8 files changed, 78 insertions, 5 deletions
diff --git a/src/cmd/compile/internal/reflectdata/reflect.go b/src/cmd/compile/internal/reflectdata/reflect.go
index 19cf2a0a12..a8df7a1a24 100644
--- a/src/cmd/compile/internal/reflectdata/reflect.go
+++ b/src/cmd/compile/internal/reflectdata/reflect.go
@@ -947,7 +947,7 @@ func writeType(t *types.Type) *obj.LSym {
 	}
 
 	dupok := 0
-	if tbase.Sym() == nil { // TODO(mdempsky): Probably need DUPOK for instantiated types too.
+	if tbase.Sym() == nil || tbase.HasShape() { // TODO(mdempsky): Probably need DUPOK for instantiated types too.
 		dupok = obj.DUPOK
 	}
 
@@ -1738,6 +1738,11 @@ func NeedEmit(typ *types.Type) bool {
 		// Need to emit to be safe (however, see TODO above).
 		return true
 
+	case typ.HasShape():
+		// Shape type; need to emit even though it lives in the .shape package.
+		// TODO: make sure the linker deduplicates them (see dupok in writeType above).
+		return true
+
 	default:
 		// Should have been emitted by an imported package.
 		return false
diff --git a/src/cmd/compile/internal/typecheck/subr.go b/src/cmd/compile/internal/typecheck/subr.go
index 25db24259c..53c3933370 100644
--- a/src/cmd/compile/internal/typecheck/subr.go
+++ b/src/cmd/compile/internal/typecheck/subr.go
@@ -1362,8 +1362,7 @@ func Shapify(t *types.Type) *types.Type {
 		return s
 	}
 
-	sym := Lookup(fmt.Sprintf(".shape%d", snum))
-	snum++
+	sym := shapePkg.Lookup(u.LinkString())
 	name := ir.NewDeclNameAt(u.Pos(), ir.OTYPE, sym)
 	s := types.NewNamed(name)
 	s.SetUnderlying(u)
@@ -1375,6 +1374,6 @@ func Shapify(t *types.Type) *types.Type {
 	return s
 }
 
-var snum int
-
 var shaped = map[*types.Type]*types.Type{}
+
+var shapePkg = types.NewPkg(".shape", ".shape")
diff --git a/test/typeparam/dedup.dir/a.go b/test/typeparam/dedup.dir/a.go
new file mode 100644
index 0000000000..f5cb6dc762
--- /dev/null
+++ b/test/typeparam/dedup.dir/a.go
@@ -0,0 +1,10 @@
+// Copyright 2021 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 a
+
+//go:noinline
+func F[T comparable](a, b T) bool {
+	return a == b
+}
diff --git a/test/typeparam/dedup.dir/b.go b/test/typeparam/dedup.dir/b.go
new file mode 100644
index 0000000000..ce037e2d8a
--- /dev/null
+++ b/test/typeparam/dedup.dir/b.go
@@ -0,0 +1,14 @@
+// Copyright 2021 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 b
+
+import "a"
+
+func B() {
+	var x int64
+	println(a.F(&x, &x))
+	var y int32
+	println(a.F(&y, &y))
+}
diff --git a/test/typeparam/dedup.dir/c.go b/test/typeparam/dedup.dir/c.go
new file mode 100644
index 0000000000..11a5d97642
--- /dev/null
+++ b/test/typeparam/dedup.dir/c.go
@@ -0,0 +1,14 @@
+// Copyright 2021 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 c
+
+import "a"
+
+func C() {
+	var x int64
+	println(a.F(&x, &x))
+	var y int32
+	println(a.F(&y, &y))
+}
diff --git a/test/typeparam/dedup.dir/main.go b/test/typeparam/dedup.dir/main.go
new file mode 100644
index 0000000000..dc3ff6f75f
--- /dev/null
+++ b/test/typeparam/dedup.dir/main.go
@@ -0,0 +1,15 @@
+// Copyright 2021 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 main
+
+import (
+	"b"
+	"c"
+)
+
+func main() {
+	b.B()
+	c.C()
+}
diff --git a/test/typeparam/dedup.go b/test/typeparam/dedup.go
new file mode 100644
index 0000000000..dca4cf3a84
--- /dev/null
+++ b/test/typeparam/dedup.go
@@ -0,0 +1,12 @@
+// rundir -G=3
+
+// Copyright 2021 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.
+
+// Note: this doesn't really test the deduplication of
+// instantiations. It just provides an easy mechanism to build a
+// binary that you can then check with objdump manually to make sure
+// deduplication is happening. TODO: automate this somehow?
+
+package ignored
diff --git a/test/typeparam/dedup.out b/test/typeparam/dedup.out
new file mode 100644
index 0000000000..1140ff52e2
--- /dev/null
+++ b/test/typeparam/dedup.out
@@ -0,0 +1,4 @@
+true
+true
+true
+true