Adding block metadata facilities into the GC package

druntime/mak/COPY

@@ -72,6 +72,7 @@ COPY=\
 	\
 	$(IMPDIR)\core\internal\gc\bits.d \
 	$(IMPDIR)\core\internal\gc\blkcache.d \
+	$(IMPDIR)\core\internal\gc\blockmeta.d \
 	$(IMPDIR)\core\internal\gc\os.d \
 	$(IMPDIR)\core\internal\gc\pooltable.d \
 	$(IMPDIR)\core\internal\gc\proxy.d \

druntime/mak/DOCS

@@ -529,6 +529,7 @@ DOCS=\
 	\
 	$(DOCDIR)\core_internal_gc_bits.html \
 	$(DOCDIR)\core_internal_gc_blkcache.html \
+	$(DOCDIR)\core_internal_gc_blockmeta.html \
 	$(DOCDIR)\core_internal_gc_os.html \
 	$(DOCDIR)\core_internal_gc_pooltable.html \
 	$(DOCDIR)\core_internal_gc_proxy.html \

druntime/mak/SRCS

@@ -75,6 +75,7 @@ SRCS=\
 	\
 	src\core\internal\gc\bits.d \
 	src\core\internal\gc\blkcache.d \
+	src\core\internal\gc\blockmeta.d \
 	src\core\internal\gc\os.d \
 	src\core\internal\gc\pooltable.d \
 	src\core\internal\gc\proxy.d \

druntime/src/core/internal/array/utils.d

@@ -263,111 +263,7 @@ void *__arrayStart()(return scope BlkInfo info) nothrow pure
  */
 bool __setArrayAllocLength(T)(ref BlkInfo info, size_t newLength, bool isShared, size_t oldLength = ~0)
 {
-    import core.atomic;
     import core.lifetime : TypeInfoSize;
-
-    size_t typeInfoSize = TypeInfoSize!T;
-
-    if (info.size <= 256)
-    {
-        import core.checkedint;
-
-        bool overflow;
-        auto newLengthPadded = addu(newLength,
-                                     addu(SMALLPAD, typeInfoSize, overflow),
-                                     overflow);
-
-        if (newLengthPadded > info.size || overflow)
-            // new size does not fit inside block
-            return false;
-
-        auto length = cast(ubyte *)(info.base + info.size - typeInfoSize - SMALLPAD);
-        if (oldLength != ~0)
-        {
-            if (isShared)
-            {
-                return cas(cast(shared)length, cast(ubyte)oldLength, cast(ubyte)newLength);
-            }
-            else
-            {
-                if (*length == cast(ubyte)oldLength)
-                    *length = cast(ubyte)newLength;
-                else
-                    return false;
-            }
-        }
-        else
-        {
-            // setting the initial length, no cas needed
-            *length = cast(ubyte)newLength;
-        }
-        if (typeInfoSize)
-        {
-            auto typeInfo = cast(TypeInfo*)(info.base + info.size - size_t.sizeof);
-            *typeInfo = cast()typeid(T);
-        }
-    }
-    else if (info.size < PAGESIZE)
-    {
-        if (newLength + MEDPAD + typeInfoSize > info.size)
-            // new size does not fit inside block
-            return false;
-        auto length = cast(ushort *)(info.base + info.size - typeInfoSize - MEDPAD);
-        if (oldLength != ~0)
-        {
-            if (isShared)
-            {
-                return cas(cast(shared)length, cast(ushort)oldLength, cast(ushort)newLength);
-            }
-            else
-            {
-                if (*length == oldLength)
-                    *length = cast(ushort)newLength;
-                else
-                    return false;
-            }
-        }
-        else
-        {
-            // setting the initial length, no cas needed
-            *length = cast(ushort)newLength;
-        }
-        if (typeInfoSize)
-        {
-            auto typeInfo = cast(TypeInfo*)(info.base + info.size - size_t.sizeof);
-            *typeInfo = cast()typeid(T);
-        }
-    }
-    else
-    {
-        if (newLength + LARGEPAD > info.size)
-            // new size does not fit inside block
-            return false;
-        auto length = cast(size_t *)(info.base);
-        if (oldLength != ~0)
-        {
-            if (isShared)
-            {
-                return cas(cast(shared)length, cast(size_t)oldLength, cast(size_t)newLength);
-            }
-            else
-            {
-                if (*length == oldLength)
-                    *length = newLength;
-                else
-                    return false;
-            }
-        }
-        else
-        {
-            // setting the initial length, no cas needed
-            *length = newLength;
-        }
-        if (typeInfoSize)
-        {
-            auto typeInfo = cast(TypeInfo*)(info.base + size_t.sizeof);
-            *typeInfo = cast()typeid(T);
-        }
-    }
-    return true; // resize succeeded
+    import core.internal.gc.blockmeta : __setArrayAllocLengthImpl;
+    return __setArrayAllocLengthImpl(info, newLength, isShared, typeid(T), oldLength, TypeInfoSize!T);
 }

