Fix fdim handling of infinities (bug 15797).

4 files changed, 43 insertions, 39 deletions

diff --git a/math/libm-test.inc b/math/libm-test.inc
index 25ea33603c..43c4a8fd9c 100644
--- a/math/libm-test.inc
+++ b/math/libm-test.inc
@@ -8144,33 +8144,37 @@ fabs_test (void)
 
 static const struct test_ff_f_data fdim_test_data[] =
   {
-    TEST_ff_f (fdim, 0, 0, 0, NO_INEXACT_EXCEPTION),
-    TEST_ff_f (fdim, 9, 0, 9, NO_INEXACT_EXCEPTION),
-    TEST_ff_f (fdim, 0, 9, 0, NO_INEXACT_EXCEPTION),
-    TEST_ff_f (fdim, -9, 0, 0, NO_INEXACT_EXCEPTION),
-    TEST_ff_f (fdim, 0, -9, 9, NO_INEXACT_EXCEPTION),
-
-    TEST_ff_f (fdim, plus_infty, 9, plus_infty, NO_INEXACT_EXCEPTION),
-    TEST_ff_f (fdim, plus_infty, -9, plus_infty, NO_INEXACT_EXCEPTION),
-    TEST_ff_f (fdim, minus_infty, 9, 0, NO_INEXACT_EXCEPTION),
-    TEST_ff_f (fdim, minus_infty, -9, 0, NO_INEXACT_EXCEPTION),
-    TEST_ff_f (fdim, 9, minus_infty, plus_infty, NO_INEXACT_EXCEPTION),
-    TEST_ff_f (fdim, -9, minus_infty, plus_infty, NO_INEXACT_EXCEPTION),
-    TEST_ff_f (fdim, 9, plus_infty, 0, NO_INEXACT_EXCEPTION),
-    TEST_ff_f (fdim, -9, plus_infty, 0, NO_INEXACT_EXCEPTION),
-
-    TEST_ff_f (fdim, 0, qnan_value, qnan_value, NO_INEXACT_EXCEPTION),
-    TEST_ff_f (fdim, 9, qnan_value, qnan_value, NO_INEXACT_EXCEPTION),
-    TEST_ff_f (fdim, -9, qnan_value, qnan_value, NO_INEXACT_EXCEPTION),
-    TEST_ff_f (fdim, qnan_value, 9, qnan_value, NO_INEXACT_EXCEPTION),
-    TEST_ff_f (fdim, qnan_value, -9, qnan_value, NO_INEXACT_EXCEPTION),
-    TEST_ff_f (fdim, plus_infty, qnan_value, qnan_value, NO_INEXACT_EXCEPTION),
-    TEST_ff_f (fdim, minus_infty, qnan_value, qnan_value, NO_INEXACT_EXCEPTION),
-    TEST_ff_f (fdim, qnan_value, plus_infty, qnan_value, NO_INEXACT_EXCEPTION),
-    TEST_ff_f (fdim, qnan_value, minus_infty, qnan_value, NO_INEXACT_EXCEPTION),
-    TEST_ff_f (fdim, qnan_value, qnan_value, qnan_value, NO_INEXACT_EXCEPTION),
-
-    TEST_ff_f (fdim, plus_infty, plus_infty, 0, NO_INEXACT_EXCEPTION),
+    TEST_ff_f (fdim, 0, 0, 0, NO_INEXACT_EXCEPTION|ERRNO_UNCHANGED),
+    TEST_ff_f (fdim, 9, 0, 9, NO_INEXACT_EXCEPTION|ERRNO_UNCHANGED),
+    TEST_ff_f (fdim, 0, 9, 0, NO_INEXACT_EXCEPTION|ERRNO_UNCHANGED),
+    TEST_ff_f (fdim, -9, 0, 0, NO_INEXACT_EXCEPTION|ERRNO_UNCHANGED),
+    TEST_ff_f (fdim, 0, -9, 9, NO_INEXACT_EXCEPTION|ERRNO_UNCHANGED),
+
+    TEST_ff_f (fdim, plus_infty, 9, plus_infty, NO_INEXACT_EXCEPTION|ERRNO_UNCHANGED),
+    TEST_ff_f (fdim, plus_infty, -9, plus_infty, NO_INEXACT_EXCEPTION|ERRNO_UNCHANGED),
