From 5a7189dcaaddc4b474f50a7449e080e9a3fb2e46 Mon Sep 17 00:00:00 2001
From: shupiaoyang <shupiaoyang1@huawei.com>
Date: Tue, 2 Dec 2025 11:57:24 +0800
Subject: [PATCH] Add support for goexperiment.RevertCopyHashKeys in runtime
 maps

---
 .../exp_revertcopyhashkeys_off.go             |  8 ++++
 .../goexperiment/exp_revertcopyhashkeys_on.go |  8 ++++
 src/internal/goexperiment/flags.go            |  3 ++
 .../runtime/maps/runtime_fast32_swiss.go      | 41 +++++++++++++++----
 .../runtime/maps/runtime_fast64_swiss.go      | 41 +++++++++++++++----
 .../runtime/maps/runtime_faststr_swiss.go     | 40 ++++++++++++++----
 6 files changed, 118 insertions(+), 23 deletions(-)
 create mode 100644 src/internal/goexperiment/exp_revertcopyhashkeys_off.go
 create mode 100644 src/internal/goexperiment/exp_revertcopyhashkeys_on.go

diff --git a/src/internal/goexperiment/exp_revertcopyhashkeys_off.go b/src/internal/goexperiment/exp_revertcopyhashkeys_off.go
new file mode 100644
index 000000000..5cf48fb0d
--- /dev/null
+++ b/src/internal/goexperiment/exp_revertcopyhashkeys_off.go
@@ -0,0 +1,8 @@
+// Code generated by mkconsts.go. DO NOT EDIT.
+
+//go:build !goexperiment.revertcopyhashkeys
+
+package goexperiment
+
+const RevertCopyHashKeys = false
+const RevertCopyHashKeysInt = 0
diff --git a/src/internal/goexperiment/exp_revertcopyhashkeys_on.go b/src/internal/goexperiment/exp_revertcopyhashkeys_on.go
new file mode 100644
index 000000000..0e5d79f33
--- /dev/null
+++ b/src/internal/goexperiment/exp_revertcopyhashkeys_on.go
@@ -0,0 +1,8 @@
+// Code generated by mkconsts.go. DO NOT EDIT.
+
+//go:build goexperiment.revertcopyhashkeys
+
+package goexperiment
+
+const RevertCopyHashKeys = true
+const RevertCopyHashKeysInt = 1
diff --git a/src/internal/goexperiment/flags.go b/src/internal/goexperiment/flags.go
index ac85fc800..953003d36 100644
--- a/src/internal/goexperiment/flags.go
+++ b/src/internal/goexperiment/flags.go
@@ -131,4 +131,7 @@ type Flags struct {
 
 	// Kunpeng malloc prefetch optimization.
 	PrefetchMalloc bool
+
+	// RevertCopyHashKeys enables the "revert" hash map implementation.
+	RevertCopyHashKeys bool
 }
diff --git a/src/internal/runtime/maps/runtime_fast32_swiss.go b/src/internal/runtime/maps/runtime_fast32_swiss.go
index 46023cc9b..9ccd4ba1d 100644
--- a/src/internal/runtime/maps/runtime_fast32_swiss.go
+++ b/src/internal/runtime/maps/runtime_fast32_swiss.go
@@ -8,6 +8,7 @@ package maps
 
 import (
 	"internal/abi"
+	"internal/goexperiment"
 	"internal/race"
 	"internal/runtime/sys"
 	"unsafe"
@@ -48,8 +49,14 @@ func runtime_mapaccess1_fast32(typ *abi.SwissMapType, m *Map, key uint32) unsafe
 		return unsafe.Pointer(&zeroVal[0])
 	}
 
-	k := key
-	hash := typ.Hasher(abi.NoEscape(unsafe.Pointer(&k)), m.seed)
+	var k uint32
+	var hash uintptr
+	if goexperiment.RevertCopyHashKeys {
+		hash = typ.Hasher(abi.NoEscape(unsafe.Pointer(&key)), m.seed)
+	} else {
+		k = key
+		hash = typ.Hasher(abi.NoEscape(unsafe.Pointer(&k)), m.seed)
+	}
 
 	// Select table.
 	idx := m.directoryIndex(hash)
@@ -117,8 +124,14 @@ func runtime_mapaccess2_fast32(typ *abi.SwissMapType, m *Map, key uint32) (unsaf
 		return unsafe.Pointer(&zeroVal[0]), false
 	}
 
