From: Keith Randall <khr@golang.org>
Date: Mon, 9 Jan 2023 22:29:49 +0000 (-0800)
Subject: cmd/compile: share compiler allocations of similar shapes
X-Git-Tag: go1.21rc1~1553
X-Git-Url: http://www.git.cypherpunks.su/?a=commitdiff_plain;h=0e42632301f17ae384e2cc1edb273860ed8f9fac;p=gostls13.git

cmd/compile: share compiler allocations of similar shapes

Use the same allocator for, e.g., []int32 and []int8. Anything with
similar base shapes and be coerced into a single allocator, which helps
reuse memory more often.

There is not much unsafe in the compiler currently. This adds quite a bit,
joining cmd/compiler/internal/base/mapfile_mmap.go and some unsafe.Sizeof calls.

Change-Id: I95d6d6e47c42b9f0a45f3556f4d7605735e65d99
Reviewed-on: https://go-review.googlesource.com/c/go/+/461084
Reviewed-by: Michael Pratt <mpratt@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
Reviewed-by: David Chase <drchase@google.com>
Run-TryBot: Keith Randall <khr@golang.org>
---

diff --git a/src/cmd/compile/internal/ssa/_gen/allocators.go b/src/cmd/compile/internal/ssa/_gen/allocators.go
index 48a2598d05..5c72fe8be1 100644
--- a/src/cmd/compile/internal/ssa/_gen/allocators.go
+++ b/src/cmd/compile/internal/ssa/_gen/allocators.go
@@ -23,6 +23,12 @@ type allocator struct {
 	maxLog   int    // log_2 of maximum allocation size
 }
 
+type derived struct {
+	name string // name for alloc/free functions
+	typ  string // the type they return/accept
+	base string // underlying allocator
+}
+
 func genAllocators() {
 	allocators := []allocator{
 		{
@@ -36,65 +42,15 @@ func genAllocators() {
 			maxLog:   32,
 		},
 		{
-			name:     "BlockSlice",
-			typ:      "[]*Block",
+			name:     "Int64Slice",
+			typ:      "[]int64",
 			capacity: "cap(%s)",
-			mak:      "make([]*Block, %s)",
-			resize:   "%s[:%s]",
-			clear:    "for i := range %[1]s {\n%[1]s[i] = nil\n}",
-			minLog:   5,
-			maxLog:   32,
-		},
-		{
-			name:     "BoolSlice",
-			typ:      "[]bool",
-			capacity: "cap(%s)",
-			mak:      "make([]bool, %s)",
-			resize:   "%s[:%s]",
-			clear:    "for i := range %[1]s {\n%[1]s[i] = false\n}",
-			minLog:   8,
-			maxLog:   32,
-		},
-		{
-			name:     "IntSlice",
-			typ:      "[]int",
-			capacity: "cap(%s)",
-			mak:      "make([]int, %s)",
+			mak:      "make([]int64, %s)",
 			resize:   "%s[:%s]",
 			clear:    "for i := range %[1]s {\n%[1]s[i] = 0\n}",
 			minLog:   5,
 			maxLog:   32,
 		},
-		{
-			name:     "Int32Slice",
-			typ:      "[]int32",
-			capacity: "cap(%s)",
-			mak:      "make([]int32, %s)",
-			resize:   "%s[:%s]",
-			clear:    "for i := range %[1]s {\n%[1]s[i] = 0\n}",
-			minLog:   6,
-			maxLog:   32,
-		},
-		{
-			name:     "Int8Slice",
-			typ:      "[]int8",
-			capacity: "cap(%s)",
-			mak:      "make([]int8, %s)",
-			resize:   "%s[:%s]",
-			clear:    "for i := range %[1]s {\n%[1]s[i] = 0\n}",
-			minLog:   8,
-			maxLog:   32,
-		},
-		{
-			name:     "IDSlice",
-			typ:      "[]ID",
-			capacity: "cap(%s)",
-			mak:      "make([]ID, %s)",
-			resize:   "%s[:%s]",
-			clear:    "for i := range %[1]s {\n%[1]s[i] = 0\n}",
-			minLog:   6,
-			maxLog:   32,
-		},
 		{
 			name:     "SparseSet",
 			typ:      "*sparseSet",
@@ -126,6 +82,38 @@ func genAllocators() {
 			maxLog:   32,
 		},
 	}
+	deriveds := []derived{
+		{
+			name: "BlockSlice",
+			typ:  "[]*Block",
+			base: "ValueSlice",
+		},
+		{
+			name: "IntSlice",
+			typ:  "[]int",
+			base: "Int64Slice",
+		},
+		{
+			name: "Int32Slice",
+			typ:  "[]int32",
+			base: "Int64Slice",
+		},
+		{
+			name: "Int8Slice",
+			typ:  "[]int8",
+			base: "Int64Slice",
+		},
+		{
+			name: "BoolSlice",
+			typ:  "[]bool",
+			base: "Int64Slice",
+		},
+		{
+			name: "IDSlice",
+			typ:  "[]ID",
+			base: "Int64Slice",
+		},
+	}
 
