diff --git a/llvm/lib/Target/AArch64/GISel/AArch64LegalizerInfo.cpp b/llvm/lib/Target/AArch64/GISel/AArch64LegalizerInfo.cpp
--- a/llvm/lib/Target/AArch64/GISel/AArch64LegalizerInfo.cpp
+++ b/llvm/lib/Target/AArch64/GISel/AArch64LegalizerInfo.cpp
@@ -699,8 +699,9 @@
 
   getActionDefinitionsBuilder(G_CTTZ)
       .lowerIf(isVector(0))
-      .clampScalar(0, s32, s64)
-      .scalarSameSizeAs(1, 0)
+      .widenScalarToNextPow2(1, /*Min=*/32)
+      .clampScalar(1, s32, s64)
+      .scalarSameSizeAs(0, 1)
       .legalIf([=](const LegalityQuery &Query) {
         return (HasCSSC && typeInSet(0, {s32, s64})(Query));
       })
diff --git a/llvm/test/CodeGen/AArch64/GlobalISel/legalize-cttz-zero-undef.mir b/llvm/test/CodeGen/AArch64/GlobalISel/legalize-cttz-zero-undef.mir
--- a/llvm/test/CodeGen/AArch64/GlobalISel/legalize-cttz-zero-undef.mir
+++ b/llvm/test/CodeGen/AArch64/GlobalISel/legalize-cttz-zero-undef.mir
@@ -16,8 +16,7 @@
     ; CHECK-NEXT: [[OR:%[0-9]+]]:_(s32) = G_OR [[DEF]], [[C]]
     ; CHECK-NEXT: [[BITREVERSE:%[0-9]+]]:_(s32) = G_BITREVERSE [[OR]]
     ; CHECK-NEXT: [[CTLZ:%[0-9]+]]:_(s32) = G_CTLZ [[BITREVERSE]](s32)
-    ; CHECK-NEXT: [[COPY:%[0-9]+]]:_(s32) = COPY [[CTLZ]](s32)
-    ; CHECK-NEXT: $w0 = COPY [[COPY]](s32)
+    ; CHECK-NEXT: $w0 = COPY [[CTLZ]](s32)
     ; CHECK-NEXT: RET_ReallyLR implicit $w0
     ; CHECK-CSSC-LABEL: name: s8
     ; CHECK-CSSC: liveins: $w0
@@ -26,8 +25,7 @@
     ; CHECK-CSSC-NEXT: [[C:%[0-9]+]]:_(s32) = G_CONSTANT i32 256
     ; CHECK-CSSC-NEXT: [[OR:%[0-9]+]]:_(s32) = G_OR [[DEF]], [[C]]
     ; CHECK-CSSC-NEXT: [[CTTZ:%[0-9]+]]:_(s32) = G_CTTZ [[OR]](s32)
-    ; CHECK-CSSC-NEXT: [[COPY:%[0-9]+]]:_(s32) = COPY [[CTTZ]](s32)
-    ; CHECK-CSSC-NEXT: $w0 = COPY [[COPY]](s32)
+    ; CHECK-CSSC-NEXT: $w0 = COPY [[CTTZ]](s32)
     ; CHECK-CSSC-NEXT: RET_ReallyLR implicit $w0
     %val:_(s8) = G_IMPLICIT_DEF
     %cttz:_(s8) = G_CTTZ_ZERO_UNDEF %val(s8)
@@ -50,8 +48,7 @@
     ; CHECK-NEXT: [[OR:%[0-9]+]]:_(s32) = G_OR [[DEF]], [[C]]
     ; CHECK-NEXT: [[BITREVERSE:%[0-9]+]]:_(s32) = G_BITREVERSE [[OR]]
     ; CHECK-NEXT: [[CTLZ:%[0-9]+]]:_(s32) = G_CTLZ [[BITREVERSE]](s32)
-    ; CHECK-NEXT: [[COPY:%[0-9]+]]:_(s32) = COPY [[CTLZ]](s32)
-    ; CHECK-NEXT: $w0 = COPY [[COPY]](s32)
+    ; CHECK-NEXT: $w0 = COPY [[CTLZ]](s32)
     ; CHECK-NEXT: RET_ReallyLR implicit $w0
     ; CHECK-CSSC-LABEL: name: s16
     ; CHECK-CSSC: liveins: $w0
@@ -60,8 +57,7 @@
     ; CHECK-CSSC-NEXT: [[C:%[0-9]+]]:_(s32) = G_CONSTANT i32 65536
     ; CHECK-CSSC-NEXT: [[OR:%[0-9]+]]:_(s32) = G_OR [[DEF]], [[C]]
     ; CHECK-CSSC-NEXT: [[CTTZ:%[0-9]+]]:_(s32) = G_CTTZ [[OR]](s32)
