module separate_compiler
import abstract_compiler
-intrude import coloring
+import layout_builders
import rapid_type_analysis
# Add separate compiler specific options
var opt_phmod_typing: OptionBool = new OptionBool("Replace coloration by perfect hashing (with mod operator)", "--phmod-typing")
# --use-and-perfect-hashing
var opt_phand_typing: OptionBool = new OptionBool("Replace coloration by perfect hashing (with and operator)", "--phand-typing")
- # --generic-resolution-tree
- var opt_typing_table_metrics: OptionBool = new OptionBool("Enable static size measuring of tables used for typing and resolution", "--typing-table-metrics")
+ # --tables-metrics
+ var opt_tables_metrics: OptionBool = new OptionBool("Enable static size measuring of tables used for vft, typing and resolution", "--tables-metrics")
redef init
do
self.option_context.add_option(self.opt_bm_typing)
self.option_context.add_option(self.opt_phmod_typing)
self.option_context.add_option(self.opt_phand_typing)
- self.option_context.add_option(self.opt_typing_table_metrics)
+ self.option_context.add_option(self.opt_tables_metrics)
end
end
class SeparateCompiler
super AbstractCompiler
- # Cache for classid
- protected var classids: HashMap[MClassType, String] = new HashMap[MClassType, String]
-
# The result of the RTA (used to know live types and methods)
var runtime_type_analysis: RapidTypeAnalysis
private var undead_types: Set[MType] = new HashSet[MType]
private var partial_types: Set[MType] = new HashSet[MType]
+ private var live_unresolved_types: Map[MClassDef, Set[MType]] = new HashMap[MClassDef, HashSet[MType]]
- private var type_layout_builder: TypingLayoutBuilder[MType]
- private var type_layout: nullable TypingLayout[MType]
- private var type_tables: nullable Map[MType, Array[nullable MType]] = null
-
- private var live_unanchored_types: Map[MClassDef, Set[MType]] = new HashMap[MClassDef, HashSet[MType]]
-
- private var resolution_layout: nullable ResolutionLayout
- private var resolution_tables: nullable Map[MClassType, Array[nullable MType]]
-
- protected var method_layout: nullable PropertyLayout[MMethod]
- protected var method_tables: Map[MClass, Array[nullable MPropDef]]
-
- protected var attr_layout: nullable PropertyLayout[MAttribute]
- protected var attr_tables: Map[MClass, Array[nullable MPropDef]]
+ private var type_layout: nullable Layout[MType]
+ private var resolution_layout: nullable Layout[MType]
+ protected var method_layout: nullable Layout[MMethod]
+ protected var attr_layout: nullable Layout[MAttribute]
init(mainmodule: MModule, mmbuilder: ModelBuilder, runtime_type_analysis: RapidTypeAnalysis) do
- super
+ super(mainmodule, mmbuilder)
self.header = new_visitor
- self.init_layout_builders
self.runtime_type_analysis = runtime_type_analysis
self.do_property_coloring
self.compile_box_kinds
end
- protected fun init_layout_builders do
- # Typing Layout
- if modelbuilder.toolcontext.opt_bm_typing.value then
- self.type_layout_builder = new BMTypeLayoutBuilder(self.mainmodule)
- else if modelbuilder.toolcontext.opt_phmod_typing.value then
- self.type_layout_builder = new PHTypeLayoutBuilder(self.mainmodule, new PHModOperator)
- self.header.add_decl("#define HASH(mask, id) ((mask)%(id))")
- else if modelbuilder.toolcontext.opt_phand_typing.value then
- self.type_layout_builder = new PHTypeLayoutBuilder(self.mainmodule, new PHAndOperator)
- self.header.add_decl("#define HASH(mask, id) ((mask)&(id))")
- else
- self.type_layout_builder = new CLTypeLayoutBuilder(self.mainmodule)
- end
- end
-
redef fun compile_header_structs do
self.header.add_decl("typedef void(*nitmethod_t)(void); /* general C type representing a Nit method. */")
self.compile_header_attribute_structs
self.header.add_decl("struct class \{ int box_kind; nitmethod_t vft[1]; \}; /* general C type representing a Nit class. */")
- # With unanchored_table, all live type resolution are stored in a big table: unanchored_table
