From 6a0c8e77f289a5c2e1b1ad0f2c8a5c5105f599a6 Mon Sep 17 00:00:00 2001
From: Ian Lance Taylor <ian@gcc.gnu.org>
Date: Tue, 15 Jan 2019 20:32:39 +0000
Subject: [PATCH] compiler, runtime: panic on uncomparable map key, even if map
 is empty

    This ports https://golang.org/cl/155918 from the master repo.

        runtime: panic on uncomparable map key, even if map is empty

        Reorg map flags a bit so we don't need any extra space for the extra flag.

    This is a pre-req for updating libgo to the Go 1.12beta2 release.

    Reviewed-on: https://go-review.googlesource.com/c/157858

From-SVN: r267950
---
 gcc/go/gofrontend/MERGE    |  2 +-
 gcc/go/gofrontend/types.cc | 62 +++++++++++++++++++-------------
 gcc/go/gofrontend/types.h  | 22 ++++++++++++
 libgo/go/reflect/type.go   | 58 +++++++++++++++++++++---------
 libgo/go/runtime/map.go    | 73 +++++++++++++++++++++-----------------
 libgo/go/runtime/type.go   | 37 +++++++++++++------
 6 files changed, 170 insertions(+), 84 deletions(-)

diff --git a/gcc/go/gofrontend/MERGE b/gcc/go/gofrontend/MERGE
index ab0a2bd4623..4d76c547bdc 100644
--- a/gcc/go/gofrontend/MERGE
+++ b/gcc/go/gofrontend/MERGE
@@ -1,4 +1,4 @@
-0d64279c01a37b2579c0c62ca4f2c3e3f81de07c
+87005025fcd0d7e7908b3aae7062b52cb80eb0f3
 
 The first line of this file holds the git revision number of the last
 merge done from the gofrontend repository.
diff --git a/gcc/go/gofrontend/types.cc b/gcc/go/gofrontend/types.cc
index 509be44e028..5a45bb2c3f4 100644
--- a/gcc/go/gofrontend/types.cc
+++ b/gcc/go/gofrontend/types.cc
@@ -5839,6 +5839,25 @@ Struct_type::do_needs_key_update()
   return false;
 }
 
+// Return whether computing the hash value of an instance of this
+// struct type might panic.
+
+bool
+Struct_type::do_hash_might_panic()
+{
+  const Struct_field_list* fields = this->fields_;
+  if (fields == NULL)
+    return false;
+  for (Struct_field_list::const_iterator pf = fields->begin();
+       pf != fields->end();
+       ++pf)
+    {
+      if (pf->type()->hash_might_panic())
+	return true;
+    }
+  return false;
+}
+
 // Return whether this struct type is permitted to be in the heap.
 
 bool
@@ -7979,21 +7998,18 @@ Map_type::make_map_type_descriptor_type()
       Type* ptdt = Type::make_type_descriptor_ptr_type();
       Type* uint8_type = Type::lookup_integer_type("uint8");
       Type* uint16_type = Type::lookup_integer_type("uint16");
-      Type* bool_type = Type::lookup_bool_type();
+      Type* uint32_type = Type::lookup_integer_type("uint32");
 
       Struct_type* sf =
-	Type::make_builtin_struct_type(11,
+	Type::make_builtin_struct_type(8,
 				       "", tdt,
 				       "key", ptdt,
 				       "elem", ptdt,
 				       "bucket", ptdt,
 				       "keysize", uint8_type,
-				       "indirectkey", bool_type,
 				       "valuesize", uint8_type,
-				       "indirectvalue", bool_type,
 				       "bucketsize", uint16_type,
-				       "reflexivekey", bool_type,
-				       "needkeyupdate", bool_type);
+				       "flags", uint32_type);
 
       ret = Type::make_builtin_named_type("MapType", sf);
     }
@@ -8011,6 +8027,7 @@ Map_type::do_type_descriptor(Gogo* gogo, Named_type* name)
   Type* mtdt = Map_type::make_map_type_descriptor_type();
   Type* uint8_type = Type::lookup_integer_type("uint8");
   Type* uint16_type = Type::lookup_integer_type("uint16");
+  Type* uint32_type = Type::lookup_integer_type("uint32");
 
   int64_t keysize;
   if (!this->key_type_->backend_type_size(gogo, &keysize))
@@ -8077,11 +8094,6 @@ Map_type::do_type_descriptor(Gogo* gogo, Named_type* name)
   else
     vals->push_back(Expression::make_integer_int64(keysize, uint8_type, bloc));
 
