Index: llvm/lib/Transforms/Utils/Local.cpp
===================================================================
--- llvm/lib/Transforms/Utils/Local.cpp
+++ llvm/lib/Transforms/Utils/Local.cpp
@@ -3391,6 +3391,11 @@
   if (DemandedBW > ITy->getScalarSizeInBits())
     return false;
 
+  // Check that the bswap/bitreverse will have legal bit width.
+  auto &DL = I->getModule()->getDataLayout();
+  if (DL.isIllegalInteger(DemandedBW))
+    return false;
+
   // Now, is the bit permutation correct for a bswap or a bitreverse? We can
   // only byteswap values with an even number of bytes.
   APInt DemandedMask = APInt::getAllOnes(DemandedBW);
Index: llvm/test/Transforms/InstCombine/bitreverse.ll
===================================================================
--- llvm/test/Transforms/InstCombine/bitreverse.ll
+++ llvm/test/Transforms/InstCombine/bitreverse.ll
@@ -261,6 +261,17 @@
   ret i8 %10
 }
 
+define i32 @illegal_width(i32 %x) {
+; CHECK-LABEL: @illegal_width
+; CHECK-NOT: call i9 @llvm.bitreverse.i9
+  %b0 = and i32 %x, 1
+  %b1 = and i32 %x, 2
+  %shift1 = mul nuw nsw i32 %b1, 64
+  %shift0 = shl nuw nsw i32 %b0, 8
+  %reverse = add i32 %shift0, %shift1
+  ret i32 %reverse
+}
+
 define i4 @shuf_4bits(<4 x i1> %x) {
 ; CHECK-LABEL: @shuf_4bits(
 ; CHECK-NEXT:    [[TMP1:%.*]] = bitcast <4 x i1> [[X:%.*]] to i4