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internal/abi,runtime: refactor map constants into one place

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Previously TryBot-tested with bucket bits = 4.
Also tested locally with bucket bits = 5.
This makes it much easier to change the size of map
buckets, and hopefully provides pointers to all the
code that in some way depends on details of map layout.

Change-Id: I9f6669d1eadd02f182d0bc3f959dc5f385fa1683
Reviewed-on: https://go-review.googlesource.com/c/go/+/462115
TryBot-Result: Gopher Robot <gobot@golang.org>
Run-TryBot: David Chase <drchase@google.com>
Reviewed-by: Austin Clements <austin@google.com>
This commit is contained in:
David Chase 2023-01-13 16:12:47 -05:00
parent e2fe35363d
commit e22bd2348c
13 changed files with 195 additions and 80 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

14
src/cmd/compile/internal/reflectdata/reflect.go
View file

@ -7,6 +7,7 @@ package reflectdata
import (
"encoding/binary"
"fmt"
"internal/abi"
"os"
"sort"
"strings"
@ -65,10 +66,17 @@ type typeSig struct {
// we include only enough information to generate a correct GC
// program for it.
// Make sure this stays in sync with runtime/map.go.
//
// A "bucket" is a "struct" {
// tophash [BUCKETSIZE]uint8
// keys [BUCKETSIZE]keyType
// elems [BUCKETSIZE]elemType
// overflow *bucket
// }
const (
BUCKETSIZE = 8
MAXKEYSIZE = 128
MAXELEMSIZE = 128
BUCKETSIZE = abi.MapBucketCount
MAXKEYSIZE = abi.MapMaxKeyBytes
MAXELEMSIZE = abi.MapMaxElemBytes
)
func structfieldSize() int { return 3 * types.PtrSize } // Sizeof(runtime.structfield{})

2
src/cmd/dist/buildtool.go vendored
View file

@ -60,8 +60,10 @@ var bootstrapDirs = []string{
"debug/macho",
"debug/pe",
"go/constant",
"internal/abi",
"internal/coverage",
"internal/buildcfg",
"internal/goarch",
"internal/goexperiment",
"internal/goroot",
"internal/goversion",

7
src/cmd/link/internal/ld/dwarf.go
View file

@ -22,6 +22,7 @@ import (
"cmd/link/internal/loader"
"cmd/link/internal/sym"
"fmt"
"internal/abi"
"internal/buildcfg"
"log"
"path"
@ -855,9 +856,9 @@ func mkinternaltypename(base string, arg1 string, arg2 string) string {
// synthesizemaptypes is way too closely married to runtime/hashmap.c
const (
MaxKeySize = 128
MaxValSize = 128
BucketSize = 8
MaxKeySize = abi.MapMaxKeyBytes
MaxValSize = abi.MapMaxElemBytes
BucketSize = abi.MapBucketCount
)
func (d *dwctxt) mkinternaltype(ctxt *Link, abbrev int, typename, keyname, valname string, f func(*dwarf.DWDie)) loader.Sym {

24
src/internal/abi/abi.go
View file

@ -100,27 +100,3 @@ func (b *IntArgRegBitmap) Set(i int) {
func (b *IntArgRegBitmap) Get(i int) bool {
return b[i/8]&(uint8(1)<<(i%8)) != 0
}
// FuncPC* intrinsics.
//
// CAREFUL: In programs with plugins, FuncPC* can return different values
// for the same function (because there are actually multiple copies of
// the same function in the address space). To be safe, don't use the
// results of this function in any == expression. It is only safe to
// use the result as an address at which to start executing code.
// FuncPCABI0 returns the entry PC of the function f, which must be a
// direct reference of a function defined as ABI0. Otherwise it is a
// compile-time error.
//
// Implemented as a compile intrinsic.
func FuncPCABI0(f any) uintptr
// FuncPCABIInternal returns the entry PC of the function f. If f is a
// direct reference of a function, it must be defined as ABIInternal.
// Otherwise it is a compile-time error. If f is not a direct reference
// of a defined function, it assumes that f is a func value. Otherwise
// the behavior is undefined.
//
// Implemented as a compile intrinsic.
func FuncPCABIInternal(f any) uintptr