-  ++p;
-  go_assert(p->is_field_name("indirectkey"));
-  vals->push_back(Expression::make_boolean(keysize > Map_type::max_key_size,
-					   bloc));
-
   ++p;
   go_assert(p->is_field_name("valuesize"));
   if (valsize > Map_type::max_val_size)
@@ -8089,25 +8101,27 @@ Map_type::do_type_descriptor(Gogo* gogo, Named_type* name)
   else
     vals->push_back(Expression::make_integer_int64(valsize, uint8_type, bloc));
 
-  ++p;
-  go_assert(p->is_field_name("indirectvalue"));
-  vals->push_back(Expression::make_boolean(valsize > Map_type::max_val_size,
-					   bloc));
-
   ++p;
   go_assert(p->is_field_name("bucketsize"));
   vals->push_back(Expression::make_integer_int64(bucketsize, uint16_type,
 						 bloc));
 
   ++p;
-  go_assert(p->is_field_name("reflexivekey"));
-  vals->push_back(Expression::make_boolean(this->key_type_->is_reflexive(),
-					   bloc));
-
-  ++p;
-  go_assert(p->is_field_name("needkeyupdate"));
-  vals->push_back(Expression::make_boolean(this->key_type_->needs_key_update(),
-					   bloc));
+  go_assert(p->is_field_name("flags"));
+  // As with the other fields, the flag bits must match the reflect
+  // and runtime packages.
+  unsigned long flags = 0;
+  if (keysize > Map_type::max_key_size)
+    flags |= 1;
+  if (valsize > Map_type::max_val_size)
+    flags |= 2;
+  if (this->key_type_->is_reflexive())
+    flags |= 4;
+  if (this->key_type_->needs_key_update())
+    flags |= 8;
+  if (this->key_type_->hash_might_panic())
+    flags |= 16;
+  vals->push_back(Expression::make_integer_ul(flags, uint32_type, bloc));
 
   ++p;
   go_assert(p == fields->end());
diff --git a/gcc/go/gofrontend/types.h b/gcc/go/gofrontend/types.h
index 9d7994106d8..cc92471d24c 100644
--- a/gcc/go/gofrontend/types.h
+++ b/gcc/go/gofrontend/types.h
@@ -635,6 +635,12 @@ class Type
   needs_key_update()
   { return this->do_needs_key_update(); }
 
+  // Return whether the hash function of this type might panic.  This
+  // is only called for types used as a key in a map type.
+  bool
+  hash_might_panic()
+  { return this->do_hash_might_panic(); }
+
   // Whether the type is permitted in the heap.
   bool
   in_heap()
@@ -1073,6 +1079,10 @@ class Type
   do_needs_key_update()
   { return false; }
 
+  virtual bool
+  do_hash_might_panic()
+  { return false; }
+
   virtual bool
   do_in_heap()
   { return true; }
@@ -2600,6 +2610,9 @@ class Struct_type : public Type
   bool
   do_needs_key_update();
 
+  bool
+  do_hash_might_panic();
+
   bool
   do_in_heap();
 
@@ -2778,6 +2791,10 @@ class Array_type : public Type
   do_needs_key_update()
   { return this->element_type_->needs_key_update(); }
 
+  bool
+  do_hash_might_panic()
+  { return this->length_ != NULL && this->element_type_->hash_might_panic(); }
+
   bool
   do_in_heap()
   { return this->length_ == NULL || this->element_type_->in_heap(); }
@@ -3170,6 +3187,11 @@ class Interface_type : public Type
   do_needs_key_update()
   { return true; }
 
+  // Hashing an unhashable type stored in an interface might panic.
+  bool
+  do_hash_might_panic()
+  { return true; }
+
   unsigned int
   do_hash_for_method(Gogo*, int) const;
 
diff --git a/libgo/go/reflect/type.go b/libgo/go/reflect/type.go
index da7796f3703..e4a9326d083 100644
--- a/libgo/go/reflect/type.go
+++ b/libgo/go/reflect/type.go
@@ -347,16 +347,13 @@ type interfaceType struct {
 // mapType represents a map type.
 type mapType struct {
 	rtype
-	key           *rtype // map key type
-	elem          *rtype // map element (value) type
-	bucket        *rtype // internal bucket structure
-	keysize       uint8  // size of key slot
-	indirectkey   uint8  // store ptr to key instead of key itself
-	valuesize     uint8  // size of value slot
-	indirectvalue uint8  // store ptr to value instead of value itself
-	bucketsize    uint16 // size of bucket
-	reflexivekey  bool   // true if k==k for all keys
-	needkeyupdate bool   // true if we need to update key on an overwrite
+	key        *rtype // map key type
+	elem       *rtype // map element (value) type
+	bucket     *rtype // internal bucket structure
+	keysize    uint8  // size of key slot
+	valuesize  uint8  // size of value slot
+	bucketsize uint16 // size of bucket
+	flags      uint32
 }
 