 	w := new(bytes.Buffer)
 	fmt.Fprintf(w, "// Code generated from _gen/allocators.go using 'go generate'; DO NOT EDIT.\n")
@@ -133,12 +121,22 @@ func genAllocators() {
 	fmt.Fprintln(w, "package ssa")
 
 	fmt.Fprintln(w, "import (")
+	fmt.Fprintln(w, "\"internal/unsafeheader\"")
 	fmt.Fprintln(w, "\"math/bits\"")
 	fmt.Fprintln(w, "\"sync\"")
+	fmt.Fprintln(w, "\"unsafe\"")
 	fmt.Fprintln(w, ")")
 	for _, a := range allocators {
 		genAllocator(w, a)
 	}
+	for _, d := range deriveds {
+		for _, base := range allocators {
+			if base.name == d.base {
+				genDerived(w, d, base)
+				break
+			}
+		}
+	}
 	// gofmt result
 	b := w.Bytes()
 	var err error
@@ -196,3 +194,32 @@ func genAllocator(w io.Writer, a allocator) {
 	}
 	fmt.Fprintf(w, "}\n")
 }
+func genDerived(w io.Writer, d derived, base allocator) {
+	fmt.Fprintf(w, "func (c *Cache) alloc%s(n int) %s {\n", d.name, d.typ)
+	if d.typ[:2] != "[]" || base.typ[:2] != "[]" {
+		panic(fmt.Sprintf("bad derived types: %s %s", d.typ, base.typ))
+	}
+	fmt.Fprintf(w, "var base %s\n", base.typ[2:])
+	fmt.Fprintf(w, "var derived %s\n", d.typ[2:])
+	fmt.Fprintf(w, "if unsafe.Sizeof(base)%%unsafe.Sizeof(derived) != 0 { panic(\"bad\") }\n")
+	fmt.Fprintf(w, "scale := unsafe.Sizeof(base)/unsafe.Sizeof(derived)\n")
+	fmt.Fprintf(w, "b := c.alloc%s(int((uintptr(n)+scale-1)/scale))\n", base.name)
+	fmt.Fprintf(w, "s := unsafeheader.Slice {\n")
+	fmt.Fprintf(w, "  Data: unsafe.Pointer(&b[0]),\n")
+	fmt.Fprintf(w, "  Len: n,\n")
+	fmt.Fprintf(w, "  Cap: cap(b)*int(scale),\n")
+	fmt.Fprintf(w, "  }\n")
+	fmt.Fprintf(w, "return *(*%s)(unsafe.Pointer(&s))\n", d.typ)
+	fmt.Fprintf(w, "}\n")
+	fmt.Fprintf(w, "func (c *Cache) free%s(s %s) {\n", d.name, d.typ)
+	fmt.Fprintf(w, "var base %s\n", base.typ[2:])
+	fmt.Fprintf(w, "var derived %s\n", d.typ[2:])
+	fmt.Fprintf(w, "scale := unsafe.Sizeof(base)/unsafe.Sizeof(derived)\n")
+	fmt.Fprintf(w, "b := unsafeheader.Slice {\n")
+	fmt.Fprintf(w, "  Data: unsafe.Pointer(&s[0]),\n")
+	fmt.Fprintf(w, "  Len: int((uintptr(len(s))+scale-1)/scale),\n")
+	fmt.Fprintf(w, "  Cap: int((uintptr(cap(s))+scale-1)/scale),\n")
+	fmt.Fprintf(w, "  }\n")
+	fmt.Fprintf(w, "c.free%s(*(*%s)(unsafe.Pointer(&b)))\n", base.name, base.typ)
+	fmt.Fprintf(w, "}\n")
+}
diff --git a/src/cmd/compile/internal/ssa/allocators.go b/src/cmd/compile/internal/ssa/allocators.go
index d782464c02..ff70795f82 100644
--- a/src/cmd/compile/internal/ssa/allocators.go
+++ b/src/cmd/compile/internal/ssa/allocators.go
@@ -3,8 +3,10 @@
 package ssa
 
 import (
+	"internal/unsafeheader"
 	"math/bits"
 	"sync"
+	"unsafe"
 )
 
 var poolFreeValueSlice [27]sync.Pool
@@ -45,232 +47,42 @@ func (c *Cache) freeValueSlice(s []*Value) {
 	poolFreeValueSlice[b-5].Put(sp)
 }
 