druntime/src/core/internal/gc/blockmeta.d

@@ -0,0 +1,209 @@
+/**
+ Functions to manipulate metadata in-block.
+
+ functionality was moved from rt.lifetime
+ */
+module core.internal.gc.blockmeta;
+
+import core.memory;
+
+alias BlkInfo = GC.BlkInfo;
+alias BlkAttr = GC.BlkAttr;
+
+enum : size_t
+{
+    PAGESIZE = 4096,
+    BIGLENGTHMASK = ~(PAGESIZE - 1),
+    SMALLPAD = 1,
+    MEDPAD = ushort.sizeof,
+    LARGEPREFIX = 16, // 16 bytes padding at the front of the array
+    LARGEPAD = LARGEPREFIX + 1,
+    MAXSMALLSIZE = 256-SMALLPAD,
+    MAXMEDSIZE = (PAGESIZE / 2) - MEDPAD
+}
+
+// size used to store the TypeInfo at the end of an allocation for structs that have a destructor
+size_t structTypeInfoSize(const TypeInfo ti) pure nothrow @nogc
+{
+    if (ti && typeid(ti) is typeid(TypeInfo_Struct)) // avoid a complete dynamic type cast
+    {
+        auto sti = cast(TypeInfo_Struct)cast(void*)ti;
+        if (sti.xdtor)
+            return size_t.sizeof;
+    }
+    return 0;
+}
+
+/**
+  Set the allocated length of the array block.  This is called
+  any time an array is appended to or its length is set.
+
+  The allocated block looks like this for blocks < PAGESIZE:
+
+  |elem0|elem1|elem2|...|elemN-1|emptyspace|N*elemsize|
+
+
+  The size of the allocated length at the end depends on the block size:
+
+  a block of 16 to 256 bytes has an 8-bit length.
+
+  a block with 512 to pagesize/2 bytes has a 16-bit length.
+
+  For blocks >= pagesize, the length is a size_t and is at the beginning of the
+  block.  The reason we have to do this is because the block can extend into
+  more pages, so we cannot trust the block length if it sits at the end of the
+  block, because it might have just been extended.  If we can prove in the
+  future that the block is unshared, we may be able to change this, but I'm not
+  sure it's important.
+
+  In order to do put the length at the front, we have to provide 16 bytes
+  buffer space in case the block has to be aligned properly.  In x86, certain
+  SSE instructions will only work if the data is 16-byte aligned.  In addition,
+  we need the sentinel byte to prevent accidental pointers to the next block.
+  Because of the extra overhead, we only do this for page size and above, where
+  the overhead is minimal compared to the block size.
+
+  So for those blocks, it looks like:
+
+  |N*elemsize|padding|elem0|elem1|...|elemN-1|emptyspace|sentinelbyte|
+
+  where elem0 starts 16 bytes after the first byte.
+  */
+bool __setArrayAllocLength(ref BlkInfo info, size_t newlength, bool isshared, const TypeInfo tinext, size_t oldlength = ~0) pure nothrow
+{
+    size_t typeInfoSize = structTypeInfoSize(tinext);
+    return __setArrayAllocLengthImpl(info, newlength, isshared, tinext, oldlength, typeInfoSize);
+}
+
+// the impl function, used both above and in core.internal.array.utils
+bool __setArrayAllocLengthImpl(ref BlkInfo info, size_t newlength, bool isshared, const TypeInfo tinext, size_t oldlength, size_t typeInfoSize) pure nothrow
+{
+    import core.atomic;
+
+    if (info.size <= 256)
+    {
+        import core.checkedint;
+
+        bool overflow;
+        auto newlength_padded = addu(newlength,
+                                     addu(SMALLPAD, typeInfoSize, overflow),
+                                     overflow);
+
+        if (newlength_padded > info.size || overflow)
+            // new size does not fit inside block
+            return false;
+
+        auto length = cast(ubyte *)(info.base + info.size - typeInfoSize - SMALLPAD);