- self.header.add_decl("struct type \{ int id; const char *name; int color; short int is_nullable; struct types *unanchored_table; int table_size; int type_table[1]; \}; /* general C type representing a Nit type. */")
+ # With resolution_table_table, all live type resolution are stored in a big table: resolution_table
+ self.header.add_decl("struct type \{ int id; const char *name; int color; short int is_nullable; struct types *resolution_table; int table_size; int type_table[1]; \}; /* general C type representing a Nit type. */")
if modelbuilder.toolcontext.opt_phmod_typing.value or modelbuilder.toolcontext.opt_phand_typing.value then
- self.header.add_decl("struct types \{ int mask; struct type *types[1]; \}; /* a list types (used for vts, fts and unanchored lists). */")
+ self.header.add_decl("struct types \{ int mask; struct type *types[1]; \}; /* a list types (used for vts, fts and unresolved lists). */")
else
- self.header.add_decl("struct types \{ struct type *types[1]; \}; /* a list types (used for vts, fts and unanchored lists). */")
+ self.header.add_decl("struct types \{ struct type *types[1]; \}; /* a list types (used for vts, fts and unresolved lists). */")
+ end
+
+ if modelbuilder.toolcontext.opt_phmod_typing.value then
+ self.header.add_decl("#define HASH(mask, id) ((mask)%(id))")
+ else if modelbuilder.toolcontext.opt_phand_typing.value then
+ self.header.add_decl("#define HASH(mask, id) ((mask)&(id))")
end
self.header.add_decl("typedef struct \{ struct type *type; struct class *class; nitattribute_t attrs[1]; \} val; /* general C type representing a Nit instance. */")
fun do_property_coloring do
var mclasses = new HashSet[MClass].from(modelbuilder.model.mclasses)
+ # Layouts
+ var method_layout_builder: PropertyLayoutBuilder[MMethod]
+ var attribute_layout_builder: PropertyLayoutBuilder[MAttribute]
+ if modelbuilder.toolcontext.opt_bm_typing.value then
+ method_layout_builder = new MMethodBMizer(self.mainmodule)
+ attribute_layout_builder = new MAttributeBMizer(self.mainmodule)
+ else if modelbuilder.toolcontext.opt_phmod_typing.value then
+ method_layout_builder = new MMethodHasher(new PHModOperator, self.mainmodule)
+ attribute_layout_builder = new MAttributeHasher(new PHModOperator, self.mainmodule)
+ else if modelbuilder.toolcontext.opt_phand_typing.value then
+ method_layout_builder = new MMethodHasher(new PHAndOperator, self.mainmodule)
+ attribute_layout_builder = new MAttributeHasher(new PHAndOperator, self.mainmodule)
+ else
+ method_layout_builder = new MMethodColorer(self.mainmodule)
+ attribute_layout_builder = new MAttributeColorer(self.mainmodule)
+ end
+
# methods coloration
- var method_coloring = new CLPropertyLayoutBuilder[MMethod](mainmodule)
- var method_layout = method_coloring.build_layout(mclasses)
+ var method_layout = method_layout_builder.build_layout(mclasses)
self.method_tables = build_method_tables(mclasses, method_layout)
self.compile_color_consts(method_layout.pos)
self.method_layout = method_layout
# attributes coloration
- var attribute_coloring = new CLPropertyLayoutBuilder[MAttribute](mainmodule)
- var attr_layout = attribute_coloring.build_layout(mclasses)
+ var attr_layout = attribute_layout_builder.build_layout(mclasses)
self.attr_tables = build_attr_tables(mclasses, attr_layout)
self.compile_color_consts(attr_layout.pos)
self.attr_layout = attr_layout
end
- fun build_method_tables(mclasses: Set[MClass], layout: PropertyLayout[MProperty]): Map[MClass, Array[nullable MPropDef]] do
+ fun build_method_tables(mclasses: Set[MClass], layout: Layout[MProperty]): Map[MClass, Array[nullable MPropDef]] do
var tables = new HashMap[MClass, Array[nullable MPropDef]]
for mclass in mclasses do
var table = new Array[nullable MPropDef]
return tables
end
- fun build_attr_tables(mclasses: Set[MClass], layout: PropertyLayout[MProperty]): Map[MClass, Array[nullable MPropDef]] do
+ fun build_attr_tables(mclasses: Set[MClass], layout: Layout[MProperty]): Map[MClass, Array[nullable MPropDef]] do
