diff --git a/llvm/include/llvm/CodeGen/GlobalISel/CombinerHelper.h b/llvm/include/llvm/CodeGen/GlobalISel/CombinerHelper.h
index 55c3b72c8e027f..6662c1055aa17a 100644
--- a/llvm/include/llvm/CodeGen/GlobalISel/CombinerHelper.h
+++ b/llvm/include/llvm/CodeGen/GlobalISel/CombinerHelper.h
@@ -150,6 +150,10 @@ class CombinerHelper {
   /// is a legal integer constant type on the target.
   bool isConstantLegalOrBeforeLegalizer(const LLT Ty) const;
 
+  /// \return true if the combine is running prior to legalization, or if \p Ty
+  /// is a legal undef type on the target.
+  bool isUndefLegalOrBeforeLegalizer(const LLT Ty) const;
+
   /// MachineRegisterInfo::replaceRegWith() and inform the observer of the changes
   void replaceRegWith(MachineRegisterInfo &MRI, Register FromReg, Register ToReg) const;
 
diff --git a/llvm/include/llvm/Target/GlobalISel/Combine.td b/llvm/include/llvm/Target/GlobalISel/Combine.td
index b0c63fc7c7b806..fee695c4333d99 100644
--- a/llvm/include/llvm/Target/GlobalISel/Combine.td
+++ b/llvm/include/llvm/Target/GlobalISel/Combine.td
@@ -428,7 +428,7 @@ def unary_undef_to_zero: GICombineRule<
 // replaced with undef.
 def propagate_undef_any_op: GICombineRule<
   (defs root:$root),
-  (match (wip_match_opcode G_ADD, G_FPTOSI, G_FPTOUI, G_SUB, G_XOR, G_TRUNC, G_BITCAST, G_ANYEXT):$root,
+  (match (wip_match_opcode G_ADD, G_FPTOSI, G_FPTOUI, G_SUB, G_XOR, G_TRUNC, G_BITCAST):$root,
          [{ return Helper.matchAnyExplicitUseIsUndef(*${root}); }]),
   (apply [{ Helper.replaceInstWithUndef(*${root}); }])>;
 
@@ -1857,6 +1857,27 @@ class integer_of_opcode<Instruction castOpcode> : GICombineRule <
 
 def integer_of_truncate : integer_of_opcode<G_TRUNC>;
 
+def anyext_undef: GICombineRule<
+   (defs root:$root),
+   (match (G_IMPLICIT_DEF $undef),
+          (G_ANYEXT $root, $undef):$Aext,
+   [{ return Helper.isUndefLegalOrBeforeLegalizer(MRI.getType(${Aext}->getOperand(0).getReg())); }]),
+   (apply [{ Helper.replaceInstWithUndef(*${Aext}); }])>;
+
+def zext_undef: GICombineRule<
+   (defs root:$root),
+   (match (G_IMPLICIT_DEF $undef),
+          (G_ZEXT $root, $undef):$Zext,
+   [{ return Helper.isConstantLegalOrBeforeLegalizer(MRI.getType(${Zext}->getOperand(0).getReg())); }]),
+   (apply [{ Helper.replaceInstWithConstant(*${Zext}, 0); }])>;
+
+def sext_undef: GICombineRule<
+   (defs root:$root),
+   (match (G_IMPLICIT_DEF $undef),
+          (G_SEXT $root, $undef):$Sext,
+   [{ return Helper.isConstantLegalOrBeforeLegalizer(MRI.getType(${Sext}->getOperand(0).getReg())); }]),
+   (apply [{ Helper.replaceInstWithConstant(*${Sext}, 0); }])>;
+
 def cast_of_cast_combines: GICombineGroup<[
   truncate_of_zext,
   truncate_of_sext,
@@ -1882,7 +1903,10 @@ def cast_combines: GICombineGroup<[
   narrow_binop_and,
   narrow_binop_or,
   narrow_binop_xor,
-  integer_of_truncate
+  integer_of_truncate,
+  anyext_undef,
+  sext_undef,
+  zext_undef
 ]>;
 
