diff --git a/llvm/lib/Target/AMDGPU/AMDGPUISelLowering.cpp b/llvm/lib/Target/AMDGPU/AMDGPUISelLowering.cpp
index e8cc87e52e65a..8a71550e5532c 100644
--- a/llvm/lib/Target/AMDGPU/AMDGPUISelLowering.cpp
+++ b/llvm/lib/Target/AMDGPU/AMDGPUISelLowering.cpp
@@ -3089,10 +3089,10 @@ SDValue AMDGPUTargetLowering::lowerCTLZResults(SDValue Op,
   assert(ResultVT == Arg.getValueType());
 
   auto const LeadingZeroes = 32u - ResultVT.getFixedSizeInBits();
+  auto SubVal = DAG.getConstant(LeadingZeroes, SL, MVT::i32);
   auto NewOp = DAG.getNode(ISD::ZERO_EXTEND, SL, MVT::i32, Arg);
-  auto ShiftVal = DAG.getConstant(LeadingZeroes, SL, MVT::i32);
-  NewOp = DAG.getNode(ISD::SHL, SL, MVT::i32, NewOp, ShiftVal);
   NewOp = DAG.getNode(Op.getOpcode(), SL, MVT::i32, NewOp);
+  NewOp = DAG.getNode(ISD::SUB, SL, MVT::i32, NewOp, SubVal);
   return DAG.getNode(ISD::TRUNCATE, SL, ResultVT, NewOp);
 }
 
diff --git a/llvm/test/CodeGen/AMDGPU/ctlz.ll b/llvm/test/CodeGen/AMDGPU/ctlz.ll
index 9307d8952293b..4decf39d04013 100644
--- a/llvm/test/CodeGen/AMDGPU/ctlz.ll
+++ b/llvm/test/CodeGen/AMDGPU/ctlz.ll
@@ -492,9 +492,9 @@ define amdgpu_kernel void @v_ctlz_i8(ptr addrspace(1) noalias %out, ptr addrspac
 ; SI-NEXT:    s_mov_b32 s4, s0
 ; SI-NEXT:    s_mov_b32 s5, s1
 ; SI-NEXT:    s_waitcnt vmcnt(0)
-; SI-NEXT:    v_lshlrev_b32_e32 v0, 24, v0
 ; SI-NEXT:    v_ffbh_u32_e32 v0, v0
 ; SI-NEXT:    v_min_u32_e32 v0, 32, v0
+; SI-NEXT:    v_subrev_i32_e32 v0, vcc, 24, v0
 ; SI-NEXT:    buffer_store_byte v0, off, s[4:7], 0
 ; SI-NEXT:    s_endpgm
 ;
@@ -512,9 +512,9 @@ define amdgpu_kernel void @v_ctlz_i8(ptr addrspace(1) noalias %out, ptr addrspac
 ; VI-NEXT:    s_mov_b32 s4, s0
 ; VI-NEXT:    s_mov_b32 s5, s1
 ; VI-NEXT:    s_waitcnt vmcnt(0)
-; VI-NEXT:    v_lshlrev_b32_e32 v0, 24, v0
 ; VI-NEXT:    v_ffbh_u32_e32 v0, v0
 ; VI-NEXT:    v_min_u32_e32 v0, 32, v0
+; VI-NEXT:    v_subrev_u32_e32 v0, vcc, 24, v0
 ; VI-NEXT:    buffer_store_byte v0, off, s[4:7], 0
 ; VI-NEXT:    s_endpgm
 ;
@@ -522,7 +522,7 @@ define amdgpu_kernel void @v_ctlz_i8(ptr addrspace(1) noalias %out, ptr addrspac
 ; EG:       ; %bb.0:
 ; EG-NEXT:    ALU 0, @8, KC0[CB0:0-32], KC1[]
 ; EG-NEXT:    TEX 0 @6
-; EG-NEXT:    ALU 16, @9, KC0[CB0:0-32], KC1[]
+; EG-NEXT:    ALU 15, @9, KC0[CB0:0-32], KC1[]
 ; EG-NEXT:    MEM_RAT MSKOR T0.XW, T1.X