var tables = new HashMap[MClass, Array[nullable MPropDef]]
for mclass in mclasses do
var table = new Array[nullable MPropDef]
end
mtypes.add_all(self.partial_types)
+ # Typing Layout
+ var layout_builder: TypingLayoutBuilder[MType]
+ if modelbuilder.toolcontext.opt_bm_typing.value then
+ layout_builder = new MTypeBMizer(self.mainmodule)
+ else if modelbuilder.toolcontext.opt_phmod_typing.value then
+ layout_builder = new MTypeHasher(new PHModOperator, self.mainmodule)
+ else if modelbuilder.toolcontext.opt_phand_typing.value then
+ layout_builder = new MTypeHasher(new PHAndOperator, self.mainmodule)
+ else
+ layout_builder = new MTypeColorer(self.mainmodule)
+ end
+
# colorize types
- self.type_layout = self.type_layout_builder.build_layout(mtypes)
+ self.type_layout = layout_builder.build_layout(mtypes)
self.type_tables = self.build_type_tables(mtypes)
- # VT and FT are stored with other unresolved types in the big unanchored_tables
- self.compile_unanchored_tables(mtypes)
+ # VT and FT are stored with other unresolved types in the big resolution_tables
+ self.compile_resolution_tables(mtypes)
return mtypes
end
supers.add(mtype)
for sup in supers do
var color: Int
- if layout isa PHTypingLayout[MType] then
+ if layout isa PHLayout[MType, MType] then
color = layout.hashes[mtype][sup]
else
color = layout.pos[sup]
return tables
end
- protected fun compile_unanchored_tables(mtypes: Set[MType]) do
- # Unanchored_tables is used to perform a type resolution at runtime in O(1)
+ protected fun compile_resolution_tables(mtypes: Set[MType]) do
+ # resolution_tables is used to perform a type resolution at runtime in O(1)
- # During the visit of the body of classes, live_unanchored_types are collected
+ # During the visit of the body of classes, live_unresolved_types are collected
# and associated to
- # Collect all live_unanchored_types (visited in the body of classes)
+ # Collect all live_unresolved_types (visited in the body of classes)
# Determinate fo each livetype what are its possible requested anchored types
- var mtype2unanchored = new HashMap[MClassType, Set[MType]]
+ var mtype2unresolved = new HashMap[MClassType, Set[MType]]
for mtype in self.runtime_type_analysis.live_types do
var set = new HashSet[MType]
for cd in mtype.collect_mclassdefs(self.mainmodule) do
- if self.live_unanchored_types.has_key(cd) then
- set.add_all(self.live_unanchored_types[cd])
+ if self.live_unresolved_types.has_key(cd) then
+ set.add_all(self.live_unresolved_types[cd])
end
end
- mtype2unanchored[mtype] = set
+ mtype2unresolved[mtype] = set
end
# Compute the table layout with the prefered method
var resolution_builder: ResolutionLayoutBuilder
if modelbuilder.toolcontext.opt_bm_typing.value then
- resolution_builder = new BMResolutionLayoutBuilder
+ resolution_builder = new ResolutionBMizer
else if modelbuilder.toolcontext.opt_phmod_typing.value then
- resolution_builder = new PHResolutionLayoutBuilder(new PHModOperator)
+ resolution_builder = new ResolutionHasher(new PHModOperator)
else if modelbuilder.toolcontext.opt_phand_typing.value then
- resolution_builder = new PHResolutionLayoutBuilder(new PHAndOperator)
+ resolution_builder = new ResolutionHasher(new PHAndOperator)
else
- resolution_builder = new CLResolutionLayoutBuilder
+ resolution_builder = new ResolutionColorer
end
- self.resolution_layout = resolution_builder.build_layout(mtype2unanchored)
- self.resolution_tables = self.build_resolution_tables(mtype2unanchored)
+ self.resolution_layout = resolution_builder.build_layout(mtype2unresolved)
+ self.resolution_tables = self.build_resolution_tables(mtype2unresolved)
- # Compile a C constant for each collected unanchored type.
- # Either to a color, or to -1 if the unanchored type is dead (no live receiver can require it)
- var all_unanchored = new HashSet[MType]
- for t in self.live_unanchored_types.values do
- all_unanchored.add_all(t)
+ # Compile a C constant for each collected unresolved type.
