cmd/compile: add cache of sizeable objects so they can be reused

We kind of have this mechanism already, just normalizing it and
using it in a bunch of places. Previously a bunch of places cached
slices only for the duration of a single function compilation. Now
we can reuse slices across a whole compiler run.

Use a sync.Pool of powers-of-two sizes. This lets us use not
too much memory, and avoid holding onto memory we're no longer
using when a GC happens.

There's a few different types we need, so generate the code for it.
Generics would be useful here, but we can't use generics in the
compiler because of bootstrapping.

Change-Id: I6cf37e7b7b2e802882aaa723a0b29770511ccd82
Reviewed-on: https://go-review.googlesource.com/c/go/+/444820
Run-TryBot: Keith Randall <khr@golang.org>
Reviewed-by: Heschi Kreinick <heschi@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
Reviewed-by: David Chase <drchase@google.com>

src/cmd/compile/internal/ssa/_gen/allocators.go

@@ -0,0 +1,198 @@
+package main
+
+// TODO: should we share backing storage for similarly-shaped types?
+// e.g. []*Value and []*Block, or even []int32 and []bool.
+
+import (
+	"bytes"
+	"fmt"
+	"go/format"
+	"io"
+	"log"
+	"os"
+)
+
+type allocator struct {
+	name     string // name for alloc/free functions
+	typ      string // the type they return/accept
+	mak      string // code to make a new object (takes power-of-2 size as fmt arg)
+	capacity string // code to calculate the capacity of an object. Should always report a power of 2.
+	resize   string // code to shrink to sub-power-of-two size (takes size as fmt arg)
+	clear    string // code for clearing object before putting it on the free list
+	minLog   int    // log_2 of minimum allocation size
+	maxLog   int    // log_2 of maximum allocation size
+}
+
+func genAllocators() {
+	allocators := []allocator{
+		{
+			name:     "ValueSlice",
+			typ:      "[]*Value",
+			capacity: "cap(%s)",
+			mak:      "make([]*Value, %s)",
+			resize:   "%s[:%s]",
+			clear:    "for i := range %[1]s {\n%[1]s[i] = nil\n}",
+			minLog:   5,
+			maxLog:   32,
+		},
+		{
+			name:     "BlockSlice",
+			typ:      "[]*Block",
+			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)",
+			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",
+			capacity: "%s.cap()",
+			mak:      "newSparseSet(%s)",
+			resize:   "", // larger-sized sparse sets are ok
+			clear:    "%s.clear()",
+			minLog:   5,
+			maxLog:   32,
+		},
+		{
+			name:     "SparseMap",
+			typ:      "*sparseMap",
+			capacity: "%s.cap()",
+			mak:      "newSparseMap(%s)",
+			resize:   "", // larger-sized sparse maps are ok
+			clear:    "%s.clear()",
+			minLog:   5,
+			maxLog:   32,
+		},
+		{
+			name:     "SparseMapPos",
+			typ:      "*sparseMapPos",
+			capacity: "%s.cap()",
+			mak:      "newSparseMapPos(%s)",
+			resize:   "", // larger-sized sparse maps are ok
+			clear:    "%s.clear()",
+			minLog:   5,
+			maxLog:   32,
+		},
+	}
+
+	w := new(bytes.Buffer)
+	fmt.Fprintf(w, "// Code generated from _gen/allocators.go; DO NOT EDIT.\n")
+	fmt.Fprintln(w)
+	fmt.Fprintln(w, "package ssa")
+
+	fmt.Fprintln(w, "import (")
+	fmt.Fprintln(w, "\"math/bits\"")
+	fmt.Fprintln(w, "\"sync\"")
+	fmt.Fprintln(w, ")")
+	for _, a := range allocators {
+		genAllocator(w, a)
+	}
+	// gofmt result
+	b := w.Bytes()
+	var err error
+	b, err = format.Source(b)
+	if err != nil {
+		fmt.Printf("%s\n", w.Bytes())
+		panic(err)
+	}
+
+	if err := os.WriteFile("../allocators.go", b, 0666); err != nil {
+		log.Fatalf("can't write output: %v\n", err)
+	}
+}
+func genAllocator(w io.Writer, a allocator) {
+	fmt.Fprintf(w, "var poolFree%s [%d]sync.Pool\n", a.name, a.maxLog-a.minLog)
+	fmt.Fprintf(w, "func (c *Cache) alloc%s(n int) %s {\n", a.name, a.typ)
+	fmt.Fprintf(w, "var s %s\n", a.typ)
+	fmt.Fprintf(w, "n2 := n\n")
+	fmt.Fprintf(w, "if n2 < %d { n2 = %d }\n", 1<<a.minLog, 1<<a.minLog)
+	fmt.Fprintf(w, "b := bits.Len(uint(n2-1))\n")
+	fmt.Fprintf(w, "v := poolFree%s[b-%d].Get()\n", a.name, a.minLog)
+	fmt.Fprintf(w, "if v == nil {\n")
+	fmt.Fprintf(w, "  s = %s\n", fmt.Sprintf(a.mak, "1<<b"))
+	fmt.Fprintf(w, "} else {\n")
+	if a.typ[0] == '*' {
+		fmt.Fprintf(w, "s = v.(%s)\n", a.typ)
+	} else {
+		fmt.Fprintf(w, "sp := v.(*%s)\n", a.typ)
+		fmt.Fprintf(w, "s = *sp\n")
+		fmt.Fprintf(w, "*sp = nil\n")
+		fmt.Fprintf(w, "c.hdr%s = append(c.hdr%s, sp)\n", a.name, a.name)
+	}
+	fmt.Fprintf(w, "}\n")
+	if a.resize != "" {
+		fmt.Fprintf(w, "s = %s\n", fmt.Sprintf(a.resize, "s", "n"))
+	}
+	fmt.Fprintf(w, "return s\n")
+	fmt.Fprintf(w, "}\n")
+	fmt.Fprintf(w, "func (c *Cache) free%s(s %s) {\n", a.name, a.typ)
+	fmt.Fprintf(w, "%s\n", fmt.Sprintf(a.clear, "s"))
+	fmt.Fprintf(w, "b := bits.Len(uint(%s) - 1)\n", fmt.Sprintf(a.capacity, "s"))
+	if a.typ[0] == '*' {
+		fmt.Fprintf(w, "poolFree%s[b-%d].Put(s)\n", a.name, a.minLog)
+	} else {
+		fmt.Fprintf(w, "var sp *%s\n", a.typ)
+		fmt.Fprintf(w, "if len(c.hdr%s) == 0 {\n", a.name)
+		fmt.Fprintf(w, "  sp = new(%s)\n", a.typ)
+		fmt.Fprintf(w, "} else {\n")
+		fmt.Fprintf(w, "  sp = c.hdr%s[len(c.hdr%s)-1]\n", a.name, a.name)
+		fmt.Fprintf(w, "  c.hdr%s[len(c.hdr%s)-1] = nil\n", a.name, a.name)
+		fmt.Fprintf(w, "  c.hdr%s = c.hdr%s[:len(c.hdr%s)-1]\n", a.name, a.name, a.name)
+		fmt.Fprintf(w, "}\n")
+		fmt.Fprintf(w, "*sp = s\n")
+		fmt.Fprintf(w, "poolFree%s[b-%d].Put(sp)\n", a.name, a.minLog)
+	}
+	fmt.Fprintf(w, "}\n")
+}

