AMDGPU: Fix introducing use of killed vgpr in gfx908 agpr copy

When searching for an existing VGPR source for an AGPR to AGPR
copy on gfx908, this wasn't verifying the vgpr wasn't killed by
other prior uses.

Author: arsenm

llvm/lib/Target/AMDGPU/SIInstrInfo.cpp

@@ -687,7 +687,8 @@ static void indirectCopyToAGPR(const SIInstrInfo &TII,
         if (!SafeToPropagate)
           break;
 
-        DefOp.setIsKill(false);
+        for (auto I = Def; I != MI; ++I)
+          I->clearRegisterKills(DefOp.getReg(), &RI);
       }
 
       MachineInstrBuilder Builder =

llvm/test/CodeGen/AMDGPU/accvgpr-copy.mir

@@ -45,6 +45,9 @@
     define amdgpu_kernel void @copy_agpr_to_agpr_tuple() #0 { ret void }
     define amdgpu_kernel void @copy_agpr_to_agpr_tuple_kill() #0 { ret void }
 
+    define amdgpu_kernel void @look_for_vgpr_killed() #0 { ret void }
+    define amdgpu_kernel void @look_for_vgpr_killed_tuple() #0 { ret void }
+
     attributes #0 = { "amdgpu-flat-work-group-size"="1,256" }
 ...
 
@@ -1517,3 +1520,83 @@ body:             |
     renamable $agpr4_agpr5_agpr6_agpr7 = COPY renamable killed $agpr0_agpr1_agpr2_agpr3, implicit $exec
     S_ENDPGM 0, implicit $agpr4_agpr5_agpr6_agpr7
 ...
+
+# Make sure the expansion of the a-to-a copy doesn't introduce a use
+# after kill of the source vgpr
+---
+name: look_for_vgpr_killed
+tracksRegLiveness: true
+body:             |
+  bb.0:
+    liveins: $agpr0
+
+    ; GFX908-LABEL: name: look_for_vgpr_killed
+    ; GFX908: liveins: $agpr0
+    ; GFX908-NEXT: {{  $}}
+    ; GFX908-NEXT: $vgpr0 = V_MOV_B32_e32 0, implicit $exec
+    ; GFX908-NEXT: $agpr0 = V_ACCVGPR_WRITE_B32_e64 $vgpr0, implicit $exec
+    ; GFX908-NEXT: S_NOP 0, implicit $vgpr0
+    ; GFX908-NEXT: $agpr1 = V_ACCVGPR_WRITE_B32_e64 $vgpr0, implicit $exec
+    ;
+    ; GFX90A-LABEL: name: look_for_vgpr_killed
+    ; GFX90A: liveins: $agpr0
+    ; GFX90A-NEXT: {{  $}}
+    ; GFX90A-NEXT: $vgpr0 = V_MOV_B32_e32 0, implicit $exec
+    ; GFX90A-NEXT: $agpr0 = V_ACCVGPR_WRITE_B32_e64 $vgpr0, implicit $exec
+    ; GFX90A-NEXT: S_NOP 0, implicit killed $vgpr0
+    ; GFX90A-NEXT: $agpr1 = V_ACCVGPR_MOV_B32 $agpr0, implicit $exec
+    ;
+    ; GFX942-LABEL: name: look_for_vgpr_killed
+    ; GFX942: liveins: $agpr0
+    ; GFX942-NEXT: {{  $}}
+    ; GFX942-NEXT: $vgpr0 = V_MOV_B32_e32 0, implicit $exec
+    ; GFX942-NEXT: $agpr0 = V_ACCVGPR_WRITE_B32_e64 $vgpr0, implicit $exec
+    ; GFX942-NEXT: S_NOP 0, implicit killed $vgpr0
+    ; GFX942-NEXT: $agpr1 = V_ACCVGPR_MOV_B32 $agpr0, implicit $exec
+    $vgpr0 = V_MOV_B32_e32 0, implicit $exec
+    $agpr0 = COPY $vgpr0
+    S_NOP 0, implicit killed $vgpr0
+    $agpr1 = COPY $agpr0
+
+...
+
+---
+name: look_for_vgpr_killed_tuple
+tracksRegLiveness: true
+body:             |
+  bb.0:
+    liveins: $agpr0
+
+    ; GFX908-LABEL: name: look_for_vgpr_killed_tuple
+    ; GFX908: liveins: $agpr0
+    ; GFX908-NEXT: {{  $}}
+    ; GFX908-NEXT: $vgpr0 = V_MOV_B32_e32 0, implicit $exec, implicit-def $vgpr0_vgpr1
+    ; GFX908-NEXT: $vgpr1 = V_MOV_B32_e32 1, implicit $exec
+    ; GFX908-NEXT: $agpr0 = V_ACCVGPR_WRITE_B32_e64 $vgpr0, implicit $exec
+    ; GFX908-NEXT: S_NOP 0, implicit $vgpr0_vgpr1
+    ; GFX908-NEXT: $agpr1 = V_ACCVGPR_WRITE_B32_e64 $vgpr0, implicit $exec
+    ;
+    ; GFX90A-LABEL: name: look_for_vgpr_killed_tuple
+    ; GFX90A: liveins: $agpr0
+    ; GFX90A-NEXT: {{  $}}
+    ; GFX90A-NEXT: $vgpr0 = V_MOV_B32_e32 0, implicit $exec, implicit-def $vgpr0_vgpr1
+    ; GFX90A-NEXT: $vgpr1 = V_MOV_B32_e32 1, implicit $exec
+    ; GFX90A-NEXT: $agpr0 = V_ACCVGPR_WRITE_B32_e64 $vgpr0, implicit $exec
+    ; GFX90A-NEXT: S_NOP 0, implicit killed $vgpr0_vgpr1
+    ; GFX90A-NEXT: $agpr1 = V_ACCVGPR_MOV_B32 $agpr0, implicit $exec
+    ;
+    ; GFX942-LABEL: name: look_for_vgpr_killed_tuple
+    ; GFX942: liveins: $agpr0
+    ; GFX942-NEXT: {{  $}}
+    ; GFX942-NEXT: $vgpr0 = V_MOV_B32_e32 0, implicit $exec, implicit-def $vgpr0_vgpr1
+    ; GFX942-NEXT: $vgpr1 = V_MOV_B32_e32 1, implicit $exec
+    ; GFX942-NEXT: $agpr0 = V_ACCVGPR_WRITE_B32_e64 $vgpr0, implicit $exec
+    ; GFX942-NEXT: S_NOP 0, implicit killed $vgpr0_vgpr1
+    ; GFX942-NEXT: $agpr1 = V_ACCVGPR_MOV_B32 $agpr0, implicit $exec
+    $vgpr0 = V_MOV_B32_e32 0, implicit $exec, implicit-def $vgpr0_vgpr1
+    $vgpr1 = V_MOV_B32_e32 1, implicit $exec
+    $agpr0 = COPY $vgpr0
+    S_NOP 0, implicit killed $vgpr0_vgpr1
+    $agpr1 = COPY $agpr0
+
+...