compiler, runtime: remove hmap field from maptypes

This is the gofrontend version of https://golang.org/cl/91796.
    
    This is part of that CL, just the compiler change and required runtime
    changes, in preparation for updating libgo to 1.11.
    
    Relevant part of original CL description:
    
        The hmap field in the maptype is only used by the runtime to check the sizes of
        the hmap structure created by the compiler and runtime agree.
    
        Comments are already present about the hmap structure definitions in the
        compiler and runtime needing to be in sync.
    
    Reviewed-on: https://go-review.googlesource.com/130976

From-SVN: r263941

gcc/go/gofrontend/MERGE

@@ -1,4 +1,4 @@
-8deaafd14414bb5cbbdf3e2673f61b6d836d7d2a
+da249ffd264154cc992e76ff03f91f700d3bf53e
 
 The first line of this file holds the git revision number of the last
 merge done from the gofrontend repository.

gcc/go/gofrontend/types.cc

@@ -7975,12 +7975,11 @@ Map_type::make_map_type_descriptor_type()
       Type* bool_type = Type::lookup_bool_type();
 
       Struct_type* sf =
-	Type::make_builtin_struct_type(12,
+	Type::make_builtin_struct_type(11,
 				       "", tdt,
 				       "key", ptdt,
 				       "elem", ptdt,
 				       "bucket", ptdt,
-				       "hmap", ptdt,
 				       "keysize", uint8_type,
 				       "indirectkey", bool_type,
 				       "valuesize", uint8_type,
@@ -8064,11 +8063,6 @@ Map_type::do_type_descriptor(Gogo* gogo, Named_type* name)
   go_assert(p->is_field_name("bucket"));
   vals->push_back(Expression::make_type_descriptor(bucket_type, bloc));
 
-  ++p;
-  go_assert(p->is_field_name("hmap"));
-  Type* hmap_type = this->hmap_type(bucket_type);
-  vals->push_back(Expression::make_type_descriptor(hmap_type, bloc));
-
   ++p;
   go_assert(p->is_field_name("keysize"));
   if (keysize > Map_type::max_key_size)

libgo/go/reflect/type.go

@@ -351,7 +351,6 @@ type mapType struct {
 	key           *rtype // map key type
 	elem          *rtype // map element (value) type
 	bucket        *rtype // internal bucket structure
-	hmap          *rtype // internal map header
 	keysize       uint8  // size of key slot
 	indirectkey   uint8  // store ptr to key instead of key itself
 	valuesize     uint8  // size of value slot

libgo/go/runtime/hashmap.go

@@ -311,20 +311,13 @@ func makemap_small() *hmap {
 // If h != nil, the map can be created directly in h.
 // If h.buckets != nil, bucket pointed to can be used as the first bucket.
 func makemap(t *maptype, hint int, h *hmap) *hmap {
-	// The size of hmap should be 48 bytes on 64 bit
-	// and 28 bytes on 32 bit platforms.
-	if sz := unsafe.Sizeof(hmap{}); sz != 8+5*sys.PtrSize {
-		println("runtime: sizeof(hmap) =", sz, ", t.hmap.size =", t.hmap.size)
-		throw("bad hmap size")
-	}
-
 	if hint < 0 || hint > int(maxSliceCap(t.bucket.size)) {
 		hint = 0
 	}
 
 	// initialize Hmap
 	if h == nil {
-		h = (*hmap)(newobject(t.hmap))
+		h = new(hmap)
 	}
 	h.hash0 = fastrand()
 
@@ -1210,11 +1203,6 @@ func ismapkey(t *_type) bool {
 
 //go:linkname reflect_makemap reflect.makemap
 func reflect_makemap(t *maptype, cap int) *hmap {
-	// Check invariants and reflects math.
-	if sz := unsafe.Sizeof(hmap{}); sz != t.hmap.size {
-		println("runtime: sizeof(hmap) =", sz, ", t.hmap.size =", t.hmap.size)
-		throw("bad hmap size")
-	}
 	if !ismapkey(t.key) {
 		throw("runtime.reflect_makemap: unsupported map key type")
 	}

libgo/go/runtime/type.go

@@ -72,7 +72,6 @@ type maptype struct {
 	key           *_type
 	elem          *_type
 	bucket        *_type // internal type representing a hash bucket
-	hmap          *_type // internal type representing a hmap
 	keysize       uint8  // size of key slot
 	indirectkey   bool   // store ptr to key instead of key itself
 	valuesize     uint8  // size of value slot