 // ptrType represents a pointer type.
@@ -1506,6 +1503,8 @@ func MapOf(key, elem Type) Type {
 	s := "map[" + *ktyp.string + "]" + *etyp.string
 
 	// Make a map type.
+	// Note: flag values must match those used in the TMAP case
+	// in ../cmd/compile/internal/gc/reflect.go:dtypesym.
 	var imap interface{} = (map[unsafe.Pointer]unsafe.Pointer)(nil)
 	mt := **(**mapType)(unsafe.Pointer(&imap))
 	mt.string = &s
@@ -1520,23 +1519,29 @@ func MapOf(key, elem Type) Type {
 	mt.ptrToThis = nil
 
 	mt.bucket = bucketOf(ktyp, etyp)
+	mt.flags = 0
 	if ktyp.size > maxKeySize {
 		mt.keysize = uint8(ptrSize)
-		mt.indirectkey = 1
+		mt.flags |= 1 // indirect key
 	} else {
 		mt.keysize = uint8(ktyp.size)
-		mt.indirectkey = 0
 	}
 	if etyp.size > maxValSize {
 		mt.valuesize = uint8(ptrSize)
-		mt.indirectvalue = 1
+		mt.flags |= 2 // indirect value
 	} else {
 		mt.valuesize = uint8(etyp.size)
-		mt.indirectvalue = 0
 	}
 	mt.bucketsize = uint16(mt.bucket.size)
-	mt.reflexivekey = isReflexive(ktyp)
-	mt.needkeyupdate = needKeyUpdate(ktyp)
+	if isReflexive(ktyp) {
+		mt.flags |= 4
+	}
+	if needKeyUpdate(ktyp) {
+		mt.flags |= 8
+	}
+	if hashMightPanic(ktyp) {
+		mt.flags |= 16
+	}
 
 	// Canonicalize before storing in lookupCache
 	ti := toType(&mt.rtype)
@@ -1715,6 +1720,27 @@ func needKeyUpdate(t *rtype) bool {
 	}
 }
 