src/cmd/compile/internal/ssa/_gen/main.go

@@ -153,6 +153,7 @@ func main() {
 
 	tasks := []func(){
 		genOp,
+		genAllocators,
 	}
 	for _, a := range archs {
 		a := a // the funcs are ran concurrently at a later time

src/cmd/compile/internal/ssa/allocators.go

@@ -0,0 +1,343 @@
+// Code generated from _gen/allocators.go; DO NOT EDIT.
+
+package ssa
+
+import (
+	"math/bits"
+	"sync"
+)
+
+var poolFreeValueSlice [27]sync.Pool
+
+func (c *Cache) allocValueSlice(n int) []*Value {
+	var s []*Value
+	n2 := n
+	if n2 < 32 {
+		n2 = 32
+	}
+	b := bits.Len(uint(n2 - 1))
+	v := poolFreeValueSlice[b-5].Get()
+	if v == nil {
+		s = make([]*Value, 1<<b)
+	} else {
+		sp := v.(*[]*Value)
+		s = *sp
+		*sp = nil
+		c.hdrValueSlice = append(c.hdrValueSlice, sp)
+	}
+	s = s[:n]
+	return s
+}
+func (c *Cache) freeValueSlice(s []*Value) {
+	for i := range s {
+		s[i] = nil
+	}
+	b := bits.Len(uint(cap(s)) - 1)
+	var sp *[]*Value
+	if len(c.hdrValueSlice) == 0 {
+		sp = new([]*Value)
+	} else {
+		sp = c.hdrValueSlice[len(c.hdrValueSlice)-1]
+		c.hdrValueSlice[len(c.hdrValueSlice)-1] = nil
+		c.hdrValueSlice = c.hdrValueSlice[:len(c.hdrValueSlice)-1]
+	}
+	*sp = s
+	poolFreeValueSlice[b-5].Put(sp)
+}
+
+var poolFreeBlockSlice [27]sync.Pool
+
+func (c *Cache) allocBlockSlice(n int) []*Block {
+	var s []*Block
+	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()
+	if v == nil {
+		s = make([]int32, 1<<b)
+	} else {
+		sp := v.(*[]int32)
+		s = *sp
+		*sp = nil
+		c.hdrInt32Slice = append(c.hdrInt32Slice, 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) {
+	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)
+	} else {
+		sp = c.hdrInt8Slice[len(c.hdrInt8Slice)-1]
+		c.hdrInt8Slice[len(c.hdrInt8Slice)-1] = nil
+		c.hdrInt8Slice = c.hdrInt8Slice[:len(c.hdrInt8Slice)-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)
+}
+
+var poolFreeSparseSet [27]sync.Pool
+
+func (c *Cache) allocSparseSet(n int) *sparseSet {
+	var s *sparseSet
+	n2 := n
+	if n2 < 32 {
+		n2 = 32
+	}
+	b := bits.Len(uint(n2 - 1))
+	v := poolFreeSparseSet[b-5].Get()
+	if v == nil {
+		s = newSparseSet(1 << b)
+	} else {
+		s = v.(*sparseSet)
+	}
+	return s
+}
+func (c *Cache) freeSparseSet(s *sparseSet) {
+	s.clear()
+	b := bits.Len(uint(s.cap()) - 1)
+	poolFreeSparseSet[b-5].Put(s)
+}
+
+var poolFreeSparseMap [27]sync.Pool
+
+func (c *Cache) allocSparseMap(n int) *sparseMap {
+	var s *sparseMap
+	n2 := n
+	if n2 < 32 {
+		n2 = 32
+	}
+	b := bits.Len(uint(n2 - 1))
+	v := poolFreeSparseMap[b-5].Get()
+	if v == nil {
+		s = newSparseMap(1 << b)
+	} else {
+		s = v.(*sparseMap)
+	}
+	return s
+}
+func (c *Cache) freeSparseMap(s *sparseMap) {
+	s.clear()
+	b := bits.Len(uint(s.cap()) - 1)
+	poolFreeSparseMap[b-5].Put(s)
+}
+
+var poolFreeSparseMapPos [27]sync.Pool
+
+func (c *Cache) allocSparseMapPos(n int) *sparseMapPos {
+	var s *sparseMapPos
+	n2 := n
+	if n2 < 32 {
+		n2 = 32
+	}
+	b := bits.Len(uint(n2 - 1))
+	v := poolFreeSparseMapPos[b-5].Get()
+	if v == nil {
+		s = newSparseMapPos(1 << b)
+	} else {
+		s = v.(*sparseMapPos)
+	}
+	return s
+}
+func (c *Cache) freeSparseMapPos(s *sparseMapPos) {
+	s.clear()
+	b := bits.Len(uint(s.cap()) - 1)
+	poolFreeSparseMapPos[b-5].Put(s)
+}