 ; EG-NEXT:    CF_END
 ; EG-NEXT:    PAD
@@ -531,15 +531,14 @@ define amdgpu_kernel void @v_ctlz_i8(ptr addrspace(1) noalias %out, ptr addrspac
 ; EG-NEXT:    ALU clause starting at 8:
 ; EG-NEXT:     MOV * T0.X, KC0[2].Z,
 ; EG-NEXT:    ALU clause starting at 9:
-; EG-NEXT:     LSHL * T0.W, T0.X, literal.x,
-; EG-NEXT:    24(3.363116e-44), 0(0.000000e+00)
-; EG-NEXT:     FFBH_UINT T1.W, PV.W,
-; EG-NEXT:     AND_INT * T2.W, KC0[2].Y, literal.x,
-; EG-NEXT:    3(4.203895e-45), 0(0.000000e+00)
-; EG-NEXT:     CNDE_INT * T0.W, T0.W, literal.x, PV.W,
-; EG-NEXT:    32(4.484155e-44), 0(0.000000e+00)
+; EG-NEXT:     FFBH_UINT * T0.W, T0.X,
+; EG-NEXT:     CNDE_INT T0.W, T0.X, literal.x, PV.W,
+; EG-NEXT:     AND_INT * T1.W, KC0[2].Y, literal.y,
+; EG-NEXT:    32(4.484155e-44), 3(4.203895e-45)
+; EG-NEXT:     ADD_INT * T0.W, PV.W, literal.x,
+; EG-NEXT:    -24(nan), 0(0.000000e+00)
 ; EG-NEXT:     AND_INT T0.W, PV.W, literal.x,
-; EG-NEXT:     LSHL * T1.W, T2.W, literal.y,
+; EG-NEXT:     LSHL * T1.W, T1.W, literal.y,
 ; EG-NEXT:    255(3.573311e-43), 3(4.203895e-45)
 ; EG-NEXT:     LSHL T0.X, PV.W, PS,
 ; EG-NEXT:     LSHL * T0.W, literal.x, PS,
@@ -556,9 +555,9 @@ define amdgpu_kernel void @v_ctlz_i8(ptr addrspace(1) noalias %out, ptr addrspac
 ; GFX10-NEXT:    s_waitcnt lgkmcnt(0)
 ; GFX10-NEXT:    global_load_ubyte v1, v0, s[2:3]
 ; GFX10-NEXT:    s_waitcnt vmcnt(0)
-; GFX10-NEXT:    v_lshlrev_b32_e32 v1, 24, v1
 ; GFX10-NEXT:    v_ffbh_u32_e32 v1, v1
 ; GFX10-NEXT:    v_min_u32_e32 v1, 32, v1
+; GFX10-NEXT:    v_subrev_nc_u32_e32 v1, 24, v1
 ; GFX10-NEXT:    global_store_byte v0, v1, s[0:1]
 ; GFX10-NEXT:    s_endpgm
 ;
@@ -582,10 +581,10 @@ define amdgpu_kernel void @v_ctlz_i8(ptr addrspace(1) noalias %out, ptr addrspac
 ; GFX11-NEXT:    s_waitcnt lgkmcnt(0)
 ; GFX11-NEXT:    global_load_u8 v1, v0, s[2:3]
 ; GFX11-NEXT:    s_waitcnt vmcnt(0)
-; GFX11-NEXT:    v_lshlrev_b32_e32 v1, 24, v1
-; GFX11-NEXT:    s_delay_alu instid0(VALU_DEP_1) | instskip(NEXT) | instid1(VALU_DEP_1)
 ; GFX11-NEXT:    v_clz_i32_u32_e32 v1, v1
+; GFX11-NEXT:    s_delay_alu instid0(VALU_DEP_1) | instskip(NEXT) | instid1(VALU_DEP_1)
 ; GFX11-NEXT:    v_min_u32_e32 v1, 32, v1
+; GFX11-NEXT:    v_subrev_nc_u32_e32 v1, 24, v1
 ; GFX11-NEXT:    global_store_b8 v0, v1, s[0:1]
 ; GFX11-NEXT:    s_nop 0
