Bug 141903 - Add calleeSaveRegisters() implementation for ARM Traditional
Summary: Add calleeSaveRegisters() implementation for ARM Traditional
Alias: None
Product: WebKit
Classification: Unclassified
Component: New Bugs (show other bugs)
Version: 528+ (Nightly build)
Hardware: Unspecified Unspecified
: P2 Normal
Assignee: Csaba Osztrogonác
Depends on:
Blocks: 108645
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Reported: 2015-02-23 05:45 PST by Csaba Osztrogonác
Modified: 2015-02-26 01:20 PST (History)
3 users (show)

See Also:

Patch (1.69 KB, patch)
2015-02-23 05:45 PST, Csaba Osztrogonác
no flags Details | Formatted Diff | Diff

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Description Csaba Osztrogonác 2015-02-23 05:45:14 PST
Add calleeSaveRegisters() implementation for ARM Traditional
Comment 1 Csaba Osztrogonác 2015-02-23 05:45:28 PST
Created attachment 247112 [details]
Comment 2 Csaba Osztrogonác 2015-02-23 06:00:00 PST
AAPCS (http://infocenter.arm.com/help/topic/com.arm.doc.ihi0042e/IHI0042E_aapcs.pdf) says that r4-r11 are callee-saved registers,
only the role of r9 isn't clear.

"The role of register r9 is platform specific. A virtual platform may assign
any role to this register and must document this usage. For example, it may
designate it as the static base (SB) in a position-independent data model,
or it may designate it as the thread register (TR) in an environment with
thread-local storage. The usage of this register may require that the value
held is persistent across all calls. A virtual platform that has no need for
such a special register may designate r9 as an additional callee-saved variable
register, v6."

But it seems GCC ARM EABI handles r9 as callee-saved register:

I checked some disassembly of example codes and JSC too,
and can confirm that r4-r11 registers are callee-saved.
Comment 3 Csaba Osztrogonác 2015-02-23 06:13:21 PST
You omitted the fp/r7 from ARM Thumb2 callee-saved register list:

But registersToPreserve() explicitly removes fp from the list:

I think it is confusing to omit r11/fp on ARM Traditional and r7/fp
on ARM Thumb2, since these registers are general callee-saved registers.
ARM EABI doesn't specify a dedicated frame pointer, additionally GCC omits
using frame pointer with O1.
Comment 4 WebKit Commit Bot 2015-02-26 01:20:43 PST
Comment on attachment 247112 [details]

Clearing flags on attachment: 247112

Committed r180667: <http://trac.webkit.org/changeset/180667>
Comment 5 WebKit Commit Bot 2015-02-26 01:20:47 PST
All reviewed patches have been landed.  Closing bug.