35
src/internal/abi/funcpc.go Normal file
View file

@ -0,0 +1,35 @@
// Copyright 2023 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.
//go:build !compiler_bootstrap
// +build !compiler_bootstrap
package abi
// The bootstrapping compiler doesn't understand "any" in the function signatures,
// and also does not implement these intrinsics.
// FuncPC* intrinsics.
//
// CAREFUL: In programs with plugins, FuncPC* can return different values
// for the same function (because there are actually multiple copies of
// the same function in the address space). To be safe, don't use the
// results of this function in any == expression. It is only safe to
// use the result as an address at which to start executing code.
// FuncPCABI0 returns the entry PC of the function f, which must be a
// direct reference of a function defined as ABI0. Otherwise it is a
// compile-time error.
//
// Implemented as a compile intrinsic.
func FuncPCABI0(f any) uintptr
// FuncPCABIInternal returns the entry PC of the function f. If f is a
// direct reference of a function, it must be defined as ABIInternal.
// Otherwise it is a compile-time error. If f is not a direct reference
// of a defined function, it assumes that f is a func value. Otherwise
// the behavior is undefined.
//
// Implemented as a compile intrinsic.
func FuncPCABIInternal(f any) uintptr

14
src/internal/abi/map.go Normal file
View file

@ -0,0 +1,14 @@
// Copyright 2023 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 abi
// Map constants common to several packages
// runtime/runtime-gdb.py:MapTypePrinter contains its own copy
const (
MapBucketCountBits = 3 // log2 of number of elements in a bucket.
MapBucketCount = 1 << MapBucketCountBits
MapMaxKeyBytes = 128 // Must fit in a uint8.
MapMaxElemBytes = 128 // Must fit in a uint8.
)

21
src/reflect/all_test.go
View file

@ -10,6 +10,7 @@ import (
"flag"
"fmt"
"go/token"
"internal/abi"
"internal/goarch"
"internal/testenv"
"io"
@ -31,6 +32,8 @@ import (
"unsafe"
)
const bucketCount = abi.MapBucketCount
var sink any
func TestBool(t *testing.T) {
@ -7162,7 +7165,7 @@ func TestGCBits(t *testing.T) {
verifyGCBits(t, TypeOf(([][10000]Xscalar)(nil)), lit(1))
verifyGCBits(t, SliceOf(ArrayOf(10000, Tscalar)), lit(1))
hdr := make([]byte, 8/goarch.PtrSize)
hdr := make([]byte, bucketCount/goarch.PtrSize)
verifyMapBucket := func(t *testing.T, k, e Type, m any, want []byte) {
verifyGCBits(t, MapBucketOf(k, e), want)
@ -7171,14 +7174,14 @@ func TestGCBits(t *testing.T) {
verifyMapBucket(t,
Tscalar, Tptr,
map[Xscalar]Xptr(nil),
join(hdr, rep(8, lit(0)), rep(8, lit(1)), lit(1)))
join(hdr, rep(bucketCount, lit(0)), rep(bucketCount, lit(1)), lit(1)))
verifyMapBucket(t,
Tscalarptr, Tptr,
map[Xscalarptr]Xptr(nil),
join(hdr, rep(8, lit(0, 1)), rep(8, lit(1)), lit(1)))
join(hdr, rep(bucketCount, lit(0, 1)), rep(bucketCount, lit(1)), lit(1)))
verifyMapBucket(t, Tint64, Tptr,
map[int64]Xptr(nil),
join(hdr, rep(8, rep(8/goarch.PtrSize, lit(0))), rep(8, lit(1)), lit(1)))
join(hdr, rep(bucketCount, rep(8/goarch.PtrSize, lit(0))), rep(bucketCount, lit(1)), lit(1)))
verifyMapBucket(t,
Tscalar, Tscalar,
map[Xscalar]Xscalar(nil),
@ -7186,23 +7189,23 @@ func TestGCBits(t *testing.T) {
verifyMapBucket(t,
ArrayOf(2, Tscalarptr), ArrayOf(3, Tptrscalar),
map[[2]Xscalarptr][3]Xptrscalar(nil),
join(hdr, rep(8*2, lit(0, 1)), rep(8*3, lit(1, 0)), lit(1)))
join(hdr, rep(bucketCount*2, lit(0, 1)), rep(bucketCount*3, lit(1, 0)), lit(1)))
verifyMapBucket(t,
ArrayOf(64/goarch.PtrSize, Tscalarptr), ArrayOf(64/goarch.PtrSize, Tptrscalar),
map[[64 / goarch.PtrSize]Xscalarptr][64 / goarch.PtrSize]Xptrscalar(nil),
join(hdr, rep(8*64/goarch.PtrSize, lit(0, 1)), rep(8*64/goarch.PtrSize, lit(1, 0)), lit(1)))
join(hdr, rep(bucketCount*64/goarch.PtrSize, lit(0, 1)), rep(bucketCount*64/goarch.PtrSize, lit(1, 0)), lit(1)))
verifyMapBucket(t,
ArrayOf(64/goarch.PtrSize+1, Tscalarptr), ArrayOf(64/goarch.PtrSize, Tptrscalar),
map[[64/goarch.PtrSize + 1]Xscalarptr][64 / goarch.PtrSize]Xptrscalar(nil),
join(hdr, rep(8, lit(1)), rep(8*64/goarch.PtrSize, lit(1, 0)), lit(1)))
join(hdr, rep(bucketCount, lit(1)), rep(bucketCount*64/goarch.PtrSize, lit(1, 0)), lit(1)))
verifyMapBucket(t,
ArrayOf(64/goarch.PtrSize, Tscalarptr), ArrayOf(64/goarch.PtrSize+1, Tptrscalar),
map[[64 / goarch.PtrSize]Xscalarptr][64/goarch.PtrSize + 1]Xptrscalar(nil),
join(hdr, rep(8*64/goarch.PtrSize, lit(0, 1)), rep(8, lit(1)), lit(1)))
join(hdr, rep(bucketCount*64/goarch.PtrSize, lit(0, 1)), rep(bucketCount, lit(1)), lit(1)))
verifyMapBucket(t,
ArrayOf(64/goarch.PtrSize+1, Tscalarptr), ArrayOf(64/goarch.PtrSize+1, Tptrscalar),
map[[64/goarch.PtrSize + 1]Xscalarptr][64/goarch.PtrSize + 1]Xptrscalar(nil),
join(hdr, rep(8, lit(1)), rep(8, lit(1)), lit(1)))
join(hdr, rep(bucketCount, lit(1)), rep(bucketCount, lit(1)), lit(1)))
}
func rep(n int, b []byte) []byte { return bytes.Repeat(b, n) }

