diff --git a/llvm/lib/Target/RISCV/RISCVISelLowering.cpp b/llvm/lib/Target/RISCV/RISCVISelLowering.cpp
--- a/llvm/lib/Target/RISCV/RISCVISelLowering.cpp
+++ b/llvm/lib/Target/RISCV/RISCVISelLowering.cpp
@@ -13147,6 +13147,11 @@
       Known.One.setBit(Log2_32(MinVLenB));
     break;
   }
+  case RISCVISD::FPCLASS: {
+    // fclass will only set one of the low 10 bits.
+    Known.Zero.setBitsFrom(10);
+    break;
+  }
   case ISD::INTRINSIC_W_CHAIN:
   case ISD::INTRINSIC_WO_CHAIN: {
     unsigned IntNo =
diff --git a/llvm/test/CodeGen/RISCV/float-intrinsics.ll b/llvm/test/CodeGen/RISCV/float-intrinsics.ll
--- a/llvm/test/CodeGen/RISCV/float-intrinsics.ll
+++ b/llvm/test/CodeGen/RISCV/float-intrinsics.ll
@@ -1755,29 +1755,25 @@
 ; RV32IF-LABEL: isqnan_fpclass:
 ; RV32IF:       # %bb.0:
 ; RV32IF-NEXT:    fclass.s a0, fa0
-; RV32IF-NEXT:    slli a0, a0, 22
-; RV32IF-NEXT:    srli a0, a0, 31
+; RV32IF-NEXT:    srli a0, a0, 9
 ; RV32IF-NEXT:    ret
 ;
 ; RV32IZFINX-LABEL: isqnan_fpclass:
 ; RV32IZFINX:       # %bb.0:
 ; RV32IZFINX-NEXT:    fclass.s a0, a0
-; RV32IZFINX-NEXT:    slli a0, a0, 22
-; RV32IZFINX-NEXT:    srli a0, a0, 31
+; RV32IZFINX-NEXT:    srli a0, a0, 9
 ; RV32IZFINX-NEXT:    ret
 ;
 ; RV64IF-LABEL: isqnan_fpclass:
 ; RV64IF:       # %bb.0:
 ; RV64IF-NEXT:    fclass.s a0, fa0
-; RV64IF-NEXT:    slli a0, a0, 54
-; RV64IF-NEXT:    srli a0, a0, 63
+; RV64IF-NEXT:    srli a0, a0, 9
 ; RV64IF-NEXT:    ret
 ;
 ; RV64IZFINX-LABEL: isqnan_fpclass:
 ; RV64IZFINX:       # %bb.0:
 ; RV64IZFINX-NEXT:    fclass.s a0, a0
-; RV64IZFINX-NEXT:    slli a0, a0, 54
-; RV64IZFINX-NEXT:    srli a0, a0, 63
+; RV64IZFINX-NEXT:    srli a0, a0, 9
 ; RV64IZFINX-NEXT:    ret
 ;
 ; RV32I-LABEL: isqnan_fpclass: