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
@@ -80,8 +80,8 @@
   getActionDefinitionsBuilder({G_IMPLICIT_DEF, G_FREEZE})
       .legalFor({p0, s1, s8, s16, s32, s64})
       .legalFor(PackedVectorAllTypeList)
+      .widenScalarToNextPow2(0)
       .clampScalar(0, s8, s64)
-      .widenScalarToNextPow2(0, 8)
       .fewerElementsIf(
           [=](const LegalityQuery &Query) {
             return Query.Types[0].isVector() &&
diff --git a/llvm/test/CodeGen/AArch64/GlobalISel/legalize-cmp.mir b/llvm/test/CodeGen/AArch64/GlobalISel/legalize-cmp.mir
--- a/llvm/test/CodeGen/AArch64/GlobalISel/legalize-cmp.mir
+++ b/llvm/test/CodeGen/AArch64/GlobalISel/legalize-cmp.mir
@@ -119,20 +119,17 @@
   ; CHECK: bb.0:
   ; CHECK:   successors: %bb.1(0x40000000), %bb.2(0x40000000)
   ; CHECK:   [[DEF:%[0-9]+]]:_(s64) = G_IMPLICIT_DEF
-  ; CHECK:   [[UV:%[0-9]+]]:_(s8), [[UV1:%[0-9]+]]:_(s8), [[UV2:%[0-9]+]]:_(s8), [[UV3:%[0-9]+]]:_(s8), [[UV4:%[0-9]+]]:_(s8), [[UV5:%[0-9]+]]:_(s8), [[UV6:%[0-9]+]]:_(s8), [[UV7:%[0-9]+]]:_(s8) = G_UNMERGE_VALUES [[DEF]](s64)
-  ; CHECK:   [[UV8:%[0-9]+]]:_(s8), [[UV9:%[0-9]+]]:_(s8), [[UV10:%[0-9]+]]:_(s8), [[UV11:%[0-9]+]]:_(s8), [[UV12:%[0-9]+]]:_(s8), [[UV13:%[0-9]+]]:_(s8), [[UV14:%[0-9]+]]:_(s8), [[UV15:%[0-9]+]]:_(s8) = G_UNMERGE_VALUES [[DEF]](s64)
-  ; CHECK:   [[UV16:%[0-9]+]]:_(s8), [[UV17:%[0-9]+]]:_(s8), [[UV18:%[0-9]+]]:_(s8), [[UV19:%[0-9]+]]:_(s8), [[UV20:%[0-9]+]]:_(s8), [[UV21:%[0-9]+]]:_(s8), [[UV22:%[0-9]+]]:_(s8), [[UV23:%[0-9]+]]:_(s8) = G_UNMERGE_VALUES [[DEF]](s64)
-  ; CHECK:   [[C:%[0-9]+]]:_(s8) = G_CONSTANT i8 0
-  ; CHECK:   [[MV:%[0-9]+]]:_(s64) = G_MERGE_VALUES [[UV]](s8), [[UV1]](s8), [[UV2]](s8), [[UV3]](s8), [[UV4]](s8), [[UV5]](s8), [[UV6]](s8), [[UV7]](s8)
-  ; CHECK:   [[MV1:%[0-9]+]]:_(s64) = G_MERGE_VALUES [[UV16]](s8), [[UV17]](s8), [[UV18]](s8), [[C]](s8), [[C]](s8), [[C]](s8), [[C]](s8), [[C]](s8)
-  ; CHECK:   [[UV24:%[0-9]+]]:_(s8), [[UV25:%[0-9]+]]:_(s8), [[UV26:%[0-9]+]]:_(s8), [[UV27:%[0-9]+]]:_(s8), [[UV28:%[0-9]+]]:_(s8), [[UV29:%[0-9]+]]:_(s8), [[UV30:%[0-9]+]]:_(s8), [[UV31:%[0-9]+]]:_(s8) = G_UNMERGE_VALUES [[DEF]](s64)
-  ; CHECK:   [[MV2:%[0-9]+]]:_(s64) = G_MERGE_VALUES [[UV8]](s8), [[UV9]](s8), [[UV10]](s8), [[UV11]](s8), [[UV12]](s8), [[UV13]](s8), [[UV14]](s8), [[UV15]](s8)
-  ; CHECK:   [[MV3:%[0-9]+]]:_(s64) = G_MERGE_VALUES [[UV24]](s8), [[UV25]](s8), [[UV26]](s8), [[C]](s8), [[C]](s8), [[C]](s8), [[C]](s8), [[C]](s8)
-  ; CHECK:   [[C1:%[0-9]+]]:_(s64) = G_CONSTANT i64 0