 def canonicalize_icmp : GICombineRule<
diff --git a/llvm/lib/CodeGen/GlobalISel/CombinerHelper.cpp b/llvm/lib/CodeGen/GlobalISel/CombinerHelper.cpp
index d95fc8cfbcf558..29074103115f59 100644
--- a/llvm/lib/CodeGen/GlobalISel/CombinerHelper.cpp
+++ b/llvm/lib/CodeGen/GlobalISel/CombinerHelper.cpp
@@ -171,6 +171,10 @@ bool CombinerHelper::isConstantLegalOrBeforeLegalizer(const LLT Ty) const {
          isLegal({TargetOpcode::G_CONSTANT, {EltTy}});
 }
 
+bool CombinerHelper::isUndefLegalOrBeforeLegalizer(const LLT Ty) const {
+  return isPreLegalize() || isLegal({TargetOpcode::G_IMPLICIT_DEF, {Ty}});
+}
+
 void CombinerHelper::replaceRegWith(MachineRegisterInfo &MRI, Register FromReg,
                                     Register ToReg) const {
   Observer.changingAllUsesOfReg(MRI, FromReg);
diff --git a/llvm/test/CodeGen/AArch64/GlobalISel/combine-cast.mir b/llvm/test/CodeGen/AArch64/GlobalISel/combine-cast.mir
index b045deebc56e03..25161652dafac4 100644
--- a/llvm/test/CodeGen/AArch64/GlobalISel/combine-cast.mir
+++ b/llvm/test/CodeGen/AArch64/GlobalISel/combine-cast.mir
@@ -217,3 +217,55 @@ body:             |
     %large:_(<2 x s64>) = G_ANYEXT %bv(<2 x s32>)
     $q0 = COPY %large(<2 x s64>)
     $d0 = COPY %bv(<2 x s32>)
+...
+---
+name:            test_combine_anyext_undef
+legalized: true
+body:             |
+  bb.1:
+    ; CHECK-PRE-LABEL: name: test_combine_anyext_undef
+    ; CHECK-PRE: %aext:_(s64) = G_IMPLICIT_DEF
+    ; CHECK-PRE-NEXT: $x0 = COPY %aext(s64)
+    ;
+    ; CHECK-POST-LABEL: name: test_combine_anyext_undef
+    ; CHECK-POST: %undef:_(s32) = G_IMPLICIT_DEF
+    ; CHECK-POST-NEXT: %aext:_(s64) = G_ANYEXT %undef(s32)
+    ; CHECK-POST-NEXT: $x0 = COPY %aext(s64)
+    %undef:_(s32) = G_IMPLICIT_DEF
+    %aext:_(s64) = G_ANYEXT %undef(s32)
+    $x0 = COPY %aext(s64)
+...
+---
+name:            test_combine_sext_undef
+legalized: true
+body:             |
+  bb.1:
+    ; CHECK-PRE-LABEL: name: test_combine_sext_undef
+    ; CHECK-PRE: %sext:_(s64) = G_CONSTANT i64 0
+    ; CHECK-PRE-NEXT: $x0 = COPY %sext(s64)
+    ;
+    ; CHECK-POST-LABEL: name: test_combine_sext_undef
+    ; CHECK-POST: %undef:_(s32) = G_IMPLICIT_DEF
+    ; CHECK-POST-NEXT: %sext:_(s64) = G_SEXT %undef(s32)
+    ; CHECK-POST-NEXT: $x0 = COPY %sext(s64)
+    %undef:_(s32) = G_IMPLICIT_DEF
+    %sext:_(s64) = G_SEXT %undef(s32)
+    $x0 = COPY %sext(s64)
+...
+---
+name:            test_combine_zext_undef
+legalized: true
+body:             |
+  bb.1:
+    ; CHECK-PRE-LABEL: name: test_combine_zext_undef
+    ; CHECK-PRE: %zext:_(s64) = G_CONSTANT i64 0
+    ; CHECK-PRE-NEXT: $x0 = COPY %zext(s64)
+    ;
+    ; CHECK-POST-LABEL: name: test_combine_zext_undef
+    ; CHECK-POST: %undef:_(s32) = G_IMPLICIT_DEF
+    ; CHECK-POST-NEXT: %zext:_(s64) = G_ZEXT %undef(s32)
+    ; CHECK-POST-NEXT: $x0 = COPY %zext(s64)
+    %undef:_(s32) = G_IMPLICIT_DEF
+    %zext:_(s64) = G_ZEXT %undef(s32)
+    $x0 = COPY %zext(s64)
+...
diff --git a/llvm/test/CodeGen/AArch64/extract-vector-elt.ll b/llvm/test/CodeGen/AArch64/extract-vector-elt.ll
index 5e5fdd6d317057..e89e1516fb1f54 100644
--- a/llvm/test/CodeGen/AArch64/extract-vector-elt.ll
+++ b/llvm/test/CodeGen/AArch64/extract-vector-elt.ll
@@ -8,17 +8,10 @@
 ; CHECK-GI-NEXT:  warning: Instruction selection used fallback path for extract_v4i32_vector_extract_const
 
