AMDGPU: Fix crash with undef vreg input operand

llvm-svn: 305814

llvm/lib/Target/AMDGPU/SIFoldOperands.cpp

@@ -470,7 +470,7 @@ static MachineOperand *getImmOrMaterializedImm(MachineRegisterInfo &MRI,
       return &Op;
 
     MachineInstr *Def = MRI.getVRegDef(Op.getReg());
-    if (Def->isMoveImmediate()) {
+    if (Def && Def->isMoveImmediate()) {
       MachineOperand &ImmSrc = Def->getOperand(1);
       if (ImmSrc.isImm())
         return &ImmSrc;

llvm/test/CodeGen/AMDGPU/constant-fold-imm-immreg.mir

@@ -68,6 +68,10 @@
     ret void
   }
 
+  define amdgpu_kernel void @undefined_vreg_operand() {
+    unreachable
+  }
+
   declare i32 @llvm.amdgcn.workitem.id.x() #1
 
   attributes #0 = { nounwind }
@@ -856,3 +860,20 @@ body:             |
     S_ENDPGM
 
 ...
+---
+# There is only an undef use operand for %1, so there is no
+# corresponding defining instruction
+
+name: undefined_vreg_operand
+tracksRegLiveness: true
+registers:
+  - { id: 0, class: vgpr_32, preferred-register: '' }
+  - { id: 1, class: vgpr_32, preferred-register: '' }
+  - { id: 2, class: vgpr_32, preferred-register: '' }
+body:             |
+  bb.0:
+    %0 = V_MOV_B32_e32 0, implicit %exec
+    %2 = V_XOR_B32_e64 killed %0, undef %1, implicit %exec
+    S_ENDPGM
+
+...