diff --git a/clang/test/Frontend/fixed_point_unary.c b/clang/test/Frontend/fixed_point_unary.c
--- a/clang/test/Frontend/fixed_point_unary.c
+++ b/clang/test/Frontend/fixed_point_unary.c
@@ -90,7 +90,7 @@
 // SIGNED-LABEL: @inc_uf(
 // SIGNED-NEXT:  entry:
 // SIGNED-NEXT:    [[TMP0:%.*]] = load i16, i16* @uf, align 2
-// SIGNED-NEXT:    [[TMP1:%.*]] = add i16 [[TMP0]], undef
+// SIGNED-NEXT:    [[TMP1:%.*]] = add i16 [[TMP0]], poison
 // SIGNED-NEXT:    store i16 [[TMP1]], i16* @uf, align 2
 // SIGNED-NEXT:    ret void
 //
@@ -271,7 +271,7 @@
 // SIGNED-LABEL: @dec_uf(
 // SIGNED-NEXT:  entry:
 // SIGNED-NEXT:    [[TMP0:%.*]] = load i16, i16* @uf, align 2
-// SIGNED-NEXT:    [[TMP1:%.*]] = sub i16 [[TMP0]], undef
+// SIGNED-NEXT:    [[TMP1:%.*]] = sub i16 [[TMP0]], poison
 // SIGNED-NEXT:    store i16 [[TMP1]], i16* @uf, align 2
 // SIGNED-NEXT:    ret void
 //
diff --git a/llvm/lib/IR/ConstantFold.cpp b/llvm/lib/IR/ConstantFold.cpp
--- a/llvm/lib/IR/ConstantFold.cpp
+++ b/llvm/lib/IR/ConstantFold.cpp
@@ -630,7 +630,7 @@
           V.convertToInteger(IntVal, APFloat::rmTowardZero, &ignored)) {
         // Undefined behavior invoked - the destination type can't represent
         // the input constant.
-        return UndefValue::get(DestTy);
+        return PoisonValue::get(DestTy);
       }
       return ConstantInt::get(FPC->getContext(), IntVal);
     }
@@ -916,7 +916,7 @@
 
   unsigned NumElts = ValTy->getNumElements();
   if (CIdx->uge(NumElts))
-    return UndefValue::get(Val->getType());
+    return PoisonValue::get(Val->getType());
 
   SmallVector<Constant*, 16> Result;
   Result.reserve(NumElts);
@@ -1144,23 +1144,21 @@
     }
     case Instruction::SDiv:
     case Instruction::UDiv:
-      // X / undef -> undef
-      if (isa<UndefValue>(C2))
-        return C2;
-      // undef / 0 -> undef
+      // X / undef -> poison
+      // X / 0 -> poison
+      if (match(C2, m_CombineOr(m_Undef(), m_Zero())))
+        return PoisonValue::get(C2->getType());
       // undef / 1 -> undef
-      if (match(C2, m_Zero()) || match(C2, m_One()))
+      if (match(C2, m_One()))
         return C1;
       // undef / X -> 0       otherwise
       return Constant::getNullValue(C1->getType());
     case Instruction::URem:
     case Instruction::SRem:
-      // X % undef -> undef
-      if (match(C2, m_Undef()))
-        return C2;
-      // undef % 0 -> undef
-      if (match(C2, m_Zero()))
-        return C1;
+      // X % undef -> poison
+      // X % 0 -> poison
+      if (match(C2, m_CombineOr(m_Undef(), m_Zero())))
+        return PoisonValue::get(C2->getType());
       // undef % X -> 0       otherwise
       return Constant::getNullValue(C1->getType());
     case Instruction::Or:                          // X | undef -> -1
@@ -1168,28 +1166,28 @@
         return C1;
       return Constant::getAllOnesValue(C1->getType()); // undef | X -> ~0
     case Instruction::LShr:
-      // X >>l undef -> undef
+      // X >>l undef -> poison
       if (isa<UndefValue>(C2))
-        return C2;
+        return PoisonValue::get(C2->getType());
       // undef >>l 0 -> undef
       if (match(C2, m_Zero()))
         return C1;
       // undef >>l X -> 0
       return Constant::getNullValue(C1->getType());
     case Instruction::AShr:
-      // X >>a undef -> undef
+      // X >>a undef -> poison
       if (isa<UndefValue>(C2))
-        return C2;
+        return PoisonValue::get(C2->getType());
       // undef >>a 0 -> undef
       if (match(C2, m_Zero()))
         return C1;
-      // TODO: undef >>a X -> undef if the shift is exact
+      // TODO: undef >>a X -> poison if the shift is exact
       // undef >>a X -> 0
       return Constant::getNullValue(C1->getType());
     case Instruction::Shl:
       // X << undef -> undef
       if (isa<UndefValue>(C2))
-        return C2;
+        return PoisonValue::get(C2->getType());
       // undef << 0 -> undef
       if (match(C2, m_Zero()))
         return C1;
@@ -1242,14 +1240,14 @@
       if (CI2->isOne())
         return C1;                                            // X / 1 == X
       if (CI2->isZero())
-        return UndefValue::get(CI2->getType());               // X / 0 == undef
+        return PoisonValue::get(CI2->getType());              // X / 0 == poison
       break;
     case Instruction::URem:
     case Instruction::SRem:
       if (CI2->isOne())
         return Constant::getNullValue(CI2->getType());        // X % 1 == 0
       if (CI2->isZero())
-        return UndefValue::get(CI2->getType());               // X % 0 == undef
+        return PoisonValue::get(CI2->getType());              // X % 0 == poison
       break;
     case Instruction::And:
       if (CI2->isZero()) return C2;                           // X & 0 == 0
@@ -1363,7 +1361,7 @@
       case Instruction::SDiv:
         assert(!CI2->isZero() && "Div by zero handled above");
         if (C2V.isAllOnesValue() && C1V.isMinSignedValue())
-          return UndefValue::get(CI1->getType());   // MIN_INT / -1 -> undef
+          return PoisonValue::get(CI1->getType());   // MIN_INT / -1 -> poison
         return ConstantInt::get(CI1->getContext(), C1V.sdiv(C2V));
       case Instruction::URem:
         assert(!CI2->isZero() && "Div by zero handled above");
@@ -1371,7 +1369,7 @@
       case Instruction::SRem:
         assert(!CI2->isZero() && "Div by zero handled above");
         if (C2V.isAllOnesValue() && C1V.isMinSignedValue())
-          return UndefValue::get(CI1->getType());   // MIN_INT % -1 -> undef
+          return PoisonValue::get(CI1->getType());   // MIN_INT % -1 -> poison
         return ConstantInt::get(CI1->getContext(), C1V.srem(C2V));
       case Instruction::And:
         return ConstantInt::get(CI1->getContext(), C1V & C2V);
@@ -1382,15 +1380,15 @@
       case Instruction::Shl:
         if (C2V.ult(C1V.getBitWidth()))
           return ConstantInt::get(CI1->getContext(), C1V.shl(C2V));
-        return UndefValue::get(C1->getType()); // too big shift is undef
+        return PoisonValue::get(C1->getType()); // too big shift is poison
       case Instruction::LShr:
         if (C2V.ult(C1V.getBitWidth()))
           return ConstantInt::get(CI1->getContext(), C1V.lshr(C2V));
-        return UndefValue::get(C1->getType()); // too big shift is undef
+        return PoisonValue::get(C1->getType()); // too big shift is poison
       case Instruction::AShr:
         if (C2V.ult(C1V.getBitWidth()))
           return ConstantInt::get(CI1->getContext(), C1V.ashr(C2V));
-        return UndefValue::get(C1->getType()); // too big shift is undef
+        return PoisonValue::get(C1->getType()); // too big shift is poison
       }
     }
 
@@ -1436,7 +1434,7 @@
     // Fast path for splatted constants.
     if (Constant *C2Splat = C2->getSplatValue()) {
       if (Instruction::isIntDivRem(Opcode) && C2Splat->isNullValue())
-        return UndefValue::get(VTy);
+        return PoisonValue::get(VTy);
       if (Constant *C1Splat = C1->getSplatValue()) {
         return ConstantVector::getSplat(
             VTy->getElementCount(),
@@ -1453,9 +1451,9 @@
         Constant *LHS = ConstantExpr::getExtractElement(C1, ExtractIdx);
         Constant *RHS = ConstantExpr::getExtractElement(C2, ExtractIdx);
 
-        // If any element of a divisor vector is zero, the whole op is undef.
+        // If any element of a divisor vector is zero, the whole op is poison.
         if (Instruction::isIntDivRem(Opcode) && RHS->isNullValue())
-          return UndefValue::get(VTy);
+          return PoisonValue::get(VTy);
 
         Result.push_back(ConstantExpr::get(Opcode, LHS, RHS));
       }
@@ -2338,7 +2336,8 @@
     return PoisonValue::get(GEPTy);
 
   if (isa<UndefValue>(C))
-    return UndefValue::get(GEPTy);
+    // If inbounds, we can choose an out-of-bounds pointer as a base pointer.
+    return InBounds ? PoisonValue::get(GEPTy) : UndefValue::get(GEPTy);
 
