
+++ b/src/cmd/compile/internal/ssa/rewriteS390X.go
@@ -38,6 +38,8 @@
return rewriteValueS390X_OpAtomicAdd32_0(v)
case OpAtomicAdd64:
return rewriteValueS390X_OpAtomicAdd64_0(v)
+ case OpAtomicAnd8:
+ return rewriteValueS390X_OpAtomicAnd8_0(v)
case OpAtomicCompareAndSwap32:
return rewriteValueS390X_OpAtomicCompareAndSwap32_0(v)
case OpAtomicCompareAndSwap64:
@@ -56,6 +58,8 @@
return rewriteValueS390X_OpAtomicLoadAcq32_0(v)
case OpAtomicLoadPtr:
return rewriteValueS390X_OpAtomicLoadPtr_0(v)
+ case OpAtomicOr8:
+ return rewriteValueS390X_OpAtomicOr8_0(v)
case OpAtomicStore32:
return rewriteValueS390X_OpAtomicStore32_0(v)
case OpAtomicStore64:
@@ -1001,6 +1005,34 @@
return true
}
}
+func rewriteValueS390X_OpAtomicAnd8_0(v *Value) bool {
+ b := v.Block
+ typ := &b.Func.Config.Types
+ // match: (AtomicAnd8 ptr val mem)
+ // result: (LANfloor ptr (RLL <typ.UInt32> (ORWconst <typ.UInt32> val [-1<<8]) (RXSBG <typ.UInt32> {s390x.NewRotateParams(59, 60, 3)} (MOVDconst [3<<3]) ptr)) mem)
+ for {
+ mem := v.Args[2]
+ ptr := v.Args[0]
+ val := v.Args[1]
+ v.reset(OpS390XLANfloor)
+ v.AddArg(ptr)
+ v0 := b.NewValue0(v.Pos, OpS390XRLL, typ.UInt32)
+ v1 := b.NewValue0(v.Pos, OpS390XORWconst, typ.UInt32)
+ v1.AuxInt = -1 << 8
+ v1.AddArg(val)
+ v0.AddArg(v1)
+ v2 := b.NewValue0(v.Pos, OpS390XRXSBG, typ.UInt32)
+ v2.Aux = s390x.NewRotateParams(59, 60, 3)
+ v3 := b.NewValue0(v.Pos, OpS390XMOVDconst, typ.UInt64)
+ v3.AuxInt = 3 << 3
+ v2.AddArg(v3)
+ v2.AddArg(ptr)
+ v0.AddArg(v2)
+ v.AddArg(v0)
+ v.AddArg(mem)
+ return true
+ }
+}
func rewriteValueS390X_OpAtomicCompareAndSwap32_0(v *Value) bool {
// match: (AtomicCompareAndSwap32 ptr old new_ mem)
// result: (LoweredAtomicCas32 ptr old new_ mem)
@@ -1121,6 +1153,33 @@
return true
}
}
+func rewriteValueS390X_OpAtomicOr8_0(v *Value) bool {
+ b := v.Block
+ typ := &b.Func.Config.Types
+ // match: (AtomicOr8 ptr val mem)
+ // result: (LAOfloor ptr (SLW <typ.UInt32> (MOVBZreg <typ.UInt32> val) (RXSBG <typ.UInt32> {s390x.NewRotateParams(59, 60, 3)} (MOVDconst [3<<3]) ptr)) mem)
+ for {
+ mem := v.Args[2]
+ ptr := v.Args[0]
+ val := v.Args[1]
+ v.reset(OpS390XLAOfloor)
+ v.AddArg(ptr)
+ v0 := b.NewValue0(v.Pos, OpS390XSLW, typ.UInt32)
+ v1 := b.NewValue0(v.Pos, OpS390XMOVBZreg, typ.UInt32)
+ v1.AddArg(val)
+ v0.AddArg(v1)
+ v2 := b.NewValue0(v.Pos, OpS390XRXSBG, typ.UInt32)
+ v2.Aux = s390x.NewRotateParams(59, 60, 3)
+ v3 := b.NewValue0(v.Pos, OpS390XMOVDconst, typ.UInt64)
+ v3.AuxInt = 3 << 3
+ v2.AddArg(v3)
+ v2.AddArg(ptr)
+ v0.AddArg(v2)
+ v.AddArg(v0)
+ v.AddArg(mem)
+ return true
+ }
+}
func rewriteValueS390X_OpAtomicStore32_0(v *Value) bool {
b := v.Block
// match: (AtomicStore32 ptr val mem)
diff --git a/src/cmd/internal/obj/s390x/rotate.go b/src/cmd/internal/obj/s390x/rotate.go
new file mode 100644
index 0000000..fd2d548
--- /dev/null
+++ b/src/cmd/internal/obj/s390x/rotate.go
@@ -0,0 +1,47 @@
+// Copyright 2019 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package s390x
+
+// RotateParams represents the immediates required for a "rotate
+// then ... selected bits instruction".
+//
+// The Start and End values are the indexes that represent
+// the masked region. They are inclusive and are in big-
+// endian order (bit 0 is the MSB, bit 63 is the LSB). They
+// may wrap around.
+//
+// Some examples:
+//
+// Masked region | Start | End
+// --------------------------+-------+----
+// 0x00_00_00_00_00_00_00_0f | 60 | 63
+// 0xf0_00_00_00_00_00_00_00 | 0 | 3
+// 0xf0_00_00_00_00_00_00_0f | 60 | 3
+//
+// The Amount value represents the amount to rotate the
+// input left by. Note that this rotation is performed
+// before the masked region is used.
