5 files changed, 43 insertions, 10 deletions
diff --git a/src/cmd/compile/internal/ssa/cache.go b/src/cmd/compile/internal/ssa/cache.go
index e149f6a4c5..b30af6304d 100644
--- a/src/cmd/compile/internal/ssa/cache.go
+++ b/src/cmd/compile/internal/ssa/cache.go
@@ -22,7 +22,8 @@ type Cache struct {
 	stackAllocState *stackAllocState
 
 	domblockstore []ID         // scratch space for computing dominators
-	scrSparse     []*sparseSet // scratch sparse sets to be re-used.
+	scrSparseSet  []*sparseSet // scratch sparse sets to be re-used.
+	scrSparseMap  []*sparseMap // scratch sparse maps to be re-used.
 
 	ValueToProgAfter []*obj.Prog
 	debugState       debugState
diff --git a/src/cmd/compile/internal/ssa/deadstore.go b/src/cmd/compile/internal/ssa/deadstore.go
index bbeb990f17..e1ce980e5c 100644
--- a/src/cmd/compile/internal/ssa/deadstore.go
+++ b/src/cmd/compile/internal/ssa/deadstore.go
@@ -19,7 +19,8 @@ func dse(f *Func) {
 	defer f.retSparseSet(loadUse)
 	storeUse := f.newSparseSet(f.NumValues())
 	defer f.retSparseSet(storeUse)
-	shadowed := newSparseMap(f.NumValues()) // TODO: cache
+	shadowed := f.newSparseMap(f.NumValues())
+	defer f.retSparseMap(shadowed)
 	for _, b := range f.Blocks {
 		// Find all the stores in this block. Categorize their uses:
 		//  loadUse contains stores which are used by a subsequent load.
diff --git a/src/cmd/compile/internal/ssa/func.go b/src/cmd/compile/internal/ssa/func.go
index 3868ee37d9..bde36a5b3f 100644
--- a/src/cmd/compile/internal/ssa/func.go
+++ b/src/cmd/compile/internal/ssa/func.go
@@ -84,9 +84,9 @@ 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.scrSparse {
+	for i, scr := range f.Cache.scrSparseSet {
 		if scr != nil && scr.cap() >= n {
-			f.Cache.scrSparse[i] = nil
+			f.Cache.scrSparseSet[i] = nil
 			scr.clear()
 			return scr
 		}
@@ -94,15 +94,40 @@ func (f *Func) newSparseSet(n int) *sparseSet {
 	return newSparseSet(n)
 }
 
-// retSparseSet returns a sparse set to the config's cache of sparse sets to be reused by f.newSparseSet.
+// 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.scrSparse {
+	for i, scr := range f.Cache.scrSparseSet {
 		if scr == nil {
-			f.Cache.scrSparse[i] = ss
+			f.Cache.scrSparseSet[i] = ss
 			return
 		}
 	}
-	f.Cache.scrSparse = append(f.Cache.scrSparse, ss)
+	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 {
+		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 {
+		if scr == nil {
+			f.Cache.scrSparseMap[i] = ss
+			return
+		}
+	}
+	f.Cache.scrSparseMap = append(f.Cache.scrSparseMap, ss)
 }
 
 // newValue allocates a new Value with the given fields and places it at the end of b.Values.
diff --git a/src/cmd/compile/internal/ssa/regalloc.go b/src/cmd/compile/internal/ssa/regalloc.go
index abc4e60d7c..ea88da3b9c 100644
--- a/src/cmd/compile/internal/ssa/regalloc.go
+++ b/src/cmd/compile/internal/ssa/regalloc.go
@@ -2183,8 +2183,10 @@ func (s *regAllocState) computeLive() {
 	s.desired = make([]desiredState, f.NumBlocks())
 	var phis []*Value
 
-	live := newSparseMap(f.NumValues())
-	t := newSparseMap(f.NumValues())
+	live := f.newSparseMap(f.NumValues())
+	defer f.retSparseMap(live)
+	t := f.newSparseMap(f.NumValues())
+	defer f.retSparseMap(t)
 
 	// Keep track of which value we want in each register.
 	var desired desiredState
diff --git a/src/cmd/compile/internal/ssa/sparsemap.go b/src/cmd/compile/internal/ssa/sparsemap.go
index 973ab3d434..c42fb99c7a 100644
--- a/src/cmd/compile/internal/ssa/sparsemap.go
+++ b/src/cmd/compile/internal/ssa/sparsemap.go
@@ -26,6 +26,10 @@ func newSparseMap(n int) *sparseMap {
 	return &sparseMap{dense: nil, sparse: make([]int32, n)}
 }
 
+func (s *sparseMap) cap() int {
+	return len(s.sparse)
+}
+
 func (s *sparseMap) size() int {
 	return len(s.dense)
 }