   Constant *Idx0 = cast<Constant>(Idxs[0]);
   if (Idxs.size() == 1 && (Idx0->isNullValue() || isa<UndefValue>(Idx0)))
diff --git a/llvm/test/CodeGen/AMDGPU/amdgpu-codegenprepare-fold-binop-select.ll b/llvm/test/CodeGen/AMDGPU/amdgpu-codegenprepare-fold-binop-select.ll
--- a/llvm/test/CodeGen/AMDGPU/amdgpu-codegenprepare-fold-binop-select.ll
+++ b/llvm/test/CodeGen/AMDGPU/amdgpu-codegenprepare-fold-binop-select.ll
@@ -42,7 +42,7 @@
 
 define <2 x i32> @select_sdiv_lhs_const_v2i32(i1 %cond) {
 ; IR-LABEL: @select_sdiv_lhs_const_v2i32(
-; IR-NEXT:    [[OP:%.*]] = select i1 [[COND:%.*]], <2 x i32> <i32 666, i32 undef>, <2 x i32> <i32 555, i32 1428>
+; IR-NEXT:    [[OP:%.*]] = select i1 [[COND:%.*]], <2 x i32> <i32 666, i32 poison>, <2 x i32> <i32 555, i32 1428>
 ; IR-NEXT:    ret <2 x i32> [[OP]]
 ;
 ; GCN-LABEL: select_sdiv_lhs_const_v2i32:
diff --git a/llvm/test/Transforms/InstCombine/apint-shift.ll b/llvm/test/Transforms/InstCombine/apint-shift.ll
--- a/llvm/test/Transforms/InstCombine/apint-shift.ll
+++ b/llvm/test/Transforms/InstCombine/apint-shift.ll
@@ -337,7 +337,7 @@
 
 define <2 x i1> @test16vec_undef(<2 x i84> %X) {
 ; CHECK-LABEL: @test16vec_undef(
-; CHECK-NEXT:    [[TMP1:%.*]] = and <2 x i84> [[X:%.*]], <i84 16, i84 undef>
+; CHECK-NEXT:    [[TMP1:%.*]] = and <2 x i84> [[X:%.*]], <i84 16, i84 poison>
 ; CHECK-NEXT:    [[CMP:%.*]] = icmp ne <2 x i84> [[TMP1]], zeroinitializer
 ; CHECK-NEXT:    ret <2 x i1> [[CMP]]
 ;
diff --git a/llvm/test/Transforms/InstCombine/canonicalize-ashr-shl-to-masking.ll b/llvm/test/Transforms/InstCombine/canonicalize-ashr-shl-to-masking.ll
--- a/llvm/test/Transforms/InstCombine/canonicalize-ashr-shl-to-masking.ll
+++ b/llvm/test/Transforms/InstCombine/canonicalize-ashr-shl-to-masking.ll
@@ -418,7 +418,7 @@
 
 define <3 x i8> @positive_sameconst_vec_undef2(<3 x i8> %x) {
 ; CHECK-LABEL: @positive_sameconst_vec_undef2(
-; CHECK-NEXT:    [[RET:%.*]] = and <3 x i8> [[X:%.*]], <i8 -8, i8 undef, i8 -8>
+; CHECK-NEXT:    [[RET:%.*]] = and <3 x i8> [[X:%.*]], <i8 -8, i8 poison, i8 -8>
 ; CHECK-NEXT:    ret <3 x i8> [[RET]]
 ;
   %tmp0 = ashr <3 x i8> %x, <i8 3, i8 undef, i8 3>
diff --git a/llvm/test/Transforms/InstCombine/canonicalize-lshr-shl-to-masking.ll b/llvm/test/Transforms/InstCombine/canonicalize-lshr-shl-to-masking.ll
--- a/llvm/test/Transforms/InstCombine/canonicalize-lshr-shl-to-masking.ll
+++ b/llvm/test/Transforms/InstCombine/canonicalize-lshr-shl-to-masking.ll
@@ -418,7 +418,7 @@
 
 define <3 x i8> @positive_sameconst_vec_undef2(<3 x i8> %x) {
 ; CHECK-LABEL: @positive_sameconst_vec_undef2(
-; CHECK-NEXT:    [[RET:%.*]] = and <3 x i8> [[X:%.*]], <i8 -8, i8 undef, i8 -8>
+; CHECK-NEXT:    [[RET:%.*]] = and <3 x i8> [[X:%.*]], <i8 -8, i8 poison, i8 -8>
 ; CHECK-NEXT:    ret <3 x i8> [[RET]]
 ;
   %tmp0 = lshr <3 x i8> %x, <i8 3, i8 undef, i8 3>
diff --git a/llvm/test/Transforms/InstCombine/canonicalize-shl-lshr-to-masking.ll b/llvm/test/Transforms/InstCombine/canonicalize-shl-lshr-to-masking.ll
--- a/llvm/test/Transforms/InstCombine/canonicalize-shl-lshr-to-masking.ll
+++ b/llvm/test/Transforms/InstCombine/canonicalize-shl-lshr-to-masking.ll
@@ -171,7 +171,7 @@
 
 define <3 x i32> @positive_sameconst_vec_undef2(<3 x i32> %x) {
 ; CHECK-LABEL: @positive_sameconst_vec_undef2(
-; CHECK-NEXT:    [[RET:%.*]] = and <3 x i32> [[X:%.*]], <i32 134217727, i32 undef, i32 134217727>
+; CHECK-NEXT:    [[RET:%.*]] = and <3 x i32> [[X:%.*]], <i32 134217727, i32 poison, i32 134217727>
 ; CHECK-NEXT:    ret <3 x i32> [[RET]]
 ;
   %tmp0 = shl <3 x i32> %x, <i32 5, i32 undef, i32 5>
diff --git a/llvm/test/Transforms/InstCombine/icmp.ll b/llvm/test/Transforms/InstCombine/icmp.ll
--- a/llvm/test/Transforms/InstCombine/icmp.ll
+++ b/llvm/test/Transforms/InstCombine/icmp.ll
@@ -2784,7 +2784,7 @@
 
