PPC: Handle the case when derived constructor is [[Call]]ed with 0 args.

Port cf53fed972896bf23c037ce7ac9f8e1512463c62

Original commit message:
ArgumentsAdaptorStub for derived constructor (the one that needs
new.target) works in this way:
 - If the constructor is invoked via the Construct stub, we know that
   actual arguments always include new.target. ``arguments`` object
   however should not include a new.target, therefore we remove it.
   We achieve this by decrementing the argument count.
 - If the constructor is invoked as a call, we do not care for a correct
   ``arguments`` array since the constructor will immediately throw on
   entrance.
The bug is that the call could actually pass 0 actual arguments, but I
decrement unconditionally :(. The fix is to detect this case and avoid
decrementing. ``arguments`` is bogus, but it is ok as constructor
throws.

Long-term we should just remove mucking about with arguments for
new.target and just get it from the stack.

R=dslomov@chromium.org, dstence@us.ibm.com, michael_dawson@ca.ibm.com
BUG=

Review URL: https://codereview.chromium.org/1125223002

Cr-Commit-Position: refs/heads/master@{#28269}

diff --git a/src/ppc/code-stubs-ppc.cc b/src/ppc/code-stubs-ppc.cc
index abcad08f35160815a94ecf827a02e46432dbd5b2..583c368b798e7925236c4ee29c490e8fc03fae90 100644 (file)
--- a/src/ppc/code-stubs-ppc.cc
+++ b/src/ppc/code-stubs-ppc.cc
@@ -1980,8 +1980,12 @@ void ArgumentsAccessStub::GenerateNewStrict(MacroAssembler* masm) {
   __ bind(&adaptor_frame);
   __ LoadP(r4, MemOperand(r5, ArgumentsAdaptorFrameConstants::kLengthOffset));
   if (has_new_target()) {
+    __ CmpSmiLiteral(r4, Smi::FromInt(0), r0);
+    Label skip_decrement;
+    __ beq(&skip_decrement);
     // Subtract 1 from smi-tagged arguments count.
     __ SubSmiLiteral(r4, r4, Smi::FromInt(1), r0);
+    __ bind(&skip_decrement);
   }
   __ StoreP(r4, MemOperand(sp, 0));
   __ SmiToPtrArrayOffset(r6, r4);