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Nim/compiler/sizealignoffsetimpl.nim
Arne Döring 1e08fff2d5 bitsize respected in size calculation. (#9756)
2018-11-19 13:48:40 +01:00

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#
#
# The Nim Compiler
#
# See the file "copying.txt", included in this
# distribution, for details about the copyright.
#
## code owner: Arne Döring
## e-mail: arne.doering@gmx.net
proc align(address, alignment: BiggestInt): BiggestInt =
result = (address + (alignment - 1)) and not (alignment - 1)
const
## a size is concidered "unknown" when it is an imported type from C
## or C++.
szUnknownSize* = -3
szIllegalRecursion* = -2
szUncomputedSize* = -1
proc computeSizeAlign(conf: ConfigRef; typ: PType): void
proc computeSubObjectAlign(conf: ConfigRef; n: PNode): BiggestInt =
## returns object alignment
case n.kind
of nkRecCase:
assert(n.sons[0].kind == nkSym)
result = computeSubObjectAlign(conf, n.sons[0])
for i in 1 ..< sonsLen(n):
let child = n.sons[i]
case child.kind
of nkOfBranch, nkElse:
let align = computeSubObjectAlign(conf, child.lastSon)
if align < 0:
return align
result = max(result, align)
else:
internalError(conf, "computeSubObjectAlign")
of nkRecList:
result = 1
for i, child in n.sons:
let align = computeSubObjectAlign(conf, n.sons[i])
if align < 0:
return align
result = max(result, align)
of nkSym:
computeSizeAlign(conf, n.sym.typ)
result = n.sym.typ.align
else:
result = 1
proc computeObjectOffsetsFoldFunction(conf: ConfigRef; n: PNode, initialOffset: BiggestInt): tuple[offset, align: BiggestInt] =
## ``offset`` is the offset within the object, after the node has been written, no padding bytes added
## ``align`` maximum alignment from all sub nodes
if n.typ != nil and n.typ.size == szIllegalRecursion:
result.offset = szIllegalRecursion
result.align = szIllegalRecursion
return
result.align = 1
case n.kind
of nkRecCase:
assert(n.sons[0].kind == nkSym)
let (kindOffset, kindAlign) = computeObjectOffsetsFoldFunction(conf, n.sons[0], initialOffset)
var maxChildAlign: BiggestInt = 0
for i in 1 ..< sonsLen(n):
let child = n.sons[i]
case child.kind
of nkOfBranch, nkElse:
# offset parameter cannot be known yet, it needs to know the alignment first
let align = computeSubObjectAlign(conf, n.sons[i].lastSon)
if align == szIllegalRecursion:
result.offset = szIllegalRecursion
result.align = szIllegalRecursion
return
if align == szUnknownSize or maxChildAlign == szUnknownSize:
maxChildAlign = szUnknownSize
else:
maxChildAlign = max(maxChildAlign, align)
else:
internalError(conf, "computeObjectOffsetsFoldFunction(record case branch)")
if maxChildAlign == szUnknownSize:
result.align = szUnknownSize
result.offset = szUnknownSize
else:
# the union neds to be aligned first, before the offsets can be assigned
let kindUnionOffset = align(kindOffset, maxChildAlign)
var maxChildOffset: BiggestInt = 0
for i in 1 ..< sonsLen(n):
let (offset, align) = computeObjectOffsetsFoldFunction(conf, n.sons[i].lastSon, kindUnionOffset)
maxChildOffset = max(maxChildOffset, offset)
result.align = max(kindAlign, maxChildAlign)
result.offset = maxChildOffset
of nkRecList:
result.align = 1 # maximum of all member alignments
var offset = initialOffset
for i, child in n.sons:
let (new_offset, align) = computeObjectOffsetsFoldFunction(conf, child, offset)
if new_offset == szIllegalRecursion:
result.offset = szIllegalRecursion
result.align = szIllegalRecursion
return
elif new_offset == szUnknownSize or offset == szUnknownSize:
# if anything is unknown, the rest becomes unknown as well
offset = szUnknownSize
result.align = szUnknownSize
else:
offset = new_offset
result.align = max(result.align, align)
# final alignment
if offset == szUnknownSize:
result.offset = szUnknownSize
else:
result.offset = align(offset, result.align)
of nkSym:
var size = szUnknownSize
var align = szUnknownSize
if n.sym.bitsize == 0: # 0 represents bitsize not set