 define <2 x i1> @icmp_and_or_lshr_cst_vec_undef(<2 x i32> %x) {
 ; CHECK-LABEL: @icmp_and_or_lshr_cst_vec_undef(
-; CHECK-NEXT:    [[TMP1:%.*]] = and <2 x i32> [[X:%.*]], <i32 3, i32 -1>
+; CHECK-NEXT:    [[TMP1:%.*]] = and <2 x i32> [[X:%.*]], <i32 3, i32 poison>
 ; CHECK-NEXT:    [[RET:%.*]] = icmp ne <2 x i32> [[TMP1]], zeroinitializer
 ; CHECK-NEXT:    ret <2 x i1> [[RET]]
 ;
@@ -2828,7 +2828,7 @@
 define <2 x i1> @icmp_and_or_lshr_cst_vec_undef_commute(<2 x i32> %xp) {
 ; CHECK-LABEL: @icmp_and_or_lshr_cst_vec_undef_commute(
 ; CHECK-NEXT:    [[X:%.*]] = srem <2 x i32> [[XP:%.*]], <i32 42, i32 42>
-; CHECK-NEXT:    [[TMP1:%.*]] = and <2 x i32> [[X]], <i32 3, i32 -1>
+; CHECK-NEXT:    [[TMP1:%.*]] = and <2 x i32> [[X]], <i32 3, i32 poison>
 ; CHECK-NEXT:    [[RET:%.*]] = icmp ne <2 x i32> [[TMP1]], zeroinitializer
 ; CHECK-NEXT:    ret <2 x i1> [[RET]]
 ;
diff --git a/llvm/test/Transforms/InstCombine/partally-redundant-left-shift-input-masking-after-truncation-variant-a.ll b/llvm/test/Transforms/InstCombine/partally-redundant-left-shift-input-masking-after-truncation-variant-a.ll
--- a/llvm/test/Transforms/InstCombine/partally-redundant-left-shift-input-masking-after-truncation-variant-a.ll
+++ b/llvm/test/Transforms/InstCombine/partally-redundant-left-shift-input-masking-after-truncation-variant-a.ll
@@ -103,7 +103,7 @@
 ; CHECK-NEXT:    call void @use8xi32(<8 x i32> [[T4]])
 ; CHECK-NEXT:    [[TMP1:%.*]] = trunc <8 x i64> [[X:%.*]] to <8 x i32>
 ; CHECK-NEXT:    [[TMP2:%.*]] = shl <8 x i32> [[TMP1]], [[T4]]
-; CHECK-NEXT:    [[T7:%.*]] = and <8 x i32> [[TMP2]], <i32 2147483647, i32 2147483647, i32 2147483647, i32 2147483647, i32 2147483647, i32 2147483647, i32 undef, i32 2147483647>
+; CHECK-NEXT:    [[T7:%.*]] = and <8 x i32> [[TMP2]], <i32 2147483647, i32 2147483647, i32 2147483647, i32 2147483647, i32 2147483647, i32 2147483647, i32 poison, i32 2147483647>
 ; CHECK-NEXT:    ret <8 x i32> [[T7]]
 ;
   %t0 = add <8 x i32> %nbits, <i32 -1, i32 -1, i32 -1, i32 -1, i32 -1, i32 -1, i32 undef, i32 -1>
@@ -138,7 +138,7 @@
 ; CHECK-NEXT:    call void @use8xi32(<8 x i32> [[T4]])
 ; CHECK-NEXT:    [[TMP1:%.*]] = trunc <8 x i64> [[X:%.*]] to <8 x i32>
 ; CHECK-NEXT:    [[TMP2:%.*]] = shl <8 x i32> [[TMP1]], [[T4]]
-; CHECK-NEXT:    [[T7:%.*]] = and <8 x i32> [[TMP2]], <i32 undef, i32 0, i32 1, i32 2147483647, i32 -1, i32 -1, i32 -1, i32 -1>
+; CHECK-NEXT:    [[T7:%.*]] = and <8 x i32> [[TMP2]], <i32 poison, i32 0, i32 1, i32 2147483647, i32 -1, i32 -1, i32 -1, i32 -1>
 ; CHECK-NEXT:    ret <8 x i32> [[T7]]
 ;
   %t0 = add <8 x i32> %nbits, <i32 -33, i32 -32, i32 -31, i32 -1, i32 0, i32 1, i32 31, i32 32>
diff --git a/llvm/test/Transforms/InstCombine/partally-redundant-left-shift-input-masking-after-truncation-variant-b.ll b/llvm/test/Transforms/InstCombine/partally-redundant-left-shift-input-masking-after-truncation-variant-b.ll
--- a/llvm/test/Transforms/InstCombine/partally-redundant-left-shift-input-masking-after-truncation-variant-b.ll
+++ b/llvm/test/Transforms/InstCombine/partally-redundant-left-shift-input-masking-after-truncation-variant-b.ll
@@ -103,7 +103,7 @@
 ; CHECK-NEXT:    call void @use8xi32(<8 x i32> [[T4]])
 ; CHECK-NEXT:    [[TMP1:%.*]] = trunc <8 x i64> [[X:%.*]] to <8 x i32>
 ; CHECK-NEXT:    [[TMP2:%.*]] = shl <8 x i32> [[TMP1]], [[T4]]
-; CHECK-NEXT:    [[T7:%.*]] = and <8 x i32> [[TMP2]], <i32 2147483647, i32 2147483647, i32 2147483647, i32 2147483647, i32 2147483647, i32 2147483647, i32 undef, i32 2147483647>
+; CHECK-NEXT:    [[T7:%.*]] = and <8 x i32> [[TMP2]], <i32 2147483647, i32 2147483647, i32 2147483647, i32 2147483647, i32 2147483647, i32 2147483647, i32 poison, i32 2147483647>
 ; CHECK-NEXT:    ret <8 x i32> [[T7]]
 ;
   %t0 = add <8 x i32> %nbits, <i32 -1, i32 -1, i32 -1, i32 -1, i32 -1, i32 -1, i32 undef, i32 -1>
@@ -138,7 +138,7 @@
 ; CHECK-NEXT:    call void @use8xi32(<8 x i32> [[T4]])
 ; CHECK-NEXT:    [[TMP1:%.*]] = trunc <8 x i64> [[X:%.*]] to <8 x i32>
 ; CHECK-NEXT:    [[TMP2:%.*]] = shl <8 x i32> [[TMP1]], [[T4]]
-; CHECK-NEXT:    [[T7:%.*]] = and <8 x i32> [[TMP2]], <i32 undef, i32 0, i32 1, i32 2147483647, i32 -1, i32 -1, i32 -1, i32 -1>
+; CHECK-NEXT:    [[T7:%.*]] = and <8 x i32> [[TMP2]], <i32 poison, i32 0, i32 1, i32 2147483647, i32 -1, i32 -1, i32 -1, i32 -1>
 ; CHECK-NEXT:    ret <8 x i32> [[T7]]
 ;
   %t0 = add <8 x i32> %nbits, <i32 -33, i32 -32, i32 -31, i32 -1, i32 0, i32 1, i32 31, i32 32>
diff --git a/llvm/test/Transforms/InstCombine/partally-redundant-left-shift-input-masking-after-truncation-variant-c.ll b/llvm/test/Transforms/InstCombine/partally-redundant-left-shift-input-masking-after-truncation-variant-c.ll
--- a/llvm/test/Transforms/InstCombine/partally-redundant-left-shift-input-masking-after-truncation-variant-c.ll
+++ b/llvm/test/Transforms/InstCombine/partally-redundant-left-shift-input-masking-after-truncation-variant-c.ll
@@ -83,7 +83,7 @@
 ; CHECK-NEXT:    call void @use8xi32(<8 x i32> [[T2]])
 ; CHECK-NEXT:    [[TMP1:%.*]] = trunc <8 x i64> [[X:%.*]] to <8 x i32>
 ; CHECK-NEXT:    [[TMP2:%.*]] = shl <8 x i32> [[TMP1]], [[T2]]
-; CHECK-NEXT:    [[T5:%.*]] = and <8 x i32> [[TMP2]], <i32 2147483647, i32 2147483647, i32 2147483647, i32 2147483647, i32 2147483647, i32 2147483647, i32 undef, i32 2147483647>
+; CHECK-NEXT:    [[T5:%.*]] = and <8 x i32> [[TMP2]], <i32 2147483647, i32 2147483647, i32 2147483647, i32 2147483647, i32 2147483647, i32 2147483647, i32 poison, i32 2147483647>
 ; CHECK-NEXT:    ret <8 x i32> [[T5]]
 ;
   %t0 = zext <8 x i32> %nbits to <8 x i64>
@@ -110,7 +110,7 @@
 ; CHECK-NEXT:    call void @use8xi32(<8 x i32> [[T2]])
 ; CHECK-NEXT:    [[TMP1:%.*]] = trunc <8 x i64> [[X:%.*]] to <8 x i32>
 ; CHECK-NEXT:    [[TMP2:%.*]] = shl <8 x i32> [[TMP1]], [[T2]]
-; CHECK-NEXT:    [[T5:%.*]] = and <8 x i32> [[TMP2]], <i32 undef, i32 1, i32 2147483647, i32 -1, i32 -1, i32 -1, i32 undef, i32 undef>
+; CHECK-NEXT:    [[T5:%.*]] = and <8 x i32> [[TMP2]], <i32 poison, i32 1, i32 2147483647, i32 -1, i32 -1, i32 -1, i32 poison, i32 poison>
 ; CHECK-NEXT:    ret <8 x i32> [[T5]]
 ;
   %t0 = zext <8 x i32> %nbits to <8 x i64>
diff --git a/llvm/test/Transforms/InstCombine/partally-redundant-left-shift-input-masking-after-truncation-variant-d.ll b/llvm/test/Transforms/InstCombine/partally-redundant-left-shift-input-masking-after-truncation-variant-d.ll
--- a/llvm/test/Transforms/InstCombine/partally-redundant-left-shift-input-masking-after-truncation-variant-d.ll
+++ b/llvm/test/Transforms/InstCombine/partally-redundant-left-shift-input-masking-after-truncation-variant-d.ll
@@ -93,7 +93,7 @@
 ; CHECK-NEXT:    call void @use8xi32(<8 x i32> [[T3]])
 ; CHECK-NEXT:    [[TMP1:%.*]] = trunc <8 x i64> [[X:%.*]] to <8 x i32>
 ; CHECK-NEXT:    [[TMP2:%.*]] = shl <8 x i32> [[TMP1]], [[T3]]
-; CHECK-NEXT:    [[T6:%.*]] = and <8 x i32> [[TMP2]], <i32 2147483647, i32 2147483647, i32 2147483647, i32 2147483647, i32 2147483647, i32 2147483647, i32 undef, i32 2147483647>
+; CHECK-NEXT:    [[T6:%.*]] = and <8 x i32> [[TMP2]], <i32 2147483647, i32 2147483647, i32 2147483647, i32 2147483647, i32 2147483647, i32 2147483647, i32 poison, i32 2147483647>
 ; CHECK-NEXT:    ret <8 x i32> [[T6]]
 ;
   %t0 = zext <8 x i32> %nbits to <8 x i64>
@@ -124,7 +124,7 @@
 ; CHECK-NEXT:    call void @use8xi32(<8 x i32> [[T3]])
 ; CHECK-NEXT:    [[TMP1:%.*]] = trunc <8 x i64> [[X:%.*]] to <8 x i32>
 ; CHECK-NEXT:    [[TMP2:%.*]] = shl <8 x i32> [[TMP1]], [[T3]]
-; CHECK-NEXT:    [[T6:%.*]] = and <8 x i32> [[TMP2]], <i32 undef, i32 1, i32 2147483647, i32 -1, i32 -1, i32 -1, i32 undef, i32 undef>
+; CHECK-NEXT:    [[T6:%.*]] = and <8 x i32> [[TMP2]], <i32 poison, i32 1, i32 2147483647, i32 -1, i32 -1, i32 -1, i32 poison, i32 poison>
 ; CHECK-NEXT:    ret <8 x i32> [[T6]]
 ;
   %t0 = zext <8 x i32> %nbits to <8 x i64>
diff --git a/llvm/test/Transforms/InstCombine/partally-redundant-left-shift-input-masking-after-truncation-variant-e.ll b/llvm/test/Transforms/InstCombine/partally-redundant-left-shift-input-masking-after-truncation-variant-e.ll
--- a/llvm/test/Transforms/InstCombine/partally-redundant-left-shift-input-masking-after-truncation-variant-e.ll
+++ b/llvm/test/Transforms/InstCombine/partally-redundant-left-shift-input-masking-after-truncation-variant-e.ll
@@ -83,7 +83,7 @@
 ; CHECK-NEXT:    call void @use8xi32(<8 x i32> [[T2]])
 ; CHECK-NEXT:    [[TMP1:%.*]] = trunc <8 x i64> [[X]] to <8 x i32>
 ; CHECK-NEXT:    [[TMP2:%.*]] = shl <8 x i32> [[TMP1]], [[T2]]
-; CHECK-NEXT:    [[T5:%.*]] = and <8 x i32> [[TMP2]], <i32 2147483647, i32 2147483647, i32 2147483647, i32 2147483647, i32 2147483647, i32 2147483647, i32 undef, i32 2147483647>
+; CHECK-NEXT:    [[T5:%.*]] = and <8 x i32> [[TMP2]], <i32 2147483647, i32 2147483647, i32 2147483647, i32 2147483647, i32 2147483647, i32 2147483647, i32 poison, i32 2147483647>
 ; CHECK-NEXT:    ret <8 x i32> [[T5]]
 ;
   %t0 = zext <8 x i32> %nbits to <8 x i64>
@@ -110,7 +110,7 @@
 ; CHECK-NEXT:    call void @use8xi32(<8 x i32> [[T2]])
 ; CHECK-NEXT:    [[TMP1:%.*]] = trunc <8 x i64> [[X]] to <8 x i32>
 ; CHECK-NEXT:    [[TMP2:%.*]] = shl <8 x i32> [[TMP1]], [[T2]]
-; CHECK-NEXT:    [[T5:%.*]] = and <8 x i32> [[TMP2]], <i32 undef, i32 1, i32 2147483647, i32 -1, i32 -1, i32 -1, i32 undef, i32 undef>
+; CHECK-NEXT:    [[T5:%.*]] = and <8 x i32> [[TMP2]], <i32 poison, i32 1, i32 2147483647, i32 -1, i32 -1, i32 -1, i32 poison, i32 poison>
 ; CHECK-NEXT:    ret <8 x i32> [[T5]]
 ;
   %t0 = zext <8 x i32> %nbits to <8 x i64>
diff --git a/llvm/test/Transforms/InstCombine/partally-redundant-left-shift-input-masking-variant-a.ll b/llvm/test/Transforms/InstCombine/partally-redundant-left-shift-input-masking-variant-a.ll
--- a/llvm/test/Transforms/InstCombine/partally-redundant-left-shift-input-masking-variant-a.ll
+++ b/llvm/test/Transforms/InstCombine/partally-redundant-left-shift-input-masking-variant-a.ll
@@ -82,7 +82,7 @@
 ; CHECK-NEXT:    call void @use8xi32(<8 x i32> [[T2]])
 ; CHECK-NEXT:    call void @use8xi32(<8 x i32> [[T4]])
 ; CHECK-NEXT:    [[TMP1:%.*]] = shl <8 x i32> [[X:%.*]], [[T4]]
-; CHECK-NEXT:    [[T5:%.*]] = and <8 x i32> [[TMP1]], <i32 2147483647, i32 2147483647, i32 2147483647, i32 2147483647, i32 2147483647, i32 2147483647, i32 undef, i32 2147483647>
+; CHECK-NEXT:    [[T5:%.*]] = and <8 x i32> [[TMP1]], <i32 2147483647, i32 2147483647, i32 2147483647, i32 2147483647, i32 2147483647, i32 2147483647, i32 poison, i32 2147483647>
 ; CHECK-NEXT:    ret <8 x i32> [[T5]]
 ;
   %t0 = add <8 x i32> %nbits, <i32 -1, i32 -1, i32 -1, i32 -1, i32 -1, i32 -1, i32 undef, i32 -1>
@@ -109,7 +109,7 @@
 ; CHECK-NEXT:    call void @use8xi32(<8 x i32> [[T2]])
 ; CHECK-NEXT:    call void @use8xi32(<8 x i32> [[T4]])
 ; CHECK-NEXT:    [[TMP1:%.*]] = shl <8 x i32> [[X:%.*]], [[T4]]
-; CHECK-NEXT:    [[T5:%.*]] = and <8 x i32> [[TMP1]], <i32 undef, i32 0, i32 1, i32 2147483647, i32 -1, i32 -1, i32 -1, i32 undef>
+; CHECK-NEXT:    [[T5:%.*]] = and <8 x i32> [[TMP1]], <i32 poison, i32 0, i32 1, i32 2147483647, i32 -1, i32 -1, i32 -1, i32 poison>
 ; CHECK-NEXT:    ret <8 x i32> [[T5]]
 ;
   %t0 = add <8 x i32> %nbits, <i32 -33, i32 -32, i32 -31, i32 -1, i32 0, i32 1, i32 31, i32 32>
diff --git a/llvm/test/Transforms/InstCombine/partally-redundant-left-shift-input-masking-variant-b.ll b/llvm/test/Transforms/InstCombine/partally-redundant-left-shift-input-masking-variant-b.ll
--- a/llvm/test/Transforms/InstCombine/partally-redundant-left-shift-input-masking-variant-b.ll
+++ b/llvm/test/Transforms/InstCombine/partally-redundant-left-shift-input-masking-variant-b.ll
@@ -82,7 +82,7 @@
 ; CHECK-NEXT:    call void @use8xi32(<8 x i32> [[T2]])
 ; CHECK-NEXT:    call void @use8xi32(<8 x i32> [[T4]])
 ; CHECK-NEXT:    [[TMP1:%.*]] = shl <8 x i32> [[X:%.*]], [[T4]]
-; CHECK-NEXT:    [[T5:%.*]] = and <8 x i32> [[TMP1]], <i32 2147483647, i32 2147483647, i32 2147483647, i32 2147483647, i32 2147483647, i32 2147483647, i32 undef, i32 2147483647>
+; CHECK-NEXT:    [[T5:%.*]] = and <8 x i32> [[TMP1]], <i32 2147483647, i32 2147483647, i32 2147483647, i32 2147483647, i32 2147483647, i32 2147483647, i32 poison, i32 2147483647>
 ; CHECK-NEXT:    ret <8 x i32> [[T5]]
 ;
   %t0 = add <8 x i32> %nbits, <i32 -1, i32 -1, i32 -1, i32 -1, i32 -1, i32 -1, i32 undef, i32 -1>
@@ -109,7 +109,7 @@
 ; CHECK-NEXT:    call void @use8xi32(<8 x i32> [[T2]])
 ; CHECK-NEXT:    call void @use8xi32(<8 x i32> [[T4]])
 ; CHECK-NEXT:    [[TMP1:%.*]] = shl <8 x i32> [[X:%.*]], [[T4]]
-; CHECK-NEXT:    [[T5:%.*]] = and <8 x i32> [[TMP1]], <i32 undef, i32 0, i32 1, i32 2147483647, i32 -1, i32 -1, i32 -1, i32 undef>
+; CHECK-NEXT:    [[T5:%.*]] = and <8 x i32> [[TMP1]], <i32 poison, i32 0, i32 1, i32 2147483647, i32 -1, i32 -1, i32 -1, i32 poison>
 ; CHECK-NEXT:    ret <8 x i32> [[T5]]
 ;
   %t0 = add <8 x i32> %nbits, <i32 -33, i32 -32, i32 -31, i32 -1, i32 0, i32 1, i32 31, i32 32>
diff --git a/llvm/test/Transforms/InstCombine/partally-redundant-left-shift-input-masking-variant-c.ll b/llvm/test/Transforms/InstCombine/partally-redundant-left-shift-input-masking-variant-c.ll
--- a/llvm/test/Transforms/InstCombine/partally-redundant-left-shift-input-masking-variant-c.ll
+++ b/llvm/test/Transforms/InstCombine/partally-redundant-left-shift-input-masking-variant-c.ll
@@ -62,7 +62,7 @@
 ; CHECK-NEXT:    call void @use8xi32(<8 x i32> [[T0]])
 ; CHECK-NEXT:    call void @use8xi32(<8 x i32> [[T2]])
 ; CHECK-NEXT:    [[TMP1:%.*]] = shl <8 x i32> [[X:%.*]], [[T2]]
-; CHECK-NEXT:    [[T3:%.*]] = and <8 x i32> [[TMP1]], <i32 2147483647, i32 2147483647, i32 2147483647, i32 2147483647, i32 2147483647, i32 2147483647, i32 undef, i32 2147483647>
+; CHECK-NEXT:    [[T3:%.*]] = and <8 x i32> [[TMP1]], <i32 2147483647, i32 2147483647, i32 2147483647, i32 2147483647, i32 2147483647, i32 2147483647, i32 poison, i32 2147483647>
 ; CHECK-NEXT:    ret <8 x i32> [[T3]]
 ;
   %t0 = lshr <8 x i32> <i32 -1, i32 -1, i32 -1, i32 -1, i32 -1, i32 -1, i32 undef, i32 -1>, %nbits
@@ -81,7 +81,7 @@
 ; CHECK-NEXT:    call void @use8xi32(<8 x i32> [[T0]])
 ; CHECK-NEXT:    call void @use8xi32(<8 x i32> [[T2]])
 ; CHECK-NEXT:    [[TMP1:%.*]] = shl <8 x i32> [[X:%.*]], [[T2]]
-; CHECK-NEXT:    [[T3:%.*]] = and <8 x i32> [[TMP1]], <i32 undef, i32 1, i32 2147483647, i32 -1, i32 -1, i32 -1, i32 -1, i32 undef>
+; CHECK-NEXT:    [[T3:%.*]] = and <8 x i32> [[TMP1]], <i32 poison, i32 1, i32 2147483647, i32 -1, i32 -1, i32 -1, i32 -1, i32 poison>
 ; CHECK-NEXT:    ret <8 x i32> [[T3]]
 ;
   %t0 = lshr <8 x i32> <i32 -1, i32 -1, i32 -1, i32 -1, i32 -1, i32 -1, i32 -1, i32 -1>, %nbits
diff --git a/llvm/test/Transforms/InstCombine/partally-redundant-left-shift-input-masking-variant-d.ll b/llvm/test/Transforms/InstCombine/partally-redundant-left-shift-input-masking-variant-d.ll
--- a/llvm/test/Transforms/InstCombine/partally-redundant-left-shift-input-masking-variant-d.ll
+++ b/llvm/test/Transforms/InstCombine/partally-redundant-left-shift-input-masking-variant-d.ll
@@ -72,7 +72,7 @@
 ; CHECK-NEXT:    call void @use8xi32(<8 x i32> [[T1]])
 ; CHECK-NEXT:    call void @use8xi32(<8 x i32> [[T3]])
 ; CHECK-NEXT:    [[TMP1:%.*]] = shl <8 x i32> [[X:%.*]], [[T3]]
-; CHECK-NEXT:    [[T4:%.*]] = and <8 x i32> [[TMP1]], <i32 2147483647, i32 2147483647, i32 2147483647, i32 2147483647, i32 2147483647, i32 2147483647, i32 undef, i32 2147483647>
+; CHECK-NEXT:    [[T4:%.*]] = and <8 x i32> [[TMP1]], <i32 2147483647, i32 2147483647, i32 2147483647, i32 2147483647, i32 2147483647, i32 2147483647, i32 poison, i32 2147483647>
 ; CHECK-NEXT:    ret <8 x i32> [[T4]]
 ;
   %t0 = shl <8 x i32> <i32 -1, i32 -1, i32 -1, i32 -1, i32 -1, i32 -1, i32 undef, i32 -1>, %nbits
@@ -95,7 +95,7 @@
 ; CHECK-NEXT:    call void @use8xi32(<8 x i32> [[T1]])
 ; CHECK-NEXT:    call void @use8xi32(<8 x i32> [[T3]])
 ; CHECK-NEXT:    [[TMP1:%.*]] = shl <8 x i32> [[X:%.*]], [[T3]]
-; CHECK-NEXT:    [[T4:%.*]] = and <8 x i32> [[TMP1]], <i32 undef, i32 1, i32 2147483647, i32 -1, i32 -1, i32 -1, i32 -1, i32 undef>
+; CHECK-NEXT:    [[T4:%.*]] = and <8 x i32> [[TMP1]], <i32 poison, i32 1, i32 2147483647, i32 -1, i32 -1, i32 -1, i32 -1, i32 poison>
 ; CHECK-NEXT:    ret <8 x i32> [[T4]]
 ;
   %t0 = shl <8 x i32> <i32 -1, i32 -1, i32 -1, i32 -1, i32 -1, i32 -1, i32 -1, i32 -1>, %nbits
diff --git a/llvm/test/Transforms/InstCombine/partally-redundant-left-shift-input-masking-variant-e.ll b/llvm/test/Transforms/InstCombine/partally-redundant-left-shift-input-masking-variant-e.ll
--- a/llvm/test/Transforms/InstCombine/partally-redundant-left-shift-input-masking-variant-e.ll
+++ b/llvm/test/Transforms/InstCombine/partally-redundant-left-shift-input-masking-variant-e.ll
@@ -62,7 +62,7 @@
 ; CHECK-NEXT:    call void @use8xi32(<8 x i32> [[T0]])
 ; CHECK-NEXT:    call void @use8xi32(<8 x i32> [[T2]])
 ; CHECK-NEXT:    [[TMP1:%.*]] = shl <8 x i32> [[X]], [[T2]]
-; CHECK-NEXT:    [[T3:%.*]] = and <8 x i32> [[TMP1]], <i32 2147483647, i32 2147483647, i32 2147483647, i32 2147483647, i32 2147483647, i32 2147483647, i32 undef, i32 2147483647>
+; CHECK-NEXT:    [[T3:%.*]] = and <8 x i32> [[TMP1]], <i32 2147483647, i32 2147483647, i32 2147483647, i32 2147483647, i32 2147483647, i32 2147483647, i32 poison, i32 2147483647>
 ; CHECK-NEXT:    ret <8 x i32> [[T3]]
 ;
   %t0 = shl <8 x i32> %x, %nbits
@@ -81,7 +81,7 @@
 ; CHECK-NEXT:    call void @use8xi32(<8 x i32> [[T0]])
 ; CHECK-NEXT:    call void @use8xi32(<8 x i32> [[T2]])
 ; CHECK-NEXT:    [[TMP1:%.*]] = shl <8 x i32> [[X]], [[T2]]
-; CHECK-NEXT:    [[T3:%.*]] = and <8 x i32> [[TMP1]], <i32 undef, i32 1, i32 2147483647, i32 -1, i32 -1, i32 -1, i32 -1, i32 undef>
+; CHECK-NEXT:    [[T3:%.*]] = and <8 x i32> [[TMP1]], <i32 poison, i32 1, i32 2147483647, i32 -1, i32 -1, i32 -1, i32 -1, i32 poison>
 ; CHECK-NEXT:    ret <8 x i32> [[T3]]
 ;
   %t0 = shl <8 x i32> %x, %nbits
diff --git a/llvm/test/Transforms/InstCombine/select-of-bittest.ll b/llvm/test/Transforms/InstCombine/select-of-bittest.ll
--- a/llvm/test/Transforms/InstCombine/select-of-bittest.ll
+++ b/llvm/test/Transforms/InstCombine/select-of-bittest.ll
@@ -82,7 +82,7 @@
 