 ; GFX11-NEXT:    s_sendmsg sendmsg(MSG_DEALLOC_VGPRS)
diff --git a/llvm/test/CodeGen/AMDGPU/ctlz_zero_undef.ll b/llvm/test/CodeGen/AMDGPU/ctlz_zero_undef.ll
index 2830e5258e92b..21aff62b9226d 100644
--- a/llvm/test/CodeGen/AMDGPU/ctlz_zero_undef.ll
+++ b/llvm/test/CodeGen/AMDGPU/ctlz_zero_undef.ll
@@ -314,8 +314,9 @@ define amdgpu_kernel void @s_ctlz_zero_undef_i8_with_select(ptr addrspace(1) noa
 ; SI-NEXT:    s_load_dwordx2 s[0:1], s[0:1], 0x9
 ; SI-NEXT:    s_mov_b32 s3, 0xf000
 ; SI-NEXT:    s_waitcnt lgkmcnt(0)
-; SI-NEXT:    s_lshl_b32 s2, s2, 24
-; SI-NEXT:    s_flbit_i32_b32 s4, s2
+; SI-NEXT:    s_and_b32 s2, s2, 0xff
+; SI-NEXT:    s_flbit_i32_b32 s2, s2
+; SI-NEXT:    s_sub_i32 s4, s2, 24
 ; SI-NEXT:    s_mov_b32 s2, -1
 ; SI-NEXT:    v_mov_b32_e32 v0, s4
 ; SI-NEXT:    buffer_store_byte v0, off, s[0:3], 0
@@ -326,8 +327,9 @@ define amdgpu_kernel void @s_ctlz_zero_undef_i8_with_select(ptr addrspace(1) noa
 ; VI-NEXT:    s_load_dword s2, s[0:1], 0x2c
 ; VI-NEXT:    s_load_dwordx2 s[0:1], s[0:1], 0x24
 ; VI-NEXT:    s_waitcnt lgkmcnt(0)
-; VI-NEXT:    s_lshl_b32 s2, s2, 24
+; VI-NEXT:    s_and_b32 s2, s2, 0xff
 ; VI-NEXT:    s_flbit_i32_b32 s2, s2
+; VI-NEXT:    s_sub_i32 s2, s2, 24
 ; VI-NEXT:    v_mov_b32_e32 v0, s0
 ; VI-NEXT:    v_mov_b32_e32 v1, s1
 ; VI-NEXT:    v_mov_b32_e32 v2, s2
@@ -347,13 +349,13 @@ define amdgpu_kernel void @s_ctlz_zero_undef_i8_with_select(ptr addrspace(1) noa
 ; EG-NEXT:    ALU clause starting at 8:
 ; EG-NEXT:     MOV * T0.X, 0.0,
 ; EG-NEXT:    ALU clause starting at 9:
-; EG-NEXT:     LSHL * T0.W, T0.X, literal.x,
-; EG-NEXT:    24(3.363116e-44), 0(0.000000e+00)
-; EG-NEXT:     FFBH_UINT T0.W, PV.W,
+; EG-NEXT:     FFBH_UINT T0.W, T0.X,
 ; EG-NEXT:     AND_INT * T1.W, KC0[2].Y, literal.x,
 ; EG-NEXT:    3(4.203895e-45), 0(0.000000e+00)
+; EG-NEXT:     ADD_INT * T0.W, PV.W, literal.x,
+; EG-NEXT:    -24(nan), 0(0.000000e+00)
 ; EG-NEXT:     AND_INT T0.W, PV.W, literal.x,
-; EG-NEXT:     LSHL * T1.W, PS, literal.y,
+; EG-NEXT:     LSHL * T1.W, T1.W, literal.y,
 ; EG-NEXT:    255(3.573311e-43), 3(4.203895e-45)
 ; EG-NEXT:     LSHL T0.X, PV.W, PS,
 ; EG-NEXT:     LSHL * T0.W, literal.x, PS,
@@ -389,8 +391,9 @@ define amdgpu_kernel void @s_ctlz_zero_undef_i16_with_select(ptr addrspace(1) no
 ; SI-NEXT:    s_load_dwordx2 s[0:1], s[0:1], 0x9
