Emulate MLS on pre-ARMv6T2. Cleaned up thumbee vs. thumb2 confusion.

Emulate MLS on pre-ARMv6T2. Cleaned up thumbee vs. thumb2 confusion.

This should unbreak things on the Raspberry Pi.

LOG=y
R=bmeurer@chromium.org

Committed: https://code.google.com/p/v8/source/detail?r=21835

[Benedikt Meurer, 2014-06-13 09:41:14]

LGTM

[Rodolph Perfetta, 2014-06-13 10:13:23]

https://codereview.chromium.org/331803003/diff/1/src/arm/assembler-arm.cc
File src/arm/assembler-arm.cc (right):

https://codereview.chromium.org/331803003/diff/1/src/arm/assembler-arm.cc#new...
src/arm/assembler-arm.cc:106: if (FLAG_enable_mls && cpu.has_thumbee())
supported_ |= 1u << MLS;
DBC: You should check for ARMv7 not ThumbEE.

ThumbEE is deprecated, the newer cores (A53, A57) don't have it.

[Benedikt Meurer, 2014-06-13 10:17:57]

On 2014/06/13 10:13:23, Rodolph Perfetta wrote:
> https://codereview.chromium.org/331803003/diff/1/src/arm/assembler-arm.cc
> File src/arm/assembler-arm.cc (right):
> 
>
https://codereview.chromium.org/331803003/diff/1/src/arm/assembler-arm.cc#new...
> src/arm/assembler-arm.cc:106: if (FLAG_enable_mls && cpu.has_thumbee())
> supported_ |= 1u << MLS;
> DBC: You should check for ARMv7 not ThumbEE.
> 
> ThumbEE is deprecated, the newer cores (A53, A57) don't have it.

This should be renamed to Thumb2. ThumbEE was the wrong name anyway.
But testing for T2 is correct, since mls was introduced with ARMv6T2.

[Sven Panne, 2014-06-13 10:28:17]

On 2014/06/13 10:17:57, Benedikt Meurer wrote:
> This should be renamed to Thumb2. ThumbEE was the wrong name anyway.
> But testing for T2 is correct, since mls was introduced with ARMv6T2.

Updated accordingly...

[Rodolph Perfetta, 2014-06-13 10:38:23]

https://codereview.chromium.org/331803003/diff/2/src/cpu.cc
File src/cpu.cc (right):

https://codereview.chromium.org/331803003/diff/2/src/cpu.cc#newcode395
src/cpu.cc:395: has_thumb2_ = HasListItem(features, "thumb2");
thumb2 doesn't get reported as such in cpuinfo:
 * ARMv7 (or higher) => thumb2
 * ARMv6T2 => thumb2
I only know of one ARMv6T2 cpu and it doesn't have an MMU so we could simplify
to ARMv7

[Sven Panne, 2014-06-13 10:49:58]

https://codereview.chromium.org/331803003/diff/2/src/cpu.cc
File src/cpu.cc (right):

https://codereview.chromium.org/331803003/diff/2/src/cpu.cc#newcode395
src/cpu.cc:395: has_thumb2_ = HasListItem(features, "thumb2");
On 2014/06/13 10:38:23, Rodolph Perfetta wrote:
> thumb2 doesn't get reported as such in cpuinfo:
>  * ARMv7 (or higher) => thumb2
>  * ARMv6T2 => thumb2
> I only know of one ARMv6T2 cpu and it doesn't have an MMU so we could simplify
> to ARMv7

This was proposed by Benedikt. We can simplify this in another CL if both of you
come to an agreement what the test should look like. :-)

[Sven Panne, 2014-06-13 10:50:26]

Committed patchset #2 manually as r21835 (presubmit successful).