 define <3 x i32> @and_lshr_and_vec_undef(<3 x i32> %arg) {
 ; CHECK-LABEL: @and_lshr_and_vec_undef(
-; CHECK-NEXT:    [[TMP1:%.*]] = and <3 x i32> [[ARG:%.*]], <i32 3, i32 undef, i32 3>
+; CHECK-NEXT:    [[TMP1:%.*]] = and <3 x i32> [[ARG:%.*]], <i32 3, i32 poison, i32 3>
 ; CHECK-NEXT:    [[TMP2:%.*]] = icmp ne <3 x i32> [[TMP1]], zeroinitializer
 ; CHECK-NEXT:    [[TMP4:%.*]] = zext <3 x i1> [[TMP2]] to <3 x i32>
 ; CHECK-NEXT:    ret <3 x i32> [[TMP4]]
@@ -91,6 +91,7 @@
   %tmp1 = icmp eq <3 x i32> %tmp, <i32 0, i32 undef, i32 0>
   %tmp2 = lshr <3 x i32> %arg, <i32 1, i32 undef, i32 1>
   %tmp3 = and <3 x i32> %tmp2, <i32 1, i32 undef, i32 1>
+  ; The second element of %tmp4 is poison because it is (undef ? poison : undef).
   %tmp4 = select <3 x i1> %tmp1, <3 x i32> %tmp3, <3 x i32> <i32 1, i32 undef, i32 1>
   ret <3 x i32> %tmp4
 }
@@ -222,7 +223,7 @@
 