 ; SI-NEXT:    s_mov_b32 s3, 0xf000
 ; SI-NEXT:    s_waitcnt lgkmcnt(0)
-; SI-NEXT:    s_lshl_b32 s2, s2, 16
-; SI-NEXT:    s_flbit_i32_b32 s4, s2
+; SI-NEXT:    s_and_b32 s2, s2, 0xffff
+; SI-NEXT:    s_flbit_i32_b32 s2, s2
+; SI-NEXT:    s_add_i32 s4, s2, -16
 ; SI-NEXT:    s_mov_b32 s2, -1
 ; SI-NEXT:    v_mov_b32_e32 v0, s4
 ; SI-NEXT:    buffer_store_short v0, off, s[0:3], 0
@@ -423,13 +426,13 @@ define amdgpu_kernel void @s_ctlz_zero_undef_i16_with_select(ptr addrspace(1) no
 ; EG-NEXT:    ALU clause starting at 8:
 ; EG-NEXT:     MOV * T0.X, 0.0,
 ; EG-NEXT:    ALU clause starting at 9:
-; EG-NEXT:     LSHL * T0.W, T0.X, literal.x,
-; EG-NEXT:    16(2.242078e-44), 0(0.000000e+00)
-; EG-NEXT:     FFBH_UINT T0.W, PV.W,
+; EG-NEXT:     FFBH_UINT T0.W, T0.X,
 ; EG-NEXT:     AND_INT * T1.W, KC0[2].Y, literal.x,
 ; EG-NEXT:    3(4.203895e-45), 0(0.000000e+00)
+; EG-NEXT:     ADD_INT * T0.W, PV.W, literal.x,
+; EG-NEXT:    -16(nan), 0(0.000000e+00)
 ; EG-NEXT:     AND_INT T0.W, PV.W, literal.x,
-; EG-NEXT:     LSHL * T1.W, PS, literal.y,
+; EG-NEXT:     LSHL * T1.W, T1.W, literal.y,
 ; EG-NEXT:    65535(9.183409e-41), 3(4.203895e-45)
 ; EG-NEXT:     LSHL T0.X, PV.W, PS,
 ; EG-NEXT:     LSHL * T0.W, literal.x, PS,
@@ -587,8 +590,8 @@ define amdgpu_kernel void @v_ctlz_zero_undef_i8_with_select(ptr addrspace(1) noa
 ; SI-NEXT:    s_mov_b32 s4, s0
 ; SI-NEXT:    s_mov_b32 s5, s1
 ; SI-NEXT:    s_waitcnt vmcnt(0)
-; SI-NEXT:    v_lshlrev_b32_e32 v1, 24, v0
-; SI-NEXT:    v_ffbh_u32_e32 v1, v1
+; SI-NEXT:    v_ffbh_u32_e32 v1, v0
+; SI-NEXT:    v_subrev_i32_e32 v1, vcc, 24, v1
 ; SI-NEXT:    v_cmp_ne_u32_e32 vcc, 0, v0
 ; SI-NEXT:    v_cndmask_b32_e32 v0, 32, v1, vcc
 ; SI-NEXT:    buffer_store_byte v0, off, s[4:7], 0
@@ -602,8 +605,8 @@ define amdgpu_kernel void @v_ctlz_zero_undef_i8_with_select(ptr addrspace(1) noa
 ; VI-NEXT:    v_mov_b32_e32 v1, s3
 ; VI-NEXT:    flat_load_ubyte v0, v[0:1]
 ; VI-NEXT:    s_waitcnt vmcnt(0)
-; VI-NEXT:    v_lshlrev_b32_e32 v1, 24, v0
-; VI-NEXT:    v_ffbh_u32_e32 v1, v1
+; VI-NEXT:    v_ffbh_u32_sdwa v1, v0 dst_sel:DWORD dst_unused:UNUSED_PAD src0_sel:WORD_0
+; VI-NEXT:    v_subrev_u32_e32 v1, vcc, 24, v1
 ; VI-NEXT:    v_cmp_ne_u16_e32 vcc, 0, v0
 ; VI-NEXT:    v_cndmask_b32_e32 v2, 32, v1, vcc
 ; VI-NEXT:    v_mov_b32_e32 v0, s0