-var poolFreeBlockSlice [27]sync.Pool
+var poolFreeInt64Slice [27]sync.Pool
 
-func (c *Cache) allocBlockSlice(n int) []*Block {
-	var s []*Block
+func (c *Cache) allocInt64Slice(n int) []int64 {
+	var s []int64
 	n2 := n
 	if n2 < 32 {
 		n2 = 32
 	}
 	b := bits.Len(uint(n2 - 1))
-	v := poolFreeBlockSlice[b-5].Get()
-	if v == nil {
-		s = make([]*Block, 1<<b)
-	} else {
-		sp := v.(*[]*Block)
-		s = *sp
-		*sp = nil
-		c.hdrBlockSlice = append(c.hdrBlockSlice, sp)
-	}
-	s = s[:n]
-	return s
-}
-func (c *Cache) freeBlockSlice(s []*Block) {
-	for i := range s {
-		s[i] = nil
-	}
-	b := bits.Len(uint(cap(s)) - 1)
-	var sp *[]*Block
-	if len(c.hdrBlockSlice) == 0 {
-		sp = new([]*Block)
-	} else {
-		sp = c.hdrBlockSlice[len(c.hdrBlockSlice)-1]
-		c.hdrBlockSlice[len(c.hdrBlockSlice)-1] = nil
-		c.hdrBlockSlice = c.hdrBlockSlice[:len(c.hdrBlockSlice)-1]
-	}
-	*sp = s
-	poolFreeBlockSlice[b-5].Put(sp)
-}
-
-var poolFreeBoolSlice [24]sync.Pool
-
-func (c *Cache) allocBoolSlice(n int) []bool {
-	var s []bool
-	n2 := n
-	if n2 < 256 {
-		n2 = 256
-	}
-	b := bits.Len(uint(n2 - 1))
-	v := poolFreeBoolSlice[b-8].Get()
-	if v == nil {
-		s = make([]bool, 1<<b)
-	} else {
-		sp := v.(*[]bool)
-		s = *sp
-		*sp = nil
-		c.hdrBoolSlice = append(c.hdrBoolSlice, sp)
-	}
-	s = s[:n]
-	return s
-}
-func (c *Cache) freeBoolSlice(s []bool) {
-	for i := range s {
-		s[i] = false
-	}
-	b := bits.Len(uint(cap(s)) - 1)
-	var sp *[]bool
-	if len(c.hdrBoolSlice) == 0 {
-		sp = new([]bool)
-	} else {
-		sp = c.hdrBoolSlice[len(c.hdrBoolSlice)-1]
-		c.hdrBoolSlice[len(c.hdrBoolSlice)-1] = nil
-		c.hdrBoolSlice = c.hdrBoolSlice[:len(c.hdrBoolSlice)-1]
-	}
-	*sp = s
-	poolFreeBoolSlice[b-8].Put(sp)
-}
-
-var poolFreeIntSlice [27]sync.Pool
-
-func (c *Cache) allocIntSlice(n int) []int {
-	var s []int
-	n2 := n
-	if n2 < 32 {
-		n2 = 32
-	}
-	b := bits.Len(uint(n2 - 1))
-	v := poolFreeIntSlice[b-5].Get()
-	if v == nil {
-		s = make([]int, 1<<b)
-	} else {
-		sp := v.(*[]int)
-		s = *sp
-		*sp = nil
-		c.hdrIntSlice = append(c.hdrIntSlice, sp)
-	}
-	s = s[:n]
-	return s
-}
-func (c *Cache) freeIntSlice(s []int) {
-	for i := range s {
-		s[i] = 0
-	}
-	b := bits.Len(uint(cap(s)) - 1)
-	var sp *[]int
-	if len(c.hdrIntSlice) == 0 {
-		sp = new([]int)
-	} else {
-		sp = c.hdrIntSlice[len(c.hdrIntSlice)-1]
-		c.hdrIntSlice[len(c.hdrIntSlice)-1] = nil
-		c.hdrIntSlice = c.hdrIntSlice[:len(c.hdrIntSlice)-1]
-	}
-	*sp = s
-	poolFreeIntSlice[b-5].Put(sp)
-}
-
-var poolFreeInt32Slice [26]sync.Pool
-
-func (c *Cache) allocInt32Slice(n int) []int32 {
-	var s []int32
-	n2 := n
-	if n2 < 64 {
-		n2 = 64
-	}