src/cmd/compile/internal/ssa/cache.go

@@ -21,18 +21,8 @@ type Cache struct {
 	// See stackalloc.go's {new,put}StackAllocState.
 	stackAllocState *stackAllocState
 
-	domblockstore   []ID            // scratch space for computing dominators
+	scrPoset []*poset // scratch poset to be reused
-	scrSparseSet    []*sparseSet    // scratch sparse sets to be re-used.
+
-	scrSparseMap    []*sparseMap    // scratch sparse maps to be re-used.
-	scrSparseMapPos []*sparseMapPos // scratch sparse maps to be re-used.
-	scrPoset        []*poset        // scratch poset to be reused
-	// deadcode contains reusable slices specifically for the deadcode pass.
-	// It gets special treatment because of the frequency with which it is run.
-	deadcode struct {
-		liveOrderStmts []*Value
-		live           []bool
-		q              []*Value
-	}
 	// Reusable regalloc state.
 	regallocValues []valState
 
@@ -40,6 +30,16 @@ type Cache struct {
 	debugState       debugState
 
 	Liveness interface{} // *gc.livenessFuncCache
+
+	// 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
 }
 
 func (c *Cache) Reset() {
@@ -64,19 +64,4 @@ func (c *Cache) Reset() {
 	for i := range c.regallocValues {
 		c.regallocValues[i] = valState{}
 	}
-
-	// liveOrderStmts gets used multiple times during compilation of a function.
-	// We don't know where the high water mark was, so reslice to cap and search.
-	c.deadcode.liveOrderStmts = c.deadcode.liveOrderStmts[:cap(c.deadcode.liveOrderStmts)]
-	no := sort.Search(len(c.deadcode.liveOrderStmts), func(i int) bool { return c.deadcode.liveOrderStmts[i] == nil })
-	xo := c.deadcode.liveOrderStmts[:no]
-	for i := range xo {
-		xo[i] = nil
-	}
-	c.deadcode.q = c.deadcode.q[:cap(c.deadcode.q)]
-	nq := sort.Search(len(c.deadcode.q), func(i int) bool { return c.deadcode.q[i] == nil })
-	xq := c.deadcode.q[:nq]
-	for i := range xq {
-		xq[i] = nil
-	}
 }

src/cmd/compile/internal/ssa/critical.go

@@ -9,7 +9,8 @@ package ssa
 // Regalloc wants a critical-edge-free CFG so it can implement phi values.
 func critical(f *Func) {
 	// maps from phi arg ID to the new block created for that argument
-	blocks := make([]*Block, f.NumValues())
+	blocks := f.Cache.allocBlockSlice(f.NumValues())
+	defer f.Cache.freeBlockSlice(blocks)
 	// need to iterate over f.Blocks without range, as we might
 	// need to split critical edges on newly constructed blocks
 	for j := 0; j < len(f.Blocks); j++ {

src/cmd/compile/internal/ssa/cse.go

@@ -31,7 +31,9 @@ func cse(f *Func) {
 	// until it reaches a fixed point.
 
 	// Make initial coarse partitions by using a subset of the conditions above.
-	a := make([]*Value, 0, f.NumValues())
+	a := f.Cache.allocValueSlice(f.NumValues())
+	defer func() { f.Cache.freeValueSlice(a) }() // inside closure to use final value of a
+	a = a[:0]
 	if f.auxmap == nil {
 		f.auxmap = auxmap{}
 	}
@@ -49,7 +51,8 @@ func cse(f *Func) {
 	partition := partitionValues(a, f.auxmap)
 
 	// map from value id back to eqclass id
-	valueEqClass := make([]ID, f.NumValues())
+	valueEqClass := f.Cache.allocIDSlice(f.NumValues())
+	defer f.Cache.freeIDSlice(valueEqClass)
 	for _, b := range f.Blocks {
 		for _, v := range b.Values {
 			// Use negative equivalence class #s for unique values.
@@ -159,7 +162,8 @@ func cse(f *Func) {
 