+        if (oldlength != ~0)
+        {
+            if (isshared)
+            {
+                return cas(cast(shared)length, cast(ubyte)oldlength, cast(ubyte)newlength);
+            }
+            else
+            {
+                if (*length == cast(ubyte)oldlength)
+                    *length = cast(ubyte)newlength;
+                else
+                    return false;
+            }
+        }
+        else
+        {
+            // setting the initial length, no cas needed
+            *length = cast(ubyte)newlength;
+        }
+        if (typeInfoSize)
+        {
+            auto typeInfo = cast(TypeInfo*)(info.base + info.size - size_t.sizeof);
+            *typeInfo = cast() tinext;
+        }
+    }
+    else if (info.size < PAGESIZE)
+    {
+        if (newlength + MEDPAD + typeInfoSize > info.size)
+            // new size does not fit inside block
+            return false;
+        auto length = cast(ushort *)(info.base + info.size - typeInfoSize - MEDPAD);
+        if (oldlength != ~0)
+        {
+            if (isshared)
+            {
+                return cas(cast(shared)length, cast(ushort)oldlength, cast(ushort)newlength);
+            }
+            else
+            {
+                if (*length == oldlength)
+                    *length = cast(ushort)newlength;
+                else
+                    return false;
+            }
+        }
+        else
+        {
+            // setting the initial length, no cas needed
+            *length = cast(ushort)newlength;
+        }
+        if (typeInfoSize)
+        {
+            auto typeInfo = cast(TypeInfo*)(info.base + info.size - size_t.sizeof);
+            *typeInfo = cast() tinext;
+        }
+    }
+    else
+    {
+        if (newlength + LARGEPAD > info.size)
+            // new size does not fit inside block
+            return false;
+        auto length = cast(size_t *)(info.base);
+        if (oldlength != ~0)
+        {
+            if (isshared)
+            {
+                return cas(cast(shared)length, cast(size_t)oldlength, cast(size_t)newlength);
+            }
+            else
+            {
+                if (*length == oldlength)
+                    *length = newlength;
+                else
+                    return false;
+            }
+        }
+        else
+        {
+            // setting the initial length, no cas needed
+            *length = newlength;
+        }
+        if (typeInfoSize)
+        {
+            auto typeInfo = cast(TypeInfo*)(info.base + size_t.sizeof);
+            *typeInfo = cast()tinext;
+        }
+    }
+    return true; // resize succeeded
+}
+
+/**
+  get the allocation size of the array for the given block (without padding or type info)
+  */
+size_t __arrayAllocLength(ref BlkInfo info, const TypeInfo tinext) pure nothrow
+{
+    if (info.size <= 256)
+        return *cast(ubyte *)(info.base + info.size - structTypeInfoSize(tinext) - SMALLPAD);
+
+    if (info.size < PAGESIZE)
+        return *cast(ushort *)(info.base + info.size - structTypeInfoSize(tinext) - MEDPAD);
+
+    return *cast(size_t *)(info.base);
+}
+
+/**
+  get the padding required to allocate size bytes.  Note that the padding is
+  NOT included in the passed in size.  Therefore, do NOT call this function
+  with the size of an allocated block.
+  */
+size_t __arrayPad(size_t size, const TypeInfo tinext) nothrow pure @trusted
+{
+    return size > MAXMEDSIZE ? LARGEPAD : ((size > MAXSMALLSIZE ? MEDPAD : SMALLPAD) + structTypeInfoSize(tinext));
+}