cmd/compile: separate out sparsemaps that need position

Make them a separate type, so the normal sparse maps don't
need the extra storage.

Change-Id: I3a0219487c35ea63723499723b0c742e321d97c4
Reviewed-on: https://go-review.googlesource.com/c/go/+/444819
Reviewed-by: Heschi Kreinick <heschi@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
Run-TryBot: Keith Randall <khr@golang.org>
Reviewed-by: David Chase <drchase@google.com>

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

@@ -5,7 +5,6 @@
 package ssa
 
 import (
-	"cmd/internal/src"
 	"math"
 )
 
@@ -86,7 +85,7 @@ func (s *biasedSparseMap) add(x uint) {
 	if int(x) < s.first || int(x) >= s.cap() {
 		return
 	}
-	s.s.set(ID(int(x)-s.first), 0, src.NoXPos)
+	s.s.set(ID(int(x)-s.first), 0)
 }
 
 // add inserts x->v into s, provided that x is in the range of keys stored in s.
@@ -94,7 +93,7 @@ func (s *biasedSparseMap) set(x uint, v int32) {
 	if int(x) < s.first || int(x) >= s.cap() {
 		return
 	}
-	s.s.set(ID(int(x)-s.first), v, src.NoXPos)
+	s.s.set(ID(int(x)-s.first), v)
 }
 
 // remove removes key x from s.

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

@@ -21,10 +21,11 @@ type Cache struct {
 	// See stackalloc.go's {new,put}StackAllocState.
 	stackAllocState *stackAllocState
 
-	domblockstore []ID         // scratch space for computing dominators
-	scrSparseSet  []*sparseSet // scratch sparse sets to be re-used.
-	scrSparseMap  []*sparseMap // scratch sparse maps to be re-used.
-	scrPoset      []*poset     // scratch poset to be reused
+	domblockstore   []ID            // scratch space for computing dominators
+	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 {

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

@@ -7,7 +7,6 @@ package ssa
 import (
 	"cmd/compile/internal/ir"
 	"cmd/compile/internal/types"
-	"cmd/internal/src"
 )
 
 // dse does dead-store elimination on the Function.
@@ -112,7 +111,7 @@ func dse(f *Func) {
 				if sz > 0x7fffffff { // work around sparseMap's int32 value type
 					sz = 0x7fffffff
 				}
-				shadowed.set(v.Args[0].ID, int32(sz), src.NoXPos)
+				shadowed.set(v.Args[0].ID, int32(sz))
 			}
 		}
 		// walk to previous store

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

@@ -151,6 +151,30 @@ func (f *Func) retSparseMap(ss *sparseMap) {
 	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 {
+		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 {
+		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
 func (f *Func) newPoset() *poset {
 	if len(f.Cache.scrPoset) > 0 {

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

@@ -308,7 +308,7 @@ func nilcheckelim2(f *Func) {
 				}
 				// This instruction is guaranteed to fault if ptr is nil.
 				// Any previous nil check op is unnecessary.
-				unnecessary.set(ptr.ID, int32(i), src.NoXPos)
+				unnecessary.set(ptr.ID, int32(i))
 			}
 		}
 		// Remove values we've clobbered with OpUnknown.

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

@@ -2498,10 +2498,10 @@ func (s *regAllocState) computeLive() {
 	s.desired = make([]desiredState, f.NumBlocks())
 	var phis []*Value
 
-	live := f.newSparseMap(f.NumValues())
-	defer f.retSparseMap(live)
-	t := f.newSparseMap(f.NumValues())
-	defer f.retSparseMap(t)
+	live := f.newSparseMapPos(f.NumValues())
+	defer f.retSparseMapPos(live)
+	t := f.newSparseMapPos(f.NumValues())
+	defer f.retSparseMapPos(t)
 