7
src/reflect/type.go
View file

@ -16,6 +16,7 @@
package reflect
import (
"internal/abi"
"internal/goarch"
"strconv"
"sync"
@ -2226,9 +2227,9 @@ func hashMightPanic(t *rtype) bool {
// Currently, that's just size and the GC program. We also fill in string
// for possible debugging use.
const (
bucketSize uintptr = 8
maxKeySize uintptr = 128
maxValSize uintptr = 128
bucketSize uintptr = abi.MapBucketCount
maxKeySize uintptr = abi.MapMaxKeyBytes
maxValSize uintptr = abi.MapMaxElemBytes
)
func bucketOf(ktyp, etyp *rtype) *rtype {

13
src/runtime/map.go
View file

@ -63,20 +63,21 @@ import (
const (
// Maximum number of key/elem pairs a bucket can hold.
bucketCntBits = 3
bucketCnt = 1 << bucketCntBits
bucketCntBits = abi.MapBucketCountBits
bucketCnt = abi.MapBucketCount
// Maximum average load of a bucket that triggers growth is 6.5.
// Maximum average load of a bucket that triggers growth is bucketCnt*13/16 (about 80% full)
// Because of minimum alignment rules, bucketCnt is known to be at least 8.
// Represent as loadFactorNum/loadFactorDen, to allow integer math.
loadFactorNum = 13
loadFactorDen = 2
loadFactorNum = (bucketCnt * 13 / 16) * loadFactorDen
// Maximum key or elem size to keep inline (instead of mallocing per element).
// Must fit in a uint8.
// Fast versions cannot handle big elems - the cutoff size for
// fast versions in cmd/compile/internal/gc/walk.go must be at most this elem.
maxKeySize = 128
maxElemSize = 128
maxKeySize = abi.MapMaxKeyBytes
maxElemSize = abi.MapMaxElemBytes
// data offset should be the size of the bmap struct, but needs to be
// aligned correctly. For amd64p32 this means 64-bit alignment

