[PATCH] D19337: [Tail duplication] Handle source registers with subregisters

[Quentin Colombet via llvm-commits]

qcolombet added inline comments.

================
Comment at: lib/CodeGen/TailDuplicator.cpp:373
@@ +372,3 @@
+              // needed to change the class of the mapped register.
+              ConstrRC = MRI->constrainRegClass(VI->second.Reg, ConstrRC);
+            }
----------------
MRI->setRegClass.

================
Comment at: lib/CodeGen/TailDuplicator.cpp:389
@@ +388,3 @@
+            // class constraints. An explicit COPY is necessary.
+            unsigned NewReg = MRI->createVirtualRegister(OrigRC);
+            BuildMI(*PredBB, MI, MI->getDebugLoc(),
----------------
Instead of using OrigRC, we should use the regclass that is required by MO.
MachineInstr::getRegClassConstraint

================
Comment at: lib/CodeGen/TailDuplicator.cpp:392
@@ +391,3 @@
+                    TII->get(TargetOpcode::COPY), NewReg)
+                .addReg(Reg);
+            LocalVRMap.erase(VI);
----------------
We need to read from Reg:subReg if Reg has a sub reg.


Repository:
  rL LLVM

http://reviews.llvm.org/D19337