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Bug 1523996 - part 2 - pack IPDL-defined struct members better; r=Alex_Gaynor

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This patch changes the layout of IPDL-defined structs to order the POD
members by decreasing size, which ensures everything is packed well.
This optimization is only applied to the internal representation; the
external interface (e.g. constructors) is entirely unchaged.

Differential Revision: https://phabricator.services.mozilla.com/D21998

--HG--
extra : moz-landing-system : lando
This commit is contained in:
Nathan Froyd 2019-03-06 13:59:39 +00:00
parent e1246d9446
commit aace5317f4
1 changed files with 22 additions and 7 deletions
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29
ipc/ipdl/ipdl/lower.py
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@ -763,6 +763,16 @@ class _CompoundTypeComponent(_HybridDecl):
class StructDecl(ipdl.ast.StructDecl, HasFQName):
def fields_ipdl_order(self):
for f in self.fields:
yield f
def fields_member_order(self):
assert len(self.packed_field_order) == len(self.fields)
for i in self.packed_field_order:
yield self.fields[i]
@staticmethod
def upgrade(structDecl):
assert isinstance(structDecl, ipdl.ast.StructDecl)
@ -2054,7 +2064,9 @@ class _ParamTraits():
write = []
read = []
for f in sd.fields:
# The iteration order here doesn't particularly matter, but we choose
# member order for ideally better cache performance.
for f in sd.fields_member_order():
writefield = cls.checkedWrite(f.ipdltype,
get('.', f),
cls.msgvar,
@ -2290,12 +2302,14 @@ def _generateCxxStruct(sd):
constreftype = Type(sd.name, const=True, ref=True)
def fieldsAsParamList():
return [Decl(f.inType(), f.argVar().name) for f in sd.fields]
return [Decl(f.inType(), f.argVar().name) for f in sd.fields_ipdl_order()]
# If this is an empty struct (no fields), then the default ctor
# and "create-with-fields" ctors are equivalent. So don't bother
# with the default ctor.
if len(sd.fields):
assert len(sd.fields) == len(sd.packed_field_order)
# Struct()
defctor = ConstructorDefn(ConstructorDecl(sd.name, force_inline=True))
@ -2304,7 +2318,8 @@ def _generateCxxStruct(sd):
# normally to their default values, and will initialize any actor member
# pointers to the correct default value of `nullptr`. Other C++ types
# with custom constructors must also provide a default constructor.
defctor.memberinits = [ExprMemberInit(f.memberVar()) for f in sd.fields]
defctor.memberinits = [ExprMemberInit(f.memberVar())
for f in sd.fields_member_order()]
struct.addstmts([defctor, Whitespace.NL])
# Struct(const field1& _f1, ...)
@ -2313,7 +2328,7 @@ def _generateCxxStruct(sd):
force_inline=True))
valctor.memberinits = [ExprMemberInit(f.memberVar(),
args=[f.argVar()])
for f in sd.fields]
for f in sd.fields_member_order()]
struct.addstmts([valctor, Whitespace.NL])
# The default copy, move, and assignment constructors, and the default
@ -2326,7 +2341,7 @@ def _generateCxxStruct(sd):
params=[Decl(constreftype, ovar.name)],
ret=Type.BOOL,
const=True))
for f in sd.fields:
for f in sd.fields_ipdl_order():
ifneq = StmtIf(ExprNot(
ExprBinary(ExprCall(f.getMethod()), '==',
ExprCall(f.getMethod(ovar)))))
@ -2347,7 +2362,7 @@ def _generateCxxStruct(sd):
# field1& f1()
# const field1& f1() const
for f in sd.fields:
for f in sd.fields_ipdl_order():
get = MethodDefn(MethodDecl(f.getMethod().name,
params=[],
ret=f.refType(),
@ -2367,7 +2382,7 @@ def _generateCxxStruct(sd):
# members
struct.addstmts([StmtDecl(Decl(f.bareType(), f.memberVar().name))
for f in sd.fields])
for f in sd.fields_member_order()])
return forwarddeclstmts, fulldecltypes, struct