diff --git a/gcc/config/loongarch/loongarch.md b/gcc/config/loongarch/loongarch.md
index f42dc102d10..a275a2d0158 100644
--- a/gcc/config/loongarch/loongarch.md
+++ b/gcc/config/loongarch/loongarch.md
@@ -4193,17 +4193,18 @@ (define_insn "fclass_<fmt>"
   [(set_attr "type" "unknown")
    (set_attr "mode" "<MODE>")])
 
-(define_int_iterator FCLASS_MASK [68 136 952])
+(define_int_iterator FCLASS_MASK [68 136 952 3])
 (define_int_attr fclass_optab
   [(68	"isinf")
    (136	"isnormal")
-   (952	"isfinite")])
+   (952	"isfinite")
+   (3	"isnan")])
 
 (define_expand "<FCLASS_MASK:fclass_optab><ANYF:mode>2"
   [(match_operand:SI   0 "register_operand" "=r")
    (match_operand:ANYF 1 "register_operand" " f")
    (const_int FCLASS_MASK)]
-  "TARGET_HARD_FLOAT"
+  "TARGET_HARD_FLOAT && (<FCLASS_MASK> != 3 || flag_signaling_nans)"
   {
     rtx ft0 = gen_reg_rtx (SImode);
     rtx t0 = gen_reg_rtx (word_mode);
diff --git a/gcc/testsuite/gcc.target/loongarch/fclass-compile.c b/gcc/testsuite/gcc.target/loongarch/fclass-compile.c
index 9c24d6e263c..3db83e7b31d 100644
--- a/gcc/testsuite/gcc.target/loongarch/fclass-compile.c
+++ b/gcc/testsuite/gcc.target/loongarch/fclass-compile.c
@@ -1,14 +1,16 @@
 /* { dg-do compile } */
-/* { dg-options "-O2 -march=loongarch64 -mfpu=64 -mabi=lp64d" } */
+/* { dg-options "-O2 -fsignaling-nans -march=loongarch64 -mfpu=64 -mabi=lp64d" } */
 /* { dg-final { scan-assembler-times "fclass\\.s" 1 } } */
 /* { dg-final { scan-assembler-times "fclass\\.d" 1 } } */
+/* { dg-final { scan-assembler-not "fcmp" } } */
 
 __attribute__ ((noipa)) int
 test_fclass_f (float f)
 {
   return __builtin_isinf (f)
 	 | __builtin_isnormal (f) << 1
-	 | __builtin_isfinite (f) << 2;
+	 | __builtin_isfinite (f) << 2
+	 | __builtin_isnan (f) << 3;
 }
 
 __attribute__ ((noipa)) int
@@ -16,5 +18,6 @@ test_fclass_d (double d)
 {
   return __builtin_isinf (d)
 	 | __builtin_isnormal (d) << 1
-	 | __builtin_isfinite (d) << 2;
+	 | __builtin_isfinite (d) << 2
+	 | __builtin_isnan (d) << 3;
 }
diff --git a/gcc/testsuite/gcc.target/loongarch/fclass-run.c b/gcc/testsuite/gcc.target/loongarch/fclass-run.c
index e5585f9d557..3852d2015b3 100644
--- a/gcc/testsuite/gcc.target/loongarch/fclass-run.c
+++ b/gcc/testsuite/gcc.target/loongarch/fclass-run.c
@@ -37,8 +37,8 @@ main (void)
   ASSERT_EQ (test_fclass_f (-f_normal), 0b110);
   ASSERT_EQ (test_fclass_f (f_subnormal), 0b100);
   ASSERT_EQ (test_fclass_f (-f_subnormal), 0b100);
-  ASSERT_EQ (test_fclass_f (f_qnan), 0);
-  ASSERT_EQ (test_fclass_f (f_snan), 0);
+  ASSERT_EQ (test_fclass_f (f_qnan), 0b1000);
+  ASSERT_EQ (test_fclass_f (f_snan), 0b1000);
 
   ASSERT_EQ (test_fclass_d (d_inf), 0b001);
   ASSERT_EQ (test_fclass_d (-d_inf), 0b001);
@@ -48,6 +48,6 @@ main (void)
   ASSERT_EQ (test_fclass_d (-d_normal), 0b110);
   ASSERT_EQ (test_fclass_d (d_subnormal), 0b100);
   ASSERT_EQ (test_fclass_d (-d_subnormal), 0b100);
-  ASSERT_EQ (test_fclass_d (d_qnan), 0);
-  ASSERT_EQ (test_fclass_d (d_snan), 0);
+  ASSERT_EQ (test_fclass_d (d_qnan), 0b1000);
+  ASSERT_EQ (test_fclass_d (d_snan), 0b1000);
 }