-	b := bits.Len(uint(n2 - 1))
-	v := poolFreeInt32Slice[b-6].Get()
+	v := poolFreeInt64Slice[b-5].Get()
 	if v == nil {
-		s = make([]int32, 1<<b)
+		s = make([]int64, 1<<b)
 	} else {
-		sp := v.(*[]int32)
+		sp := v.(*[]int64)
 		s = *sp
 		*sp = nil
-		c.hdrInt32Slice = append(c.hdrInt32Slice, sp)
+		c.hdrInt64Slice = append(c.hdrInt64Slice, sp)
 	}
 	s = s[:n]
 	return s
 }
-func (c *Cache) freeInt32Slice(s []int32) {
-	for i := range s {
-		s[i] = 0
-	}
-	b := bits.Len(uint(cap(s)) - 1)
-	var sp *[]int32
-	if len(c.hdrInt32Slice) == 0 {
-		sp = new([]int32)
-	} else {
-		sp = c.hdrInt32Slice[len(c.hdrInt32Slice)-1]
-		c.hdrInt32Slice[len(c.hdrInt32Slice)-1] = nil
-		c.hdrInt32Slice = c.hdrInt32Slice[:len(c.hdrInt32Slice)-1]
-	}
-	*sp = s
-	poolFreeInt32Slice[b-6].Put(sp)
-}
-
-var poolFreeInt8Slice [24]sync.Pool
-
-func (c *Cache) allocInt8Slice(n int) []int8 {
-	var s []int8
-	n2 := n
-	if n2 < 256 {
-		n2 = 256
-	}
-	b := bits.Len(uint(n2 - 1))
-	v := poolFreeInt8Slice[b-8].Get()
-	if v == nil {
-		s = make([]int8, 1<<b)
-	} else {
-		sp := v.(*[]int8)
-		s = *sp
-		*sp = nil
-		c.hdrInt8Slice = append(c.hdrInt8Slice, sp)
-	}
-	s = s[:n]
-	return s
-}
-func (c *Cache) freeInt8Slice(s []int8) {
+func (c *Cache) freeInt64Slice(s []int64) {
 	for i := range s {
 		s[i] = 0
 	}
 	b := bits.Len(uint(cap(s)) - 1)
-	var sp *[]int8
-	if len(c.hdrInt8Slice) == 0 {
-		sp = new([]int8)
+	var sp *[]int64
+	if len(c.hdrInt64Slice) == 0 {
+		sp = new([]int64)
 	} else {
-		sp = c.hdrInt8Slice[len(c.hdrInt8Slice)-1]
-		c.hdrInt8Slice[len(c.hdrInt8Slice)-1] = nil
-		c.hdrInt8Slice = c.hdrInt8Slice[:len(c.hdrInt8Slice)-1]
+		sp = c.hdrInt64Slice[len(c.hdrInt64Slice)-1]
+		c.hdrInt64Slice[len(c.hdrInt64Slice)-1] = nil
+		c.hdrInt64Slice = c.hdrInt64Slice[:len(c.hdrInt64Slice)-1]
 	}
 	*sp = s
-	poolFreeInt8Slice[b-8].Put(sp)
-}
-
-var poolFreeIDSlice [26]sync.Pool
-
-func (c *Cache) allocIDSlice(n int) []ID {
-	var s []ID
-	n2 := n
-	if n2 < 64 {
-		n2 = 64
-	}
-	b := bits.Len(uint(n2 - 1))
-	v := poolFreeIDSlice[b-6].Get()
-	if v == nil {
-		s = make([]ID, 1<<b)
-	} else {
-		sp := v.(*[]ID)
-		s = *sp
-		*sp = nil
-		c.hdrIDSlice = append(c.hdrIDSlice, sp)
-	}
-	s = s[:n]
-	return s
-}
-func (c *Cache) freeIDSlice(s []ID) {
-	for i := range s {
-		s[i] = 0
-	}
-	b := bits.Len(uint(cap(s)) - 1)
-	var sp *[]ID
-	if len(c.hdrIDSlice) == 0 {
-		sp = new([]ID)
-	} else {
-		sp = c.hdrIDSlice[len(c.hdrIDSlice)-1]
-		c.hdrIDSlice[len(c.hdrIDSlice)-1] = nil
-		c.hdrIDSlice = c.hdrIDSlice[:len(c.hdrIDSlice)-1]
-	}
-	*sp = s
-	poolFreeIDSlice[b-6].Put(sp)
+	poolFreeInt64Slice[b-5].Put(sp)
 }
 