-  ; CHECK:   [[XOR:%[0-9]+]]:_(s64) = G_XOR [[MV]], [[MV2]]
-  ; CHECK:   [[XOR1:%[0-9]+]]:_(s64) = G_XOR [[MV1]], [[MV3]]
+  ; CHECK:   [[C:%[0-9]+]]:_(s64) = G_CONSTANT i64 -1
+  ; CHECK:   [[C1:%[0-9]+]]:_(s64) = G_CONSTANT i64 16777215
+  ; CHECK:   [[AND:%[0-9]+]]:_(s64) = G_AND [[DEF]], [[C]]
+  ; CHECK:   [[AND1:%[0-9]+]]:_(s64) = G_AND [[DEF]], [[C1]]
+  ; CHECK:   [[AND2:%[0-9]+]]:_(s64) = G_AND [[DEF]], [[C]]
+  ; CHECK:   [[AND3:%[0-9]+]]:_(s64) = G_AND [[DEF]], [[C1]]
+  ; CHECK:   [[C2:%[0-9]+]]:_(s64) = G_CONSTANT i64 0
+  ; CHECK:   [[XOR:%[0-9]+]]:_(s64) = G_XOR [[AND]], [[AND2]]
+  ; CHECK:   [[XOR1:%[0-9]+]]:_(s64) = G_XOR [[AND1]], [[AND3]]
   ; CHECK:   [[OR:%[0-9]+]]:_(s64) = G_OR [[XOR]], [[XOR1]]
-  ; CHECK:   [[ICMP:%[0-9]+]]:_(s32) = G_ICMP intpred(eq), [[OR]](s64), [[C1]]
+  ; CHECK:   [[ICMP:%[0-9]+]]:_(s32) = G_ICMP intpred(eq), [[OR]](s64), [[C2]]
   ; CHECK:   %cmp:_(s1) = G_TRUNC [[ICMP]](s32)
   ; CHECK:   G_BRCOND %cmp(s1), %bb.1
   ; CHECK:   G_BR %bb.2
@@ -160,20 +157,17 @@
   ; CHECK: bb.0:
   ; CHECK:   successors: %bb.1(0x40000000), %bb.2(0x40000000)
   ; CHECK:   [[DEF:%[0-9]+]]:_(s64) = G_IMPLICIT_DEF
-  ; CHECK:   [[UV:%[0-9]+]]:_(s8), [[UV1:%[0-9]+]]:_(s8), [[UV2:%[0-9]+]]:_(s8), [[UV3:%[0-9]+]]:_(s8), [[UV4:%[0-9]+]]:_(s8), [[UV5:%[0-9]+]]:_(s8), [[UV6:%[0-9]+]]:_(s8), [[UV7:%[0-9]+]]:_(s8) = G_UNMERGE_VALUES [[DEF]](s64)
-  ; CHECK:   [[UV8:%[0-9]+]]:_(s8), [[UV9:%[0-9]+]]:_(s8), [[UV10:%[0-9]+]]:_(s8), [[UV11:%[0-9]+]]:_(s8), [[UV12:%[0-9]+]]:_(s8), [[UV13:%[0-9]+]]:_(s8), [[UV14:%[0-9]+]]:_(s8), [[UV15:%[0-9]+]]:_(s8) = G_UNMERGE_VALUES [[DEF]](s64)
-  ; CHECK:   [[UV16:%[0-9]+]]:_(s8), [[UV17:%[0-9]+]]:_(s8), [[UV18:%[0-9]+]]:_(s8), [[UV19:%[0-9]+]]:_(s8), [[UV20:%[0-9]+]]:_(s8), [[UV21:%[0-9]+]]:_(s8), [[UV22:%[0-9]+]]:_(s8), [[UV23:%[0-9]+]]:_(s8) = G_UNMERGE_VALUES [[DEF]](s64)
-  ; CHECK:   [[C:%[0-9]+]]:_(s8) = G_CONSTANT i8 0
-  ; CHECK:   [[MV:%[0-9]+]]:_(s64) = G_MERGE_VALUES [[UV]](s8), [[UV1]](s8), [[UV2]](s8), [[UV3]](s8), [[UV4]](s8), [[UV5]](s8), [[UV6]](s8), [[UV7]](s8)
-  ; CHECK:   [[MV1:%[0-9]+]]:_(s64) = G_MERGE_VALUES [[UV16]](s8), [[UV17]](s8), [[UV18]](s8), [[C]](s8), [[C]](s8), [[C]](s8), [[C]](s8), [[C]](s8)
-  ; CHECK:   [[UV24:%[0-9]+]]:_(s8), [[UV25:%[0-9]+]]:_(s8), [[UV26:%[0-9]+]]:_(s8), [[UV27:%[0-9]+]]:_(s8), [[UV28:%[0-9]+]]:_(s8), [[UV29:%[0-9]+]]:_(s8), [[UV30:%[0-9]+]]:_(s8), [[UV31:%[0-9]+]]:_(s8) = G_UNMERGE_VALUES [[DEF]](s64)