+ # Either to a color, or to -1 if the unresolved type is dead (no live receiver can require it)
+ var all_unresolved = new HashSet[MType]
+ for t in self.live_unresolved_types.values do
+ all_unresolved.add_all(t)
end
- var all_unanchored_types_colors = new HashMap[MType, Int]
- for t in all_unanchored do
+ var all_unresolved_types_colors = new HashMap[MType, Int]
+ for t in all_unresolved do
if self.resolution_layout.pos.has_key(t) then
- all_unanchored_types_colors[t] = self.resolution_layout.pos[t]
+ all_unresolved_types_colors[t] = self.resolution_layout.pos[t]
else
- all_unanchored_types_colors[t] = -1
+ all_unresolved_types_colors[t] = -1
end
end
- self.compile_color_consts(all_unanchored_types_colors)
+ self.compile_color_consts(all_unresolved_types_colors)
#print "tables"
- #for k, v in unanchored_types_tables.as(not null) do
+ #for k, v in unresolved_types_tables.as(not null) do
# print "{k}: {v.join(", ")}"
#end
#print ""
var table = new Array[nullable MType]
for mtype in mtypes do
var color: Int
- if layout isa PHResolutionLayout then
+ if layout isa PHLayout[MClassType, MType] then
color = layout.hashes[mclasstype][mtype]
else
color = layout.pos[mtype]
self.header.add_decl("const char *name;")
self.header.add_decl("int color;")
self.header.add_decl("short int is_nullable;")
- self.header.add_decl("const struct types *unanchored_table;")
+ self.header.add_decl("const struct types *resolution_table;")
self.header.add_decl("int table_size;")
self.header.add_decl("int type_table[{self.type_tables[mtype].length}];")
self.header.add_decl("\};")
v.add_decl("{self.type_layout.ids[mtype]},")
v.add_decl("\"{mtype}\", /* class_name_string */")
var layout = self.type_layout
- if layout isa PHTypingLayout[MType] then
+ if layout isa PHLayout[MType, MType] then
v.add_decl("{layout.masks[mtype]},")
else
v.add_decl("{layout.pos[mtype]},")
else
v.add_decl("0,")
end
- if compile_type_unanchored_table(mtype) then
- v.add_decl("(struct types*) &unanchored_table_{c_name},")
+ if compile_type_resolution_table(mtype) then
+ v.add_decl("(struct types*) &resolution_table_{c_name},")
else
v.add_decl("NULL,")
end
v.add_decl("\};")
end
- fun compile_type_unanchored_table(mtype: MType): Bool do
+ fun compile_type_resolution_table(mtype: MType): Bool do
var mclass_type: MClassType
if mtype isa MNullableType then
var layout = self.resolution_layout
- # extern const struct unanchored_table_X unanchored_table_X
- self.header.add_decl("extern const struct unanchored_table_{mtype.c_name} unanchored_table_{mtype.c_name};")
- self.header.add_decl("struct unanchored_table_{mtype.c_name} \{")
- if layout isa PHResolutionLayout then
+ # extern const struct resolution_table_X resolution_table_X
+ self.header.add_decl("extern const struct resolution_table_{mtype.c_name} resolution_table_{mtype.c_name};")
+ self.header.add_decl("struct resolution_table_{mtype.c_name} \{")
+ if layout isa PHLayout[MClassType, MType] then
self.header.add_decl("int mask;")
end
self.header.add_decl("struct type *types[{self.resolution_tables[mclass_type].length}];")
# const struct fts_table_X fts_table_X
var v = new_visitor
- v.add_decl("const struct unanchored_table_{mtype.c_name} unanchored_table_{mtype.c_name} = \{")
- if layout isa PHResolutionLayout then
+ v.add_decl("const struct resolution_table_{mtype.c_name} resolution_table_{mtype.c_name} = \{")
+ if layout isa PHLayout[MClassType, MType] then
v.add_decl("{layout.masks[mclass_type]},")
end
v.add_decl("\{")
var v = new_visitor