 	// Compute substitutions we would like to do. We substitute v for w
 	// if v and w are in the same equivalence class and v dominates w.
-	rewrite := make([]*Value, f.NumValues())
+	rewrite := f.Cache.allocValueSlice(f.NumValues())
+	defer f.Cache.freeValueSlice(rewrite)
 	byDom := new(partitionByDom) // reusable partitionByDom to reduce allocs
 	for _, e := range partition {
 		byDom.a = e

src/cmd/compile/internal/ssa/deadcode.go

@@ -9,12 +9,12 @@ import (
 )
 
 // findlive returns the reachable blocks and live values in f.
-// The caller should call f.retDeadcodeLive(live) when it is done with it.
+// The caller should call f.Cache.freeBoolSlice(live) when it is done with it.
 func findlive(f *Func) (reachable []bool, live []bool) {
 	reachable = ReachableBlocks(f)
 	var order []*Value
 	live, order = liveValues(f, reachable)
-	f.retDeadcodeLiveOrderStmts(order)
+	f.Cache.freeValueSlice(order)
 	return
 }
 
@@ -51,21 +51,11 @@ func ReachableBlocks(f *Func) []bool {
 // to be statements in reversed data flow order.
 // The second result is used to help conserve statement boundaries for debugging.
 // reachable is a map from block ID to whether the block is reachable.
-// The caller should call f.retDeadcodeLive(live) and f.retDeadcodeLiveOrderStmts(liveOrderStmts)
+// The caller should call f.Cache.freeBoolSlice(live) and f.Cache.freeValueSlice(liveOrderStmts).
 // when they are done with the return values.
 func liveValues(f *Func, reachable []bool) (live []bool, liveOrderStmts []*Value) {
-	live = f.newDeadcodeLive()
+	live = f.Cache.allocBoolSlice(f.NumValues())
-	if cap(live) < f.NumValues() {
+	liveOrderStmts = f.Cache.allocValueSlice(f.NumValues())[:0]
-		live = make([]bool, f.NumValues())
-	} else {
-		live = live[:f.NumValues()]
-		for i := range live {
-			live[i] = false
-		}
-	}
-
-	liveOrderStmts = f.newDeadcodeLiveOrderStmts()
-	liveOrderStmts = liveOrderStmts[:0]
 
 	// After regalloc, consider all values to be live.
 	// See the comment at the top of regalloc.go and in deadcode for details.
@@ -101,8 +91,8 @@ func liveValues(f *Func, reachable []bool) (live []bool, liveOrderStmts []*Value
 	}
 
 	// Find all live values
-	q := f.Cache.deadcode.q[:0]
+	q := f.Cache.allocValueSlice(f.NumValues())[:0]
-	defer func() { f.Cache.deadcode.q = q }()
+	defer f.Cache.freeValueSlice(q)
 
 	// Starting set: all control values of reachable blocks are live.
 	// Calls are live (because callee can observe the memory state).
@@ -149,6 +139,7 @@ func liveValues(f *Func, reachable []bool) (live []bool, liveOrderStmts []*Value
 	for len(q) > 0 {
 		// pop a reachable value
 		v := q[len(q)-1]
+		q[len(q)-1] = nil
 		q = q[:len(q)-1]
 		for i, x := range v.Args {
 			if v.Op == OpPhi && !reachable[v.Block.Preds[i].b.ID] {
@@ -213,8 +204,8 @@ func deadcode(f *Func) {
 
 	// Find live values.
 	live, order := liveValues(f, reachable)
-	defer f.retDeadcodeLive(live)
+	defer func() { f.Cache.freeBoolSlice(live) }()
-	defer f.retDeadcodeLiveOrderStmts(order)
+	defer func() { f.Cache.freeValueSlice(order) }()
 
 	// Remove dead & duplicate entries from namedValues map.
 	s := f.newSparseSet(f.NumValues())

src/cmd/compile/internal/ssa/dom.go

@@ -21,7 +21,8 @@ type blockAndIndex struct {
 // postorderWithNumbering provides a DFS postordering.
 // This seems to make loop-finding more robust.
 func postorderWithNumbering(f *Func, ponums []int32) []*Block {
-	seen := make([]bool, f.NumBlocks())
+	seen := f.Cache.allocBoolSlice(f.NumBlocks())
+	defer f.Cache.freeBoolSlice(seen)
 
 	// result ordering
 	order := make([]*Block, 0, len(f.Blocks))
@@ -56,44 +57,6 @@ func postorderWithNumbering(f *Func, ponums []int32) []*Block {
 
 type linkedBlocks func(*Block) []Edge
 
-const nscratchslices = 7
-
-// experimentally, functions with 512 or fewer blocks account
-// for 75% of memory (size) allocation for dominator computation
-// in make.bash.
-const minscratchblocks = 512
-
-func (cache *Cache) scratchBlocksForDom(maxBlockID int) (a, b, c, d, e, f, g []ID) {
-	tot := maxBlockID * nscratchslices
-	scratch := cache.domblockstore
-	if len(scratch) < tot {
-		// req = min(1.5*tot, nscratchslices*minscratchblocks)
-		// 50% padding allows for graph growth in later phases.
-		req := (tot * 3) >> 1
-		if req < nscratchslices*minscratchblocks {
-			req = nscratchslices * minscratchblocks
-		}
-		scratch = make([]ID, req)
-		cache.domblockstore = scratch
-	} else {
-		// Clear as much of scratch as we will (re)use
-		scratch = scratch[0:tot]
-		for i := range scratch {
-			scratch[i] = 0
-		}
-	}
-
-	a = scratch[0*maxBlockID : 1*maxBlockID]
-	b = scratch[1*maxBlockID : 2*maxBlockID]
-	c = scratch[2*maxBlockID : 3*maxBlockID]
-	d = scratch[3*maxBlockID : 4*maxBlockID]
-	e = scratch[4*maxBlockID : 5*maxBlockID]
-	f = scratch[5*maxBlockID : 6*maxBlockID]
-	g = scratch[6*maxBlockID : 7*maxBlockID]
-
-	return
-}
-
 func dominators(f *Func) []*Block {
 	preds := func(b *Block) []Edge { return b.Preds }
 	succs := func(b *Block) []Edge { return b.Succs }
@@ -110,12 +73,21 @@ func (f *Func) dominatorsLTOrig(entry *Block, predFn linkedBlocks, succFn linked
 	// Adapted directly from the original TOPLAS article's "simple" algorithm
 
