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internal/runtime/maps: assume constant elem offset with int64 and string keys

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Note this doesn't work with int32 keys because alignment padding can change
the offset of the element.

Change-Id: I27804d3cfc7cc1b7f995f7e29630f0824f0ee899
Reviewed-on: https://go-review.googlesource.com/c/go/+/629418
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Michael Pratt <mpratt@google.com>
Reviewed-by: Russ Cox <rsc@golang.org>
This commit is contained in:
Keith Randall 2024-11-18 16:23:43 -08:00
parent 253a9933d1
commit c14fc500c7
3 changed files with 15 additions and 8 deletions
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6
src/cmd/compile/internal/reflectdata/map_swiss.go
View File

@ -269,6 +269,12 @@ func writeSwissMapType(t *types.Type, lsym *obj.LSym, c rttype.Cursor) {
slotTyp := gtyp.Field(1).Type.Elem()
elemOff := slotTyp.Field(1).Offset
if AlgType(t.Key()) == types.AMEM64 && elemOff != 8 {
base.Fatalf("runtime assumes elemOff for 8-byte keys is 8, got %d", elemOff)
}
if AlgType(t.Key()) == types.ASTRING && elemOff != int64(2*types.PtrSize) {
base.Fatalf("runtime assumes elemOff for string keys is %d, got %d", 2*types.PtrSize, elemOff)
}
c.Field("Key").WritePtr(s1)
c.Field("Elem").WritePtr(s2)

8
src/internal/runtime/maps/runtime_fast64_swiss.go
View File

@ -39,7 +39,7 @@ func runtime_mapaccess1_fast64(typ *abi.SwissMapType, m *Map, key uint64) unsafe
slotSize := typ.SlotSize
for full != 0 {
if key == *(*uint64)(slotKey) && full&(1<<7) != 0 {
slotElem := unsafe.Pointer(uintptr(slotKey) + typ.ElemOff)
slotElem := unsafe.Pointer(uintptr(slotKey) + 8)
return slotElem
}
slotKey = unsafe.Pointer(uintptr(slotKey) + slotSize)
@ -66,7 +66,7 @@ func runtime_mapaccess1_fast64(typ *abi.SwissMapType, m *Map, key uint64) unsafe
slotKey := g.key(typ, i)
if key == *(*uint64)(slotKey) {
slotElem := unsafe.Pointer(uintptr(slotKey) + typ.ElemOff)
slotElem := unsafe.Pointer(uintptr(slotKey) + 8)
return slotElem
}
match = match.removeFirst()
@ -107,7 +107,7 @@ func runtime_mapaccess2_fast64(typ *abi.SwissMapType, m *Map, key uint64) (unsaf
slotSize := typ.SlotSize
for full != 0 {
if key == *(*uint64)(slotKey) && full&(1<<7) != 0 {
slotElem := unsafe.Pointer(uintptr(slotKey) + typ.ElemOff)
slotElem := unsafe.Pointer(uintptr(slotKey) + 8)
return slotElem, true
}
slotKey = unsafe.Pointer(uintptr(slotKey) + slotSize)
@ -134,7 +134,7 @@ func runtime_mapaccess2_fast64(typ *abi.SwissMapType, m *Map, key uint64) (unsaf
slotKey := g.key(typ, i)
if key == *(*uint64)(slotKey) {
slotElem := unsafe.Pointer(uintptr(slotKey) + typ.ElemOff)
slotElem := unsafe.Pointer(uintptr(slotKey) + 8)
return slotElem, true
}
match = match.removeFirst()

9
src/internal/runtime/maps/runtime_faststr_swiss.go
View File

@ -8,6 +8,7 @@ package maps
import (
"internal/abi"
"internal/goarch"
"internal/race"
"internal/runtime/sys"
"unsafe"
@ -48,7 +49,7 @@ func (m *Map) getWithoutKeySmallFastStr(typ *abi.SwissMapType, key string) unsaf
// There's exactly one slot that passed the quick test. Do the single expensive comparison.
slotKey = g.key(typ, uintptr(j))
if key == *(*string)(slotKey) {
return unsafe.Pointer(uintptr(slotKey) + typ.ElemOff)
return unsafe.Pointer(uintptr(slotKey) + 2*goarch.PtrSize)
}
return nil
}
@ -62,7 +63,7 @@ dohash:
for range abi.SwissMapGroupSlots {
if uint8(ctrls) == h2 && key == *(*string)(slotKey) {
return unsafe.Pointer(uintptr(slotKey) + typ.ElemOff)
return unsafe.Pointer(uintptr(slotKey) + 2*goarch.PtrSize)
}
slotKey = unsafe.Pointer(uintptr(slotKey) + slotSize)
ctrls >>= 8
@ -141,7 +142,7 @@ func runtime_mapaccess1_faststr(typ *abi.SwissMapType, m *Map, key string) unsaf
slotKey := g.key(typ, i)
if key == *(*string)(slotKey) {
slotElem := unsafe.Pointer(uintptr(slotKey) + typ.ElemOff)
slotElem := unsafe.Pointer(uintptr(slotKey) + 2*goarch.PtrSize)
return slotElem
}
match = match.removeFirst()
@ -199,7 +200,7 @@ func runtime_mapaccess2_faststr(typ *abi.SwissMapType, m *Map, key string) (unsa
slotKey := g.key(typ, i)
if key == *(*string)(slotKey) {
slotElem := unsafe.Pointer(uintptr(slotKey) + typ.ElemOff)
slotElem := unsafe.Pointer(uintptr(slotKey) + 2*goarch.PtrSize)
return slotElem, true
}
match = match.removeFirst()