[AMDGPU] Do not combine dpp with physreg def

We will remove dpp mov along with the physreg def otherwise.

Differential Revision: https://reviews.llvm.org/D69063

llvm-svn: 375030

1 files changed, 4 insertions, 0 deletions

diff --git a/llvm/lib/Target/AMDGPU/GCNDPPCombine.cpp b/llvm/lib/Target/AMDGPU/GCNDPPCombine.cpp
index a517250ae24..f8adda72950 100644
--- a/llvm/lib/Target/AMDGPU/GCNDPPCombine.cpp
+++ b/llvm/lib/Target/AMDGPU/GCNDPPCombine.cpp
@@ -353,6 +353,10 @@ bool GCNDPPCombine::combineDPPMov(MachineInstr &MovMI) const {
   auto *DstOpnd = TII->getNamedOperand(MovMI, AMDGPU::OpName::vdst);
   assert(DstOpnd && DstOpnd->isReg());
   auto DPPMovReg = DstOpnd->getReg();
+  if (DPPMovReg.isPhysical()) {
+    LLVM_DEBUG(dbgs() << "  failed: dpp move writes physreg\n");
+    return false;
+  }
   if (execMayBeModifiedBeforeAnyUse(*MRI, DPPMovReg, MovMI)) {
     LLVM_DEBUG(dbgs() << "  failed: EXEC mask should remain the same"
                          " for all uses\n");