Index: llvm/lib/Analysis/ValueTracking.cpp
===================================================================
--- llvm/lib/Analysis/ValueTracking.cpp
+++ llvm/lib/Analysis/ValueTracking.cpp
@@ -1690,7 +1690,8 @@
           Known.Zero.setBitsFrom(31);
         break;
       case Intrinsic::vscale: {
-        if (!II->getFunction()->hasFnAttribute(Attribute::VScaleRange))
+        if (!II->getFunction() ||
+            !II->getFunction()->hasFnAttribute(Attribute::VScaleRange))
           break;
 
         auto VScaleRange = II->getFunction()
Index: llvm/lib/Transforms/InstCombine/InstCombineCasts.cpp
===================================================================
--- llvm/lib/Transforms/InstCombine/InstCombineCasts.cpp
+++ llvm/lib/Transforms/InstCombine/InstCombineCasts.cpp
@@ -963,7 +963,8 @@
   }
 
   if (match(Src, m_VScale(DL))) {
-    if (Trunc.getFunction()->hasFnAttribute(Attribute::VScaleRange)) {
+    if (Trunc.getFunction() &&
+        Trunc.getFunction()->hasFnAttribute(Attribute::VScaleRange)) {
       unsigned MaxVScale = Trunc.getFunction()
                                ->getFnAttribute(Attribute::VScaleRange)
                                .getVScaleRangeArgs()
@@ -1334,7 +1335,8 @@
   }
 
   if (match(Src, m_VScale(DL))) {
-    if (CI.getFunction()->hasFnAttribute(Attribute::VScaleRange)) {
+    if (CI.getFunction() &&
+        CI.getFunction()->hasFnAttribute(Attribute::VScaleRange)) {
       unsigned MaxVScale = CI.getFunction()
                                ->getFnAttribute(Attribute::VScaleRange)
                                .getVScaleRangeArgs()
@@ -1604,7 +1606,8 @@
   }
 
   if (match(Src, m_VScale(DL))) {
-    if (CI.getFunction()->hasFnAttribute(Attribute::VScaleRange)) {
+    if (CI.getFunction() &&
+        CI.getFunction()->hasFnAttribute(Attribute::VScaleRange)) {
       unsigned MaxVScale = CI.getFunction()
                                ->getFnAttribute(Attribute::VScaleRange)
                                .getVScaleRangeArgs()
Index: llvm/unittests/Analysis/ValueTrackingTest.cpp
===================================================================
--- llvm/unittests/Analysis/ValueTrackingTest.cpp
+++ llvm/unittests/Analysis/ValueTrackingTest.cpp
@@ -12,6 +12,7 @@
 #include "llvm/IR/ConstantRange.h"
 #include "llvm/IR/Dominators.h"
 #include "llvm/IR/Function.h"
+#include "llvm/IR/IRBuilder.h"
 #include "llvm/IR/InstIterator.h"
 #include "llvm/IR/Instructions.h"
 #include "llvm/IR/LLVMContext.h"
@@ -1597,6 +1598,25 @@
   EXPECT_EQ(Known.getMaxValue(), 131071);
 }
 
+TEST_F(ComputeKnownBitsTest, ComputeKnownBitsUnknownVScale) {
+  parseAssembly("define i32 @test(i32 %a) {\n"
+                "  %A = add i32 %a, 1\n"
+                "  ret i32 %A;\n"
+                "}\n"
+                "declare i32 @llvm.vscale.i32()\n");
+
+  IRBuilder<> Builder(Context);
+  Function *TheFn = Intrinsic::getDeclaration(M.get(), Intrinsic::vscale,
+                                              {Builder.getInt32Ty()});
+  CallInst *CI = Builder.CreateCall(TheFn, {}, {}, "");
+
+  KnownBits Known = computeKnownBits(CI, M->getDataLayout(), /* Depth */ 0);
+  // There is no parent function so we cannot look up the vscale_range
+  // attribute to determine the number of bits.
+  EXPECT_EQ(Known.One.getZExtValue(), 0u);
+  EXPECT_EQ(Known.Zero.getZExtValue(), 0u);
+}
+
 // 512 + [32, 64) doesn't produce overlapping bits.
 // Make sure we get all the individual bits properly.
 TEST_F(ComputeKnownBitsTest, ComputeKnownBitsAddWithRangeNoOverlap) {