 define <3 x i32> @f_var0_vec_undef(<3 x i32> %arg, <3 x i32> %arg1) {
 ; CHECK-LABEL: @f_var0_vec_undef(
-; CHECK-NEXT:    [[TMP1:%.*]] = or <3 x i32> [[ARG1:%.*]], <i32 2, i32 undef, i32 2>
+; CHECK-NEXT:    [[TMP1:%.*]] = or <3 x i32> [[ARG1:%.*]], <i32 2, i32 poison, i32 2>
 ; CHECK-NEXT:    [[TMP2:%.*]] = and <3 x i32> [[TMP1]], [[ARG:%.*]]
 ; CHECK-NEXT:    [[TMP3:%.*]] = icmp ne <3 x i32> [[TMP2]], zeroinitializer
 ; CHECK-NEXT:    [[TMP5:%.*]] = zext <3 x i1> [[TMP3]] to <3 x i32>
@@ -232,6 +233,7 @@
   %tmp2 = icmp eq <3 x i32> %tmp, <i32 0, i32 undef, i32 0>
   %tmp3 = lshr <3 x i32> %arg, <i32 1, i32 undef, i32 1>
   %tmp4 = and <3 x i32> %tmp3, <i32 1, i32 undef, i32 1>
+  ; The second element of %tmp5 is poison because it is (undef ? poison : undef).
   %tmp5 = select <3 x i1> %tmp2, <3 x i32> %tmp4, <3 x i32> <i32 1, i32 undef, i32 1>
   ret <3 x i32> %tmp5
 }
diff --git a/llvm/test/Transforms/InstCombine/shift-add.ll b/llvm/test/Transforms/InstCombine/shift-add.ll
--- a/llvm/test/Transforms/InstCombine/shift-add.ll
+++ b/llvm/test/Transforms/InstCombine/shift-add.ll
@@ -40,7 +40,7 @@
 define <4 x i32> @shl_C1_add_A_C2_v4i32(<4 x i16> %A) {
 ; CHECK-LABEL: @shl_C1_add_A_C2_v4i32(
 ; CHECK-NEXT:    [[B:%.*]] = zext <4 x i16> [[A:%.*]] to <4 x i32>
-; CHECK-NEXT:    [[D:%.*]] = shl <4 x i32> <i32 6, i32 4, i32 undef, i32 -458752>, [[B]]
+; CHECK-NEXT:    [[D:%.*]] = shl <4 x i32> <i32 6, i32 4, i32 poison, i32 -458752>, [[B]]
 ; CHECK-NEXT:    ret <4 x i32> [[D]]
 ;
   %B = zext <4 x i16> %A to <4 x i32>
@@ -52,7 +52,7 @@
 define <4 x i32> @ashr_C1_add_A_C2_v4i32(<4 x i32> %A) {
 ; CHECK-LABEL: @ashr_C1_add_A_C2_v4i32(
 ; CHECK-NEXT:    [[B:%.*]] = and <4 x i32> [[A:%.*]], <i32 0, i32 15, i32 255, i32 65535>
-; CHECK-NEXT:    [[D:%.*]] = ashr <4 x i32> <i32 6, i32 1, i32 undef, i32 -1>, [[B]]
+; CHECK-NEXT:    [[D:%.*]] = ashr <4 x i32> <i32 6, i32 1, i32 poison, i32 -1>, [[B]]
 ; CHECK-NEXT:    ret <4 x i32> [[D]]
 ;
   %B = and <4 x i32> %A, <i32 0, i32 15, i32 255, i32 65535>
@@ -64,7 +64,7 @@
 define <4 x i32> @lshr_C1_add_A_C2_v4i32(<4 x i32> %A) {
 ; CHECK-LABEL: @lshr_C1_add_A_C2_v4i32(
 ; CHECK-NEXT:    [[B:%.*]] = and <4 x i32> [[A:%.*]], <i32 0, i32 15, i32 255, i32 65535>
-; CHECK-NEXT:    [[D:%.*]] = lshr <4 x i32> <i32 6, i32 1, i32 undef, i32 65535>, [[B]]
+; CHECK-NEXT:    [[D:%.*]] = lshr <4 x i32> <i32 6, i32 1, i32 poison, i32 65535>, [[B]]
 ; CHECK-NEXT:    ret <4 x i32> [[D]]
 ;
   %B = and <4 x i32> %A, <i32 0, i32 15, i32 255, i32 65535>
@@ -78,7 +78,7 @@
 ; CHECK-NEXT:    [[A:%.*]] = zext i16 [[I:%.*]] to i32
 ; CHECK-NEXT:    [[B:%.*]] = insertelement <4 x i32> undef, i32 [[A]], i32 0
 ; CHECK-NEXT:    [[C:%.*]] = shufflevector <4 x i32> [[B]], <4 x i32> undef, <4 x i32> zeroinitializer
-; CHECK-NEXT:    [[E:%.*]] = shl <4 x i32> <i32 6, i32 4, i32 undef, i32 -458752>, [[C]]
+; CHECK-NEXT:    [[E:%.*]] = shl <4 x i32> <i32 6, i32 4, i32 poison, i32 -458752>, [[C]]
 ; CHECK-NEXT:    ret <4 x i32> [[E]]
 ;
   %A = zext i16 %I to i32
@@ -94,7 +94,7 @@
 ; CHECK-NEXT:    [[A:%.*]] = zext i16 [[I:%.*]] to i32
 ; CHECK-NEXT:    [[B:%.*]] = insertelement <4 x i32> undef, i32 [[A]], i32 0
 ; CHECK-NEXT:    [[C:%.*]] = shufflevector <4 x i32> [[B]], <4 x i32> undef, <4 x i32> zeroinitializer
-; CHECK-NEXT:    [[E:%.*]] = ashr <4 x i32> <i32 6, i32 1, i32 undef, i32 -1>, [[C]]
+; CHECK-NEXT:    [[E:%.*]] = ashr <4 x i32> <i32 6, i32 1, i32 poison, i32 -1>, [[C]]
 ; CHECK-NEXT:    ret <4 x i32> [[E]]
 ;
   %A = zext i16 %I to i32
@@ -110,7 +110,7 @@
 ; CHECK-NEXT:    [[A:%.*]] = zext i16 [[I:%.*]] to i32
 ; CHECK-NEXT:    [[B:%.*]] = insertelement <4 x i32> undef, i32 [[A]], i32 0
 ; CHECK-NEXT:    [[C:%.*]] = shufflevector <4 x i32> [[B]], <4 x i32> undef, <4 x i32> zeroinitializer
-; CHECK-NEXT:    [[E:%.*]] = lshr <4 x i32> <i32 6, i32 1, i32 undef, i32 65535>, [[C]]
+; CHECK-NEXT:    [[E:%.*]] = lshr <4 x i32> <i32 6, i32 1, i32 poison, i32 65535>, [[C]]
 ; CHECK-NEXT:    ret <4 x i32> [[E]]
 ;
   %A = zext i16 %I to i32
diff --git a/llvm/test/Transforms/InstSimplify/ConstProp/InsertElement.ll b/llvm/test/Transforms/InstSimplify/ConstProp/InsertElement.ll
--- a/llvm/test/Transforms/InstSimplify/ConstProp/InsertElement.ll
+++ b/llvm/test/Transforms/InstSimplify/ConstProp/InsertElement.ll
@@ -25,7 +25,7 @@
 
