A64: Update DoAllocate() to use a W register for the size

A64: Update DoAllocate() to use a W register for the size

Inputs should always be 32bit

BUG=none
R=m.m.capewell@googlemail.com, ulan@chromium.org
LOG=n

Committed: https://code.google.com/p/v8/source/detail?r=19426

[m.m.capewell, 2014-02-17 15:48:44]

https://codereview.chromium.org/167123004/diff/1/src/a64/lithium-codegen-a64.cc
File src/a64/lithium-codegen-a64.cc (right):

https://codereview.chromium.org/167123004/diff/1/src/a64/lithium-codegen-a64....
src/a64/lithium-codegen-a64.cc:1519: __ Sub(temp1, ToRegister32(instr->size()),
kPointerSize);
I'm surprised that this builds, as temp1 is X and the result of ToRegister32, W.
Use temp1.W() if you're certain that size > kPointerSize (and thus can't be
negative.)

https://codereview.chromium.org/167123004/diff/1/src/a64/lithium-codegen-a64....
src/a64/lithium-codegen-a64.cc:1549: __ SmiTag(size, x10);
I don't think you need a mov here. You can call the X() method on a register to
get its X-sized equivalent, so you could:

Register untagged_size = ToRegister32(instr->size());
__ SmiTag(size, untagged_size.X());

[jochen (gone - plz use gerrit), 2014-02-17 16:17:26]

https://codereview.chromium.org/167123004/diff/1/src/a64/lithium-codegen-a64.cc
File src/a64/lithium-codegen-a64.cc (right):

https://codereview.chromium.org/167123004/diff/1/src/a64/lithium-codegen-a64....
src/a64/lithium-codegen-a64.cc:1508: Register size =
ToRegister32(instr->size());
I have to extend this to X() as well

https://codereview.chromium.org/167123004/diff/1/src/a64/lithium-codegen-a64....
src/a64/lithium-codegen-a64.cc:1519: __ Sub(temp1, ToRegister32(instr->size()),
kPointerSize);
On 2014/02/17 15:48:44, m.m.capewell wrote:
> I'm surprised that this builds, as temp1 is X and the result of ToRegister32,
W.
> Use temp1.W() if you're certain that size > kPointerSize (and thus can't be
> negative.)

size has to be at leat 2*kPointerSize, otherwise the loop below will run havoc
anyway

https://codereview.chromium.org/167123004/diff/1/src/a64/lithium-codegen-a64....
src/a64/lithium-codegen-a64.cc:1549: __ SmiTag(size, x10);
On 2014/02/17 15:48:44, m.m.capewell wrote:
> I don't think you need a mov here. You can call the X() method on a register
to
> get its X-sized equivalent, so you could:
> 
> Register untagged_size = ToRegister32(instr->size());
> __ SmiTag(size, untagged_size.X());

Because the shift will kill the upper 32bits anyway, makes sense.

[jochen (gone - plz use gerrit), 2014-02-17 16:17:26]

https://codereview.chromium.org/167123004/diff/1/src/a64/lithium-codegen-a64.cc
File src/a64/lithium-codegen-a64.cc (right):

https://codereview.chromium.org/167123004/diff/1/src/a64/lithium-codegen-a64....
src/a64/lithium-codegen-a64.cc:1508: Register size =
ToRegister32(instr->size());
I have to extend this to X() as well

https://codereview.chromium.org/167123004/diff/1/src/a64/lithium-codegen-a64....
src/a64/lithium-codegen-a64.cc:1519: __ Sub(temp1, ToRegister32(instr->size()),
kPointerSize);
On 2014/02/17 15:48:44, m.m.capewell wrote:
> I'm surprised that this builds, as temp1 is X and the result of ToRegister32,
W.
> Use temp1.W() if you're certain that size > kPointerSize (and thus can't be
> negative.)

size has to be at leat 2*kPointerSize, otherwise the loop below will run havoc
anyway

https://codereview.chromium.org/167123004/diff/1/src/a64/lithium-codegen-a64....
src/a64/lithium-codegen-a64.cc:1549: __ SmiTag(size, x10);
On 2014/02/17 15:48:44, m.m.capewell wrote:
> I don't think you need a mov here. You can call the X() method on a register
to
> get its X-sized equivalent, so you could:
> 
> Register untagged_size = ToRegister32(instr->size());
> __ SmiTag(size, untagged_size.X());

Because the shift will kill the upper 32bits anyway, makes sense.

[m.m.capewell, 2014-02-17 16:39:20]

lgtm

[jochen (gone - plz use gerrit), 2014-02-18 08:59:11]

Committed patchset #2 manually as r19426 (presubmit successful).