-  ; CHECK:   [[MV2:%[0-9]+]]:_(s64) = G_MERGE_VALUES [[UV8]](s8), [[UV9]](s8), [[UV10]](s8), [[UV11]](s8), [[UV12]](s8), [[UV13]](s8), [[UV14]](s8), [[UV15]](s8)
-  ; CHECK:   [[MV3:%[0-9]+]]:_(s64) = G_MERGE_VALUES [[UV24]](s8), [[UV25]](s8), [[UV26]](s8), [[C]](s8), [[C]](s8), [[C]](s8), [[C]](s8), [[C]](s8)
-  ; CHECK:   [[C1:%[0-9]+]]:_(s64) = G_CONSTANT i64 0
-  ; CHECK:   [[XOR:%[0-9]+]]:_(s64) = G_XOR [[MV]], [[MV2]]
-  ; CHECK:   [[XOR1:%[0-9]+]]:_(s64) = G_XOR [[MV1]], [[MV3]]
+  ; CHECK:   [[C:%[0-9]+]]:_(s64) = G_CONSTANT i64 -1
+  ; CHECK:   [[C1:%[0-9]+]]:_(s64) = G_CONSTANT i64 16777215
+  ; CHECK:   [[AND:%[0-9]+]]:_(s64) = G_AND [[DEF]], [[C]]
+  ; CHECK:   [[AND1:%[0-9]+]]:_(s64) = G_AND [[DEF]], [[C1]]
+  ; CHECK:   [[AND2:%[0-9]+]]:_(s64) = G_AND [[DEF]], [[C]]
+  ; CHECK:   [[AND3:%[0-9]+]]:_(s64) = G_AND [[DEF]], [[C1]]
+  ; CHECK:   [[C2:%[0-9]+]]:_(s64) = G_CONSTANT i64 0
+  ; CHECK:   [[XOR:%[0-9]+]]:_(s64) = G_XOR [[AND]], [[AND2]]
+  ; CHECK:   [[XOR1:%[0-9]+]]:_(s64) = G_XOR [[AND1]], [[AND3]]
   ; CHECK:   [[OR:%[0-9]+]]:_(s64) = G_OR [[XOR]], [[XOR1]]
-  ; CHECK:   [[ICMP:%[0-9]+]]:_(s32) = G_ICMP intpred(ne), [[OR]](s64), [[C1]]
+  ; CHECK:   [[ICMP:%[0-9]+]]:_(s32) = G_ICMP intpred(ne), [[OR]](s64), [[C2]]
   ; CHECK:   %cmp:_(s1) = G_TRUNC [[ICMP]](s32)
   ; CHECK:   G_BRCOND %cmp(s1), %bb.1
   ; CHECK:   G_BR %bb.2
@@ -201,20 +195,17 @@
   ; CHECK: bb.0:
   ; CHECK:   successors: %bb.1(0x40000000), %bb.2(0x40000000)
   ; CHECK:   [[DEF:%[0-9]+]]:_(s64) = G_IMPLICIT_DEF
-  ; CHECK:   [[UV:%[0-9]+]]:_(s32), [[UV1:%[0-9]+]]:_(s32) = G_UNMERGE_VALUES [[DEF]](s64)
-  ; CHECK:   [[UV2:%[0-9]+]]:_(s32), [[UV3:%[0-9]+]]:_(s32) = G_UNMERGE_VALUES [[DEF]](s64)
-  ; CHECK:   [[UV4:%[0-9]+]]:_(s32), [[UV5:%[0-9]+]]:_(s32) = G_UNMERGE_VALUES [[DEF]](s64)
-  ; CHECK:   [[C:%[0-9]+]]:_(s32) = G_CONSTANT i32 0
-  ; CHECK:   [[MV:%[0-9]+]]:_(s64) = G_MERGE_VALUES [[UV]](s32), [[UV1]](s32)
-  ; CHECK:   [[MV1:%[0-9]+]]:_(s64) = G_MERGE_VALUES [[UV4]](s32), [[C]](s32)
-  ; CHECK:   [[UV6:%[0-9]+]]:_(s32), [[UV7:%[0-9]+]]:_(s32) = G_UNMERGE_VALUES [[DEF]](s64)
-  ; CHECK:   [[MV2:%[0-9]+]]:_(s64) = G_MERGE_VALUES [[UV2]](s32), [[UV3]](s32)
-  ; CHECK:   [[MV3:%[0-9]+]]:_(s64) = G_MERGE_VALUES [[UV6]](s32), [[C]](s32)
-  ; CHECK:   [[C1:%[0-9]+]]:_(s64) = G_CONSTANT i64 0
-  ; CHECK:   [[XOR:%[0-9]+]]:_(s64) = G_XOR [[MV]], [[MV2]]
-  ; CHECK:   [[XOR1:%[0-9]+]]:_(s64) = G_XOR [[MV1]], [[MV3]]
+  ; CHECK:   [[C:%[0-9]+]]:_(s64) = G_CONSTANT i64 -1