v.add_decl("/* runtime class {c_name} */")
- var idnum = classids.length
- var idname = "ID_" + c_name
- self.classids[mtype] = idname
- #self.header.add_decl("#define {idname} {idnum} /* {c_name} */")
self.header.add_decl("struct class_{c_name} \{")
self.header.add_decl("int box_kind;")
v.add("if(type == NULL) \{")
v.add_abort("type null")
v.add("\}")
- v.add("if(type->unanchored_table == NULL) \{")
+ v.add("if(type->resolution_table == NULL) \{")
v.add("fprintf(stderr, \"Insantiation of a dead type: %s\\n\", type->name);")
v.add_abort("type dead")
v.add("\}")
# Stats
+ private var type_tables: Map[MType, Array[nullable MType]] = new HashMap[MType, Array[nullable MType]]
+ private var resolution_tables: Map[MClassType, Array[nullable MType]] = new HashMap[MClassType, Array[nullable MType]]
+ protected var method_tables: Map[MClass, Array[nullable MPropDef]] = new HashMap[MClass, Array[nullable MPropDef]]
+ protected var attr_tables: Map[MClass, Array[nullable MPropDef]] = new HashMap[MClass, Array[nullable MPropDef]]
+
redef fun display_stats
do
super
- if self.modelbuilder.toolcontext.opt_typing_table_metrics.value then
+ if self.modelbuilder.toolcontext.opt_tables_metrics.value then
display_sizes
end
end
fun display_sizes
do
- print "# size of tables"
- print "\trs size\trs hole\tst size\tst hole"
- var rt_table = 0
- var rt_holes = 0
- var st_table = 0
- var st_holes = 0
- var rtables = resolution_tables
- if rtables != null then
- for unanch, table in rtables do
- rt_table += table.length
- for e in table do if e == null then rt_holes += 1
- end
- end
-
- var ttables = type_tables
- if ttables != null then
- for t, table in ttables do
- st_table += table.length
- for e in table do if e == null then st_holes += 1
- end
- end
- print "\t{rt_table}\t{rt_holes}\t{st_table}\t{st_holes}"
+ print "# size of subtyping tables"
+ print "\ttotal \tholes"
+ var total = 0
+ var holes = 0
+ for t, table in type_tables do
+ total += table.length
+ for e in table do if e == null then holes += 1
+ end
+ print "\t{total}\t{holes}"
+
+ print "# size of resolution tables"
+ print "\ttotal \tholes"
+ total = 0
+ holes = 0
+ for t, table in resolution_tables do
+ total += table.length
+ for e in table do if e == null then holes += 1
+ end
+ print "\t{total}\t{holes}"
+
+ print "# size of methods tables"
+ print "\ttotal \tholes"
+ total = 0
+ holes = 0
+ for t, table in method_tables do
+ total += table.length
+ for e in table do if e == null then holes += 1
+ end
+ print "\t{total}\t{holes}"
+
+ print "# size of attributes tables"
+ print "\ttotal \tholes"
+ total = 0
+ holes = 0
+ for t, table in attr_tables do
+ total += table.length
+ for e in table do if e == null then holes += 1
+ end
+ print "\t{total}\t{holes}"
end
end
return res
end
+ redef fun supercall(m: MMethodDef, recvtype: MClassType, args: Array[RuntimeVariable]): nullable RuntimeVariable
+ do
+ # FIXME implements a polymorphic access in tables
+ m = m.lookup_next_definition(m.mclassdef.mmodule, m.mclassdef.bound_mtype)
+ return self.call(m, recvtype, args)
+ end
+
redef fun vararg_instance(mpropdef, recv, varargs, elttype)
do
# A vararg must be stored into an new array
# The trick is that the dymaic type of the array may depends on the receiver
# of the method (ie recv) if the static type is unresolved
- # This is more complex than usual because the unanchored type must not be resolved
+ # This is more complex than usual because the unresolved type must not be resolved