 	maxBlockID := entry.Func.NumBlocks()
-	semi, vertex, label, parent, ancestor, bucketHead, bucketLink := f.Cache.scratchBlocksForDom(maxBlockID)
+	scratch := f.Cache.allocIDSlice(7 * maxBlockID)
+	defer f.Cache.freeIDSlice(scratch)
+	semi := scratch[0*maxBlockID : 1*maxBlockID]
+	vertex := scratch[1*maxBlockID : 2*maxBlockID]
+	label := scratch[2*maxBlockID : 3*maxBlockID]
+	parent := scratch[3*maxBlockID : 4*maxBlockID]
+	ancestor := scratch[4*maxBlockID : 5*maxBlockID]
+	bucketHead := scratch[5*maxBlockID : 6*maxBlockID]
+	bucketLink := scratch[6*maxBlockID : 7*maxBlockID]
 
 	// This version uses integers for most of the computation,
 	// to make the work arrays smaller and pointer-free.
 	// fromID translates from ID to *Block where that is needed.
-	fromID := make([]*Block, maxBlockID)
+	fromID := f.Cache.allocBlockSlice(maxBlockID)
+	defer f.Cache.freeBlockSlice(fromID)
 	for _, v := range f.Blocks {
 		fromID[v.ID] = v
 	}
@@ -243,7 +215,8 @@ func dominatorsSimple(f *Func) []*Block {
 	post := f.postorder()
 
 	// Make map from block id to order index (for intersect call)
-	postnum := make([]int, f.NumBlocks())
+	postnum := f.Cache.allocIntSlice(f.NumBlocks())
+	defer f.Cache.freeIntSlice(postnum)
 	for i, b := range post {
 		postnum[b.ID] = i
 	}

src/cmd/compile/internal/ssa/flagalloc.go

@@ -11,7 +11,8 @@ func flagalloc(f *Func) {
 	// Compute the in-register flag value we want at the end of
 	// each block. This is basically a best-effort live variable
 	// analysis, so it can be much simpler than a full analysis.
-	end := make([]*Value, f.NumBlocks())
+	end := f.Cache.allocValueSlice(f.NumBlocks())
+	defer f.Cache.freeValueSlice(end)
 	po := f.postorder()
 	for n := 0; n < 2; n++ {
 		for _, b := range po {

src/cmd/compile/internal/ssa/func.go

@@ -105,74 +105,35 @@ func (f *Func) NumValues() int {
 
 // newSparseSet returns a sparse set that can store at least up to n integers.
 func (f *Func) newSparseSet(n int) *sparseSet {
-	for i, scr := range f.Cache.scrSparseSet {
+	return f.Cache.allocSparseSet(n)
-		if scr != nil && scr.cap() >= n {
-			f.Cache.scrSparseSet[i] = nil
-			scr.clear()
-			return scr
-		}
-	}
-	return newSparseSet(n)
 }
 
 // retSparseSet returns a sparse set to the config's cache of sparse
 // sets to be reused by f.newSparseSet.
 func (f *Func) retSparseSet(ss *sparseSet) {
-	for i, scr := range f.Cache.scrSparseSet {
+	f.Cache.freeSparseSet(ss)
-		if scr == nil {
-			f.Cache.scrSparseSet[i] = ss
-			return
-		}
-	}
-	f.Cache.scrSparseSet = append(f.Cache.scrSparseSet, ss)
 }
 
 // newSparseMap returns a sparse map that can store at least up to n integers.
 func (f *Func) newSparseMap(n int) *sparseMap {
-	for i, scr := range f.Cache.scrSparseMap {
+	return f.Cache.allocSparseMap(n)
-		if scr != nil && scr.cap() >= n {
-			f.Cache.scrSparseMap[i] = nil
-			scr.clear()
-			return scr
-		}
-	}
-	return newSparseMap(n)
 }
 
 // retSparseMap returns a sparse map to the config's cache of sparse
 // sets to be reused by f.newSparseMap.
 func (f *Func) retSparseMap(ss *sparseMap) {
-	for i, scr := range f.Cache.scrSparseMap {
+	f.Cache.freeSparseMap(ss)
-		if scr == nil {
-			f.Cache.scrSparseMap[i] = ss
-			return
-		}
-	}
-	f.Cache.scrSparseMap = append(f.Cache.scrSparseMap, ss)
 }
 