 var poolFreeSparseSet [27]sync.Pool
@@ -341,3 +153,159 @@ func (c *Cache) freeSparseMapPos(s *sparseMapPos) {
 	b := bits.Len(uint(s.cap()) - 1)
 	poolFreeSparseMapPos[b-5].Put(s)
 }
+func (c *Cache) allocBlockSlice(n int) []*Block {
+	var base *Value
+	var derived *Block
+	if unsafe.Sizeof(base)%unsafe.Sizeof(derived) != 0 {
+		panic("bad")
+	}
+	scale := unsafe.Sizeof(base) / unsafe.Sizeof(derived)
+	b := c.allocValueSlice(int((uintptr(n) + scale - 1) / scale))
+	s := unsafeheader.Slice{
+		Data: unsafe.Pointer(&b[0]),
+		Len:  n,
+		Cap:  cap(b) * int(scale),
+	}
+	return *(*[]*Block)(unsafe.Pointer(&s))
+}
+func (c *Cache) freeBlockSlice(s []*Block) {
+	var base *Value
+	var derived *Block
+	scale := unsafe.Sizeof(base) / unsafe.Sizeof(derived)
+	b := unsafeheader.Slice{
+		Data: unsafe.Pointer(&s[0]),
+		Len:  int((uintptr(len(s)) + scale - 1) / scale),
+		Cap:  int((uintptr(cap(s)) + scale - 1) / scale),
+	}
+	c.freeValueSlice(*(*[]*Value)(unsafe.Pointer(&b)))
+}
+func (c *Cache) allocIntSlice(n int) []int {
+	var base int64
+	var derived int
+	if unsafe.Sizeof(base)%unsafe.Sizeof(derived) != 0 {
+		panic("bad")
+	}
+	scale := unsafe.Sizeof(base) / unsafe.Sizeof(derived)
+	b := c.allocInt64Slice(int((uintptr(n) + scale - 1) / scale))
+	s := unsafeheader.Slice{
+		Data: unsafe.Pointer(&b[0]),
+		Len:  n,
+		Cap:  cap(b) * int(scale),
+	}
+	return *(*[]int)(unsafe.Pointer(&s))
+}
+func (c *Cache) freeIntSlice(s []int) {
+	var base int64
+	var derived int
+	scale := unsafe.Sizeof(base) / unsafe.Sizeof(derived)
+	b := unsafeheader.Slice{
+		Data: unsafe.Pointer(&s[0]),
+		Len:  int((uintptr(len(s)) + scale - 1) / scale),
+		Cap:  int((uintptr(cap(s)) + scale - 1) / scale),
+	}
+	c.freeInt64Slice(*(*[]int64)(unsafe.Pointer(&b)))
+}
+func (c *Cache) allocInt32Slice(n int) []int32 {
+	var base int64
+	var derived int32
+	if unsafe.Sizeof(base)%unsafe.Sizeof(derived) != 0 {
+		panic("bad")
+	}
+	scale := unsafe.Sizeof(base) / unsafe.Sizeof(derived)
+	b := c.allocInt64Slice(int((uintptr(n) + scale - 1) / scale))
+	s := unsafeheader.Slice{
+		Data: unsafe.Pointer(&b[0]),
+		Len:  n,
+		Cap:  cap(b) * int(scale),
+	}
+	return *(*[]int32)(unsafe.Pointer(&s))
+}
+func (c *Cache) freeInt32Slice(s []int32) {
+	var base int64
+	var derived int32
+	scale := unsafe.Sizeof(base) / unsafe.Sizeof(derived)
+	b := unsafeheader.Slice{
+		Data: unsafe.Pointer(&s[0]),
+		Len:  int((uintptr(len(s)) + scale - 1) / scale),
+		Cap:  int((uintptr(cap(s)) + scale - 1) / scale),
+	}
+	c.freeInt64Slice(*(*[]int64)(unsafe.Pointer(&b)))
+}
+func (c *Cache) allocInt8Slice(n int) []int8 {
+	var base int64
+	var derived int8
+	if unsafe.Sizeof(base)%unsafe.Sizeof(derived) != 0 {
+		panic("bad")
+	}
+	scale := unsafe.Sizeof(base) / unsafe.Sizeof(derived)
