remove 'movt' if there is no user of it

Author: Baoshan Pang

llvm/lib/Target/AMDGPU/SIShrinkInstructions.cpp

@@ -797,7 +797,7 @@ MachineInstr *SIShrinkInstructions::matchSwap(MachineInstr &MovT) const {
     dropInstructionKeepingImpDefs(*MovY);
     MachineInstr *Next = &*std::next(MovT.getIterator());
 
-    if (T.isVirtual() && MRI->use_nodbg_empty(T)) {
+    if (MRI->use_nodbg_empty(T)) {
       dropInstructionKeepingImpDefs(MovT);
     } else {
       Xop.setIsKill(false);

llvm/test/CodeGen/AMDGPU/v_swap_b32.mir

@@ -1,11 +1,9 @@
 # RUN: llc -simplify-mir -mtriple=amdgcn -mcpu=gfx900 -run-pass=si-shrink-instructions -verify-machineinstrs %s -o - | FileCheck -check-prefix=GCN %s
-# RUN: llc -simplify-mir -mtriple=amdgcn -mcpu=gfx900 -passes=si-shrink-instructions -verify-machineinstrs %s -o - | FileCheck -check-prefix=GCN %s
 
 # GCN-LABEL: name: swap_phys_condensed
 # GCN: bb.0:
 # GCN-NEXT: liveins:
 # GCN-NEXT: {{^[ ]*$}}
-# GCN-NEXT: $vgpr2 = V_MOV_B32_e32 $vgpr0, implicit $exec
 # GCN-NEXT: $vgpr0, $vgpr1 = V_SWAP_B32 $vgpr1, $vgpr0, implicit $exec
 # GCN-NEXT: S_SETPC_B64_return
 ---
@@ -24,7 +22,6 @@ body:             |
 # GCN: bb.0:
 # GCN-NEXT: liveins:
 # GCN-NEXT: {{^[ ]*$}}
-# GCN-NEXT: $vgpr2 = V_MOV_B32_e32 $vgpr0, implicit $exec
 # GCN-NEXT: $vgpr3 = V_MOV_B32_e32 killed $vgpr4, implicit $exec
 # GCN-NEXT: $vgpr0, $vgpr1 = V_SWAP_B32 $vgpr1, $vgpr0, implicit $exec
 # GCN-NEXT: $vgpr5 = V_MOV_B32_e32 killed $vgpr6, implicit $exec
@@ -47,7 +44,6 @@ body:             |
 # GCN: bb.0:
 # GCN-NEXT: liveins:
 # GCN-NEXT: {{^[ ]*$}}
-# GCN-NEXT: $vgpr2 = V_MOV_B32_e32 $vgpr0, implicit $exec
 # GCN-NEXT: $vgpr0, $vgpr1 = V_SWAP_B32 $vgpr1, $vgpr0, implicit $exec
 # GCN-NEXT: S_SETPC_B64_return
 ---
@@ -66,7 +62,6 @@ body:             |
 # GCN: bb.0:
 # GCN-NEXT: liveins:
 # GCN-NEXT: {{^[ ]*$}}
-# GCN-NEXT: $vgpr2 = V_MOV_B32_e32 $vgpr0, implicit $exec
 # GCN-NEXT: $vgpr0, $vgpr1 = V_SWAP_B32 $vgpr1, $vgpr0, implicit $exec
 # GCN-NEXT: S_SETPC_B64_return
 ---
@@ -85,7 +80,6 @@ body:             |
 # GCN: bb.0:
 # GCN-NEXT: liveins:
 # GCN-NEXT: {{^[ ]*$}}
-# GCN-NEXT: $vgpr4_vgpr5 = COPY $vgpr0_vgpr1
 # GCN-NEXT: $vgpr0, $vgpr2 = V_SWAP_B32 $vgpr2, $vgpr0, implicit $exec
 # GCN-NEXT: $vgpr1, $vgpr3 = V_SWAP_B32 $vgpr3, $vgpr1, implicit $exec
 ---
@@ -936,8 +930,7 @@ body:             |
 ...
 
 # GCN-LABEL: implicit_ops_mov_t_swap_b32
-# GCN:      $vgpr3 = V_MOV_B32_e32 $vgpr0, implicit $exec, implicit $vgpr2, implicit killed $vgpr1_vgpr2, implicit-def $vgpr1
-# GCN-NEXT: $vgpr0, $vgpr1 = V_SWAP_B32 $vgpr1, $vgpr0, implicit $exec
+# GCN: $vgpr0, $vgpr1 = V_SWAP_B32 $vgpr1, $vgpr0, implicit $exec
 
 ---
 name:            implicit_ops_mov_t_swap_b32