computeSizeAlign(conf, n.sym.typ)
size = n.sym.typ.size.int
align = n.sym.typ.align.int
result.align = align
if initialOffset == szUnknownSize or size == szUnknownSize:
n.sym.offset = szUnknownSize
result.offset = szUnknownSize
else:
n.sym.offset = align(initialOffset, align).int
result.offset = n.sym.offset + n.sym.typ.size
else:
result.align = szUnknownSize
result.offset = szUnknownSize
proc computePackedObjectOffsetsFoldFunction(conf: ConfigRef; n: PNode, initialOffset: BiggestInt, debug: bool): BiggestInt =
## ``result`` is the offset within the object, after the node has been written, no padding bytes added
case n.kind
of nkRecCase:
assert(n.sons[0].kind == nkSym)
let kindOffset = computePackedObjectOffsetsFoldFunction(conf, n.sons[0], initialOffset, debug)
# the union neds to be aligned first, before the offsets can be assigned
let kindUnionOffset = kindOffset
var maxChildOffset: BiggestInt = kindUnionOffset
for i in 1 ..< sonsLen(n):
let offset = computePackedObjectOffsetsFoldFunction(conf, n.sons[i].lastSon, kindUnionOffset, debug)
maxChildOffset = max(maxChildOffset, offset)
result = maxChildOffset
of nkRecList:
result = initialOffset
for i, child in n.sons:
result = computePackedObjectOffsetsFoldFunction(conf, child, result, debug)
if result == szIllegalRecursion:
break
of nkSym:
computeSizeAlign(conf, n.sym.typ)
n.sym.offset = initialOffset.int
result = n.sym.offset + n.sym.typ.size
else:
result = szUnknownSize
# TODO this one needs an alignment map of the individual types
proc computeSizeAlign(conf: ConfigRef; typ: PType) =
## computes and sets ``size`` and ``align`` members of ``typ``
let hasSize = typ.size != szUncomputedSize
let hasAlign = typ.align != szUncomputedSize
if hasSize and hasAlign:
# nothing to do, size and align already computed
return
# This function can only calculate both, size and align at the same time.
# If one of them is already set this value is stored here and reapplied
let revertSize = typ.size
let revertAlign = typ.align
defer:
if hasSize:
typ.size = revertSize
if hasAlign:
typ.align = revertAlign
if typ.size == szIllegalRecursion or typ.align == szIllegalRecursion:
# we are already computing the size of the type
# --> illegal recursion in type
return
# mark computation in progress
typ.size = szIllegalRecursion
typ.align = szIllegalRecursion
var maxAlign, sizeAccum, length: BiggestInt
var tk = typ.kind
case tk
of tyProc:
if typ.callConv == ccClosure:
typ.size = 2 * conf.target.ptrSize
else:
typ.size = conf.target.ptrSize
typ.align = int16(conf.target.ptrSize)
of tyNil:
typ.size = conf.target.ptrSize
typ.align = int16(conf.target.ptrSize)
of tyString:
if tfHasAsgn in typ.flags:
typ.size = conf.target.ptrSize * 2
else:
typ.size = conf.target.ptrSize
typ.align = int16(conf.target.ptrSize)
of tyCString, tySequence, tyPtr, tyRef, tyVar, tyLent, tyOpenArray:
let base = typ.lastSon
if base == typ:
# this is not the correct location to detect ``type A = ptr A``
typ.size = szIllegalRecursion
typ.align = szIllegalRecursion
return
# recursive tuplers are not allowed and should be detected in the frontend
if base.kind == tyTuple:
computeSizeAlign(conf, base)
if base.size == szIllegalRecursion:
typ.size = szIllegalRecursion
typ.align = szIllegalRecursion
return
typ.align = int16(conf.target.ptrSize)
if typ.kind == tySequence and tfHasAsgn in typ.flags:
typ.size = conf.target.ptrSize * 2
else:
typ.size = conf.target.ptrSize
of tyArray:
computeSizeAlign(conf, typ.sons[1])
let elemSize = typ.sons[1].size
if elemSize < 0:
typ.size = elemSize
typ.align = int16(elemSize)
else:
typ.size = lengthOrd(conf, typ.sons[0]) * elemSize
typ.align = typ.sons[1].align
of tyUncheckedArray:
let base = typ.lastSon
computeSizeAlign(conf, base)
typ.size = szUnknownSize
typ.align = base.align
of tyEnum:
if firstOrd(conf, typ) < 0:
typ.size = 4 # use signed int32
typ.align = 4
else:
length = lastOrd(conf, typ) # BUGFIX: use lastOrd!
