diff --git a/llvm/include/llvm/Analysis/TargetTransformInfoImpl.h b/llvm/include/llvm/Analysis/TargetTransformInfoImpl.h
--- a/llvm/include/llvm/Analysis/TargetTransformInfoImpl.h
+++ b/llvm/include/llvm/Analysis/TargetTransformInfoImpl.h
@@ -809,7 +809,12 @@
         uint64_t Field = ConstIdx->getZExtValue();
         BaseOffset += DL.getStructLayout(STy)->getElementOffset(Field);
       } else {
-        int64_t ElementSize = DL.getTypeAllocSize(GTI.getIndexedType());
+        // If this operand is a scalable type, bail out early.
+        // TODO: handle scalable vectors
+        if (isa<ScalableVectorType>(TargetType))
+          return TTI::TCC_Basic;
+        int64_t ElementSize =
+            DL.getTypeAllocSize(GTI.getIndexedType()).getFixedSize();
         if (ConstIdx) {
           BaseOffset +=
               ConstIdx->getValue().sextOrTrunc(PtrSizeBits) * ElementSize;
diff --git a/llvm/test/Analysis/CostModel/AArch64/cost-scalable-vector-gep.ll b/llvm/test/Analysis/CostModel/AArch64/cost-scalable-vector-gep.ll
new file mode 100644
--- /dev/null
+++ b/llvm/test/Analysis/CostModel/AArch64/cost-scalable-vector-gep.ll
@@ -0,0 +1,15 @@
+; RUN: opt -cost-model -analyze -mtriple=aarch64--linux-gnu -mattr=+sve < %s 2>%t | FileCheck %s
+; RUN: FileCheck --check-prefix=WARN --allow-empty %s < %t
+
+; This regression test is verifying that a GEP instruction performed on a
+; scalable vector does not produce a 'assumption that TypeSize is not scalable'
+; warning when performing cost analysis.
+
+; If this check fails please read test/CodeGen/AArch64/README for instructions on how to resolve it.
+; WARN-NOT: warning: {{.*}}TypeSize is not scalable
+
+; CHECK: Cost Model: Found an estimated cost of 1 for instruction:   %retval = getelementptr
+define <vscale x 16 x i8>* @gep_scalable_vector(<vscale x 16 x i8>* %ptr) {
+  %retval = getelementptr <vscale x 16 x i8>, <vscale x 16 x i8>* %ptr, i32 2
+  ret <vscale x 16 x i8>* %retval
+}