 // newSparseMapPos returns a sparse map that can store at least up to n integers.
 func (f *Func) newSparseMapPos(n int) *sparseMapPos {
-	for i, scr := range f.Cache.scrSparseMapPos {
+	return f.Cache.allocSparseMapPos(n)
-		if scr != nil && scr.cap() >= n {
-			f.Cache.scrSparseMapPos[i] = nil
-			scr.clear()
-			return scr
-		}
-	}
-	return newSparseMapPos(n)
 }
 
 // retSparseMapPos returns a sparse map to the config's cache of sparse
 // sets to be reused by f.newSparseMapPos.
 func (f *Func) retSparseMapPos(ss *sparseMapPos) {
-	for i, scr := range f.Cache.scrSparseMapPos {
+	f.Cache.freeSparseMapPos(ss)
-		if scr == nil {
-			f.Cache.scrSparseMapPos[i] = ss
-			return
-		}
-	}
-	f.Cache.scrSparseMapPos = append(f.Cache.scrSparseMapPos, ss)
 }
 
 // newPoset returns a new poset from the internal cache
@@ -190,33 +151,6 @@ func (f *Func) retPoset(po *poset) {
 	f.Cache.scrPoset = append(f.Cache.scrPoset, po)
 }
 
-// newDeadcodeLive returns a slice for the
-// deadcode pass to use to indicate which values are live.
-func (f *Func) newDeadcodeLive() []bool {
-	r := f.Cache.deadcode.live
-	f.Cache.deadcode.live = nil
-	return r
-}
-
-// retDeadcodeLive returns a deadcode live value slice for re-use.
-func (f *Func) retDeadcodeLive(live []bool) {
-	f.Cache.deadcode.live = live
-}
-
-// newDeadcodeLiveOrderStmts returns a slice for the
-// deadcode pass to use to indicate which values
-// need special treatment for statement boundaries.
-func (f *Func) newDeadcodeLiveOrderStmts() []*Value {
-	r := f.Cache.deadcode.liveOrderStmts
-	f.Cache.deadcode.liveOrderStmts = nil
-	return r
-}
-
-// retDeadcodeLiveOrderStmts returns a deadcode liveOrderStmts slice for re-use.
-func (f *Func) retDeadcodeLiveOrderStmts(liveOrderStmts []*Value) {
-	f.Cache.deadcode.liveOrderStmts = liveOrderStmts
-}
-
 func (f *Func) localSlotAddr(slot LocalSlot) *LocalSlot {
 	a, ok := f.CanonicalLocalSlots[slot]
 	if !ok {

src/cmd/compile/internal/ssa/layout.go

@@ -20,9 +20,12 @@ func layoutRegallocOrder(f *Func) []*Block {
 
 func layoutOrder(f *Func) []*Block {
 	order := make([]*Block, 0, f.NumBlocks())
-	scheduled := make([]bool, f.NumBlocks())
+	scheduled := f.Cache.allocBoolSlice(f.NumBlocks())
-	idToBlock := make([]*Block, f.NumBlocks())
+	defer f.Cache.freeBoolSlice(scheduled)
-	indegree := make([]int, f.NumBlocks())
+	idToBlock := f.Cache.allocBlockSlice(f.NumBlocks())
+	defer f.Cache.freeBlockSlice(idToBlock)
+	indegree := f.Cache.allocIntSlice(f.NumBlocks())
+	defer f.Cache.freeIntSlice(indegree)
 	posdegree := f.newSparseSet(f.NumBlocks()) // blocks with positive remaining degree
 	defer f.retSparseSet(posdegree)
 	// blocks with zero remaining degree. Use slice to simulate a LIFO queue to implement

src/cmd/compile/internal/ssa/likelyadjust.go

@@ -117,8 +117,10 @@ func likelyadjust(f *Func) {
 	// in their rank order.  0 is default, more positive
 	// is less likely. It's possible to assign a negative
 	// unlikeliness (though not currently the case).
-	certain := make([]int8, f.NumBlocks()) // In the long run, all outcomes are at least this bad. Mainly for Exit
+	certain := f.Cache.allocInt8Slice(f.NumBlocks()) // In the long run, all outcomes are at least this bad. Mainly for Exit
-	local := make([]int8, f.NumBlocks())   // for our immediate predecessors.
+	defer f.Cache.freeInt8Slice(certain)
+	local := f.Cache.allocInt8Slice(f.NumBlocks()) // for our immediate predecessors.
+	defer f.Cache.freeInt8Slice(local)
 
 	po := f.postorder()
 	nest := f.loopnest()
@@ -277,7 +279,8 @@ func loopnestfor(f *Func) *loopnest {
 	sdom := f.Sdom()
 	b2l := make([]*loop, f.NumBlocks())
 	loops := make([]*loop, 0)
-	visited := make([]bool, f.NumBlocks())
+	visited := f.Cache.allocBoolSlice(f.NumBlocks())
+	defer f.Cache.freeBoolSlice(visited)
 	sawIrred := false
 
 	if f.pass.debug > 2 {
@@ -369,7 +372,8 @@ func loopnestfor(f *Func) *loopnest {
 	ln := &loopnest{f: f, b2l: b2l, po: po, sdom: sdom, loops: loops, hasIrreducible: sawIrred}
 
 	// Calculate containsUnavoidableCall for regalloc
-	dominatedByCall := make([]bool, f.NumBlocks())
+	dominatedByCall := f.Cache.allocBoolSlice(f.NumBlocks())
+	defer f.Cache.freeBoolSlice(dominatedByCall)
 	for _, b := range po {
 		if checkContainsCall(b) {
 			dominatedByCall[b.ID] = true

src/cmd/compile/internal/ssa/loopreschedchecks.go

@@ -94,7 +94,8 @@ func insertLoopReschedChecks(f *Func) {
 		lastMems[f.Entry.ID] = f.Entry.NewValue0(f.Entry.Pos, OpInitMem, types.TypeMem)
 	}
 