@@ -615,7 +618,7 @@ define amdgpu_kernel void @v_ctlz_zero_undef_i8_with_select(ptr addrspace(1) noa
 ; EG:       ; %bb.0:
 ; EG-NEXT:    ALU 0, @8, KC0[CB0:0-32], KC1[]
 ; EG-NEXT:    TEX 0 @6
-; EG-NEXT:    ALU 16, @9, KC0[CB0:0-32], KC1[]
+; EG-NEXT:    ALU 15, @9, KC0[CB0:0-32], KC1[]
 ; EG-NEXT:    MEM_RAT MSKOR T0.XW, T1.X
 ; EG-NEXT:    CF_END
 ; EG-NEXT:    PAD
@@ -624,11 +627,10 @@ define amdgpu_kernel void @v_ctlz_zero_undef_i8_with_select(ptr addrspace(1) noa
 ; EG-NEXT:    ALU clause starting at 8:
 ; EG-NEXT:     MOV * T0.X, KC0[2].Z,
 ; EG-NEXT:    ALU clause starting at 9:
-; EG-NEXT:     LSHL * T0.W, T0.X, literal.x,
-; EG-NEXT:    24(3.363116e-44), 0(0.000000e+00)
-; EG-NEXT:     FFBH_UINT T0.W, PV.W,
-; EG-NEXT:     AND_INT * T1.W, KC0[2].Y, literal.x,
-; EG-NEXT:    3(4.203895e-45), 0(0.000000e+00)
+; EG-NEXT:     FFBH_UINT * T0.W, T0.X,
+; EG-NEXT:     ADD_INT T0.W, PV.W, literal.x,
+; EG-NEXT:     AND_INT * T1.W, KC0[2].Y, literal.y,
+; EG-NEXT:    -24(nan), 3(4.203895e-45)
 ; EG-NEXT:     CNDE_INT * T0.W, T0.X, literal.x, PV.W,
 ; EG-NEXT:    32(4.484155e-44), 0(0.000000e+00)
 ; EG-NEXT:     AND_INT T0.W, PV.W, literal.x,
@@ -683,8 +685,8 @@ define amdgpu_kernel void @v_ctlz_zero_undef_i16_with_select(ptr addrspace(1) no
 ; SI-NEXT:    v_lshlrev_b32_e32 v0, 8, v0
 ; SI-NEXT:    s_waitcnt vmcnt(0)
 ; SI-NEXT:    v_or_b32_e32 v0, v0, v1
-; SI-NEXT:    v_lshlrev_b32_e32 v1, 16, v0
-; SI-NEXT:    v_ffbh_u32_e32 v1, v1
+; SI-NEXT:    v_ffbh_u32_e32 v1, v0
+; SI-NEXT:    v_add_i32_e32 v1, vcc, -16, v1
 ; SI-NEXT:    v_cmp_ne_u32_e32 vcc, 0, v0
 ; SI-NEXT:    v_cndmask_b32_e32 v0, 32, v1, vcc
 ; SI-NEXT:    buffer_store_short v0, off, s[4:7], 0
@@ -719,7 +721,7 @@ define amdgpu_kernel void @v_ctlz_zero_undef_i16_with_select(ptr addrspace(1) no
 ; EG:       ; %bb.0:
 ; EG-NEXT:    ALU 0, @8, KC0[CB0:0-32], KC1[]
 ; EG-NEXT:    TEX 0 @6
-; EG-NEXT:    ALU 16, @9, KC0[CB0:0-32], KC1[]
+; EG-NEXT:    ALU 15, @9, KC0[CB0:0-32], KC1[]
 ; EG-NEXT:    MEM_RAT MSKOR T0.XW, T1.X
 ; EG-NEXT:    CF_END
 ; EG-NEXT:    PAD
@@ -728,11 +730,10 @@ define amdgpu_kernel void @v_ctlz_zero_undef_i16_with_select(ptr addrspace(1) no
 ; EG-NEXT:    ALU clause starting at 8:
 ; EG-NEXT:     MOV * T0.X, KC0[2].Z,
 ; EG-NEXT:    ALU clause starting at 9:
-; EG-NEXT:     LSHL * T0.W, T0.X, literal.x,