-	k := key
-	hash := typ.Hasher(abi.NoEscape(unsafe.Pointer(&k)), m.seed)
+	var k uint32
+	var hash uintptr
+	if goexperiment.RevertCopyHashKeys {
+		hash = typ.Hasher(abi.NoEscape(unsafe.Pointer(&key)), m.seed)
+	} else {
+		k = key
+		hash = typ.Hasher(abi.NoEscape(unsafe.Pointer(&k)), m.seed)
+	}
 
 	// Select table.
 	idx := m.directoryIndex(hash)
@@ -205,8 +218,14 @@ func runtime_mapassign_fast32(typ *abi.SwissMapType, m *Map, key uint32) unsafe.
 		fatal("concurrent map writes")
 	}
 
-	k := key
-	hash := typ.Hasher(abi.NoEscape(unsafe.Pointer(&k)), m.seed)
+	var k uint32
+	var hash uintptr
+	if goexperiment.RevertCopyHashKeys {
+		hash = typ.Hasher(abi.NoEscape(unsafe.Pointer(&key)), m.seed)
+	} else {
+		k = key
+		hash = typ.Hasher(abi.NoEscape(unsafe.Pointer(&k)), m.seed)
+	}
 
 	// Set writing after calling Hasher, since Hasher may panic, in which
 	// case we have not actually done a write.
@@ -339,8 +358,14 @@ func runtime_mapassign_fast32ptr(typ *abi.SwissMapType, m *Map, key unsafe.Point
 		fatal("concurrent map writes")
 	}
 
-	k := key
-	hash := typ.Hasher(abi.NoEscape(unsafe.Pointer(&k)), m.seed)
+	var k unsafe.Pointer
+	var hash uintptr
+	if goexperiment.RevertCopyHashKeys {
+		hash = typ.Hasher(abi.NoEscape(unsafe.Pointer(&key)), m.seed)
+	} else {
+		k = key
+		hash = typ.Hasher(abi.NoEscape(unsafe.Pointer(&k)), m.seed)
+	}
 
 	// Set writing after calling Hasher, since Hasher may panic, in which
 	// case we have not actually done a write.
diff --git a/src/internal/runtime/maps/runtime_fast64_swiss.go b/src/internal/runtime/maps/runtime_fast64_swiss.go
index 6bc6b2f0b..9cd5d1ca6 100644
--- a/src/internal/runtime/maps/runtime_fast64_swiss.go
+++ b/src/internal/runtime/maps/runtime_fast64_swiss.go
@@ -8,6 +8,7 @@ package maps
 
 import (
 	"internal/abi"
+	"internal/goexperiment"
 	"internal/race"
 	"internal/runtime/sys"
 	"unsafe"
@@ -48,8 +49,14 @@ func runtime_mapaccess1_fast64(typ *abi.SwissMapType, m *Map, key uint64) unsafe
 		return unsafe.Pointer(&zeroVal[0])
 	}
 
-	k := key
-	hash := typ.Hasher(abi.NoEscape(unsafe.Pointer(&k)), m.seed)
+	var k uint64
+	var hash uintptr
+	if goexperiment.RevertCopyHashKeys {
+		hash = typ.Hasher(abi.NoEscape(unsafe.Pointer(&key)), m.seed)
+	} else {
+		k = key
+		hash = typ.Hasher(abi.NoEscape(unsafe.Pointer(&k)), m.seed)
+	}
 
 	// Select table.
 	idx := m.directoryIndex(hash)
@@ -117,8 +124,14 @@ func runtime_mapaccess2_fast64(typ *abi.SwissMapType, m *Map, key uint64) (unsaf
 		return unsafe.Pointer(&zeroVal[0]), false
 	}
 
-	k := key
-	hash := typ.Hasher(abi.NoEscape(unsafe.Pointer(&k)), m.seed)
+	var k uint64
+	var hash uintptr
+	if goexperiment.RevertCopyHashKeys {
+		hash = typ.Hasher(abi.NoEscape(unsafe.Pointer(&key)), m.seed)
+	} else {
+		k = key
+		hash = typ.Hasher(abi.NoEscape(unsafe.Pointer(&k)), m.seed)
+	}
 
 	// Select table.
 	idx := m.directoryIndex(hash)
@@ -205,8 +218,14 @@ func runtime_mapassign_fast64(typ *abi.SwissMapType, m *Map, key uint64) unsafe.
 		fatal("concurrent map writes")
 	}
 
-	k := key
-	hash := typ.Hasher(abi.NoEscape(unsafe.Pointer(&k)), m.seed)
+	var k uint64
+	var hash uintptr
+	if goexperiment.RevertCopyHashKeys {
+		hash = typ.Hasher(abi.NoEscape(unsafe.Pointer(&key)), m.seed)
+	} else {
+		k = key
+		hash = typ.Hasher(abi.NoEscape(unsafe.Pointer(&k)), m.seed)
+	}
 
