[AArch64] Keep flags on condition vreg when instantiating a CB branch.

Reversing a CB* instruction used to drop the flags on the condition. On the
included testcase, this lead to a read from an undefined vreg.
Using addOperand keeps the flags, here <undef>.

Differential Revision: http://reviews.llvm.org/D6159

llvm-svn: 221507

1 files changed, 2 insertions, 1 deletions

diff --git a/llvm/lib/Target/AArch64/AArch64InstrInfo.cpp b/llvm/lib/Target/AArch64/AArch64InstrInfo.cpp
index c5bf3c79477..1451407de0e 100644
--- a/llvm/lib/Target/AArch64/AArch64InstrInfo.cpp
+++ b/llvm/lib/Target/AArch64/AArch64InstrInfo.cpp
@@ -261,8 +261,9 @@ void AArch64InstrInfo::instantiateCondBranch(
     BuildMI(&MBB, DL, get(AArch64::Bcc)).addImm(Cond[0].getImm()).addMBB(TBB);
   } else {
     // Folded compare-and-branch
+    // Note that we use addOperand instead of addReg to keep the flags.
     const MachineInstrBuilder MIB =
-        BuildMI(&MBB, DL, get(Cond[1].getImm())).addReg(Cond[2].getReg());
+        BuildMI(&MBB, DL, get(Cond[1].getImm())).addOperand(Cond[2]);
     if (Cond.size() > 3)
       MIB.addImm(Cond[3].getImm());
     MIB.addMBB(TBB);