if length + 1 < `shl`(1, 8):
typ.size = 1
typ.align = 1
elif length + 1 < `shl`(1, 16):
typ.size = 2
typ.align = 2
elif length + 1 < `shl`(BiggestInt(1), 32):
typ.size = 4
typ.align = 4
else:
typ.size = 8
typ.align = 8
of tySet:
if typ.sons[0].kind == tyGenericParam:
typ.size = szUncomputedSize
typ.align = szUncomputedSize # in original version this was 1
else:
length = lengthOrd(conf, typ.sons[0])
if length <= 8:
typ.size = 1
elif length <= 16:
typ.size = 2
elif length <= 32:
typ.size = 4
elif length <= 64:
typ.size = 8
elif align(length, 8) mod 8 == 0:
typ.size = align(length, 8) div 8
else:
typ.size = align(length, 8) div 8 + 1
typ.align = int16(typ.size)
of tyRange:
computeSizeAlign(conf, typ.sons[0])
typ.size = typ.sons[0].size
typ.align = typ.sons[0].align
of tyTuple:
maxAlign = 1
sizeAccum = 0
for i in countup(0, sonsLen(typ) - 1):
let child = typ.sons[i]
computeSizeAlign(conf, child)
if child.size == szIllegalRecursion:
typ.size = szIllegalRecursion
typ.align = szIllegalRecursion
return
maxAlign = max(maxAlign, child.align)
sizeAccum = align(sizeAccum, child.align) + child.size
typ.size = align(sizeAccum, maxAlign)
typ.align = int16(maxAlign)
of tyObject:
var headerSize: BiggestInt
var headerAlign: int16
if typ.sons[0] != nil:
# compute header size
if conf.cmd == cmdCompileToCpp:
# if the target is C++ the members of this type are written
# into the padding byets at the end of the parent type. At the
# moment it is not supported to calculate that.
headerSize = szUnknownSize
headerAlign = szUncomputedSize
else:
var st = typ.sons[0]
while st.kind in skipPtrs:
st = st.sons[^1]
computeSizeAlign(conf, st)
if st.size == szIllegalRecursion:
typ.size = st.size
typ.align = st.align
return
headerSize = st.size
headerAlign = st.align
elif isObjectWithTypeFieldPredicate(typ):
# this branch is taken for RootObj
headerSize = conf.target.intSize
headerAlign = conf.target.intSize.int16
else:
headerSize = 0
headerAlign = 1
let (offset, align) =
if tfPacked in typ.flags:
(computePackedObjectOffsetsFoldFunction(conf, typ.n, headerSize, false), BiggestInt(1))
else:
computeObjectOffsetsFoldFunction(conf, typ.n, headerSize)
if offset == szIllegalRecursion:
typ.size = szIllegalRecursion
typ.align = szIllegalRecursion
return
if offset == szUnknownSize or (
typ.sym != nil and
typ.sym.flags * {sfCompilerProc, sfImportc} == {sfImportc}):
typ.size = szUnknownSize
typ.align = szUnknownSize
return
# header size is already in size from computeObjectOffsetsFoldFunction
# maxAlign is probably not changed at all from headerAlign
if tfPacked in typ.flags:
typ.size = offset
typ.align = 1
else:
typ.align = int16(max(align, headerAlign))
typ.size = align(offset, typ.align)
of tyInferred:
if typ.len > 1:
computeSizeAlign(conf, typ.lastSon)
typ.size = typ.lastSon.size
typ.align = typ.lastSon.align
of tyGenericInst, tyDistinct, tyGenericBody, tyAlias:
computeSizeAlign(conf, typ.lastSon)
typ.size = typ.lastSon.size
typ.align = typ.lastSon.align
of tyTypeClasses:
if typ.isResolvedUserTypeClass:
computeSizeAlign(conf, typ.lastSon)
typ.size = typ.lastSon.size
typ.align = typ.lastSon.align
else:
typ.size = szUncomputedSize
typ.align = szUncomputedSize
of tyTypeDesc:
computeSizeAlign(conf, typ.base)
typ.size = typ.base.size
typ.align = typ.base.align
of tyForward:
# is this really illegal recursion, or maybe just unknown?
typ.size = szIllegalRecursion
typ.align = szIllegalRecursion
of tyStatic:
if typ.n != nil:
computeSizeAlign(conf, typ.lastSon)
typ.size = typ.lastSon.size
typ.align = typ.lastSon.align
else:
typ.size = szUncomputedSize
typ.align = szUncomputedSize
else:
typ.size = szUncomputedSize
typ.align = szUncomputedSize
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