+// hashMightPanic reports whether the hash of a map key of type t might panic.
+func hashMightPanic(t *rtype) bool {
+	switch t.Kind() {
+	case Interface:
+		return true
+	case Array:
+		tt := (*arrayType)(unsafe.Pointer(t))
+		return hashMightPanic(tt.elem)
+	case Struct:
+		tt := (*structType)(unsafe.Pointer(t))
+		for _, f := range tt.fields {
+			if hashMightPanic(f.typ) {
+				return true
+			}
+		}
+		return false
+	default:
+		return false
+	}
+}
+
 // Make sure these routines stay in sync with ../../runtime/map.go!
 // These types exist only for GC, so we only fill out GC relevant info.
 // Currently, that's just size and the GC program. We also fill in string
diff --git a/libgo/go/runtime/map.go b/libgo/go/runtime/map.go
index 8e97bc56930..52462c7e117 100644
--- a/libgo/go/runtime/map.go
+++ b/libgo/go/runtime/map.go
@@ -414,14 +414,17 @@ func mapaccess1(t *maptype, h *hmap, key unsafe.Pointer) unsafe.Pointer {
 	if msanenabled && h != nil {
 		msanread(key, t.key.size)
 	}
+	hashfn := t.key.hashfn
+	equalfn := t.key.equalfn
 	if h == nil || h.count == 0 {
+		if t.hashMightPanic() {
+			hashfn(key, 0) // see issue 23734
+		}
 		return unsafe.Pointer(&zeroVal[0])
 	}
 	if h.flags&hashWriting != 0 {
 		throw("concurrent map read and map write")
 	}
-	hashfn := t.key.hashfn
-	equalfn := t.key.equalfn
 	hash := hashfn(key, uintptr(h.hash0))
 	m := bucketMask(h.B)
 	b := (*bmap)(add(h.buckets, (hash&m)*uintptr(t.bucketsize)))
@@ -442,12 +445,12 @@ func mapaccess1(t *maptype, h *hmap, key unsafe.Pointer) unsafe.Pointer {
 				continue
 			}
 			k := add(unsafe.Pointer(b), dataOffset+i*uintptr(t.keysize))
-			if t.indirectkey {
+			if t.indirectkey() {
 				k = *((*unsafe.Pointer)(k))
 			}
 			if equalfn(key, k) {
 				v := add(unsafe.Pointer(b), dataOffset+bucketCnt*uintptr(t.keysize)+i*uintptr(t.valuesize))
-				if t.indirectvalue {
+				if t.indirectvalue() {
 					v = *((*unsafe.Pointer)(v))
 				}
 				return v
@@ -472,14 +475,17 @@ func mapaccess2(t *maptype, h *hmap, key unsafe.Pointer) (unsafe.Pointer, bool)
 	if msanenabled && h != nil {
 		msanread(key, t.key.size)
 	}
+	hashfn := t.key.hashfn
+	equalfn := t.key.equalfn
 	if h == nil || h.count == 0 {
+		if t.hashMightPanic() {
+			hashfn(key, 0) // see issue 23734
+		}
 		return unsafe.Pointer(&zeroVal[0]), false
 	}
 	if h.flags&hashWriting != 0 {
 		throw("concurrent map read and map write")
 	}
-	hashfn := t.key.hashfn
-	equalfn := t.key.equalfn
 	hash := hashfn(key, uintptr(h.hash0))
 	m := bucketMask(h.B)
 	b := (*bmap)(unsafe.Pointer(uintptr(h.buckets) + (hash&m)*uintptr(t.bucketsize)))
@@ -500,12 +506,12 @@ func mapaccess2(t *maptype, h *hmap, key unsafe.Pointer) (unsafe.Pointer, bool)
 				continue
 			}
 			k := add(unsafe.Pointer(b), dataOffset+i*uintptr(t.keysize))
-			if t.indirectkey {
+			if t.indirectkey() {
 				k = *((*unsafe.Pointer)(k))
 			}
 			if equalfn(key, k) {
 				v := add(unsafe.Pointer(b), dataOffset+bucketCnt*uintptr(t.keysize)+i*uintptr(t.valuesize))
-				if t.indirectvalue {
+				if t.indirectvalue() {
 					v = *((*unsafe.Pointer)(v))
 				}
 				return v, true
@@ -547,12 +553,12 @@ func mapaccessK(t *maptype, h *hmap, key unsafe.Pointer) (unsafe.Pointer, unsafe
 				continue
 			}
 			k := add(unsafe.Pointer(b), dataOffset+i*uintptr(t.keysize))
-			if t.indirectkey {
+			if t.indirectkey() {
 				k = *((*unsafe.Pointer)(k))
 			}
 			if equalfn(key, k) {
 				v := add(unsafe.Pointer(b), dataOffset+bucketCnt*uintptr(t.keysize)+i*uintptr(t.valuesize))
-				if t.indirectvalue {
+				if t.indirectvalue() {
 					v = *((*unsafe.Pointer)(v))
 				}
 				return k, v
@@ -634,14 +640,14 @@ again:
 				continue
 			}
 			k := add(unsafe.Pointer(b), dataOffset+i*uintptr(t.keysize))
-			if t.indirectkey {
+			if t.indirectkey() {
 				k = *((*unsafe.Pointer)(k))
 			}
 			if !equalfn(key, k) {
 				continue
 			}
 			// already have a mapping for key. Update it.
-			if t.needkeyupdate {
+			if t.needkeyupdate() {
 				typedmemmove(t.key, k, key)
 			}
 			val = add(unsafe.Pointer(b), dataOffset+bucketCnt*uintptr(t.keysize)+i*uintptr(t.valuesize))
@@ -672,12 +678,12 @@ again:
 	}
 
