MIPS: replace RegExpCEntryStub with DirectCEntryStub.

MIPS: replace RegExpCEntryStub with DirectCEntryStub.

Port r16618 (0eebc593)

Original commit message:
RegExpCEntryStub is therefore removed.

BUG=none
TEST=none

[Paul Lind, 2013-09-19 18:07:10]

inline question on your stack adjustment....

https://codereview.chromium.org/24233003/diff/1/src/mips/regexp-macro-assembl...
File src/mips/regexp-macro-assembler-mips.cc (right):

https://codereview.chromium.org/24233003/diff/1/src/mips/regexp-macro-assembl...
src/mips/regexp-macro-assembler-mips.cc:1089: __ lw(sp, MemOperand(sp, 16 +
stack_alignment + kCArgsSlotsSize));
Where does the magic number 16 come from? You're calling PrepareCallCFunction()
with 3 args, but those fit within the (4) on-stack ArgsSlots. You already
account for that with kCArgsSlotsSize. The only un-accounted for thing is the
return address. That would be 4 bytes, or maybe 8 to preserve alignment.

[kilvadyb, 2013-09-19 18:37:26]

https://codereview.chromium.org/24233003/diff/1/src/mips/regexp-macro-assembl...
File src/mips/regexp-macro-assembler-mips.cc (right):

https://codereview.chromium.org/24233003/diff/1/src/mips/regexp-macro-assembl...
src/mips/regexp-macro-assembler-mips.cc:1089: __ lw(sp, MemOperand(sp, 16 +
stack_alignment + kCArgsSlotsSize));
On 2013/09/19 18:07:10, Paul Lind wrote:
> Where does the magic number 16 come from? You're calling
PrepareCallCFunction()
> with 3 args, but those fit within the (4) on-stack ArgsSlots. You already
> account for that with kCArgsSlotsSize. The only un-accounted for thing is the
> return address. That would be 4 bytes, or maybe 8 to preserve alignment.
The 16 comes from the allocation done by PrepareCallCFunction (3 arguments and 1
for the original stake pointer). Previous
RegExpMacroAssemblerMIPS::CallCFunctionUsingStub used the magic 16 also. I
couldn't find a good name for that. The kCArgsSlotsSize value comes from
DirectCEntryStub::Generate's stack allocation. There is no stack release/pop in
DirectCEntryStub::Generate as that function can be called from other places
where LeaveExitFrame takes care of the sp.