Index: llvm/lib/Target/AMDGPU/AMDGPURegisterBankInfo.cpp
===================================================================
--- llvm/lib/Target/AMDGPU/AMDGPURegisterBankInfo.cpp
+++ llvm/lib/Target/AMDGPU/AMDGPURegisterBankInfo.cpp
@@ -459,7 +459,8 @@
 
   InstructionMappings AltMappings;
   switch (MI.getOpcode()) {
-  case TargetOpcode::G_CONSTANT: {
+  case TargetOpcode::G_CONSTANT:
+  case TargetOpcode::G_IMPLICIT_DEF: {
     unsigned Size = getSizeInBits(MI.getOperand(0).getReg(), MRI, *TRI);
     if (Size == 1) {
       static const OpRegBankEntry<1> Table[3] = {
@@ -2117,7 +2118,8 @@
   unsigned Opc = MI.getOpcode();
   MachineRegisterInfo &MRI = OpdMapper.getMRI();
   switch (Opc) {
-  case AMDGPU::G_CONSTANT: {
+  case AMDGPU::G_CONSTANT:
+  case AMDGPU::G_IMPLICIT_DEF: {
     Register DstReg = MI.getOperand(0).getReg();
     LLT DstTy = MRI.getType(DstReg);
     if (DstTy != LLT::scalar(1))
@@ -2138,9 +2140,13 @@
     LLVMContext &Ctx = B.getMF().getFunction().getContext();
 
     MI.getOperand(0).setReg(NewDstReg);
-    MI.getOperand(1).setCImm(
-        ConstantInt::get(IntegerType::getInt32Ty(Ctx),
-                         MI.getOperand(1).getCImm()->getZExtValue()));
+
+    if (Opc != AMDGPU::G_IMPLICIT_DEF) {
+      MI.getOperand(1).setCImm(
+          ConstantInt::get(IntegerType::getInt32Ty(Ctx),
+                           MI.getOperand(1).getCImm()->getZExtValue()));
+    }
+
     MRI.setRegBank(NewDstReg, *DstBank);
     B.buildTrunc(DefRegs[0], NewDstReg);
     return;
Index: llvm/test/CodeGen/AMDGPU/GlobalISel/regbankselect-implicit-def.mir
===================================================================
--- llvm/test/CodeGen/AMDGPU/GlobalISel/regbankselect-implicit-def.mir
+++ llvm/test/CodeGen/AMDGPU/GlobalISel/regbankselect-implicit-def.mir
@@ -1,6 +1,6 @@
 # NOTE: Assertions have been autogenerated by utils/update_mir_test_checks.py
-# RUN: llc -march=amdgcn -mcpu=hawaii -run-pass=regbankselect -regbankselect-fast -verify-machineinstrs -o - %s | FileCheck %s
-# RUN: llc -march=amdgcn -mcpu=hawaii -run-pass=regbankselect -regbankselect-greedy -verify-machineinstrs -o - %s | FileCheck %s
+# RUN: llc -march=amdgcn -mcpu=hawaii -run-pass=regbankselect -regbankselect-fast -verify-machineinstrs -o - %s | FileCheck -check-prefixes=CHECK,FAST %s
+# RUN: llc -march=amdgcn -mcpu=hawaii -run-pass=regbankselect -regbankselect-greedy -verify-machineinstrs -o - %s | FileCheck -check-prefixes=CHECK,GREEDY %s
 
