diff --git a/llvm/lib/Transforms/InstCombine/InstCombineSimplifyDemanded.cpp b/llvm/lib/Transforms/InstCombine/InstCombineSimplifyDemanded.cpp
--- a/llvm/lib/Transforms/InstCombine/InstCombineSimplifyDemanded.cpp
+++ b/llvm/lib/Transforms/InstCombine/InstCombineSimplifyDemanded.cpp
@@ -130,9 +130,6 @@
   if (Depth == MaxAnalysisRecursionDepth)
     return nullptr;
 
-  if (isa<ScalableVectorType>(VTy))
-    return nullptr;
-
   Instruction *I = dyn_cast<Instruction>(V);
   if (!I) {
     computeKnownBits(V, Known, Depth, CxtI);
@@ -424,7 +421,9 @@
 
     if (auto *DstVTy = dyn_cast<VectorType>(VTy)) {
       if (auto *SrcVTy = dyn_cast<VectorType>(I->getOperand(0)->getType())) {
-        if (cast<FixedVectorType>(DstVTy)->getNumElements() !=
+        if (isa<ScalableVectorType>(DstVTy) ||
+            isa<ScalableVectorType>(SrcVTy) ||
+            cast<FixedVectorType>(DstVTy)->getNumElements() !=
             cast<FixedVectorType>(SrcVTy)->getNumElements())
           // Don't touch a bitcast between vectors of different element counts.
           return nullptr;
diff --git a/llvm/test/Transforms/InstCombine/mul-masked-bits.ll b/llvm/test/Transforms/InstCombine/mul-masked-bits.ll
--- a/llvm/test/Transforms/InstCombine/mul-masked-bits.ll
+++ b/llvm/test/Transforms/InstCombine/mul-masked-bits.ll
@@ -82,8 +82,7 @@
 ; CHECK-LABEL: @combine_mul_self_demandedbits_vector2(
 ; CHECK-NEXT:    [[TMP1:%.*]] = freeze <vscale x 2 x i32> [[X:%.*]]
 ; CHECK-NEXT:    [[TMP2:%.*]] = mul <vscale x 2 x i32> [[TMP1]], [[TMP1]]
-; CHECK-NEXT:    [[TMP3:%.*]] = and <vscale x 2 x i32> [[TMP2]], shufflevector (<vscale x 2 x i32> insertelement (<vscale x 2 x i32> poison, i32 -3, i32 0), <vscale x 2 x i32> poison, <vscale x 2 x i32> zeroinitializer)
-; CHECK-NEXT:    ret <vscale x 2 x i32> [[TMP3]]
+; CHECK-NEXT:    ret <vscale x 2 x i32> [[TMP2]]
 ;
   %1 = freeze <vscale x 2 x i32> %x
   %2 = mul <vscale x 2 x i32> %1, %1
diff --git a/llvm/test/Transforms/InstCombine/udiv-simplify.ll b/llvm/test/Transforms/InstCombine/udiv-simplify.ll
--- a/llvm/test/Transforms/InstCombine/udiv-simplify.ll
+++ b/llvm/test/Transforms/InstCombine/udiv-simplify.ll
@@ -106,8 +106,7 @@
 
 define <vscale x 1 x i32> @udiv_demanded3(<vscale x 1 x i32> %a) {
 ; CHECK-LABEL: @udiv_demanded3(
-; CHECK-NEXT:    [[O:%.*]] = or <vscale x 1 x i32> [[A:%.*]], shufflevector (<vscale x 1 x i32> insertelement (<vscale x 1 x i32> poison, i32 3, i32 0), <vscale x 1 x i32> poison, <vscale x 1 x i32> zeroinitializer)
-; CHECK-NEXT:    [[U:%.*]] = udiv <vscale x 1 x i32> [[O]], shufflevector (<vscale x 1 x i32> insertelement (<vscale x 1 x i32> poison, i32 12, i32 0), <vscale x 1 x i32> poison, <vscale x 1 x i32> zeroinitializer)
+; CHECK-NEXT:    [[U:%.*]] = udiv <vscale x 1 x i32> [[A:%.*]], shufflevector (<vscale x 1 x i32> insertelement (<vscale x 1 x i32> poison, i32 12, i32 0), <vscale x 1 x i32> poison, <vscale x 1 x i32> zeroinitializer)
 ; CHECK-NEXT:    ret <vscale x 1 x i32> [[U]]
 ;
   %o = or <vscale x 1 x i32> %a, shufflevector (<vscale x 1 x i32> insertelement (<vscale x 1 x i32> poison, i32 3, i32 0), <vscale x 1 x i32> poison, <vscale x 1 x i32> zeroinitializer)