+type RotateParams struct {
+ Start uint8 // big-endian start bit index [0..63]
+ End uint8 // big-endian end bit index [0..63]
+ Amount uint8 // amount to rotate left
+}
+
+func NewRotateParams(start, end, amount int64) RotateParams {
+ if start&^63 != 0 {
+ panic("start out of bounds")
+ }
+ if end&^63 != 0 {
+ panic("end out of bounds")
+ }
+ if amount&^63 != 0 {
+ panic("amount out of bounds")
+ }
+ return RotateParams{
+ Start: uint8(start),
+ End: uint8(end),
+ Amount: uint8(amount),
+ }
+}
diff --git a/src/runtime/internal/atomic/asm_s390x.s b/src/runtime/internal/atomic/asm_s390x.s
index 78abd48..9a19bc0 100644
--- a/src/runtime/internal/atomic/asm_s390x.s
+++ b/src/runtime/internal/atomic/asm_s390x.s
@@ -176,37 +176,27 @@
TEXT ·Or8(SB), NOSPLIT, $0-9
MOVD ptr+0(FP), R3
MOVBZ val+8(FP), R4
- // Calculate shift.
- MOVD R3, R5
- AND $3, R5
- XOR $3, R5 // big endian - flip direction
- SLD $3, R5 // MUL $8, R5
- SLD R5, R4
- // Align ptr down to 4 bytes so we can use 32-bit load/store.
- AND $-4, R3
- MOVWZ 0(R3), R6
-again:
- OR R4, R6, R7
- CS R6, R7, 0(R3) // if R6==(R3) then (R3)=R7 else R6=(R3)
- BNE again
+ // We don't have atomic operations that work on individual bytes so we
+ // need to align addr down to a word boundary and create a mask
+ // containing v to OR with the entire word atomically.
+ MOVD $(3<<3), R5
+ RXSBG $59, $60, $3, R3, R5 // R5 = 24 - ((addr % 4) * 8) = ((addr & 3) << 3) ^ (3 << 3)
+ ANDW $~3, R3 // R3 = floor(addr, 4) = addr &^ 3
+ SLW R5, R4 // R4 = uint32(v) << R5
+ LAO R4, R6, 0(R3) // R6 = *R3; *R3 |= R4; (atomic)
RET
// func And8(addr *uint8, v uint8)
TEXT ·And8(SB), NOSPLIT, $0-9
MOVD ptr+0(FP), R3
MOVBZ val+8(FP), R4
- // Calculate shift.
- MOVD R3, R5
- AND $3, R5
- XOR $3, R5 // big endian - flip direction
- SLD $3, R5 // MUL $8, R5
- OR $-256, R4 // create 0xffffffffffffffxx
- RLLG R5, R4
- // Align ptr down to 4 bytes so we can use 32-bit load/store.
- AND $-4, R3
- MOVWZ 0(R3), R6
-again:
- AND R4, R6, R7
- CS R6, R7, 0(R3) // if R6==(R3) then (R3)=R7 else R6=(R3)
- BNE again
+ // We don't have atomic operations that work on individual bytes so we
+ // need to align addr down to a word boundary and create a mask
+ // containing v to AND with the entire word atomically.
+ ORW $~0xff, R4 // R4 = uint32(v) | 0xffffff00
+ MOVD $(3<<3), R5
+ RXSBG $59, $60, $3, R3, R5 // R5 = 24 - ((addr % 4) * 8) = ((addr & 3) << 3) ^ (3 << 3)
+ ANDW $~3, R3 // R3 = floor(addr, 4) = addr &^ 3
+ RLL R5, R4, R4 // R4 = rotl(R4, R5)
+ LAN R4, R6, 0(R3) // R6 = *R3; *R3 &= R4; (atomic)
RET
diff --git a/src/runtime/internal/atomic/bench_test.go b/src/runtime/internal/atomic/bench_test.go
index 083a75c..de71b0f 100644
--- a/src/runtime/internal/atomic/bench_test.go
+++ b/src/runtime/internal/atomic/bench_test.go
@@ -43,6 +43,46 @@
}
}
+func BenchmarkAnd8(b *testing.B) {
+ var x [512]uint8 // give byte its own cache line
+ sink = &x
+ for i := 0; i < b.N; i++ {
+ atomic.And8(&x[255], uint8(i))
+ }
+}
+
+func BenchmarkAnd8Parallel(b *testing.B) {
+ var x [512]uint8 // give byte its own cache line
+ sink = &x
+ b.RunParallel(func(pb *testing.PB) {
+ i := uint8(0)
+ for pb.Next() {
+ atomic.And8(&x[255], i)
+ i++
+ }
+ })
+}
+
+func BenchmarkOr8(b *testing.B) {
+ var x [512]uint8 // give byte its own cache line
+ sink = &x
+ for i := 0; i < b.N; i++ {
+ atomic.Or8(&x[255], uint8(i))
+ }
+}
+
+func BenchmarkOr8Parallel(b *testing.B) {
+ var x [512]uint8 // give byte its own cache line
+ sink = &x
+ b.RunParallel(func(pb *testing.PB) {
+ i := uint8(0)
+ for pb.Next() {
+ atomic.Or8(&x[255], i)
+ i++
+ }
+ })
+}
+
func BenchmarkXadd(b *testing.B) {
var x uint32
ptr := &x
