[AMDGPU] Do not combine dpp mov reading physregs

[rampitec]

Summary

We cannot be sure physregs will stay unchanged.

[arsenm]

LGTM

llvm/lib/Target/AMDGPU/GCNDPPCombine.cpp

bool GCNDPPCombine::combineDPPMov(MachineInstr &MovMI) const {
   const bool MaskAllLanes = RowMaskOpnd->getImm() == 0xF &&
                             BankMaskOpnd->getImm() == 0xF;
 
   auto *BCZOpnd = TII->getNamedOperand(MovMI, AMDGPU::OpName::bound_ctrl);
   assert(BCZOpnd && BCZOpnd->isImm());
   bool BoundCtrlZero = BCZOpnd->getImm();
 
   auto *OldOpnd = TII->getNamedOperand(MovMI, AMDGPU::OpName::old);
+  auto *SrcOpnd = TII->getNamedOperand(MovMI, AMDGPU::OpName::src0);
   assert(OldOpnd && OldOpnd->isReg());
+  assert(SrcOpnd && SrcOpnd->isReg());
+  if (OldOpnd->getReg().isPhysical() || SrcOpnd->getReg().isPhysical()) {
+    LLVM_DEBUG(dbgs() << "  failed: dpp move reads physreg\n");
+    return false;
+  }
 
   auto * const OldOpndValue = getOldOpndValue(*OldOpnd);
   // OldOpndValue is either undef (IMPLICIT_DEF) or immediate or something else
   // We could use: assert(!OldOpndValue || OldOpndValue->isImm())
   // but the third option is used to distinguish undef from non-immediate
   // to reuse IMPLICIT_DEF instruction later
   assert(!OldOpndValue || OldOpndValue->isImm() || OldOpndValue == OldOpnd);
 

llvm/test/CodeGen/AMDGPU/dpp_combine.mir

 name: phys_dpp_mov_dst
 tracksRegLiveness: true
 body: |
   bb.0:
     $vgpr0 = V_MOV_B32_dpp undef %1:vgpr_32, undef %0:vgpr_32, 1, 15, 15, 1, implicit $exec
     %2:vgpr_32 = V_CEIL_F32_e32 $vgpr0, implicit $exec
 ...
 
+# Do not combine a dpp mov which reads a physreg.
+# GCN-LABEL: name: phys_dpp_mov_old_src
+# GCN: %0:vgpr_32 = V_MOV_B32_dpp undef $vgpr0, undef %1:vgpr_32, 1, 15, 15, 1, implicit $exec
+# GCN: %2:vgpr_32 = V_CEIL_F32_e32 %0, implicit $exec
+name: phys_dpp_mov_old_src
+tracksRegLiveness: true
+body: |
+  bb.0:
+    %1:vgpr_32 = V_MOV_B32_dpp undef $vgpr0, undef %0:vgpr_32, 1, 15, 15, 1, implicit $exec
+    %2:vgpr_32 = V_CEIL_F32_e32 %1, implicit $exec
+...
+
+# Do not combine a dpp mov which reads a physreg.
+# GCN-LABEL: name: phys_dpp_mov_src
+# GCN: %0:vgpr_32 = V_MOV_B32_dpp undef %1:vgpr_32, undef $vgpr0, 1, 15, 15, 1, implicit $exec
+# GCN: %2:vgpr_32 = V_CEIL_F32_e32 %0, implicit $exec
+name: phys_dpp_mov_src
+tracksRegLiveness: true
+body: |
+  bb.0:
+    %1:vgpr_32 = V_MOV_B32_dpp undef %0:vgpr_32, undef $vgpr0, 1, 15, 15, 1, implicit $exec
+    %2:vgpr_32 = V_CEIL_F32_e32 %1, implicit $exec
+...
+
 # GCN-LABEL: name: dpp_reg_sequence_both_combined
 # GCN: %0:vreg_64 = COPY $vgpr0_vgpr1
 # GCN: %1:vreg_64 = COPY $vgpr2_vgpr3
 # GCN: %2:vgpr_32 = V_MOV_B32_e32 5, implicit $exec
 # GCN: %9:vgpr_32 = IMPLICIT_DEF
 # GCN: %8:vgpr_32 = IMPLICIT_DEF
 # GCN: %6:vgpr_32 = V_ADD_I32_dpp %9, %1.sub0, %2, 1, 15, 15, 1, implicit-def $vcc, implicit $exec
 # GCN: %7:vgpr_32 = V_ADDC_U32_dpp %8, %1.sub1, %2, 1, 15, 15, 1, implicit-def $vcc, implicit $vcc, implicit $exec