-; EG-NEXT:    16(2.242078e-44), 0(0.000000e+00)
-; EG-NEXT:     FFBH_UINT T0.W, PV.W,
-; EG-NEXT:     AND_INT * T1.W, KC0[2].Y, literal.x,
-; EG-NEXT:    3(4.203895e-45), 0(0.000000e+00)
+; EG-NEXT:     FFBH_UINT * T0.W, T0.X,
+; EG-NEXT:     ADD_INT T0.W, PV.W, literal.x,
+; EG-NEXT:     AND_INT * T1.W, KC0[2].Y, literal.y,
+; EG-NEXT:    -16(nan), 3(4.203895e-45)
 ; EG-NEXT:     CNDE_INT * T0.W, T0.X, literal.x, PV.W,
 ; EG-NEXT:    32(4.484155e-44), 0(0.000000e+00)
 ; EG-NEXT:     AND_INT T0.W, PV.W, literal.x,
@@ -1101,8 +1102,8 @@ define amdgpu_kernel void @v_ctlz_zero_undef_i8(ptr addrspace(1) noalias %out, p
 ; SI-NEXT:    s_mov_b32 s4, s0
 ; SI-NEXT:    s_mov_b32 s5, s1
 ; SI-NEXT:    s_waitcnt vmcnt(0)
-; SI-NEXT:    v_lshlrev_b32_e32 v0, 24, v0
 ; SI-NEXT:    v_ffbh_u32_e32 v0, v0
+; SI-NEXT:    v_subrev_i32_e32 v0, vcc, 24, v0
 ; SI-NEXT:    buffer_store_byte v0, off, s[4:7], 0
 ; SI-NEXT:    s_endpgm
 ;
@@ -1115,8 +1116,8 @@ define amdgpu_kernel void @v_ctlz_zero_undef_i8(ptr addrspace(1) noalias %out, p
 ; VI-NEXT:    v_addc_u32_e32 v1, vcc, 0, v1, vcc
 ; VI-NEXT:    flat_load_ubyte v0, v[0:1]
 ; VI-NEXT:    s_waitcnt vmcnt(0)
-; VI-NEXT:    v_lshlrev_b32_e32 v0, 24, v0
-; VI-NEXT:    v_ffbh_u32_e32 v2, v0
+; VI-NEXT:    v_ffbh_u32_e32 v0, v0
+; VI-NEXT:    v_subrev_u32_e32 v2, vcc, 24, v0
 ; VI-NEXT:    v_mov_b32_e32 v0, s0
 ; VI-NEXT:    v_mov_b32_e32 v1, s1
 ; VI-NEXT:    flat_store_byte v[0:1], v2
@@ -1135,13 +1136,13 @@ define amdgpu_kernel void @v_ctlz_zero_undef_i8(ptr addrspace(1) noalias %out, p
 ; EG-NEXT:    ALU clause starting at 8:
 ; EG-NEXT:     ADD_INT * T0.X, KC0[2].Z, T0.X,
 ; EG-NEXT:    ALU clause starting at 9:
-; EG-NEXT:     LSHL * T0.W, T0.X, literal.x,
-; EG-NEXT:    24(3.363116e-44), 0(0.000000e+00)
-; EG-NEXT:     FFBH_UINT T0.W, PV.W,
+; EG-NEXT:     FFBH_UINT T0.W, T0.X,
 ; EG-NEXT:     AND_INT * T1.W, KC0[2].Y, literal.x,
 ; EG-NEXT:    3(4.203895e-45), 0(0.000000e+00)
+; EG-NEXT:     ADD_INT * T0.W, PV.W, literal.x,
+; EG-NEXT:    -24(nan), 0(0.000000e+00)
 ; EG-NEXT:     AND_INT T0.W, PV.W, literal.x,
-; EG-NEXT:     LSHL * T1.W, PS, literal.y,
+; EG-NEXT:     LSHL * T1.W, T1.W, literal.y,
 ; EG-NEXT:    255(3.573311e-43), 3(4.203895e-45)
 ; EG-NEXT:     LSHL T0.X, PV.W, PS,
 ; EG-NEXT:     LSHL * T0.W, literal.x, PS,