Added a test to represent prologepilog marks the src tuple

as implicit-def while expanding of SI_SPILL_AV96_SAVE.

Author: Pravin Jagtap

llvm/test/CodeGen/AMDGPU/av-spill-implicit-def-tuple.mir

@@ -0,0 +1,31 @@
+# NOTE: Assertions have been autogenerated by utils/update_mir_test_checks.py
+# RUN: llc -mtriple=amdgcn -mcpu=gfx908 %s -o - -run-pass prologepilog -verify-machineinstrs | FileCheck -check-prefix=GFX908 %s
+
+---
+name:  test_implicit_def
+tracksRegLiveness: true
+stack:
+  - { id: 0, name: '', type: spill-slot, offset: 0, size: 12, alignment: 4 }
+machineFunctionInfo:
+  scratchRSrcReg:  $sgpr0_sgpr1_sgpr2_sgpr3
+  stackPtrOffsetReg: '$sgpr32'
+  hasSpilledVGPRs: true
+body: |
+  bb.0:
+    successors:
+    liveins: $vgpr0, $vgpr1
+
+    ; GFX908-LABEL: name: test_implicit_def
+    ; GFX908: liveins: $vgpr0, $vgpr1, $vgpr2, $vgpr3, $vgpr4
+    ; GFX908-NEXT: {{  $}}
+    ; GFX908-NEXT: renamable $agpr0 = COPY renamable $vgpr0, implicit $exec
+    ; GFX908-NEXT: renamable $agpr2 = COPY renamable $vgpr1, implicit $exec
+    ; GFX908-NEXT: $vgpr4 = V_ACCVGPR_READ_B32_e64 $agpr0, implicit $exec, implicit-def $agpr0_agpr1_agpr2, implicit $agpr0_agpr1_agpr2
+    ; GFX908-NEXT: $vgpr3 = V_ACCVGPR_READ_B32_e64 $agpr1, implicit $exec
+    ; GFX908-NEXT: $vgpr2 = V_ACCVGPR_READ_B32_e64 $agpr2, implicit $exec, implicit $agpr0_agpr1_agpr2
+    ; GFX908-NEXT: S_ENDPGM 0
+    renamable $agpr0 = COPY renamable $vgpr0, implicit $exec
+    renamable $agpr2 = COPY renamable $vgpr1, implicit $exec
+    SI_SPILL_AV96_SAVE $agpr0_agpr1_agpr2, %stack.0, $sgpr32, 0, implicit $exec :: (store (s96) into %stack.0, align 4, addrspace 5)
+    S_ENDPGM 0
+...