[PATCH] D20102: [ScheduleDAG] Make sure to process all def operands before any use operands

[Andrew Trick via llvm-commits]

atrick added inline comments.

================
Comment at: llvm/trunk/lib/CodeGen/ScheduleDAGInstrs.cpp:974-975
@@ +973,4 @@
+      const MachineOperand &MO = MI->getOperand(j);
+      if (!MO.isReg() || !MO.isUse())
+        continue;
+      unsigned Reg = MO.getReg();
----------------
MatzeB wrote:
> MatzeB wrote:
> > MatzeB wrote:
> > > atrick wrote:
> > > > MatzeB wrote:
> > > > > This will subregister defs which are uses as well, should be `!MO.readsReg())!
> > > > Matthias, can you clarify? We don't want addPhysRefDefs to be called twice for the same subreg!
> > > Something like this:
> > > `%vreg0:sub0 = ...` is both a definition and a use! (at least if lanemask tracking is not enabled), we still need to record it as a use. physregs never have subregister indexes so MO.readsReg() will never return true for physreg definitions.
> > It would also be nice to split addPhysRegDeps() into addPhysRegUseDeps() and addPhysRegDefDeps().
> Hmm it looks like the code before this patch only used output dependencies for this case. So this change is fine in preserving that behavior.
I *think* Matthias is saying that this patch will fail to call addVRegUseDeps for subregs. So, that needs to be fixed but in a way that doesn't call addPhysRegDeps twice on the same operand.

Maybe Matthias can suggest a fix!


Repository:
  rL LLVM

http://reviews.llvm.org/D20102