-	memDefsAtBlockEnds := make([]*Value, f.NumBlocks()) // For each block, the mem def seen at its bottom. Could be from earlier block.
+	memDefsAtBlockEnds := f.Cache.allocValueSlice(f.NumBlocks()) // For each block, the mem def seen at its bottom. Could be from earlier block.
+	defer f.Cache.freeValueSlice(memDefsAtBlockEnds)
 
 	// Propagate last mem definitions forward through successor blocks.
 	for i := len(po) - 1; i >= 0; i-- {
@@ -404,7 +405,8 @@ outer:
 func findLastMems(f *Func) []*Value {
 
 	var stores []*Value
-	lastMems := make([]*Value, f.NumBlocks())
+	lastMems := f.Cache.allocValueSlice(f.NumBlocks())
+	defer f.Cache.freeValueSlice(lastMems)
 	storeUse := f.newSparseSet(f.NumValues())
 	defer f.retSparseSet(storeUse)
 	for _, b := range f.Blocks {

src/cmd/compile/internal/ssa/looprotate.go

@@ -30,7 +30,8 @@ func loopRotate(f *Func) {
 		return
 	}
 
-	idToIdx := make([]int, f.NumBlocks())
+	idToIdx := f.Cache.allocIntSlice(f.NumBlocks())
+	defer f.Cache.freeIntSlice(idToIdx)
 	for i, b := range f.Blocks {
 		idToIdx[b.ID] = i
 	}
@@ -92,20 +93,21 @@ func loopRotate(f *Func) {
 	// Some blocks that are not part of a loop may be placed
 	// between loop blocks. In order to avoid these blocks from
 	// being overwritten, use a temporary slice.
-	newOrder := make([]*Block, 0, f.NumBlocks())
+	oldOrder := f.Cache.allocBlockSlice(len(f.Blocks))
-	for _, b := range f.Blocks {
+	defer f.Cache.freeBlockSlice(oldOrder)
+	copy(oldOrder, f.Blocks)
+	for _, b := range oldOrder {
 		if _, ok := move[b.ID]; ok {
 			continue
 		}
-		newOrder = append(newOrder, b)
+		f.Blocks[j] = b
 		j++
 		for _, a := range after[b.ID] {
-			newOrder = append(newOrder, a)
+			f.Blocks[j] = a
 			j++
 		}
 	}
-	if j != len(f.Blocks) {
+	if j != len(oldOrder) {
 		f.Fatalf("bad reordering in looprotate")
 	}
-	f.Blocks = newOrder
 }

src/cmd/compile/internal/ssa/nilcheck.go

@@ -41,7 +41,8 @@ func nilcheckelim(f *Func) {
 	// map from value ID to bool indicating if value is known to be non-nil
 	// in the current dominator path being walked. This slice is updated by
 	// walkStates to maintain the known non-nil values.
-	nonNilValues := make([]bool, f.NumValues())
+	nonNilValues := f.Cache.allocBoolSlice(f.NumValues())
+	defer f.Cache.freeBoolSlice(nonNilValues)
 
 	// make an initial pass identifying any non-nil values
 	for _, b := range f.Blocks {
@@ -86,7 +87,8 @@ func nilcheckelim(f *Func) {
 	// allocate auxiliary date structures for computing store order
 	sset := f.newSparseSet(f.NumValues())
 	defer f.retSparseSet(sset)
-	storeNumber := make([]int32, f.NumValues())
+	storeNumber := f.Cache.allocInt32Slice(f.NumValues())
+	defer f.Cache.freeInt32Slice(storeNumber)
 
 	// perform a depth first walk of the dominee tree
 	for len(work) > 0 {

src/cmd/compile/internal/ssa/print.go

@@ -124,7 +124,7 @@ func (p stringFuncPrinter) named(n LocalSlot, vals []*Value) {
 
 func fprintFunc(p funcPrinter, f *Func) {
 	reachable, live := findlive(f)
-	defer f.retDeadcodeLive(live)
+	defer f.Cache.freeBoolSlice(live)
 	p.header(f)
 	printed := make([]bool, f.NumValues())
 	for _, b := range f.Blocks {

src/cmd/compile/internal/ssa/regalloc.go

@@ -146,6 +146,7 @@ func regalloc(f *Func) {
 	var s regAllocState
 	s.init(f)
 	s.regalloc(f)
+	s.close()
 }
 
 type register uint8
@@ -357,6 +358,12 @@ func (s *regAllocState) clobberRegs(m regMask) {
 // setOrig records that c's original value is the same as
 // v's original value.
 func (s *regAllocState) setOrig(c *Value, v *Value) {
+	if int(c.ID) >= cap(s.orig) {
+		x := s.f.Cache.allocValueSlice(int(c.ID) + 1)
+		copy(x, s.orig)
+		s.f.Cache.freeValueSlice(s.orig)
+		s.orig = x
+	}
 	for int(c.ID) >= len(s.orig) {
 		s.orig = append(s.orig, nil)
 	}
@@ -664,7 +671,7 @@ func (s *regAllocState) init(f *Func) {
 		s.f.Cache.regallocValues = make([]valState, nv)
 	}
 	s.values = s.f.Cache.regallocValues
-	s.orig = make([]*Value, nv)
+	s.orig = s.f.Cache.allocValueSlice(nv)
 	s.copies = make(map[*Value]bool)
 	for _, b := range s.visitOrder {
 		for _, v := range b.Values {
@@ -728,6 +735,10 @@ func (s *regAllocState) init(f *Func) {
 	}
 }
 