-    ; CHECK-CSSC-NEXT: [[COPY:%[0-9]+]]:_(s32) = COPY [[CTTZ]](s32)
-    ; CHECK-CSSC-NEXT: $w0 = COPY [[COPY]](s32)
+    ; CHECK-CSSC-NEXT: $w0 = COPY [[CTTZ]](s32)
     ; CHECK-CSSC-NEXT: RET_ReallyLR implicit $w0
     %val:_(s16) = G_IMPLICIT_DEF
     %cttz:_(s16) = G_CTTZ_ZERO_UNDEF %val(s16)
diff --git a/llvm/test/CodeGen/AArch64/GlobalISel/legalize-cttz.mir b/llvm/test/CodeGen/AArch64/GlobalISel/legalize-cttz.mir
--- a/llvm/test/CodeGen/AArch64/GlobalISel/legalize-cttz.mir
+++ b/llvm/test/CodeGen/AArch64/GlobalISel/legalize-cttz.mir
@@ -17,8 +17,7 @@
     ; CHECK-NEXT: [[OR:%[0-9]+]]:_(s32) = G_OR [[DEF]], [[C]]
     ; CHECK-NEXT: [[BITREVERSE:%[0-9]+]]:_(s32) = G_BITREVERSE [[OR]]
     ; CHECK-NEXT: [[CTLZ:%[0-9]+]]:_(s32) = G_CTLZ [[BITREVERSE]](s32)
-    ; CHECK-NEXT: [[COPY:%[0-9]+]]:_(s32) = COPY [[CTLZ]](s32)
-    ; CHECK-NEXT: $w0 = COPY [[COPY]](s32)
+    ; CHECK-NEXT: $w0 = COPY [[CTLZ]](s32)
     ; CHECK-NEXT: RET_ReallyLR implicit $w0
     ; CHECK-CSSC-LABEL: name: s8
     ; CHECK-CSSC: liveins: $w0
@@ -27,8 +26,7 @@
     ; CHECK-CSSC-NEXT: [[C:%[0-9]+]]:_(s32) = G_CONSTANT i32 256
     ; CHECK-CSSC-NEXT: [[OR:%[0-9]+]]:_(s32) = G_OR [[DEF]], [[C]]
     ; CHECK-CSSC-NEXT: [[CTTZ:%[0-9]+]]:_(s32) = G_CTTZ [[OR]](s32)
-    ; CHECK-CSSC-NEXT: [[COPY:%[0-9]+]]:_(s32) = COPY [[CTTZ]](s32)
-    ; CHECK-CSSC-NEXT: $w0 = COPY [[COPY]](s32)
+    ; CHECK-CSSC-NEXT: $w0 = COPY [[CTTZ]](s32)
     ; CHECK-CSSC-NEXT: RET_ReallyLR implicit $w0
     %val:_(s8) = G_IMPLICIT_DEF
     %cttz:_(s8) = G_CTTZ %val(s8)
@@ -51,8 +49,7 @@
     ; CHECK-NEXT: [[OR:%[0-9]+]]:_(s32) = G_OR [[DEF]], [[C]]
     ; CHECK-NEXT: [[BITREVERSE:%[0-9]+]]:_(s32) = G_BITREVERSE [[OR]]
     ; CHECK-NEXT: [[CTLZ:%[0-9]+]]:_(s32) = G_CTLZ [[BITREVERSE]](s32)
-    ; CHECK-NEXT: [[COPY:%[0-9]+]]:_(s32) = COPY [[CTLZ]](s32)
-    ; CHECK-NEXT: $w0 = COPY [[COPY]](s32)
+    ; CHECK-NEXT: $w0 = COPY [[CTLZ]](s32)
     ; CHECK-NEXT: RET_ReallyLR implicit $w0
     ; CHECK-CSSC-LABEL: name: s16
     ; CHECK-CSSC: liveins: $w0
@@ -61,8 +58,7 @@
     ; CHECK-CSSC-NEXT: [[C:%[0-9]+]]:_(s32) = G_CONSTANT i32 65536
     ; CHECK-CSSC-NEXT: [[OR:%[0-9]+]]:_(s32) = G_OR [[DEF]], [[C]]
     ; CHECK-CSSC-NEXT: [[CTTZ:%[0-9]+]]:_(s32) = G_CTTZ [[OR]](s32)
-    ; CHECK-CSSC-NEXT: [[COPY:%[0-9]+]]:_(s32) = COPY [[CTTZ]](s32)
-    ; CHECK-CSSC-NEXT: $w0 = COPY [[COPY]](s32)
+    ; CHECK-CSSC-NEXT: $w0 = COPY [[CTTZ]](s32)
     ; CHECK-CSSC-NEXT: RET_ReallyLR implicit $w0
     %val:_(s16) = G_IMPLICIT_DEF
     %cttz:_(s16) = G_CTTZ %val(s16)
@@ -166,3 +162,104 @@
     RET_ReallyLR implicit $q0
 
 ...