 	// Keep track of which value we want in each register.
 	var desired desiredState
@@ -2630,7 +2630,7 @@ func (s *regAllocState) computeLive() {
 					d := e.val + delta
 					if !t.contains(e.key) || d < t.get(e.key) {
 						update = true
-						t.set(e.key, d, e.aux)
+						t.set(e.key, d, e.pos)
 					}
 				}
 				// Also add the correct arg from the saved phi values.
@@ -2653,7 +2653,7 @@ func (s *regAllocState) computeLive() {
 					l = make([]liveInfo, 0, t.size())
 				}
 				for _, e := range t.contents() {
-					l = append(l, liveInfo{e.key, e.val, e.aux})
+					l = append(l, liveInfo{e.key, e.val, e.pos})
 				}
 				s.live[p.ID] = l
 				changed = true

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

@@ -4,15 +4,12 @@
 
 package ssa
 
-import "cmd/internal/src"
-
 // from https://research.swtch.com/sparse
 // in turn, from Briggs and Torczon
 
 type sparseEntry struct {
 	key ID
 	val int32
-	aux src.XPos
 }
 
 type sparseMap struct {
@@ -49,14 +46,13 @@ func (s *sparseMap) get(k ID) int32 {
 	return -1
 }
 
-func (s *sparseMap) set(k ID, v int32, a src.XPos) {
+func (s *sparseMap) set(k ID, v int32) {
 	i := s.sparse[k]
 	if i < int32(len(s.dense)) && s.dense[i].key == k {
 		s.dense[i].val = v
-		s.dense[i].aux = a
 		return
 	}
-	s.dense = append(s.dense, sparseEntry{k, v, a})
+	s.dense = append(s.dense, sparseEntry{k, v})
 	s.sparse[k] = int32(len(s.dense)) - 1
 }
 
@@ -70,7 +66,7 @@ func (s *sparseMap) setBit(k ID, v uint) {
 		s.dense[i].val |= 1 << v
 		return
 	}
-	s.dense = append(s.dense, sparseEntry{k, 1 << v, src.NoXPos})
+	s.dense = append(s.dense, sparseEntry{k, 1 << v})
 	s.sparse[k] = int32(len(s.dense)) - 1
 }
 

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

@@ -0,0 +1,79 @@
+// Copyright 2022 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 ssa
+
+import "cmd/internal/src"
+
+// from https://research.swtch.com/sparse
+// in turn, from Briggs and Torczon
+
+type sparseEntryPos struct {
+	key ID
+	val int32
+	pos src.XPos
+}
+
+type sparseMapPos struct {
+	dense  []sparseEntryPos
+	sparse []int32
+}
+
+// newSparseMapPos returns a sparseMapPos that can map
+// integers between 0 and n-1 to the pair <int32,src.XPos>.
+func newSparseMapPos(n int) *sparseMapPos {
+	return &sparseMapPos{dense: nil, sparse: make([]int32, n)}
+}
+
+func (s *sparseMapPos) cap() int {
+	return len(s.sparse)
+}
+
+func (s *sparseMapPos) size() int {
+	return len(s.dense)
+}
+
+func (s *sparseMapPos) contains(k ID) bool {
+	i := s.sparse[k]
+	return i < int32(len(s.dense)) && s.dense[i].key == k
+}
+
+// get returns the value for key k, or -1 if k does
+// not appear in the map.
+func (s *sparseMapPos) get(k ID) int32 {
+	i := s.sparse[k]
+	if i < int32(len(s.dense)) && s.dense[i].key == k {
+		return s.dense[i].val
+	}
+	return -1
+}
+
+func (s *sparseMapPos) set(k ID, v int32, a src.XPos) {
+	i := s.sparse[k]
+	if i < int32(len(s.dense)) && s.dense[i].key == k {
+		s.dense[i].val = v
+		s.dense[i].pos = a
+		return
+	}
+	s.dense = append(s.dense, sparseEntryPos{k, v, a})
+	s.sparse[k] = int32(len(s.dense)) - 1
+}
+
+func (s *sparseMapPos) remove(k ID) {
+	i := s.sparse[k]
+	if i < int32(len(s.dense)) && s.dense[i].key == k {
+		y := s.dense[len(s.dense)-1]
+		s.dense[i] = y
+		s.sparse[y.key] = i
+		s.dense = s.dense[:len(s.dense)-1]
+	}
+}
+
+func (s *sparseMapPos) clear() {
+	s.dense = s.dense[:0]
+}
+
+func (s *sparseMapPos) contents() []sparseEntryPos {
+	return s.dense
+}