+  ; CHECK:   [[C1:%[0-9]+]]:_(s64) = G_CONSTANT i64 4294967295
+  ; CHECK:   [[AND:%[0-9]+]]:_(s64) = G_AND [[DEF]], [[C]]
+  ; CHECK:   [[AND1:%[0-9]+]]:_(s64) = G_AND [[DEF]], [[C1]]
+  ; CHECK:   [[AND2:%[0-9]+]]:_(s64) = G_AND [[DEF]], [[C]]
+  ; CHECK:   [[AND3:%[0-9]+]]:_(s64) = G_AND [[DEF]], [[C1]]
+  ; CHECK:   [[C2:%[0-9]+]]:_(s64) = G_CONSTANT i64 0
+  ; CHECK:   [[XOR:%[0-9]+]]:_(s64) = G_XOR [[AND]], [[AND2]]
+  ; CHECK:   [[XOR1:%[0-9]+]]:_(s64) = G_XOR [[AND1]], [[AND3]]
   ; CHECK:   [[OR:%[0-9]+]]:_(s64) = G_OR [[XOR]], [[XOR1]]
-  ; CHECK:   [[ICMP:%[0-9]+]]:_(s32) = G_ICMP intpred(eq), [[OR]](s64), [[C1]]
+  ; CHECK:   [[ICMP:%[0-9]+]]:_(s32) = G_ICMP intpred(eq), [[OR]](s64), [[C2]]
   ; CHECK:   %cmp:_(s1) = G_TRUNC [[ICMP]](s32)
   ; CHECK:   G_BRCOND %cmp(s1), %bb.1
   ; CHECK:   G_BR %bb.2
diff --git a/llvm/test/CodeGen/AArch64/GlobalISel/legalize-extracts.mir b/llvm/test/CodeGen/AArch64/GlobalISel/legalize-extracts.mir
--- a/llvm/test/CodeGen/AArch64/GlobalISel/legalize-extracts.mir
+++ b/llvm/test/CodeGen/AArch64/GlobalISel/legalize-extracts.mir
@@ -319,9 +319,7 @@
     ; CHECK-LABEL: name: s64_from_s264
     ; CHECK: liveins: $x0
     ; CHECK: [[DEF:%[0-9]+]]:_(s64) = G_IMPLICIT_DEF
-    ; CHECK: [[UV:%[0-9]+]]:_(s8), [[UV1:%[0-9]+]]:_(s8), [[UV2:%[0-9]+]]:_(s8), [[UV3:%[0-9]+]]:_(s8), [[UV4:%[0-9]+]]:_(s8), [[UV5:%[0-9]+]]:_(s8), [[UV6:%[0-9]+]]:_(s8), [[UV7:%[0-9]+]]:_(s8) = G_UNMERGE_VALUES [[DEF]](s64)
-    ; CHECK: [[MV:%[0-9]+]]:_(s64) = G_MERGE_VALUES [[UV]](s8), [[UV1]](s8), [[UV2]](s8), [[UV3]](s8), [[UV4]](s8), [[UV5]](s8), [[UV6]](s8), [[UV7]](s8)
-    ; CHECK: %extract:_(s64) = COPY [[MV]](s64)
+    ; CHECK: %extract:_(s64) = COPY [[DEF]](s64)
     ; CHECK: $x0 = COPY %extract(s64)
     ; CHECK: RET_ReallyLR implicit $x0
     %val:_(s264) = G_IMPLICIT_DEF
diff --git a/llvm/test/CodeGen/AArch64/GlobalISel/legalize-undef.mir b/llvm/test/CodeGen/AArch64/GlobalISel/legalize-undef.mir
--- a/llvm/test/CodeGen/AArch64/GlobalISel/legalize-undef.mir
+++ b/llvm/test/CodeGen/AArch64/GlobalISel/legalize-undef.mir
@@ -98,3 +98,14 @@
     %0:_(<8 x s16>) = G_IMPLICIT_DEF
     $q0 = COPY %0
 ...
+---
+name: test_implicit_def_s88
+body: |
+  bb.0:
+    liveins:
+    ; CHECK-LABEL: name: test_implicit_def_s88
+    ; CHECK: [[DEF:%[0-9]+]]:_(s64) = G_IMPLICIT_DEF
+    ; CHECK: $x0 = COPY [[DEF]](s64)
+    %undef:_(s88) = G_IMPLICIT_DEF
+    %trunc:_(s64) = G_TRUNC %undef
+    $x0 = COPY %trunc(s64)