+	b := c.allocInt64Slice(int((uintptr(n) + scale - 1) / scale))
+	s := unsafeheader.Slice{
+		Data: unsafe.Pointer(&b[0]),
+		Len:  n,
+		Cap:  cap(b) * int(scale),
+	}
+	return *(*[]int8)(unsafe.Pointer(&s))
+}
+func (c *Cache) freeInt8Slice(s []int8) {
+	var base int64
+	var derived int8
+	scale := unsafe.Sizeof(base) / unsafe.Sizeof(derived)
+	b := unsafeheader.Slice{
+		Data: unsafe.Pointer(&s[0]),
+		Len:  int((uintptr(len(s)) + scale - 1) / scale),
+		Cap:  int((uintptr(cap(s)) + scale - 1) / scale),
+	}
+	c.freeInt64Slice(*(*[]int64)(unsafe.Pointer(&b)))
+}
+func (c *Cache) allocBoolSlice(n int) []bool {
+	var base int64
+	var derived bool
+	if unsafe.Sizeof(base)%unsafe.Sizeof(derived) != 0 {
+		panic("bad")
+	}
+	scale := unsafe.Sizeof(base) / unsafe.Sizeof(derived)
+	b := c.allocInt64Slice(int((uintptr(n) + scale - 1) / scale))
+	s := unsafeheader.Slice{
+		Data: unsafe.Pointer(&b[0]),
+		Len:  n,
+		Cap:  cap(b) * int(scale),
+	}
+	return *(*[]bool)(unsafe.Pointer(&s))
+}
+func (c *Cache) freeBoolSlice(s []bool) {
+	var base int64
+	var derived bool
+	scale := unsafe.Sizeof(base) / unsafe.Sizeof(derived)
+	b := unsafeheader.Slice{
+		Data: unsafe.Pointer(&s[0]),
+		Len:  int((uintptr(len(s)) + scale - 1) / scale),
+		Cap:  int((uintptr(cap(s)) + scale - 1) / scale),
+	}
+	c.freeInt64Slice(*(*[]int64)(unsafe.Pointer(&b)))
+}
+func (c *Cache) allocIDSlice(n int) []ID {
+	var base int64
+	var derived ID
+	if unsafe.Sizeof(base)%unsafe.Sizeof(derived) != 0 {
+		panic("bad")
+	}
+	scale := unsafe.Sizeof(base) / unsafe.Sizeof(derived)
+	b := c.allocInt64Slice(int((uintptr(n) + scale - 1) / scale))
+	s := unsafeheader.Slice{
+		Data: unsafe.Pointer(&b[0]),
+		Len:  n,
+		Cap:  cap(b) * int(scale),
+	}
+	return *(*[]ID)(unsafe.Pointer(&s))
+}
+func (c *Cache) freeIDSlice(s []ID) {
+	var base int64
+	var derived ID
+	scale := unsafe.Sizeof(base) / unsafe.Sizeof(derived)
+	b := unsafeheader.Slice{
+		Data: unsafe.Pointer(&s[0]),
+		Len:  int((uintptr(len(s)) + scale - 1) / scale),
+		Cap:  int((uintptr(cap(s)) + scale - 1) / scale),
+	}
+	c.freeInt64Slice(*(*[]int64)(unsafe.Pointer(&b)))
+}
diff --git a/src/cmd/compile/internal/ssa/cache.go b/src/cmd/compile/internal/ssa/cache.go
index dd17f5fa15..ba36edd390 100644
--- a/src/cmd/compile/internal/ssa/cache.go
+++ b/src/cmd/compile/internal/ssa/cache.go
@@ -34,12 +34,7 @@ type Cache struct {
 	// Free "headers" for use by the allocators in allocators.go.
 	// Used to put slices in sync.Pools without allocation.
 	hdrValueSlice []*[]*Value
-	hdrBlockSlice []*[]*Block
-	hdrBoolSlice  []*[]bool
-	hdrIntSlice   []*[]int
-	hdrInt32Slice []*[]int32
-	hdrInt8Slice  []*[]int8
-	hdrIDSlice    []*[]ID
+	hdrInt64Slice []*[]int64
 }
 
 func (c *Cache) Reset() {