 define i64 @extract_v2i64_undef_index(<2 x i64> %a, i32 %c) {
-; CHECK-SD-LABEL: extract_v2i64_undef_index:
-; CHECK-SD:       // %bb.0: // %entry
-; CHECK-SD-NEXT:    fmov x0, d0
-; CHECK-SD-NEXT:    ret
-;
-; CHECK-GI-LABEL: extract_v2i64_undef_index:
-; CHECK-GI:       // %bb.0: // %entry
-; CHECK-GI-NEXT:    str q0, [sp, #-16]!
-; CHECK-GI-NEXT:    .cfi_def_cfa_offset 16
-; CHECK-GI-NEXT:    ldr x0, [sp], #16
-; CHECK-GI-NEXT:    ret
+; CHECK-LABEL: extract_v2i64_undef_index:
+; CHECK:       // %bb.0: // %entry
+; CHECK-NEXT:    fmov x0, d0
+; CHECK-NEXT:    ret
 entry:
   %d = extractelement <2 x i64> %a, i32 undef
   ret i64 %d
diff --git a/llvm/test/CodeGen/AMDGPU/GlobalISel/combine-amdgpu-cvt-f32-ubyte.mir b/llvm/test/CodeGen/AMDGPU/GlobalISel/combine-amdgpu-cvt-f32-ubyte.mir
index 7893bfa1d38f08..9b39afd32ac378 100644
--- a/llvm/test/CodeGen/AMDGPU/GlobalISel/combine-amdgpu-cvt-f32-ubyte.mir
+++ b/llvm/test/CodeGen/AMDGPU/GlobalISel/combine-amdgpu-cvt-f32-ubyte.mir
@@ -261,8 +261,7 @@ body:             |
     ; CHECK-LABEL: name: cvt_f32_ubyte0_zext_lshr_16
     ; CHECK: liveins: $vgpr0
     ; CHECK-NEXT: {{  $}}
-    ; CHECK-NEXT: %shift:_(s16) = G_IMPLICIT_DEF
-    ; CHECK-NEXT: %zext:_(s32) = G_ZEXT %shift(s16)
+    ; CHECK-NEXT: %zext:_(s32) = G_CONSTANT i32 0
     ; CHECK-NEXT: %result:_(s32) = G_AMDGPU_CVT_F32_UBYTE0 %zext
     ; CHECK-NEXT: $vgpr0 = COPY %result(s32)
     %arg:_(s32) = COPY $vgpr0
@@ -284,8 +283,7 @@ body:             |
     ; CHECK-LABEL: name: cvt_f32_ubyte0_zext_lshr_24
     ; CHECK: liveins: $vgpr0
     ; CHECK-NEXT: {{  $}}
-    ; CHECK-NEXT: %shift:_(s16) = G_IMPLICIT_DEF
-    ; CHECK-NEXT: %zext:_(s32) = G_ZEXT %shift(s16)
+    ; CHECK-NEXT: %zext:_(s32) = G_CONSTANT i32 0
     ; CHECK-NEXT: %result:_(s32) = G_AMDGPU_CVT_F32_UBYTE0 %zext
     ; CHECK-NEXT: $vgpr0 = COPY %result(s32)