 define <4 x i64> @insertelement_undef() {
 ; CHECK-LABEL: @insertelement_undef(
-; CHECK-NEXT:    ret <4 x i64> undef
+; CHECK-NEXT:    ret <4 x i64> poison
 ;
   %vec1 = insertelement <4 x i64> undef, i64 -1, i32 0
   %vec2 = insertelement <4 x i64> %vec1, i64 -2, i32 1
diff --git a/llvm/test/Transforms/InstSimplify/ConstProp/cast.ll b/llvm/test/Transforms/InstSimplify/ConstProp/cast.ll
--- a/llvm/test/Transforms/InstSimplify/ConstProp/cast.ll
+++ b/llvm/test/Transforms/InstSimplify/ConstProp/cast.ll
@@ -5,7 +5,7 @@
 
 define i8 @overflow_fptosi() {
 ; CHECK-LABEL: @overflow_fptosi(
-; CHECK-NEXT:    ret i8 undef
+; CHECK-NEXT:    ret i8 poison
 ;
   %i = fptosi double 1.56e+02 to i8
   ret i8 %i
@@ -13,7 +13,7 @@
 
 define i8 @overflow_fptoui() {
 ; CHECK-LABEL: @overflow_fptoui(
-; CHECK-NEXT:    ret i8 undef
+; CHECK-NEXT:    ret i8 poison
 ;
   %i = fptoui double 2.56e+02 to i8
   ret i8 %i
diff --git a/llvm/test/Transforms/InstSimplify/ConstProp/poison.ll b/llvm/test/Transforms/InstSimplify/ConstProp/poison.ll
--- a/llvm/test/Transforms/InstSimplify/ConstProp/poison.ll
+++ b/llvm/test/Transforms/InstSimplify/ConstProp/poison.ll
@@ -104,13 +104,13 @@
 
 define void @other_ops(i8 %x) {
 ; CHECK-LABEL: @other_ops(
-; CHECK-NEXT:    call void (...) @use(i1 poison, i1 poison, i8 poison, i8 poison, i8* poison)
+; CHECK-NEXT:    call void (...) @use(i1 poison, i1 poison, i8 poison, i8 poison, i8* poison, i8* poison)
 ; CHECK-NEXT:    ret void
 ;
   %i1 = icmp eq i8 poison, 1
   %i2 = fcmp oeq float poison, 1.0
   %i3 = select i1 poison, i8 1, i8 2
   %i4 = select i1 true, i8 poison, i8 %x
-  call void (...) @use(i1 %i1, i1 %i2, i8 %i3, i8 %i4, i8* getelementptr (i8, i8* poison, i64 1))
+  call void (...) @use(i1 %i1, i1 %i2, i8 %i3, i8 %i4, i8* getelementptr (i8, i8* poison, i64 1), i8* getelementptr inbounds (i8, i8* undef, i64 1))
   ret void
 }
diff --git a/llvm/test/Transforms/InstSimplify/ConstProp/shift.ll b/llvm/test/Transforms/InstSimplify/ConstProp/shift.ll
--- a/llvm/test/Transforms/InstSimplify/ConstProp/shift.ll
+++ b/llvm/test/Transforms/InstSimplify/ConstProp/shift.ll
@@ -3,15 +3,15 @@
 ; CHECK-LABEL: shift_undef_64
 define void @shift_undef_64(i64* %p) {
   %r1 = lshr i64 -1, 4294967296 ; 2^32
-  ; CHECK: store i64 undef
+  ; CHECK: store i64 poison
   store i64 %r1, i64* %p
 
   %r2 = ashr i64 -1, 4294967297 ; 2^32 + 1
-  ; CHECK: store i64 undef
+  ; CHECK: store i64 poison
   store i64 %r2, i64* %p
 
   %r3 = shl i64 -1, 4294967298 ; 2^32 + 2
-  ; CHECK: store i64 undef
+  ; CHECK: store i64 poison
   store i64 %r3, i64* %p
 
   ret void
@@ -20,15 +20,15 @@
 ; CHECK-LABEL: shift_undef_65
 define void @shift_undef_65(i65* %p) {
   %r1 = lshr i65 2, 18446744073709551617
-  ; CHECK: store i65 undef
+  ; CHECK: store i65 poison
   store i65 %r1, i65* %p
 
   %r2 = ashr i65 4, 18446744073709551617
-  ; CHECK: store i65 undef
+  ; CHECK: store i65 poison
   store i65 %r2, i65* %p
 
   %r3 = shl i65 1, 18446744073709551617
-  ; CHECK: store i65 undef
+  ; CHECK: store i65 poison
   store i65 %r3, i65* %p
 
   ret void
@@ -37,15 +37,15 @@
 ; CHECK-LABEL: shift_undef_256
 define void @shift_undef_256(i256* %p) {
   %r1 = lshr i256 2, 18446744073709551617
-  ; CHECK: store i256 undef
+  ; CHECK: store i256 poison
   store i256 %r1, i256* %p
 
   %r2 = ashr i256 4, 18446744073709551618
-  ; CHECK: store i256 undef
+  ; CHECK: store i256 poison
   store i256 %r2, i256* %p
 
   %r3 = shl i256 1, 18446744073709551619
-  ; CHECK: store i256 undef
+  ; CHECK: store i256 poison
   store i256 %r3, i256* %p
 
   ret void
@@ -54,15 +54,15 @@
 ; CHECK-LABEL: shift_undef_511
 define void @shift_undef_511(i511* %p) {
   %r1 = lshr i511 -1, 1208925819614629174706276 ; 2^80 + 100
-  ; CHECK: store i511 undef
+  ; CHECK: store i511 poison
   store i511 %r1, i511* %p
 
   %r2 = ashr i511 -2, 1208925819614629174706200
-  ; CHECK: store i511 undef
+  ; CHECK: store i511 poison
   store i511 %r2, i511* %p
 
   %r3 = shl i511 -3, 1208925819614629174706180
-  ; CHECK: store i511 undef
+  ; CHECK: store i511 poison
   store i511 %r3, i511* %p
 
   ret void
diff --git a/llvm/test/Transforms/InstSimplify/ConstProp/vector-undef-elts.ll b/llvm/test/Transforms/InstSimplify/ConstProp/vector-undef-elts.ll
--- a/llvm/test/Transforms/InstSimplify/ConstProp/vector-undef-elts.ll
+++ b/llvm/test/Transforms/InstSimplify/ConstProp/vector-undef-elts.ll
@@ -5,7 +5,7 @@
 
 define <3 x i8> @shl() {
 ; CHECK-LABEL: @shl(
-; CHECK-NEXT:    ret <3 x i8> <i8 undef, i8 0, i8 0>
+; CHECK-NEXT:    ret <3 x i8> <i8 poison, i8 0, i8 0>
 ;
   %c = shl <3 x i8> undef, <i8 undef, i8 4, i8 1>
   ret <3 x i8> %c
diff --git a/llvm/test/Transforms/InstSimplify/ConstProp/vscale.ll b/llvm/test/Transforms/InstSimplify/ConstProp/vscale.ll
--- a/llvm/test/Transforms/InstSimplify/ConstProp/vscale.ll
+++ b/llvm/test/Transforms/InstSimplify/ConstProp/vscale.ll
@@ -75,7 +75,7 @@
 
 define <vscale x 4 x i32> @udiv() {
 ; CHECK-LABEL: @udiv(
-; CHECK-NEXT:    ret <vscale x 4 x i32> undef
+; CHECK-NEXT:    ret <vscale x 4 x i32> poison
 ;
   %r = udiv <vscale x 4 x i32> undef, undef
   ret <vscale x 4 x i32> %r
@@ -83,7 +83,7 @@
 
 define <vscale x 4 x i32> @udiv_splat_zero() {
 ; CHECK-LABEL: @udiv_splat_zero(
-; CHECK-NEXT:    ret <vscale x 4 x i32> undef
+; CHECK-NEXT:    ret <vscale x 4 x i32> poison
 ;
   %r = udiv <vscale x 4 x i32> zeroinitializer, zeroinitializer
   ret <vscale x 4 x i32> %r
@@ -91,7 +91,7 @@
 
 define <vscale x 4 x i32> @sdiv() {
 ; CHECK-LABEL: @sdiv(
-; CHECK-NEXT:    ret <vscale x 4 x i32> undef
+; CHECK-NEXT:    ret <vscale x 4 x i32> poison
 ;
   %r = sdiv <vscale x 4 x i32> undef, undef
   ret <vscale x 4 x i32> %r
@@ -107,7 +107,7 @@
 
 define <vscale x 4 x i32> @urem() {
 ; CHECK-LABEL: @urem(
-; CHECK-NEXT:    ret <vscale x 4 x i32> undef
+; CHECK-NEXT:    ret <vscale x 4 x i32> poison
 ;
   %r = urem <vscale x 4 x i32> undef, undef
   ret <vscale x 4 x i32> %r
@@ -115,7 +115,7 @@
 
 define <vscale x 4 x i32> @srem() {
 ; CHECK-LABEL: @srem(
-; CHECK-NEXT:    ret <vscale x 4 x i32> undef
+; CHECK-NEXT:    ret <vscale x 4 x i32> poison
 ;
   %r = srem <vscale x 4 x i32> undef, undef
   ret <vscale x 4 x i32> %r
@@ -135,7 +135,7 @@
 
 define <vscale x 4 x i32> @shl() {
 ; CHECK-LABEL: @shl(
-; CHECK-NEXT:    ret <vscale x 4 x i32> undef
+; CHECK-NEXT:    ret <vscale x 4 x i32> poison
 ;
   %r = shl <vscale x 4 x i32> undef, undef
   ret <vscale x 4 x i32> %r
@@ -143,7 +143,7 @@
 
 define <vscale x 4 x i32> @lshr() {
 ; CHECK-LABEL: @lshr(
-; CHECK-NEXT:    ret <vscale x 4 x i32> undef
+; CHECK-NEXT:    ret <vscale x 4 x i32> poison
 ;
   %r = lshr <vscale x 4 x i32> undef, undef
   ret <vscale x 4 x i32> %r
@@ -151,7 +151,7 @@
 
 define <vscale x 4 x i32> @ashr() {
 ; CHECK-LABEL: @ashr(
-; CHECK-NEXT:    ret <vscale x 4 x i32> undef
+; CHECK-NEXT:    ret <vscale x 4 x i32> poison
 ;
   %r = ashr <vscale x 4 x i32> undef, undef
   ret <vscale x 4 x i32> %r
diff --git a/llvm/test/Transforms/InstSimplify/div.ll b/llvm/test/Transforms/InstSimplify/div.ll
--- a/llvm/test/Transforms/InstSimplify/div.ll
+++ b/llvm/test/Transforms/InstSimplify/div.ll
@@ -25,11 +25,11 @@
   ret <2 x i32> %B
 }
 