 ---
 name: test_implicit_def_s32_vgpr_use
@@ -132,8 +132,9 @@
     ; CHECK-NEXT: {{  $}}
     ; CHECK-NEXT: [[COPY:%[0-9]+]]:sgpr(s32) = COPY $sgpr8
     ; CHECK-NEXT: [[COPY1:%[0-9]+]]:sgpr(s32) = COPY $sgpr9
-    ; CHECK-NEXT: [[DEF:%[0-9]+]]:sgpr(s1) = G_IMPLICIT_DEF
-    ; CHECK-NEXT: [[ZEXT:%[0-9]+]]:sgpr(s32) = G_ZEXT [[DEF]](s1)
+    ; CHECK-NEXT: [[DEF:%[0-9]+]]:sgpr(s32) = G_IMPLICIT_DEF
+    ; CHECK-NEXT: [[TRUNC:%[0-9]+]]:sgpr(s1) = G_TRUNC [[DEF]](s32)
+    ; CHECK-NEXT: [[ZEXT:%[0-9]+]]:sgpr(s32) = G_ZEXT [[TRUNC]](s1)
     ; CHECK-NEXT: [[SELECT:%[0-9]+]]:sgpr(s32) = G_SELECT [[ZEXT]](s32), [[COPY]], [[COPY1]]
     ; CHECK-NEXT: S_ENDPGM 0, implicit [[SELECT]](s32)
     %0:_(s32) = COPY $sgpr8
@@ -155,8 +156,9 @@
     ; CHECK-NEXT: {{  $}}
     ; CHECK-NEXT: [[COPY:%[0-9]+]]:vgpr(s32) = COPY $vgpr0
     ; CHECK-NEXT: [[COPY1:%[0-9]+]]:vgpr(s32) = COPY $vgpr1
-    ; CHECK-NEXT: [[DEF:%[0-9]+]]:sgpr(s1) = G_IMPLICIT_DEF
-    ; CHECK-NEXT: [[COPY2:%[0-9]+]]:vcc(s1) = COPY [[DEF]](s1)
+    ; CHECK-NEXT: [[DEF:%[0-9]+]]:sgpr(s32) = G_IMPLICIT_DEF
+    ; CHECK-NEXT: [[TRUNC:%[0-9]+]]:sgpr(s1) = G_TRUNC [[DEF]](s32)
+    ; CHECK-NEXT: [[COPY2:%[0-9]+]]:vcc(s1) = COPY [[TRUNC]](s1)
     ; CHECK-NEXT: [[SELECT:%[0-9]+]]:vgpr(s32) = G_SELECT [[COPY2]](s1), [[COPY]], [[COPY1]]
     ; CHECK-NEXT: S_ENDPGM 0, implicit [[SELECT]](s32)
     %0:_(s32) = COPY $vgpr0
@@ -173,15 +175,24 @@
 body: |
   bb.0:
     liveins: $vgpr0, $vgpr1
-    ; CHECK-LABEL: name: test_implicit_def_s1_explicit_vcc_use_0
-    ; CHECK: liveins: $vgpr0, $vgpr1
-    ; CHECK-NEXT: {{  $}}
-    ; CHECK-NEXT: [[COPY:%[0-9]+]]:vgpr(s32) = COPY $vgpr0
-    ; CHECK-NEXT: [[COPY1:%[0-9]+]]:vgpr(s32) = COPY $vgpr1
-    ; CHECK-NEXT: [[DEF:%[0-9]+]]:sgpr(s1) = G_IMPLICIT_DEF
-    ; CHECK-NEXT: [[COPY2:%[0-9]+]]:vcc(s1) = COPY [[DEF]](s1)
-    ; CHECK-NEXT: [[SELECT:%[0-9]+]]:vgpr(s32) = G_SELECT [[COPY2]](s1), [[COPY]], [[COPY1]]
-    ; CHECK-NEXT: S_ENDPGM 0, implicit [[SELECT]](s32)
+    ; FAST-LABEL: name: test_implicit_def_s1_explicit_vcc_use_0
+    ; FAST: liveins: $vgpr0, $vgpr1
+    ; FAST-NEXT: {{  $}}
+    ; FAST-NEXT: [[COPY:%[0-9]+]]:vgpr(s32) = COPY $vgpr0
+    ; FAST-NEXT: [[COPY1:%[0-9]+]]:vgpr(s32) = COPY $vgpr1
+    ; FAST-NEXT: [[DEF:%[0-9]+]]:sgpr(s32) = G_IMPLICIT_DEF
+    ; FAST-NEXT: [[TRUNC:%[0-9]+]]:sgpr(s1) = G_TRUNC [[DEF]](s32)
+    ; FAST-NEXT: [[COPY2:%[0-9]+]]:vcc(s1) = COPY [[TRUNC]](s1)
+    ; FAST-NEXT: [[SELECT:%[0-9]+]]:vgpr(s32) = G_SELECT [[COPY2]](s1), [[COPY]], [[COPY1]]
+    ; FAST-NEXT: S_ENDPGM 0, implicit [[SELECT]](s32)
+    ; GREEDY-LABEL: name: test_implicit_def_s1_explicit_vcc_use_0
+    ; GREEDY: liveins: $vgpr0, $vgpr1
+    ; GREEDY-NEXT: {{  $}}
+    ; GREEDY-NEXT: [[COPY:%[0-9]+]]:vgpr(s32) = COPY $vgpr0
+    ; GREEDY-NEXT: [[COPY1:%[0-9]+]]:vgpr(s32) = COPY $vgpr1
+    ; GREEDY-NEXT: [[DEF:%[0-9]+]]:vcc(s1) = G_IMPLICIT_DEF
+    ; GREEDY-NEXT: [[SELECT:%[0-9]+]]:vgpr(s32) = G_SELECT [[DEF]](s1), [[COPY]], [[COPY1]]
+    ; GREEDY-NEXT: S_ENDPGM 0, implicit [[SELECT]](s32)
     %0:_(s32) = COPY $vgpr0
     %1:_(s32) = COPY $vgpr1
     %2:vcc(s1) = G_IMPLICIT_DEF
@@ -195,10 +206,14 @@
 legalized:       true
 body: |
   bb.0:
-    ; CHECK-LABEL: name: test_implicit_def_s1_explicit_vcc_use_1
-    ; CHECK: [[DEF:%[0-9]+]]:sgpr(s1) = G_IMPLICIT_DEF
-    ; CHECK-NEXT: [[COPY:%[0-9]+]]:vcc(s1) = COPY [[DEF]](s1)
-    ; CHECK-NEXT: S_ENDPGM 0, implicit [[COPY]](s1)
+    ; FAST-LABEL: name: test_implicit_def_s1_explicit_vcc_use_1
+    ; FAST: [[DEF:%[0-9]+]]:sgpr(s32) = G_IMPLICIT_DEF
+    ; FAST-NEXT: [[TRUNC:%[0-9]+]]:sgpr(s1) = G_TRUNC [[DEF]](s32)
+    ; FAST-NEXT: [[COPY:%[0-9]+]]:vcc(s1) = COPY [[TRUNC]](s1)
+    ; FAST-NEXT: S_ENDPGM 0, implicit [[COPY]](s1)
+    ; GREEDY-LABEL: name: test_implicit_def_s1_explicit_vcc_use_1
+    ; GREEDY: [[DEF:%[0-9]+]]:vcc(s1) = G_IMPLICIT_DEF
+    ; GREEDY-NEXT: S_ENDPGM 0, implicit [[DEF]](s1)
     %2:vcc(s1) = G_IMPLICIT_DEF
     S_ENDPGM 0, implicit %2