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Issue
104663004:
Preview of a first step towards unification of hydrogen calls (Closed)
DescriptionThis is a preview of a first step towards unification of the hydrogen
call machinery. The change replaces CallNamed, CallKeyed,
CallConstantFunction and CallKnownGlobal hydrogen instructions with two
new instructions with a more lower level semantics:
1. CallJSFunction for direct calls of JSFunction objects (no
argument adaptation)
2. CallWithDescriptor for calls of a given Code object according to
the supplied calling convention.
Details:
CallJSFunction should be straightforward, the main difference from the
existing InvokeFunction instruction is the absence of argument adaptor
handling. (As a next step, we will replace InvokeFunction with an
equivalent hydrogen code.)
For CallWithDescriptor, the calling conventions are represented by a
tweaked version of CallStubInterfaceDescriptor. In addition to the
parameter-register mapping, we also define parameter-representation
mapping there. The CallWithDescriptor instruction has variable number of
parameters now - this required some simple tweaks in Lithium, which
assumed fixed number of arguments in some places.
The calling conventions used in the calls are initialized in the
CallDescriptors class (code-stubs.h, <arch>/code-stubs-<arch>.cc), and
they live in a new table in the Isolate class. I should say I am not
quite sure about Representation::Integer32() representation for some of
the params of ArgumentAdaptorCall - it is not clear to me wether the
params could not end up on the stack and thus confuse the GC.
The change also includes an earlier small change to argument adaptor
(https://codereview.chromium.org/98463007) that avoids passing a naked
pointer to the code entry as a parameter. I am sorry for packaging that
with an already biggish change.
Performance implications:
Locally, I see a small regression (.2% or so). It is hard to say where
exactly it comes from, but I do see inefficient call sequences to the
adaptor trampoline. For example:
;;; <@78,#24> constant-t
bf85aa515a mov edi,0x5a51aa85 ;; debug: position 29
;;; <@72,#53> load-named-field
8b7717 mov esi,[edi+0x17] ;; debug: position 195
;;; <@80,#51> constant-s
b902000000 mov ecx,0x2 ;; debug: position 195
;;; <@81,#51> gap
894df0 mov [ebp+0xf0],ecx
;;; <@82,#103> constant-i
bb01000000 mov ebx,0x1
;;; <@84,#102> constant-i
b902000000 mov ecx,0x2
;;; <@85,#102> gap
89d8 mov eax,ebx
89cb mov ebx,ecx
8b4df0 mov ecx,[ebp+0xf0]
;;; <@86,#58> call-with-descriptor
e8ef57fcff call ArgumentsAdaptorTrampoline (0x2d80e6e0) ;; code: BUILTIN
Note the silly handling of ecx; the hydrogen for this code is:
0 4 s27 Constant 1 range:1_1 <|@
0 3 t30 Constant 0x5bc1aa85 <JS Function xyz (SharedFunctionInfo 0x5bc1a919)> type:object <|@
0 1 t36 LoadNamedField t30.[in-object]@24 <|@
0 1 t38 Constant 0x2300e6a1 <Code> <|@
0 1 i102 Constant 2 range:2_2 <|@
0 1 i103 Constant 1 range:1_1 <|@
0 2 t41 CallWithDescriptor t38 t30 t36 s27 i103 i102 #2 changes[*] <|@
BUG=
R=verwaest@chromium.org, danno@chromium.org
Committed: https://code.google.com/p/v8/source/detail?r=18626
Patch Set 1 #
Total comments: 25
Patch Set 2 : Rebase #Patch Set 3 : Addressing review comments #Patch Set 4 : ARM storage mode fix #
Total comments: 3
Patch Set 5 : Addressed code review comments #
Total comments: 18
Patch Set 6 : Addressed review comments #Patch Set 7 : Merge fix #
Messages
Total messages: 9 (0 generated)
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