https://codereview.chromium.org/209933003/diff/1/src/arm64/lithium-codegen-arm64.h
File src/arm64/lithium-codegen-arm64.h (right):
https://codereview.chromium.org/209933003/diff/1/src/arm64/lithium-codegen-arm64.h#newcode385
src/arm64/lithium-codegen-arm64.h:385:
codegen_->masm_->Mov(to_be_pushed_lr, lr);
On 2014/03/24 11:31:26, ulan wrote:
On 2014/03/24 11:16:59, vincent.belliard.arm wrote:
> On 2014/03/24 11:09:25, ulan wrote:
> > to_be_pushed_lr is ip0, how do we guarantee that this doesn't get
clobbered
> from
> > this point until the StoreRegistersStateStub gets control?
>
> This register is reserved by the UseScratchRegisterScope so it
cannot be used
by
> the call (which will use the next register: ip1).
>
> After the call, we jump directly to the stub code (which has its own
context)
> which starts also by a UseScratchRegisterScope which also reserves
> to_be_pushed_lr.
Right, and what if the ip0 is not available in the current scope
because it was
already reserved before PushSafepointRegistersScope?
In debug, Acquire checks that the register is available. If each
instruction which use a PushSafepointRegistersScope is used by the at
least one test (I hope all are used) and if the tests are run in debug,
it will ensure that the register will be available.
In release, the register could be unavailable and still acquired (no
test is done during acquire). If it's not available, we will clobber it.
However, it doesn't matter because as we enter
PushSafepointRegistersScope, only the safepoint registers must be saved
and ip0, ip1 can be cloberred.
https://codereview.chromium.org/209933003/
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