965229 - ARM simulator: scratch volatile registers across system ABI calls

Status: RESOLVED FIXED

(Core :: JavaScript Engine: JIT, defect)

Description

[Douglas Crosher [:dougc]]

It would help detect compiler error if the simulator scratched the volatile registers across system ABI calls.

Some of the calls assume that not all the registers are scratched.  This is an efficiency optimization.  For example calls to __aeabi_idivmod and __aeabi_uidivmod.  Need to audit all calls and decide how to manage this.

Comment 1

[Douglas Crosher [:dougc]]

Attachment: Scratch volatile registers across system ABI calls

Here's that patch moved from bug 959597.  This is not adequate alone because it is still necessary to avoid scratching some registers for some calls.

Comment 2

[Douglas Crosher [:dougc]]

Attachment: Scratch volatile registers across system ABI calls

Revised to avoid scratching the volatile float registers when calling __aeabi_idivmod or __aeabi_uidivmod because the ARM backend assumes that the float registers are not volatile across these calls - a performance optimization.

Requesting review again because there were substantive changes, and I am not certain about the style.

Comment 3

[Nicolas B. Pierron [:nbp]]

(In reply to Douglas Crosher [:dougc] from comment #2)
> Requesting review again because there were substantive changes, and I am not
> certain about the style.

The style looks good.
In the previous obsolete patch, I noticed a

void Foo::bar(void)
{
}

"void" arguments are valid in C, to prevent making it a variadic function by defining a function with no arguments, but I do not think this has any meaning in C++.

Comment 4

[Ryan VanderMeulen [:RyanVM]]

https://hg.mozilla.org/integration/mozilla-inbound/rev/f5590c1dcf70

Comment 5

[Ryan VanderMeulen [:RyanVM]]

https://hg.mozilla.org/mozilla-central/rev/f5590c1dcf70