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
@@ -1836,7 +1836,7 @@
   Type *ResultTy;
   if (VectorType *VT = dyn_cast<VectorType>(C1->getType()))
     ResultTy = VectorType::get(Type::getInt1Ty(C1->getContext()),
-                               VT->getNumElements());
+                               VT->getElementCount());
   else
     ResultTy = Type::getInt1Ty(C1->getContext());
 
@@ -1967,6 +1967,11 @@
                                         R==APFloat::cmpEqual);
     }
   } else if (C1->getType()->isVectorTy()) {
+    // Do not iterate on scalable vector. The number of elements is unknown at
+    // compile-time.
+    if (C1->getType()->getVectorIsScalable())
+      return nullptr;
+
     // If we can constant fold the comparison of each element, constant fold
     // the whole vector comparison.
     SmallVector<Constant*, 4> ResElts;
diff --git a/llvm/lib/IR/Constants.cpp b/llvm/lib/IR/Constants.cpp
--- a/llvm/lib/IR/Constants.cpp
+++ b/llvm/lib/IR/Constants.cpp
@@ -2176,7 +2176,7 @@
 
   Type *ResultTy = Type::getInt1Ty(LHS->getContext());
   if (VectorType *VT = dyn_cast<VectorType>(LHS->getType()))
-    ResultTy = VectorType::get(ResultTy, VT->getNumElements());
+    ResultTy = VectorType::get(ResultTy, VT->getElementCount());
 
   LLVMContextImpl *pImpl = LHS->getType()->getContext().pImpl;
   return pImpl->ExprConstants.getOrCreate(ResultTy, Key);
@@ -2201,7 +2201,7 @@
 
   Type *ResultTy = Type::getInt1Ty(LHS->getContext());
   if (VectorType *VT = dyn_cast<VectorType>(LHS->getType()))
-    ResultTy = VectorType::get(ResultTy, VT->getNumElements());
+    ResultTy = VectorType::get(ResultTy, VT->getElementCount());
 
   LLVMContextImpl *pImpl = LHS->getType()->getContext().pImpl;
   return pImpl->ExprConstants.getOrCreate(ResultTy, Key);
diff --git a/llvm/test/Analysis/ConstantFolding/vscale.ll b/llvm/test/Analysis/ConstantFolding/vscale.ll
--- a/llvm/test/Analysis/ConstantFolding/vscale.ll
+++ b/llvm/test/Analysis/ConstantFolding/vscale.ll
@@ -210,3 +210,51 @@
   %r = select <vscale x 4 x i1> undef, <vscale x 4 x i32> zeroinitializer, <vscale x 4 x i32> undef
   ret <vscale x 4 x i32> %r
 }
+
+define <vscale x 4 x i1> @icmp_undef() {
+; CHECK-LABEL: @icmp_undef(
+; CHECK-NEXT:    ret <vscale x 4 x i1> undef
+;
+  %r = icmp eq <vscale x 4 x i32> undef, undef
+  ret <vscale x 4 x i1> %r
+}
+
+define <vscale x 4 x i1> @icmp_zero() {
+; CHECK-LABEL: @icmp_zero(
+; CHECK-NEXT:    ret <vscale x 4 x i1> icmp eq (<vscale x 4 x i32> zeroinitializer, <vscale x 4 x i32> zeroinitializer)
+;
+  %r = icmp eq <vscale x 4 x i32> zeroinitializer, zeroinitializer
+  ret <vscale x 4 x i1> %r
+}
+
+define <vscale x 4 x i1> @fcmp_true() {
+; CHECK-LABEL: @fcmp_true(
+; CHECK-NEXT:    ret <vscale x 4 x i1> shufflevector (<vscale x 4 x i1> insertelement (<vscale x 4 x i1> undef, i1 true, i32 0), <vscale x 4 x i1> undef, <vscale x 4 x i32> zeroinitializer)
+;
+  %r = fcmp true <vscale x 4 x float> undef, undef
+  ret <vscale x 4 x i1> %r
+}
+
+define <vscale x 4 x i1> @fcmp_false() {
+; CHECK-LABEL: @fcmp_false(
+; CHECK-NEXT:    ret <vscale x 4 x i1> zeroinitializer
+;
+  %r = fcmp false <vscale x 4 x float> undef, undef
+  ret <vscale x 4 x i1> %r
+}
+
+define <vscale x 4 x i1> @fcmp_undef() {
+; CHECK-LABEL: @fcmp_undef(
+; CHECK-NEXT:    ret <vscale x 4 x i1> undef
+;
+  %r = icmp ne <vscale x 4 x i32> undef, undef
+  ret <vscale x 4 x i1> %r
+}
+
+define <vscale x 4 x i1> @fcmp_not_equality() {
+; CHECK-LABEL: @fcmp_not_equality(
+; CHECK-NEXT:    ret <vscale x 4 x i1> shufflevector (<vscale x 4 x i1> insertelement (<vscale x 4 x i1> undef, i1 true, i32 0), <vscale x 4 x i1> undef, <vscale x 4 x i32> zeroinitializer)
+;
+  %r = icmp ule <vscale x 4 x i32> undef, zeroinitializer
+  ret <vscale x 4 x i1> %r
+}