+---
+name:            s35
+alignment:       4
+tracksRegLiveness: true
+body:             |
+  bb.1:
+    liveins: $x0
+
+    ; CHECK-LABEL: name: s35
+    ; CHECK: liveins: $x0
+    ; CHECK-NEXT: {{  $}}
+    ; CHECK-NEXT: [[COPY:%[0-9]+]]:_(s64) = COPY $x0
+    ; CHECK-NEXT: [[C:%[0-9]+]]:_(s64) = G_CONSTANT i64 34359738368
+    ; CHECK-NEXT: [[OR:%[0-9]+]]:_(s64) = G_OR [[COPY]], [[C]]
+    ; CHECK-NEXT: [[BITREVERSE:%[0-9]+]]:_(s64) = G_BITREVERSE [[OR]]
+    ; CHECK-NEXT: [[CTLZ:%[0-9]+]]:_(s64) = G_CTLZ [[BITREVERSE]](s64)
+    ; CHECK-NEXT: $x0 = COPY [[CTLZ]](s64)
+    ; CHECK-NEXT: RET_ReallyLR implicit $x0
+    ; CHECK-CSSC-LABEL: name: s35
+    ; CHECK-CSSC: liveins: $x0
+    ; CHECK-CSSC-NEXT: {{  $}}
+    ; CHECK-CSSC-NEXT: [[COPY:%[0-9]+]]:_(s64) = COPY $x0
+    ; CHECK-CSSC-NEXT: [[C:%[0-9]+]]:_(s64) = G_CONSTANT i64 34359738368
+    ; CHECK-CSSC-NEXT: [[OR:%[0-9]+]]:_(s64) = G_OR [[COPY]], [[C]]
+    ; CHECK-CSSC-NEXT: [[CTTZ:%[0-9]+]]:_(s64) = G_CTTZ [[OR]](s64)
+    ; CHECK-CSSC-NEXT: $x0 = COPY [[CTTZ]](s64)
+    ; CHECK-CSSC-NEXT: RET_ReallyLR implicit $x0
+    %1:_(s64) = COPY $x0
+    %0:_(s35) = G_TRUNC %1(s64)
+    %2:_(s35) = G_CTTZ %0(s35)
+    %3:_(s64) = G_ANYEXT %2(s35)
+    $x0 = COPY %3(s64)
+    RET_ReallyLR implicit $x0
+...
+---
+name:            s65
+alignment:       4
+tracksRegLiveness: true
+body:             |
+  bb.1:
+    liveins: $x0, $x1
+
+    ; CHECK-LABEL: name: s65
+    ; CHECK: liveins: $x0, $x1
+    ; CHECK-NEXT: {{  $}}
+    ; CHECK-NEXT: [[COPY:%[0-9]+]]:_(s64) = COPY $x0
+    ; CHECK-NEXT: [[COPY1:%[0-9]+]]:_(s64) = COPY $x1
+    ; CHECK-NEXT: [[C:%[0-9]+]]:_(s64) = G_CONSTANT i64 0
+    ; CHECK-NEXT: [[C1:%[0-9]+]]:_(s64) = G_CONSTANT i64 2
+    ; CHECK-NEXT: [[OR:%[0-9]+]]:_(s64) = G_OR [[COPY]], [[C]]
+    ; CHECK-NEXT: [[OR1:%[0-9]+]]:_(s64) = G_OR [[COPY1]], [[C1]]
+    ; CHECK-NEXT: [[ICMP:%[0-9]+]]:_(s32) = G_ICMP intpred(eq), [[OR]](s64), [[C]]
+    ; CHECK-NEXT: [[BITREVERSE:%[0-9]+]]:_(s64) = G_BITREVERSE [[OR1]]
+    ; CHECK-NEXT: [[CTLZ:%[0-9]+]]:_(s64) = G_CTLZ [[BITREVERSE]](s64)
+    ; CHECK-NEXT: [[C2:%[0-9]+]]:_(s64) = G_CONSTANT i64 64
+    ; CHECK-NEXT: [[UADDO:%[0-9]+]]:_(s64), [[UADDO1:%[0-9]+]]:_(s32) = G_UADDO [[CTLZ]], [[C2]]
+    ; CHECK-NEXT: [[C3:%[0-9]+]]:_(s32) = G_CONSTANT i32 1
+    ; CHECK-NEXT: [[AND:%[0-9]+]]:_(s32) = G_AND [[UADDO1]], [[C3]]
+    ; CHECK-NEXT: [[UADDE:%[0-9]+]]:_(s64), [[UADDE1:%[0-9]+]]:_(s32) = G_UADDE [[C]], [[C]], [[AND]]