+func (s *regAllocState) close() {
+	s.f.Cache.freeValueSlice(s.orig)
+}
+
 // Adds a use record for id at distance dist from the start of the block.
 // All calls to addUse must happen with nonincreasing dist.
 func (s *regAllocState) addUse(id ID, dist int32, pos src.XPos) {

src/cmd/compile/internal/ssa/schedule.go

@@ -94,13 +94,15 @@ func (op Op) isLoweredGetClosurePtr() bool {
 func schedule(f *Func) {
 	// For each value, the number of times it is used in the block
 	// by values that have not been scheduled yet.
-	uses := make([]int32, f.NumValues())
+	uses := f.Cache.allocInt32Slice(f.NumValues())
+	defer f.Cache.freeInt32Slice(uses)
 
 	// reusable priority queue
 	priq := new(ValHeap)
 
 	// "priority" for a value
-	score := make([]int8, f.NumValues())
+	score := f.Cache.allocInt8Slice(f.NumValues())
+	defer f.Cache.freeInt8Slice(score)
 
 	// scheduling order. We queue values in this list in reverse order.
 	// A constant bound allows this to be stack-allocated. 64 is
@@ -108,7 +110,8 @@ func schedule(f *Func) {
 	order := make([]*Value, 0, 64)
 
 	// maps mem values to the next live memory value
-	nextMem := make([]*Value, f.NumValues())
+	nextMem := f.Cache.allocValueSlice(f.NumValues())
+	defer f.Cache.freeValueSlice(nextMem)
 	// additional pretend arguments for each Value. Used to enforce load/store ordering.
 	additionalArgs := make([][]*Value, f.NumValues())
 

src/cmd/compile/internal/ssa/stackalloc.go

@@ -25,8 +25,6 @@ type stackAllocState struct {
 	values    []stackValState
 	interfere [][]ID // interfere[v.id] = values that interfere with v.
 	names     []LocalSlot
-	slots     []int
-	used      []bool
 
 	nArgSlot, // Number of Values sourced to arg slot
 	nNotNeed, // Number of Values not needing a stack slot
@@ -57,12 +55,6 @@ func putStackAllocState(s *stackAllocState) {
 	for i := range s.names {
 		s.names[i] = LocalSlot{}
 	}
-	for i := range s.slots {
-		s.slots[i] = 0
-	}
-	for i := range s.used {
-		s.used[i] = false
-	}
 	s.f.Cache.stackAllocState = s
 	s.f = nil
 	s.live = nil
@@ -218,25 +210,15 @@ func (s *stackAllocState) stackalloc() {
 
 	// Each time we assign a stack slot to a value v, we remember
 	// the slot we used via an index into locations[v.Type].
-	slots := s.slots
+	slots := f.Cache.allocIntSlice(f.NumValues())
-	if n := f.NumValues(); cap(slots) >= n {
+	defer f.Cache.freeIntSlice(slots)
-		slots = slots[:n]
-	} else {
-		slots = make([]int, n)
-		s.slots = slots
-	}
 	for i := range slots {
 		slots[i] = -1
 	}
 
 	// Pick a stack slot for each value needing one.
-	var used []bool
+	used := f.Cache.allocBoolSlice(f.NumValues())
-	if n := f.NumValues(); cap(s.used) >= n {
+	defer f.Cache.freeBoolSlice(used)
-		used = s.used[:n]
-	} else {
-		used = make([]bool, n)
-		s.used = used
-	}
 	for _, b := range f.Blocks {
 		for _, v := range b.Values {
 			if !s.values[v.ID].needSlot {

src/cmd/compile/internal/ssa/tighten.go

@@ -10,7 +10,8 @@ package ssa
 // A Value can be moved to any block that
 // dominates all blocks in which it is used.
 func tighten(f *Func) {
-	canMove := make([]bool, f.NumValues())
+	canMove := f.Cache.allocBoolSlice(f.NumValues())
+	defer f.Cache.freeBoolSlice(canMove)
 	for _, b := range f.Blocks {
 		for _, v := range b.Values {
 			if v.Op.isLoweredGetClosurePtr() {
@@ -52,7 +53,8 @@ func tighten(f *Func) {
 	lca := makeLCArange(f)
 
 	// For each moveable value, record the block that dominates all uses found so far.
-	target := make([]*Block, f.NumValues())
+	target := f.Cache.allocBlockSlice(f.NumValues())
+	defer f.Cache.freeBlockSlice(target)
 
 	// Grab loop information.
 	// We use this to make sure we don't tighten a value into a (deeper) loop.

src/cmd/compile/internal/ssa/writebarrier.go

@@ -139,7 +139,8 @@ func writebarrier(f *Func) {
 			// allocate auxiliary data structures for computing store order
 			sset = f.newSparseSet(f.NumValues())
 			defer f.retSparseSet(sset)
-			storeNumber = make([]int32, f.NumValues())
+			storeNumber = f.Cache.allocInt32Slice(f.NumValues())
+			defer f.Cache.freeInt32Slice(storeNumber)
 		}
 
 		// order values in store order