[PATCH] D71013: [AIX] Allow vararg calls when all arguments reside in registers.

[Chris Bowler via Phabricator via llvm-commits]

cebowleratibm marked 4 inline comments as done.
cebowleratibm added inline comments.


================
Comment at: llvm/lib/Target/PowerPC/PPCISelLowering.cpp:7034
+      if (!GPR2.isRegLoc() || GPR2.getValNo() != GPR1.getValNo())
+        continue;
+      assert(GPR2.needsCustom() && "A second custom GPR is expected");
----------------
hubert.reinterpretcast wrote:
> cebowleratibm wrote:
> > hubert.reinterpretcast wrote:
> > > What sort of situation leads to this?
> > The matching ValNo should be an assertion.  I should have written:
> > 
> >        // If no GPRs were left then there may be no more ArgLocs remaining.
> >       if (I + 1 == e)
> >         continue;
> >       CCValAssign &GPR2 = ArgLocs[++I];
> >       // If no GPRs were left then there may be non-reg ArgLocs remaining.
> >       if (!GPR2.isRegLoc()))
> >         continue;
> >       assert(GPR2.getValNo() == GPR1.getValNo() && GPR2.needsCustom() &&
> >              "A second custom GPR is expected!");
> > 
> If we observed one custom reg and we are dealing with the var arg case. My understanding is that, if we were unable to allocate a second GPR for the vararg case, the loop would have hit `report_fatal_error`.
Yes we should have emitted an error.  So the final assertion checks that contract.  If we see a RegLoc that follows the "GPR1" RegLoc, then we expect that to be the second custom reg and have the same ValNo as the first.


CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D71013/new/

https://reviews.llvm.org/D71013