[AMDGPU] Fix mfma scheduling crash

An SUnit can be neither intruction not SDNode. It is all
null if represents a nop. Fixed a crash on using SU->getInstr().

Differential Revision: https://reviews.llvm.org/D69395

1 files changed, 6 insertions, 1 deletions

diff --git a/llvm/lib/Target/AMDGPU/AMDGPUSubtarget.cpp b/llvm/lib/Target/AMDGPU/AMDGPUSubtarget.cpp
index 3bb6dd4571c..46e4d76367f 100644
--- a/llvm/lib/Target/AMDGPU/AMDGPUSubtarget.cpp
+++ b/llvm/lib/Target/AMDGPU/AMDGPUSubtarget.cpp
@@ -773,6 +773,11 @@ struct FillMFMAShadowMutation : ScheduleDAGMutation {
     return MI && TII->isSALU(*MI) && !MI->isTerminator();
   }
 
+  bool isVALU(const SUnit *SU) const {
+    const MachineInstr *MI = SU->getInstr();
+    return MI && TII->isVALU(*MI);
+  }
+
   bool canAddEdge(const SUnit *Succ, const SUnit *Pred) const {
     if (Pred->NodeNum < Succ->NodeNum)
       return true;
@@ -821,7 +826,7 @@ struct FillMFMAShadowMutation : ScheduleDAGMutation {
 
       for (SDep &SI : From->Succs) {
         SUnit *SUv = SI.getSUnit();
-        if (SUv != From && TII->isVALU(*SUv->getInstr()) && canAddEdge(SUv, SU))
+        if (SUv != From && isVALU(SUv) && canAddEdge(SUv, SU))
           SUv->addPred(SDep(SU, SDep::Artificial), false);
       }