34
src/runtime/map_test.go
View file

@ -6,6 +6,7 @@ package runtime_test
import (
"fmt"
"internal/abi"
"internal/goarch"
"math"
"reflect"
@ -506,7 +507,12 @@ func TestMapNanGrowIterator(t *testing.T) {
}
func TestMapIterOrder(t *testing.T) {
for _, n := range [...]int{3, 7, 9, 15} {
sizes := []int{3, 7, 9, 15}
if abi.MapBucketCountBits >= 5 {
// it gets flaky (often only one iteration order) at size 3 when abi.MapBucketCountBits >=5.
t.Fatalf("This test becomes flaky if abi.MapBucketCountBits(=%d) is 5 or larger", abi.MapBucketCountBits)
}
for _, n := range sizes {
for i := 0; i < 1000; i++ {
// Make m be {0: true, 1: true, ..., n-1: true}.
m := make(map[int]bool)
@ -673,6 +679,17 @@ func TestIgnoreBogusMapHint(t *testing.T) {
}
}
const bs = abi.MapBucketCount
// belowOverflow should be a pretty-full pair of buckets;
// atOverflow is 1/8 bs larger = 13/8 buckets or two buckets
// that are 13/16 full each, which is the overflow boundary.
// Adding one to that should ensure overflow to the next higher size.
const (
belowOverflow = bs * 3 / 2 // 1.5 bs = 2 buckets @ 75%
atOverflow = belowOverflow + bs/8 // 2 buckets at 13/16 fill.
)
var mapBucketTests = [...]struct {
n int // n is the number of map elements
noescape int // number of expected buckets for non-escaping map
@ -682,11 +699,16 @@ var mapBucketTests = [...]struct {
{-1, 1, 1},
{0, 1, 1},
{1, 1, 1},
{8, 1, 1},
{9, 2, 2},
{13, 2, 2},
{14, 4, 4},
{26, 4, 4},
{bs, 1, 1},
{bs + 1, 2, 2},
{belowOverflow, 2, 2}, // 1.5 bs = 2 buckets @ 75%
{atOverflow + 1, 4, 4}, // 13/8 bs + 1 == overflow to 4
{2 * belowOverflow, 4, 4}, // 3 bs = 4 buckets @75%
{2*atOverflow + 1, 8, 8}, // 13/4 bs + 1 = overflow to 8
{4 * belowOverflow, 8, 8}, // 6 bs = 8 buckets @ 75%
{4*atOverflow + 1, 16, 16}, // 13/2 bs + 1 = overflow to 16
}
func TestMapBuckets(t *testing.T) {

3
src/runtime/runtime-gdb.py
View file

@ -160,6 +160,7 @@ class MapTypePrinter:
return str(self.val.type)
def children(self):
MapBucketCount = 8 # see internal/abi.go:MapBucketCount
B = self.val['B']
buckets = self.val['buckets']
oldbuckets = self.val['oldbuckets']
@ -178,7 +179,7 @@ class MapTypePrinter:
bp = oldbp
while bp:
b = bp.dereference()
for i in xrange(8):
for i in xrange(MapBucketCount):
if b['tophash'][i] != 0:
k = b['keys'][i]
v = b['values'][i]

10
src/runtime/runtime-gdb_test.go
View file

@ -8,6 +8,7 @@ import (
"bytes"
"flag"
"fmt"
"internal/abi"
"internal/testenv"
"os"
"os/exec"
@ -114,13 +115,16 @@ func checkCleanBacktrace(t *testing.T, backtrace string) {
// TODO(mundaym): check for unknown frames (e.g. "??").
}
const helloSource = `
// NOTE: the maps below are allocated larger than abi.MapBucketCount
// to ensure that they are not "optimized out".
var helloSource = `
import "fmt"
import "runtime"
var gslice []string
func main() {
mapvar := make(map[string]string, 13)
slicemap := make(map[string][]string,11)
mapvar := make(map[string]string, ` + strconv.FormatInt(abi.MapBucketCount+9, 10) + `)
slicemap := make(map[string][]string,` + strconv.FormatInt(abi.MapBucketCount+3, 10) + `)
chanint := make(chan int, 10)
chanstr := make(chan string, 10)
chanint <- 99

91
test/codegen/maps.go
View file

@ -124,31 +124,78 @@ func MapClearSideEffect(m map[int]int) int {
}
func MapLiteralSizing(x int) (map[int]int, map[int]int) {
// amd64:"MOVL\t[$]10,"
// This is tested for internal/abi/maps.go:MapBucketCountBits={3,4,5}
// amd64:"MOVL\t[$]33,"
m := map[int]int{
0: 0,
1: 1,
2: 2,
3: 3,
4: 4,
5: 5,
6: 6,
7: 7,
8: 8,
9: 9,
0: 0,
1: 1,
2: 2,
3: 3,
4: 4,
5: 5,
6: 6,
7: 7,
8: 8,
9: 9,
10: 10,
11: 11,
12: 12,
13: 13,
14: 14,
15: 15,
16: 16,
17: 17,
18: 18,
19: 19,
20: 20,
21: 21,
22: 22,
23: 23,
24: 24,
25: 25,
26: 26,
27: 27,
28: 28,
29: 29,
30: 30,
31: 32,
32: 32,
}
// amd64:"MOVL\t[$]10,"
// amd64:"MOVL\t[$]33,"
n := map[int]int{
0: x,
1: x,
2: x,
3: x,
4: x,
5: x,
6: x,
7: x,
8: x,
9: x,
0: 0,
1: 1,
2: 2,
3: 3,
4: 4,
5: 5,
6: 6,
7: 7,
8: 8,
9: 9,
10: 10,
11: 11,
12: 12,
13: 13,
14: 14,
15: 15,
16: 16,
17: 17,
18: 18,
19: 19,
20: 20,
21: 21,
22: 22,
23: 23,
24: 24,
25: 25,
26: 26,
27: 27,
28: 28,
29: 29,
30: 30,
31: 32,
32: 32,
}
return m, n
}