# with the current receiver (ie self).
# Therefore to isolate the resolution from self, a local Frame is created.
# One can see this implementation as an inlined method of the receiver whose only
do
var compiler = self.compiler
if mtype isa MGenericType and mtype.need_anchor then
- link_unanchored_type(self.frame.mpropdef.mclassdef, mtype)
+ link_unresolved_type(self.frame.mpropdef.mclassdef, mtype)
var recv = self.frame.arguments.first
var recv_type_info = self.type_info(recv)
if compiler.modelbuilder.toolcontext.opt_phmod_typing.value or compiler.modelbuilder.toolcontext.opt_phand_typing.value then
- return self.new_expr("NEW_{mtype.mclass.c_name}((struct type *) {recv_type_info}->unanchored_table->types[HASH({recv_type_info}->unanchored_table->mask, {mtype.const_color})])", mtype)
+ return self.new_expr("NEW_{mtype.mclass.c_name}((struct type *) {recv_type_info}->resolution_table->types[HASH({recv_type_info}->resolution_table->mask, {mtype.const_color})])", mtype)
else
- return self.new_expr("NEW_{mtype.mclass.c_name}((struct type *) {recv_type_info}->unanchored_table->types[{mtype.const_color}])", mtype)
+ return self.new_expr("NEW_{mtype.mclass.c_name}((struct type *) {recv_type_info}->resolution_table->types[{mtype.const_color}])", mtype)
end
end
compiler.undead_types.add(mtype)
var type_struct = self.get_name("type_struct")
self.add_decl("struct type* {type_struct};")
- # Either with unanchored_table with a direct resolution
- link_unanchored_type(self.frame.mpropdef.mclassdef, ntype)
+ # Either with resolution_table with a direct resolution
+ link_unresolved_type(self.frame.mpropdef.mclassdef, ntype)
if compiler.modelbuilder.toolcontext.opt_phmod_typing.value or compiler.modelbuilder.toolcontext.opt_phand_typing.value then
- self.add("{type_struct} = {recv_type_info}->unanchored_table->types[HASH({recv_type_info}->unanchored_table->mask, {ntype.const_color})];")
+ self.add("{type_struct} = {recv_type_info}->resolution_table->types[HASH({recv_type_info}->resolution_table->mask, {ntype.const_color})];")
else
- self.add("{type_struct} = {recv_type_info}->unanchored_table->types[{ntype.const_color}];")
+ self.add("{type_struct} = {recv_type_info}->resolution_table->types[{ntype.const_color}];")
end
if compiler.modelbuilder.toolcontext.opt_typing_test_metrics.value then
self.compiler.count_type_test_unresolved[tag] += 1
assert mtype isa MGenericType
var compiler = self.compiler
if mtype.need_anchor then
- link_unanchored_type(self.frame.mpropdef.mclassdef, mtype)
+ link_unresolved_type(self.frame.mpropdef.mclassdef, mtype)
var recv = self.frame.arguments.first
var recv_type_info = self.type_info(recv)
if compiler.modelbuilder.toolcontext.opt_phmod_typing.value or compiler.modelbuilder.toolcontext.opt_phand_typing.value then
- return self.new_expr("NEW_{mtype.mclass.c_name}({length}, (struct type *) {recv_type_info}->unanchored_table->types[HASH({recv_type_info}->unanchored_table->mask, {mtype.const_color})])", mtype)
+ return self.new_expr("NEW_{mtype.mclass.c_name}({length}, (struct type *) {recv_type_info}->resolution_table->types[HASH({recv_type_info}->resolution_table->mask, {mtype.const_color})])", mtype)
else
- return self.new_expr("NEW_{mtype.mclass.c_name}({length}, (struct type *) {recv_type_info}->unanchored_table->types[{mtype.const_color}])", mtype)
+ return self.new_expr("NEW_{mtype.mclass.c_name}({length}, (struct type *) {recv_type_info}->resolution_table->types[{mtype.const_color}])", mtype)
end
end
compiler.undead_types.add(mtype)
self.ret(res)
end
- fun link_unanchored_type(mclassdef: MClassDef, mtype: MType) do
+ fun link_unresolved_type(mclassdef: MClassDef, mtype: MType) do
assert mtype.need_anchor
var compiler = self.compiler
- if not compiler.live_unanchored_types.has_key(self.frame.mpropdef.mclassdef) then
- compiler.live_unanchored_types[self.frame.mpropdef.mclassdef] = new HashSet[MType]
+ if not compiler.live_unresolved_types.has_key(self.frame.mpropdef.mclassdef) then
+ compiler.live_unresolved_types[self.frame.mpropdef.mclassdef] = new HashSet[MType]
end
- compiler.live_unanchored_types[self.frame.mpropdef.mclassdef].add(mtype)
+ compiler.live_unresolved_types[self.frame.mpropdef.mclassdef].add(mtype)
end
end
nitlanguage / nit.git / blobdiff