 	// store new key/value at insert position
-	if t.indirectkey {
+	if t.indirectkey() {
 		kmem := newobject(t.key)
 		*(*unsafe.Pointer)(insertk) = kmem
 		insertk = kmem
 	}
-	if t.indirectvalue {
+	if t.indirectvalue() {
 		vmem := newobject(t.elem)
 		*(*unsafe.Pointer)(val) = vmem
 	}
@@ -690,7 +696,7 @@ done:
 		throw("concurrent map writes")
 	}
 	h.flags &^= hashWriting
-	if t.indirectvalue {
+	if t.indirectvalue() {
 		val = *((*unsafe.Pointer)(val))
 	}
 	return val
@@ -706,15 +712,18 @@ func mapdelete(t *maptype, h *hmap, key unsafe.Pointer) {
 	if msanenabled && h != nil {
 		msanread(key, t.key.size)
 	}
+	hashfn := t.key.hashfn
+	equalfn := t.key.equalfn
 	if h == nil || h.count == 0 {
+		if t.hashMightPanic() {
+			hashfn(key, 0) // see issue 23734
+		}
 		return
 	}
 	if h.flags&hashWriting != 0 {
 		throw("concurrent map writes")
 	}
 
-	hashfn := t.key.hashfn
-	equalfn := t.key.equalfn
 	hash := hashfn(key, uintptr(h.hash0))
 
 	// Set hashWriting after calling alg.hash, since alg.hash may panic,
@@ -735,20 +744,20 @@ search:
 			}
 			k := add(unsafe.Pointer(b), dataOffset+i*uintptr(t.keysize))
 			k2 := k
-			if t.indirectkey {
+			if t.indirectkey() {
 				k2 = *((*unsafe.Pointer)(k2))
 			}
 			if !equalfn(key, k2) {
 				continue
 			}
 			// Only clear key if there are pointers in it.
-			if t.indirectkey {
+			if t.indirectkey() {
 				*(*unsafe.Pointer)(k) = nil
 			} else if t.key.kind&kindNoPointers == 0 {
 				memclrHasPointers(k, t.key.size)
 			}
 			v := add(unsafe.Pointer(b), dataOffset+bucketCnt*uintptr(t.keysize)+i*uintptr(t.valuesize))
-			if t.indirectvalue {
+			if t.indirectvalue() {
 				*(*unsafe.Pointer)(v) = nil
 			} else if t.elem.kind&kindNoPointers == 0 {
 				memclrHasPointers(v, t.elem.size)
@@ -894,7 +903,7 @@ next:
 			continue
 		}
 		k := add(unsafe.Pointer(b), dataOffset+uintptr(offi)*uintptr(t.keysize))
-		if t.indirectkey {
+		if t.indirectkey() {
 			k = *((*unsafe.Pointer)(k))
 		}
 		v := add(unsafe.Pointer(b), dataOffset+bucketCnt*uintptr(t.keysize)+uintptr(offi)*uintptr(t.valuesize))
@@ -906,7 +915,7 @@ next:
 			// through the oldbucket, skipping any keys that will go
 			// to the other new bucket (each oldbucket expands to two
 			// buckets during a grow).
-			if t.reflexivekey || equalfn(k, k) {
+			if t.reflexivekey() || equalfn(k, k) {
 				// If the item in the oldbucket is not destined for
 				// the current new bucket in the iteration, skip it.
 				hash := hashfn(k, uintptr(h.hash0))
@@ -927,13 +936,13 @@ next:
 			}
 		}
 		if (b.tophash[offi] != evacuatedX && b.tophash[offi] != evacuatedY) ||
-			!(t.reflexivekey || equalfn(k, k)) {
+			!(t.reflexivekey() || equalfn(k, k)) {
 			// This is the golden data, we can return it.
 			// OR
 			// key!=key, so the entry can't be deleted or updated, so we can just return it.
 			// That's lucky for us because when key!=key we can't look it up successfully.
 			it.key = k
-			if t.indirectvalue {
+			if t.indirectvalue() {
 				v = *((*unsafe.Pointer)(v))
 			}
 			it.value = v
@@ -1157,7 +1166,7 @@ func evacuate(t *maptype, h *hmap, oldbucket uintptr) {
 					throw("bad map state")
 				}
 				k2 := k
-				if t.indirectkey {
+				if t.indirectkey() {
 					k2 = *((*unsafe.Pointer)(k2))
 				}
 				var useY uint8
@@ -1165,7 +1174,7 @@ func evacuate(t *maptype, h *hmap, oldbucket uintptr) {
 					// Compute hash to make our evacuation decision (whether we need
 					// to send this key/value to bucket x or bucket y).
 					hash := t.key.hashfn(k2, uintptr(h.hash0))
-					if h.flags&iterator != 0 && !t.reflexivekey && !t.key.equalfn(k2, k2) {
+					if h.flags&iterator != 0 && !t.reflexivekey() && !t.key.equalfn(k2, k2) {
 						// If key != key (NaNs), then the hash could be (and probably
 						// will be) entirely different from the old hash. Moreover,
 						// it isn't reproducible. Reproducibility is required in the
@@ -1200,12 +1209,12 @@ func evacuate(t *maptype, h *hmap, oldbucket uintptr) {
 					dst.v = add(dst.k, bucketCnt*uintptr(t.keysize))
 				}
 				dst.b.tophash[dst.i&(bucketCnt-1)] = top // mask dst.i as an optimization, to avoid a bounds check
-				if t.indirectkey {
+				if t.indirectkey() {
 					*(*unsafe.Pointer)(dst.k) = k2 // copy pointer
 				} else {
 					typedmemmove(t.key, dst.k, k) // copy value
 				}
-				if t.indirectvalue {
+				if t.indirectvalue() {
 					*(*unsafe.Pointer)(dst.v) = *(*unsafe.Pointer)(v)
 				} else {
 					typedmemmove(t.elem, dst.v, v)
@@ -1271,12 +1280,12 @@ func reflect_makemap(t *maptype, cap int) *hmap {
 	if !ismapkey(t.key) {
 		throw("runtime.reflect_makemap: unsupported map key type")
 	}
-	if t.key.size > maxKeySize && (!t.indirectkey || t.keysize != uint8(sys.PtrSize)) ||
-		t.key.size <= maxKeySize && (t.indirectkey || t.keysize != uint8(t.key.size)) {
+	if t.key.size > maxKeySize && (!t.indirectkey() || t.keysize != uint8(sys.PtrSize)) ||
+		t.key.size <= maxKeySize && (t.indirectkey() || t.keysize != uint8(t.key.size)) {
 		throw("key size wrong")
 	}
-	if t.elem.size > maxValueSize && (!t.indirectvalue || t.valuesize != uint8(sys.PtrSize)) ||
-		t.elem.size <= maxValueSize && (t.indirectvalue || t.valuesize != uint8(t.elem.size)) {
+	if t.elem.size > maxValueSize && (!t.indirectvalue() || t.valuesize != uint8(sys.PtrSize)) ||
+		t.elem.size <= maxValueSize && (t.indirectvalue() || t.valuesize != uint8(t.elem.size)) {
 		throw("value size wrong")
 	}
 	if t.key.align > bucketCnt {
diff --git a/libgo/go/runtime/type.go b/libgo/go/runtime/type.go
index 8fd38c3f396..5cafa38e18b 100644
--- a/libgo/go/runtime/type.go
+++ b/libgo/go/runtime/type.go
@@ -86,17 +86,32 @@ type interfacetype struct {
 }
 