-; Division-by-zero is undef. UB in any vector lane means the whole op is undef.
+; Division-by-zero is poison. UB in any vector lane means the whole op is poison.
 
 define <2 x i8> @sdiv_zero_elt_vec_constfold(<2 x i8> %x) {
 ; CHECK-LABEL: @sdiv_zero_elt_vec_constfold(
-; CHECK-NEXT:    ret <2 x i8> undef
+; CHECK-NEXT:    ret <2 x i8> poison
 ;
   %div = sdiv <2 x i8> <i8 1, i8 2>, <i8 0, i8 -42>
   ret <2 x i8> %div
@@ -37,12 +37,13 @@
 
 define <2 x i8> @udiv_zero_elt_vec_constfold(<2 x i8> %x) {
 ; CHECK-LABEL: @udiv_zero_elt_vec_constfold(
-; CHECK-NEXT:    ret <2 x i8> undef
+; CHECK-NEXT:    ret <2 x i8> poison
 ;
   %div = udiv <2 x i8> <i8 1, i8 2>, <i8 42, i8 0>
   ret <2 x i8> %div
 }
 
+; TODO: instsimplify should fold these to poison
 define <2 x i8> @sdiv_zero_elt_vec(<2 x i8> %x) {
 ; CHECK-LABEL: @sdiv_zero_elt_vec(
 ; CHECK-NEXT:    ret <2 x i8> undef
@@ -193,4 +194,11 @@
   ret i32 %urem
 }
 
+define i8 @sdiv_minusone_divisor() {
+; CHECK-LABEL: @sdiv_minusone_divisor
+; CHECK-NEXT:   ret i8 poison
+  %v = sdiv i8 -128, -1
+  ret i8 %v
+}
+
 !0 = !{i32 0, i32 3}
diff --git a/llvm/test/Transforms/InstSimplify/rem.ll b/llvm/test/Transforms/InstSimplify/rem.ll
--- a/llvm/test/Transforms/InstSimplify/rem.ll
+++ b/llvm/test/Transforms/InstSimplify/rem.ll
@@ -25,11 +25,11 @@
   ret <2 x i32> %B
 }
 
-; Division-by-zero is undef. UB in any vector lane means the whole op is undef.
+; Division-by-zero is poison. UB in any vector lane means the whole op is poison.
 
 define <2 x i8> @srem_zero_elt_vec_constfold(<2 x i8> %x) {
 ; CHECK-LABEL: @srem_zero_elt_vec_constfold(
-; CHECK-NEXT:    ret <2 x i8> undef
+; CHECK-NEXT:    ret <2 x i8> poison
 ;
   %rem = srem <2 x i8> <i8 1, i8 2>, <i8 0, i8 -42>
   ret <2 x i8> %rem
@@ -37,12 +37,13 @@
 
 define <2 x i8> @urem_zero_elt_vec_constfold(<2 x i8> %x) {
 ; CHECK-LABEL: @urem_zero_elt_vec_constfold(
-; CHECK-NEXT:    ret <2 x i8> undef
+; CHECK-NEXT:    ret <2 x i8> poison
 ;
   %rem = urem <2 x i8> <i8 1, i8 2>, <i8 42, i8 0>
   ret <2 x i8> %rem
 }
 
+; TODO: instsimplify should fold these to poison
 define <2 x i8> @srem_zero_elt_vec(<2 x i8> %x) {
 ; CHECK-LABEL: @srem_zero_elt_vec(
 ; CHECK-NEXT:    ret <2 x i8> undef
@@ -325,3 +326,9 @@
   ret <2 x i32> %r
 }
 
+define i8 @srem_minusone_divisor() {
+; CHECK-LABEL: @srem_minusone_divisor
+; CHECK-NEXT:   ret i8 poison
+  %v = srem i8 -128, -1
+  ret i8 %v
+}
diff --git a/llvm/test/Transforms/InstSimplify/undef.ll b/llvm/test/Transforms/InstSimplify/undef.ll
--- a/llvm/test/Transforms/InstSimplify/undef.ll
+++ b/llvm/test/Transforms/InstSimplify/undef.ll
@@ -90,7 +90,7 @@
 
 define i64 @test11() {
 ; CHECK-LABEL: @test11(
-; CHECK:         ret i64 undef
+; CHECK:         ret i64 poison
 ;
   %r = shl i64 undef, undef
   ret i64 %r
@@ -106,7 +106,7 @@
 
 define i64 @test12() {
 ; CHECK-LABEL: @test12(
-; CHECK:         ret i64 undef
+; CHECK:         ret i64 poison
 ;
   %r = ashr i64 undef, undef
   ret i64 %r
@@ -122,7 +122,7 @@
 
 define i64 @test13() {
 ; CHECK-LABEL: @test13(
-; CHECK:         ret i64 undef
+; CHECK:         ret i64 poison
 ;
   %r = lshr i64 undef, undef
   ret i64 %r
@@ -235,7 +235,7 @@
 
 define i32 @test24() {
 ; CHECK-LABEL: @test24(
-; CHECK:         ret i32 undef
+; CHECK:         ret i32 poison
 ;
   %b = udiv i32 undef, 0
   ret i32 %b
@@ -243,7 +243,7 @@
 
 define i32 @test25() {
 ; CHECK-LABEL: @test25(
-; CHECK:         ret i32 undef
+; CHECK:         ret i32 poison
 ;
   %b = lshr i32 0, undef
   ret i32 %b
@@ -251,7 +251,7 @@
 
 define i32 @test26() {
 ; CHECK-LABEL: @test26(
-; CHECK:         ret i32 undef
+; CHECK:         ret i32 poison
 ;
   %b = ashr i32 0, undef
   ret i32 %b
@@ -259,7 +259,7 @@
 
 define i32 @test27() {
 ; CHECK-LABEL: @test27(
-; CHECK:         ret i32 undef
+; CHECK:         ret i32 poison
 ;
   %b = shl i32 0, undef
   ret i32 %b
@@ -339,7 +339,7 @@
 
 define i32 @test37() {
 ; CHECK-LABEL: @test37(
-; CHECK:         ret i32 undef
+; CHECK:         ret i32 poison
 ;
   %b = udiv i32 undef, undef
   ret i32 %b
@@ -355,7 +355,7 @@
 