+    ; CHECK-NEXT: [[BITREVERSE1:%[0-9]+]]:_(s64) = G_BITREVERSE [[OR]]
+    ; CHECK-NEXT: [[CTLZ1:%[0-9]+]]:_(s64) = G_CTLZ [[BITREVERSE1]](s64)
+    ; CHECK-NEXT: [[AND1:%[0-9]+]]:_(s32) = G_AND [[ICMP]], [[C3]]
+    ; CHECK-NEXT: [[SELECT:%[0-9]+]]:_(s64) = G_SELECT [[AND1]](s32), [[UADDO]], [[CTLZ1]]
+    ; CHECK-NEXT: [[SELECT1:%[0-9]+]]:_(s64) = G_SELECT [[AND1]](s32), [[UADDE]], [[C]]
+    ; CHECK-NEXT: $x0 = COPY [[SELECT]](s64)
+    ; CHECK-NEXT: $x1 = COPY [[SELECT1]](s64)
+    ; CHECK-NEXT: RET_ReallyLR implicit $x0, implicit $x1
+    ; CHECK-CSSC-LABEL: name: s65
+    ; CHECK-CSSC: liveins: $x0, $x1
+    ; CHECK-CSSC-NEXT: {{  $}}
+    ; CHECK-CSSC-NEXT: [[COPY:%[0-9]+]]:_(s64) = COPY $x0
+    ; CHECK-CSSC-NEXT: [[COPY1:%[0-9]+]]:_(s64) = COPY $x1
+    ; CHECK-CSSC-NEXT: [[C:%[0-9]+]]:_(s64) = G_CONSTANT i64 0
+    ; CHECK-CSSC-NEXT: [[C1:%[0-9]+]]:_(s64) = G_CONSTANT i64 2
+    ; CHECK-CSSC-NEXT: [[OR:%[0-9]+]]:_(s64) = G_OR [[COPY]], [[C]]
+    ; CHECK-CSSC-NEXT: [[OR1:%[0-9]+]]:_(s64) = G_OR [[COPY1]], [[C1]]
+    ; CHECK-CSSC-NEXT: [[ICMP:%[0-9]+]]:_(s32) = G_ICMP intpred(eq), [[OR]](s64), [[C]]
+    ; CHECK-CSSC-NEXT: [[CTTZ:%[0-9]+]]:_(s64) = G_CTTZ [[OR1]](s64)
+    ; CHECK-CSSC-NEXT: [[C2:%[0-9]+]]:_(s64) = G_CONSTANT i64 64
+    ; CHECK-CSSC-NEXT: [[UADDO:%[0-9]+]]:_(s64), [[UADDO1:%[0-9]+]]:_(s32) = G_UADDO [[CTTZ]], [[C2]]
+    ; CHECK-CSSC-NEXT: [[C3:%[0-9]+]]:_(s32) = G_CONSTANT i32 1
+    ; CHECK-CSSC-NEXT: [[AND:%[0-9]+]]:_(s32) = G_AND [[UADDO1]], [[C3]]
+    ; CHECK-CSSC-NEXT: [[UADDE:%[0-9]+]]:_(s64), [[UADDE1:%[0-9]+]]:_(s32) = G_UADDE [[C]], [[C]], [[AND]]
+    ; CHECK-CSSC-NEXT: [[CTTZ1:%[0-9]+]]:_(s64) = G_CTTZ [[OR]](s64)
+    ; CHECK-CSSC-NEXT: [[AND1:%[0-9]+]]:_(s32) = G_AND [[ICMP]], [[C3]]
+    ; CHECK-CSSC-NEXT: [[SELECT:%[0-9]+]]:_(s64) = G_SELECT [[AND1]](s32), [[UADDO]], [[CTTZ1]]
+    ; CHECK-CSSC-NEXT: [[SELECT1:%[0-9]+]]:_(s64) = G_SELECT [[AND1]](s32), [[UADDE]], [[C]]
+    ; CHECK-CSSC-NEXT: $x0 = COPY [[SELECT]](s64)
+    ; CHECK-CSSC-NEXT: $x1 = COPY [[SELECT1]](s64)
+    ; CHECK-CSSC-NEXT: RET_ReallyLR implicit $x0, implicit $x1
+    %1:_(s64) = COPY $x0
+    %2:_(s64) = COPY $x1
+    %3:_(s128) = G_MERGE_VALUES %1(s64), %2(s64)
+    %0:_(s65) = G_TRUNC %3(s128)
+    %4:_(s65) = G_CTTZ %0(s65)
+    %7:_(s128) = G_ANYEXT %4(s65)
+    %5:_(s64), %6:_(s64) = G_UNMERGE_VALUES %7(s128)
+    $x0 = COPY %5(s64)
+    $x1 = COPY %6(s64)
+    RET_ReallyLR implicit $x0, implicit $x1
+...