     %arg:_(s32) = COPY $vgpr0
diff --git a/llvm/test/CodeGen/AMDGPU/shrink-add-sub-constant.ll b/llvm/test/CodeGen/AMDGPU/shrink-add-sub-constant.ll
index a1a466fb04440d..384a2c63122b85 100644
--- a/llvm/test/CodeGen/AMDGPU/shrink-add-sub-constant.ll
+++ b/llvm/test/CodeGen/AMDGPU/shrink-add-sub-constant.ll
@@ -4074,14 +4074,12 @@ define amdgpu_kernel void @v_test_v2i16_x_add_undef_neg32(ptr addrspace(1) %out,
 ; VI-GISEL-NEXT:    v_addc_u32_e32 v1, vcc, 0, v1, vcc
 ; VI-GISEL-NEXT:    flat_load_dword v3, v[0:1]
 ; VI-GISEL-NEXT:    v_mov_b32_e32 v0, s0
+; VI-GISEL-NEXT:    v_mov_b32_e32 v1, s1
 ; VI-GISEL-NEXT:    v_add_u32_e32 v0, vcc, v0, v2
 ; VI-GISEL-NEXT:    v_not_b32_e32 v2, 31
-; VI-GISEL-NEXT:    v_mov_b32_e32 v1, s1
-; VI-GISEL-NEXT:    s_and_b32 s0, 0xffff, s0
 ; VI-GISEL-NEXT:    v_addc_u32_e32 v1, vcc, 0, v1, vcc
 ; VI-GISEL-NEXT:    s_waitcnt vmcnt(0)
 ; VI-GISEL-NEXT:    v_add_u16_sdwa v2, v3, v2 dst_sel:WORD_1 dst_unused:UNUSED_PAD src0_sel:WORD_1 src1_sel:DWORD
-; VI-GISEL-NEXT:    v_or_b32_e32 v2, s0, v2
 ; VI-GISEL-NEXT:    flat_store_dword v[0:1], v2
 ; VI-GISEL-NEXT:    s_endpgm
 ;
@@ -4191,15 +4189,12 @@ define amdgpu_kernel void @v_test_v2i16_x_add_neg32_undef(ptr addrspace(1) %out,
 ; VI-GISEL-NEXT:    v_add_u32_e32 v0, vcc, v0, v2
 ; VI-GISEL-NEXT:    v_addc_u32_e32 v1, vcc, 0, v1, vcc
 ; VI-GISEL-NEXT:    flat_load_dword v3, v[0:1]
-; VI-GISEL-NEXT:    s_and_b32 s2, 0xffff, s0
 ; VI-GISEL-NEXT:    v_mov_b32_e32 v0, s0
 ; VI-GISEL-NEXT:    v_mov_b32_e32 v1, s1
 ; VI-GISEL-NEXT:    v_add_u32_e32 v0, vcc, v0, v2
-; VI-GISEL-NEXT:    s_lshl_b32 s0, s2, 16
 ; VI-GISEL-NEXT:    v_addc_u32_e32 v1, vcc, 0, v1, vcc
 ; VI-GISEL-NEXT:    s_waitcnt vmcnt(0)
 ; VI-GISEL-NEXT:    v_add_u16_e32 v2, 0xffe0, v3
-; VI-GISEL-NEXT:    v_or_b32_e32 v2, s0, v2
 ; VI-GISEL-NEXT:    flat_store_dword v[0:1], v2
 ; VI-GISEL-NEXT:    s_endpgm
 ;