compiler, reflect, runtime: remove zero field from type descriptor

    
    Type descriptors picked up a zero field because the gc map
    implementation used it.  However, it's since been dropped by the gc
    library.  It was never used by gccgo.  Drop it now in preparation for
    upgrading to the Go 1.5 library.
    
    Reviewed-on: https://go-review.googlesource.com/16486

From-SVN: r229546

4 files changed, 3 insertions, 23 deletions

diff --git a/libgo/go/reflect/type.go b/libgo/go/reflect/type.go
index 61b1955..5cdfba5 100644
--- a/libgo/go/reflect/type.go
+++ b/libgo/go/reflect/type.go
@@ -262,7 +262,6 @@ type rtype struct {
 	string        *string        // string form; unnecessary  but undeniably useful
 	*uncommonType                // (relatively) uncommon fields
 	ptrToThis     *rtype         // type for pointer to this type, if used in binary or has methods
-	zero          unsafe.Pointer // pointer to zero value
 }
 
 // Method on non-interface type
@@ -1129,7 +1128,6 @@ func (t *rtype) ptrTo() *rtype {
 
 	p.uncommonType = nil
 	p.ptrToThis = nil
-	p.zero = unsafe.Pointer(&make([]byte, p.size)[0])
 	p.elem = t
 
 	if t.kind&kindNoPointers != 0 {
@@ -1505,7 +1503,6 @@ func ChanOf(dir ChanDir, t Type) Type {
 	ch.elem = typ
 	ch.uncommonType = nil
 	ch.ptrToThis = nil
-	ch.zero = unsafe.Pointer(&make([]byte, ch.size)[0])
 
 	ch.gc = unsafe.Pointer(&chanGC{
 		width: ch.size,
@@ -1561,7 +1558,6 @@ func MapOf(key, elem Type) Type {
 	mt.elem = etyp
 	mt.uncommonType = nil
 	mt.ptrToThis = nil
-	mt.zero = unsafe.Pointer(&make([]byte, mt.size)[0])
 	// mt.gc = unsafe.Pointer(&ptrGC{
 	// 	width:  unsafe.Sizeof(uintptr(0)),
 	// 	op:     _GC_PTR,
@@ -1848,7 +1844,6 @@ func SliceOf(t Type) Type {
 	slice.elem = typ
 	slice.uncommonType = nil
 	slice.ptrToThis = nil
-	slice.zero = unsafe.Pointer(&make([]byte, slice.size)[0])
 
 	if typ.size == 0 {
 		slice.gc = unsafe.Pointer(&sliceEmptyGCProg)
@@ -1920,7 +1915,6 @@ func arrayOf(count int, elem Type) Type {
 	// TODO:
 	array.uncommonType = nil
 	array.ptrToThis = nil
-	array.zero = unsafe.Pointer(&make([]byte, array.size)[0])
 	array.len = uintptr(count)
 	array.slice = slice.(*rtype)
 
diff --git a/libgo/runtime/go-type.h b/libgo/runtime/go-type.h
index 72c9f56..eb063ec 100644
--- a/libgo/runtime/go-type.h
+++ b/libgo/runtime/go-type.h
@@ -108,11 +108,6 @@ struct __go_type_descriptor
   /* The descriptor for the type which is a pointer to this type.
      This may be NULL.  */
   const struct __go_type_descriptor *__pointer_to_this;
-
-  /* A pointer to a zero value for this type.  All types will point to
-     the same zero value, go$zerovalue, which is a common variable so
-     that it will be large enough.  */
-  void *__zero;
 };
 
 /* The information we store for each method of a type.  */
diff --git a/libgo/runtime/go-unsafe-pointer.c b/libgo/runtime/go-unsafe-pointer.c
index a59ae85..ce82fcd 100644
--- a/libgo/runtime/go-unsafe-pointer.c
+++ b/libgo/runtime/go-unsafe-pointer.c
@@ -10,9 +10,6 @@
 #include "go-type.h"
 #include "mgc0.h"
 
-/* A pointer with a zero value.  */
-static void *zero_pointer;
-
 /* This file provides the type descriptor for the unsafe.Pointer type.
    The unsafe package is defined by the compiler itself, which means
    that there is no package to compile to define the type
@@ -64,9 +61,7 @@ const struct __go_type_descriptor unsafe_Pointer =
   /* __uncommon */
   NULL,
   /* __pointer_to_this */
-  NULL,
-  /* __zero */
-  &zero_pointer
+  NULL
 };
 
 /* We also need the type descriptor for the pointer to unsafe.Pointer,
@@ -109,9 +104,7 @@ const struct __go_ptr_type pointer_unsafe_Pointer =
     /* __uncommon */
     NULL,
     /* __pointer_to_this */
-    NULL,
-    /* __zero */
-    &zero_pointer
+    NULL
   },
   /* __element_type */
   &unsafe_Pointer
diff --git a/libgo/runtime/proc.c b/libgo/runtime/proc.c
index db8b94f..8f82f5b 100644
--- a/libgo/runtime/proc.c
+++ b/libgo/runtime/proc.c
@@ -538,9 +538,7 @@ static struct __go_channel_type chan_bool_type_descriptor =
       /* __uncommon */
       NULL,
       /* __pointer_to_this */
-      NULL,
-      /* __zero */
-      NULL /* This value doesn't matter */
+      NULL
     },
     /* __element_type */
     &bool_type_descriptor,