 type maptype struct {
-	typ           _type
-	key           *_type
-	elem          *_type
-	bucket        *_type // internal type representing a hash bucket
-	keysize       uint8  // size of key slot
-	indirectkey   bool   // store ptr to key instead of key itself
-	valuesize     uint8  // size of value slot
-	indirectvalue bool   // store ptr to value instead of value itself
-	bucketsize    uint16 // size of bucket
-	reflexivekey  bool   // true if k==k for all keys
-	needkeyupdate bool   // true if we need to update key on an overwrite
+	typ        _type
+	key        *_type
+	elem       *_type
+	bucket     *_type // internal type representing a hash bucket
+	keysize    uint8  // size of key slot
+	valuesize  uint8  // size of value slot
+	bucketsize uint16 // size of bucket
+	flags      uint32
+}
+
+// Note: flag values must match those used in the TMAP case
+// in ../cmd/compile/internal/gc/reflect.go:dtypesym.
+func (mt *maptype) indirectkey() bool { // store ptr to key instead of key itself
+	return mt.flags&1 != 0
+}
+func (mt *maptype) indirectvalue() bool { // store ptr to value instead of value itself
+	return mt.flags&2 != 0
+}
+func (mt *maptype) reflexivekey() bool { // true if k==k for all keys
+	return mt.flags&4 != 0
+}
+func (mt *maptype) needkeyupdate() bool { // true if we need to update key on an overwrite
+	return mt.flags&8 != 0
+}
+func (mt *maptype) hashMightPanic() bool { // true if hash function might panic
+	return mt.flags&16 != 0
 }
 
 type arraytype struct {
-- 
2.30.2