diff --git a/gcc/testsuite/gcc.dg/pr85811.c b/gcc/testsuite/gcc.dg/pr85811.c
new file mode 100644
index 0000000..868f66c
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/pr85811.c
@@ -0,0 +1,15 @@
+/* { dg-do compile } */
+/* { dg-options "-O2 -fdump-tree-optimized" } */
+#include <stdio.h>
+
+int main() {
+  const double negval = -1.0;
+  const double nanval = 0.0 / 0.0;
+  const double val = __builtin_fmax(negval, nanval);
+  const double absval = __builtin_fabs(val);
+  printf("fabs(%.16e) = %.16e\n", val, absval);
+  return absval >= 0 ? 0 : 1;
+}
+
+/* We hope not to see:  printf ("fabs(%.16e) = %.16e\n", val_4, val_4); */
+/* { dg-final { scan-tree-dump-not "val_\[0-9\]*, val_\[0-9\]*" "optimized" } } */
diff --git a/gcc/testsuite/gcc.dg/fold-isfinite-1.c b/gcc/testsuite/gcc.dg/fold-isfinite-1.c
new file mode 100644
index 0000000..2ea0192
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/fold-isfinite-1.c
@@ -0,0 +1,21 @@
+/* { dg-do compile } */
+/* { dg-require-effective-target inf } */
+/* { dg-options "-O2 -fdump-tree-optimized" } */
+
+int foo(int x)
+{
+  return __builtin_finite((double)x);
+}
+
+int foof(int x)
+{
+  return __builtin_finitef((float)x);
+}
+
+int fool(int x)
+{
+  return __builtin_finitel((long double)x);
+}
+
+/* { dg-final { scan-tree-dump-times "_finite" 0 "optimized" } } */
+/* { dg-final { scan-tree-dump-times " u> " 0 "optimized" } } */
diff --git a/gcc/testsuite/gcc.dg/fold-isfinite-2.c b/gcc/testsuite/gcc.dg/fold-isfinite-2.c
new file mode 100644
index 0000000..ff70d8d
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/fold-isfinite-2.c
@@ -0,0 +1,21 @@
+/* { dg-do compile } */
+/* { dg-require-effective-target inf } */
+/* { dg-options "-O2 -fdump-tree-optimized" } */
+
+int foo(unsigned int x)
+{
+  return __builtin_finite((double)x);
+}
+
+int foof(unsigned int x)
+{
+  return __builtin_finitef((float)x);
+}
+
+int fool(unsigned int x)
+{
+  return __builtin_finitel((long double)x);
+}
+
+/* { dg-final { scan-tree-dump-times "_finite" 0 "optimized" } } */
+/* { dg-final { scan-tree-dump-times " u> " 0 "optimized" } } */
diff --git a/gcc/testsuite/gcc.dg/fold-isinf-1.c b/gcc/testsuite/gcc.dg/fold-isinf-1.c
new file mode 100644
index 0000000..485816e
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/fold-isinf-1.c
@@ -0,0 +1,21 @@
+/* { dg-do compile } */
+/* { dg-require-effective-target inf } */
+/* { dg-options "-O2 -fdump-tree-optimized" } */
+
+int foo(int x)
+{
+  return __builtin_isinf((double)x);
+}
+
+int foof(int x)
+{
+  return __builtin_isinff((float)x);
+}
+
+int fool(int x)
+{
+  return __builtin_isinfl((long double)x);
+}
+
+/* { dg-final { scan-tree-dump-times "_isinf" 0 "optimized" } } */
+/* { dg-final { scan-tree-dump-times " u<= " 0 "optimized" } } */
diff --git a/gcc/testsuite/gcc.dg/fold-isinf-2.c b/gcc/testsuite/gcc.dg/fold-isinf-2.c
new file mode 100644
index 0000000..a236ca1
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/fold-isinf-2.c
@@ -0,0 +1,21 @@
+/* { dg-do compile } */
+/* { dg-require-effective-target inf } */
+/* { dg-options "-O2 -fdump-tree-optimized" } */
+
+int foo(unsigned int x)
+{
+  return __builtin_isinf((double)x);
+}
+
+int foof(unsigned int x)
+{
+  return __builtin_isinff((float)x);
+}
+
+int fool(unsigned int x)
+{
+  return __builtin_isinfl((long double)x);
+}
+
+/* { dg-final { scan-tree-dump-times "_isinf" 0 "optimized" } } */
+/* { dg-final { scan-tree-dump-times " u<= " 0 "optimized" } } */
diff --git a/gcc/testsuite/gcc.dg/fold-isnan-1.c b/gcc/testsuite/gcc.dg/fold-isnan-1.c
new file mode 100644
index 0000000..05ee930
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/fold-isnan-1.c
@@ -0,0 +1,21 @@
+/* { dg-do compile } */
+/* { dg-require-effective-target inf } */
+/* { dg-options "-O2 -fdump-tree-optimized" } */
+
+int foo(int x)
+{
+  return __builtin_isnan((double)x);
+}
+
+int foof(int x)
+{
+  return __builtin_isnanf((float)x);
+}
+
+int fool(int x)
+{
+  return __builtin_isnanl((long double)x);
+}
+
+/* { dg-final { scan-tree-dump-times "_isnan" 0 "optimized" } } */
+/* { dg-final { scan-tree-dump-times " unord " 0 "optimized" } } */
diff --git a/gcc/testsuite/gcc.dg/fold-isnan-2.c b/gcc/testsuite/gcc.dg/fold-isnan-2.c
new file mode 100644
index 0000000..32b8833
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/fold-isnan-2.c
@@ -0,0 +1,21 @@
+/* { dg-do compile } */
+/* { dg-require-effective-target inf } */
+/* { dg-options "-O2 -fdump-tree-optimized" } */
+
+int foo(unsigned int x)
+{
+  return __builtin_isnan((double)x);
+}
+
+int foof(unsigned int x)
+{
+  return __builtin_isnanf((float)x);
+}
+
+int fool(unsigned int x)
+{
+  return __builtin_isnanl((long double)x);
+}
+
+/* { dg-final { scan-tree-dump-times "_isnan" 0 "optimized" } } */
+/* { dg-final { scan-tree-dump-times " unord " 0 "optimized" } } */