AMDGPU: Preserve vcc undef flags when inverting branch

If the branch was on a read-undef of vcc, passes that used
analyzeBranch to invert the branch condition wouldn't preserve
the undef flag resulting in a verifier error.

Fixes verifier failures in a future commit.

Also fix verifier error when inserting copy for vccz
corruption bug.

llvm-svn: 286133

1 files changed, 16 insertions, 3 deletions

diff --git a/llvm/lib/Target/AMDGPU/SIInstrInfo.cpp b/llvm/lib/Target/AMDGPU/SIInstrInfo.cpp
index 94b484ed0b3..02cbc882bf8 100644
--- a/llvm/lib/Target/AMDGPU/SIInstrInfo.cpp
+++ b/llvm/lib/Target/AMDGPU/SIInstrInfo.cpp
@@ -1196,6 +1196,7 @@ bool SIInstrInfo::analyzeBranchImpl(MachineBasicBlock &MBB,
 
   MachineBasicBlock *CondBB = I->getOperand(0).getMBB();
   Cond.push_back(MachineOperand::CreateImm(Pred));
+  Cond.push_back(I->getOperand(1)); // Save the branch register.
 
   ++I;
 
@@ -1298,9 +1299,16 @@ unsigned SIInstrInfo::insertBranch(MachineBasicBlock &MBB,
     = getBranchOpcode(static_cast<BranchPredicate>(Cond[0].getImm()));
 
   if (!FBB) {
-    BuildMI(&MBB, DL, get(Opcode))
+    Cond[1].isUndef();
+    MachineInstr *CondBr =
+      BuildMI(&MBB, DL, get(Opcode))
       .addMBB(TBB);
 
+    // Copy the flags onto the implicit condition register operand.
+    MachineOperand &CondReg = CondBr->getOperand(1);
+    CondReg.setIsUndef(Cond[1].isUndef());
+    CondReg.setIsKill(Cond[1].isKill());
+
     if (BytesAdded)
       *BytesAdded = 4;
     return 1;
@@ -1308,11 +1316,16 @@ unsigned SIInstrInfo::insertBranch(MachineBasicBlock &MBB,
 
   assert(TBB && FBB);
 
-  BuildMI(&MBB, DL, get(Opcode))
+  MachineInstr *CondBr =
+    BuildMI(&MBB, DL, get(Opcode))
     .addMBB(TBB);
   BuildMI(&MBB, DL, get(AMDGPU::S_BRANCH))
     .addMBB(FBB);
 
+  MachineOperand &CondReg = CondBr->getOperand(1);
+  CondReg.setIsUndef(Cond[1].isUndef());
+  CondReg.setIsKill(Cond[1].isKill());
+
   if (BytesAdded)
       *BytesAdded = 8;
 
@@ -1321,7 +1334,7 @@ unsigned SIInstrInfo::insertBranch(MachineBasicBlock &MBB,
 
 bool SIInstrInfo::reverseBranchCondition(
   SmallVectorImpl<MachineOperand> &Cond) const {
-  assert(Cond.size() == 1);
+  assert(Cond.size() == 2);
   Cond[0].setImm(-Cond[0].getImm());
   return false;
 }