 	// Set writing after calling Hasher, since Hasher may panic, in which
 	// case we have not actually done a write.
@@ -377,8 +396,14 @@ func runtime_mapassign_fast64ptr(typ *abi.SwissMapType, m *Map, key unsafe.Point
 		fatal("concurrent map writes")
 	}
 
-	k := key
-	hash := typ.Hasher(abi.NoEscape(unsafe.Pointer(&k)), m.seed)
+	var k unsafe.Pointer
+	var hash uintptr
+	if goexperiment.RevertCopyHashKeys {
+		hash = typ.Hasher(abi.NoEscape(unsafe.Pointer(&key)), m.seed)
+	} else {
+		k = key
+		hash = typ.Hasher(abi.NoEscape(unsafe.Pointer(&k)), m.seed)
+	}
 
 	// Set writing after calling Hasher, since Hasher may panic, in which
 	// case we have not actually done a write.
diff --git a/src/internal/runtime/maps/runtime_faststr_swiss.go b/src/internal/runtime/maps/runtime_faststr_swiss.go
index 077c05ae8..f4c4de6c8 100644
--- a/src/internal/runtime/maps/runtime_faststr_swiss.go
+++ b/src/internal/runtime/maps/runtime_faststr_swiss.go
@@ -9,6 +9,7 @@ package maps
 import (
 	"internal/abi"
 	"internal/goarch"
+	"internal/goexperiment"
 	"internal/race"
 	"internal/runtime/sys"
 	"unsafe"
@@ -56,7 +57,14 @@ func (m *Map) getWithoutKeySmallFastStr(typ *abi.SwissMapType, key string) unsaf
 
 dohash:
 	// This path will cost 1 hash and 1+ε comparisons.
-	hash := typ.Hasher(abi.NoEscape(unsafe.Pointer(&key)), m.seed)
+	var k string
+	var hash uintptr
+	if goexperiment.RevertCopyHashKeys {
+		hash = typ.Hasher(abi.NoEscape(unsafe.Pointer(&key)), m.seed)
+	} else {
+		k = key
+		hash = typ.Hasher(abi.NoEscape(unsafe.Pointer(&k)), m.seed)
+	}
 	h2 := uint8(h2(hash))
 	ctrls = *g.ctrls()
 	slotKey = g.key(typ, 0)
@@ -124,8 +132,14 @@ func runtime_mapaccess1_faststr(typ *abi.SwissMapType, m *Map, key string) unsaf
 		return elem
 	}
 
-	k := key
-	hash := typ.Hasher(abi.NoEscape(unsafe.Pointer(&k)), m.seed)
+	var k string
+	var hash uintptr
+	if goexperiment.RevertCopyHashKeys {
+		hash = typ.Hasher(abi.NoEscape(unsafe.Pointer(&key)), m.seed)
+	} else {
+		k = key
+		hash = typ.Hasher(abi.NoEscape(unsafe.Pointer(&k)), m.seed)
+	}
 
 	// Select table.
 	idx := m.directoryIndex(hash)
@@ -183,8 +197,14 @@ func runtime_mapaccess2_faststr(typ *abi.SwissMapType, m *Map, key string) (unsa
 		return elem, true
 	}
 
-	k := key
-	hash := typ.Hasher(abi.NoEscape(unsafe.Pointer(&k)), m.seed)
+	var k string
+	var hash uintptr
+	if goexperiment.RevertCopyHashKeys {
+		hash = typ.Hasher(abi.NoEscape(unsafe.Pointer(&key)), m.seed)
+	} else {
+		k = key
+		hash = typ.Hasher(abi.NoEscape(unsafe.Pointer(&k)), m.seed)
+	}
 
 	// Select table.
 	idx := m.directoryIndex(hash)
@@ -273,8 +293,14 @@ func runtime_mapassign_faststr(typ *abi.SwissMapType, m *Map, key string) unsafe
 		fatal("concurrent map writes")
 	}
 
-	k := key
-	hash := typ.Hasher(abi.NoEscape(unsafe.Pointer(&k)), m.seed)
+	var k string
+	var hash uintptr
+	if goexperiment.RevertCopyHashKeys {
+		hash = typ.Hasher(abi.NoEscape(unsafe.Pointer(&key)), m.seed)
+	} else {
+		k = key
+		hash = typ.Hasher(abi.NoEscape(unsafe.Pointer(&k)), m.seed)
+	}
 
 	// Set writing after calling Hasher, since Hasher may panic, in which
 	// case we have not actually done a write.
-- 
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