 define i32 @test39() {
 ; CHECK-LABEL: @test39(
-; CHECK:         ret i32 undef
+; CHECK:         ret i32 poison
 ;
   %b = udiv i32 0, undef
   ret i32 %b
diff --git a/llvm/test/Transforms/SROA/phi-gep.ll b/llvm/test/Transforms/SROA/phi-gep.ll
--- a/llvm/test/Transforms/SROA/phi-gep.ll
+++ b/llvm/test/Transforms/SROA/phi-gep.ll
@@ -348,7 +348,7 @@
 ; CHECK-NEXT:    [[PHI:%.*]] = phi %pair* [ [[ALLOCA]], [[ENTRY:%.*]] ], [ [[SELECT:%.*]], [[WHILE_BODY]] ]
 ; CHECK-NEXT:    [[SELECT]] = select i1 undef, %pair* [[PHI]], %pair* undef
 ; CHECK-NEXT:    [[PHI_SROA_GEP:%.*]] = getelementptr inbounds [[PAIR]], %pair* [[PHI]], i64 1
-; CHECK-NEXT:    [[SELECT_SROA_SEL:%.*]] = select i1 undef, %pair* [[PHI_SROA_GEP]], %pair* undef
+; CHECK-NEXT:    [[SELECT_SROA_SEL:%.*]] = select i1 undef, %pair* [[PHI_SROA_GEP]], %pair* poison
 ; CHECK-NEXT:    br i1 undef, label [[EXIT:%.*]], label [[WHILE_BODY]]
 ; CHECK:       exit:
 ; CHECK-NEXT:    unreachable
diff --git a/llvm/test/Transforms/SROA/select-gep.ll b/llvm/test/Transforms/SROA/select-gep.ll
--- a/llvm/test/Transforms/SROA/select-gep.ll
+++ b/llvm/test/Transforms/SROA/select-gep.ll
@@ -83,7 +83,7 @@
 ; CHECK-LABEL: @test_sroa_select_gep_undef(
 ; CHECK-NEXT:  bb:
 ; CHECK-NEXT:    [[A_SROA_0:%.*]] = alloca i32, align 4
-; CHECK-NEXT:    [[SELECT_SROA_SEL:%.*]] = select i1 [[COND:%.*]], i32* [[A_SROA_0]], i32* undef
+; CHECK-NEXT:    [[SELECT_SROA_SEL:%.*]] = select i1 [[COND:%.*]], i32* [[A_SROA_0]], i32* poison
 ; CHECK-NEXT:    [[LOAD:%.*]] = load i32, i32* [[SELECT_SROA_SEL]], align 4
 ; CHECK-NEXT:    ret i32 [[LOAD]]
 ;
diff --git a/llvm/test/Transforms/VectorCombine/X86/insert-binop-with-constant.ll b/llvm/test/Transforms/VectorCombine/X86/insert-binop-with-constant.ll
--- a/llvm/test/Transforms/VectorCombine/X86/insert-binop-with-constant.ll
+++ b/llvm/test/Transforms/VectorCombine/X86/insert-binop-with-constant.ll
@@ -189,7 +189,7 @@
 define <2 x i64> @shl_constant_op1(i64 %x) {
 ; CHECK-LABEL: @shl_constant_op1(
 ; CHECK-NEXT:    [[BO_SCALAR:%.*]] = shl nuw i64 [[X:%.*]], 5
-; CHECK-NEXT:    [[BO:%.*]] = insertelement <2 x i64> <i64 0, i64 undef>, i64 [[BO_SCALAR]], i64 0
+; CHECK-NEXT:    [[BO:%.*]] = insertelement <2 x i64> <i64 0, i64 poison>, i64 [[BO_SCALAR]], i64 0
 ; CHECK-NEXT:    ret <2 x i64> [[BO]]
 ;
   %ins = insertelement <2 x i64> undef, i64 %x, i32 0
@@ -246,7 +246,7 @@
 define <2 x i64> @ashr_constant_op1(i64 %x) {
 ; CHECK-LABEL: @ashr_constant_op1(
 ; CHECK-NEXT:    [[BO_SCALAR:%.*]] = ashr i64 [[X:%.*]], 5
-; CHECK-NEXT:    [[BO:%.*]] = insertelement <2 x i64> <i64 0, i64 undef>, i64 [[BO_SCALAR]], i64 0
+; CHECK-NEXT:    [[BO:%.*]] = insertelement <2 x i64> <i64 0, i64 poison>, i64 [[BO_SCALAR]], i64 0
 ; CHECK-NEXT:    ret <2 x i64> [[BO]]
 ;
   %ins = insertelement <2 x i64> undef, i64 %x, i32 0
@@ -290,7 +290,7 @@
 define <2 x i64> @lshr_constant_op1(i64 %x) {
 ; CHECK-LABEL: @lshr_constant_op1(
 ; CHECK-NEXT:    [[BO_SCALAR:%.*]] = lshr exact i64 [[X:%.*]], 2
-; CHECK-NEXT:    [[BO:%.*]] = insertelement <2 x i64> <i64 undef, i64 0>, i64 [[BO_SCALAR]], i64 1
+; CHECK-NEXT:    [[BO:%.*]] = insertelement <2 x i64> <i64 poison, i64 0>, i64 [[BO_SCALAR]], i64 1
 ; CHECK-NEXT:    ret <2 x i64> [[BO]]
 ;
   %ins = insertelement <2 x i64> undef, i64 %x, i32 1
@@ -334,7 +334,7 @@
 define <2 x i64> @urem_constant_op1(i64 %x) {
 ; CHECK-LABEL: @urem_constant_op1(
 ; CHECK-NEXT:    [[BO_SCALAR:%.*]] = urem i64 [[X:%.*]], 2
-; CHECK-NEXT:    [[BO:%.*]] = insertelement <2 x i64> <i64 undef, i64 0>, i64 [[BO_SCALAR]], i64 1
+; CHECK-NEXT:    [[BO:%.*]] = insertelement <2 x i64> <i64 poison, i64 0>, i64 [[BO_SCALAR]], i64 1
 ; CHECK-NEXT:    ret <2 x i64> [[BO]]
 ;
   %ins = insertelement <2 x i64> undef, i64 %x, i32 1
@@ -378,7 +378,7 @@
 define <2 x i64> @srem_constant_op1(i64 %x) {
 ; CHECK-LABEL: @srem_constant_op1(
 ; CHECK-NEXT:    [[BO_SCALAR:%.*]] = srem i64 [[X:%.*]], 2
-; CHECK-NEXT:    [[BO:%.*]] = insertelement <2 x i64> <i64 undef, i64 0>, i64 [[BO_SCALAR]], i64 1
+; CHECK-NEXT:    [[BO:%.*]] = insertelement <2 x i64> <i64 poison, i64 0>, i64 [[BO_SCALAR]], i64 1
 ; CHECK-NEXT:    ret <2 x i64> [[BO]]
 ;
   %ins = insertelement <2 x i64> undef, i64 %x, i32 1
@@ -422,7 +422,7 @@
 define <2 x i64> @udiv_constant_op1(i64 %x) {
 ; CHECK-LABEL: @udiv_constant_op1(
 ; CHECK-NEXT:    [[BO_SCALAR:%.*]] = udiv i64 [[X:%.*]], 2
-; CHECK-NEXT:    [[BO:%.*]] = insertelement <2 x i64> <i64 undef, i64 0>, i64 [[BO_SCALAR]], i64 1
+; CHECK-NEXT:    [[BO:%.*]] = insertelement <2 x i64> <i64 poison, i64 0>, i64 [[BO_SCALAR]], i64 1
 ; CHECK-NEXT:    ret <2 x i64> [[BO]]
 ;
   %ins = insertelement <2 x i64> undef, i64 %x, i32 1
@@ -466,7 +466,7 @@
 define <2 x i64> @sdiv_constant_op1(i64 %x) {
 ; CHECK-LABEL: @sdiv_constant_op1(
 ; CHECK-NEXT:    [[BO_SCALAR:%.*]] = sdiv exact i64 [[X:%.*]], 2
-; CHECK-NEXT:    [[BO:%.*]] = insertelement <2 x i64> <i64 undef, i64 0>, i64 [[BO_SCALAR]], i64 1
+; CHECK-NEXT:    [[BO:%.*]] = insertelement <2 x i64> <i64 poison, i64 0>, i64 [[BO_SCALAR]], i64 1
 ; CHECK-NEXT:    ret <2 x i64> [[BO]]
 ;
   %ins = insertelement <2 x i64> undef, i64 %x, i32 1
diff --git a/llvm/test/Transforms/VectorCombine/X86/insert-binop.ll b/llvm/test/Transforms/VectorCombine/X86/insert-binop.ll
--- a/llvm/test/Transforms/VectorCombine/X86/insert-binop.ll
+++ b/llvm/test/Transforms/VectorCombine/X86/insert-binop.ll
@@ -128,7 +128,7 @@
 define <2 x i64> @ins1_ins1_udiv(i64 %x, i64 %y) {
 ; CHECK-LABEL: @ins1_ins1_udiv(
 ; CHECK-NEXT:    [[R_SCALAR:%.*]] = udiv i64 [[X:%.*]], [[Y:%.*]]
-; CHECK-NEXT:    [[R:%.*]] = insertelement <2 x i64> <i64 6, i64 undef>, i64 [[R_SCALAR]], i64 1
+; CHECK-NEXT:    [[R:%.*]] = insertelement <2 x i64> <i64 6, i64 poison>, i64 [[R_SCALAR]], i64 1
 ; CHECK-NEXT:    ret <2 x i64> [[R]]
 ;
   %i0 = insertelement <2 x i64> <i64 42, i64 undef>, i64 %x, i32 1
@@ -143,7 +143,7 @@
 define <2 x i64> @ins1_ins1_urem(i64 %x, i64 %y) {
 ; CHECK-LABEL: @ins1_ins1_urem(
 ; CHECK-NEXT:    [[R_SCALAR:%.*]] = urem i64 [[X:%.*]], [[Y:%.*]]
-; CHECK-NEXT:    [[R:%.*]] = insertelement <2 x i64> <i64 undef, i64 0>, i64 [[R_SCALAR]], i64 1
+; CHECK-NEXT:    [[R:%.*]] = insertelement <2 x i64> <i64 poison, i64 0>, i64 [[R_SCALAR]], i64 1
 ; CHECK-NEXT:    ret <2 x i64> [[R]]
 ;
   %i0 = insertelement <2 x i64> <i64 42, i64 undef>, i64 %x, i64 1
diff --git a/llvm/unittests/IR/ConstantsTest.cpp b/llvm/unittests/IR/ConstantsTest.cpp
--- a/llvm/unittests/IR/ConstantsTest.cpp
+++ b/llvm/unittests/IR/ConstantsTest.cpp
@@ -27,7 +27,7 @@
   Constant* Zero = ConstantInt::get(Int1, 0);
   Constant* NegOne = ConstantInt::get(Int1, static_cast<uint64_t>(-1), true);
   EXPECT_EQ(NegOne, ConstantInt::getSigned(Int1, -1));
-  Constant* Undef = UndefValue::get(Int1);
+  Constant* Poison = PoisonValue::get(Int1);
 
   // Input:  @b = constant i1 add(i1 1 , i1 1)
   // Output: @b = constant i1 false
@@ -53,21 +53,21 @@
   // @g = constant i1 false
   EXPECT_EQ(Zero, ConstantExpr::getSub(One, One));
 
-  // @h = constant i1 shl(i1 1 , i1 1)  ; undefined
-  // @h = constant i1 undef
-  EXPECT_EQ(Undef, ConstantExpr::getShl(One, One));
+  // @h = constant i1 shl(i1 1 , i1 1)  ; poison
+  // @h = constant i1 poison
+  EXPECT_EQ(Poison, ConstantExpr::getShl(One, One));
 
   // @i = constant i1 shl(i1 1 , i1 0)
   // @i = constant i1 true
   EXPECT_EQ(One, ConstantExpr::getShl(One, Zero));
 
-  // @j = constant i1 lshr(i1 1, i1 1)  ; undefined
-  // @j = constant i1 undef
-  EXPECT_EQ(Undef, ConstantExpr::getLShr(One, One));
+  // @j = constant i1 lshr(i1 1, i1 1)  ; poison
+  // @j = constant i1 poison
+  EXPECT_EQ(Poison, ConstantExpr::getLShr(One, One));
 
-  // @m = constant i1 ashr(i1 1, i1 1)  ; undefined
-  // @m = constant i1 undef
-  EXPECT_EQ(Undef, ConstantExpr::getAShr(One, One));
+  // @m = constant i1 ashr(i1 1, i1 1)  ; poison
+  // @m = constant i1 poison
+  EXPECT_EQ(Poison, ConstantExpr::getAShr(One, One));
 
   // @n = constant i1 mul(i1 -1, i1 1)
   // @n = constant i1 true
@@ -218,7 +218,6 @@
   Constant *Elt = ConstantInt::get(Int16Ty, 2015);
   Constant *Poison16 = PoisonValue::get(Int16Ty);
   Constant *Undef64  = UndefValue::get(Int64Ty);
-  Constant *UndefV16 = UndefValue::get(P6->getType());
   Constant *PoisonV16 = PoisonValue::get(P6->getType());
 
   #define P0STR "ptrtoint (i32** @dummy to i32)"
@@ -295,8 +294,8 @@
 
   EXPECT_EQ(Elt, ConstantExpr::getExtractElement(
                  ConstantExpr::getInsertElement(P6, Elt, One), One));
-  EXPECT_EQ(UndefV16, ConstantExpr::getInsertElement(P6, Elt, Two));
-  EXPECT_EQ(UndefV16, ConstantExpr::getInsertElement(P6, Elt, Big));
+  EXPECT_EQ(PoisonV16, ConstantExpr::getInsertElement(P6, Elt, Two));
+  EXPECT_EQ(PoisonV16, ConstantExpr::getInsertElement(P6, Elt, Big));
   EXPECT_EQ(PoisonV16, ConstantExpr::getInsertElement(P6, Elt, Undef64));
 }