+    TEST_ff_f (fdim, minus_infty, 9, 0, NO_INEXACT_EXCEPTION|ERRNO_UNCHANGED),
+    TEST_ff_f (fdim, minus_infty, -9, 0, NO_INEXACT_EXCEPTION|ERRNO_UNCHANGED),
+    TEST_ff_f (fdim, 9, minus_infty, plus_infty, NO_INEXACT_EXCEPTION|ERRNO_UNCHANGED),
+    TEST_ff_f (fdim, -9, minus_infty, plus_infty, NO_INEXACT_EXCEPTION|ERRNO_UNCHANGED),
+    TEST_ff_f (fdim, 9, plus_infty, 0, NO_INEXACT_EXCEPTION|ERRNO_UNCHANGED),
+    TEST_ff_f (fdim, -9, plus_infty, 0, NO_INEXACT_EXCEPTION|ERRNO_UNCHANGED),
+
+    TEST_ff_f (fdim, 0, qnan_value, qnan_value, NO_INEXACT_EXCEPTION|ERRNO_UNCHANGED),
+    TEST_ff_f (fdim, 9, qnan_value, qnan_value, NO_INEXACT_EXCEPTION|ERRNO_UNCHANGED),
+    TEST_ff_f (fdim, -9, qnan_value, qnan_value, NO_INEXACT_EXCEPTION|ERRNO_UNCHANGED),
+    TEST_ff_f (fdim, qnan_value, 0, qnan_value, NO_INEXACT_EXCEPTION|ERRNO_UNCHANGED),
+    TEST_ff_f (fdim, qnan_value, 9, qnan_value, NO_INEXACT_EXCEPTION|ERRNO_UNCHANGED),
+    TEST_ff_f (fdim, qnan_value, -9, qnan_value, NO_INEXACT_EXCEPTION|ERRNO_UNCHANGED),
+    TEST_ff_f (fdim, plus_infty, qnan_value, qnan_value, NO_INEXACT_EXCEPTION|ERRNO_UNCHANGED),
+    TEST_ff_f (fdim, minus_infty, qnan_value, qnan_value, NO_INEXACT_EXCEPTION|ERRNO_UNCHANGED),
+    TEST_ff_f (fdim, qnan_value, plus_infty, qnan_value, NO_INEXACT_EXCEPTION|ERRNO_UNCHANGED),
+    TEST_ff_f (fdim, qnan_value, minus_infty, qnan_value, NO_INEXACT_EXCEPTION|ERRNO_UNCHANGED),
+    TEST_ff_f (fdim, qnan_value, qnan_value, qnan_value, NO_INEXACT_EXCEPTION|ERRNO_UNCHANGED),
+
+    TEST_ff_f (fdim, plus_infty, plus_infty, 0, NO_INEXACT_EXCEPTION|ERRNO_UNCHANGED),
+    TEST_ff_f (fdim, plus_infty, minus_infty, plus_infty, NO_INEXACT_EXCEPTION|ERRNO_UNCHANGED),
+    TEST_ff_f (fdim, minus_infty, plus_infty, 0, NO_INEXACT_EXCEPTION|ERRNO_UNCHANGED),
+    TEST_ff_f (fdim, minus_infty, minus_infty, 0, NO_INEXACT_EXCEPTION|ERRNO_UNCHANGED),
   };
 
 static void
diff --git a/math/s_fdim.c b/math/s_fdim.c
index 2f97948b2e..f8fd80490d 100644
--- a/math/s_fdim.c
+++ b/math/s_fdim.c
@@ -26,16 +26,16 @@ __fdim (double x, double y)
   int clsx = fpclassify (x);
   int clsy = fpclassify (y);
 
-  if (clsx == FP_NAN || clsy == FP_NAN
-      || (y < 0 && clsx == FP_INFINITE && clsy == FP_INFINITE))
-    /* Raise invalid flag.  */
+  if (clsx == FP_NAN || clsy == FP_NAN)
+    /* Raise invalid flag for signaling but not quiet NaN.  */
     return x - y;
 
   if (x <= y)
     return 0.0;
 
   double r = x - y;
-  if (fpclassify (r) == FP_INFINITE)
+  if (fpclassify (r) == FP_INFINITE
+      && clsx != FP_INFINITE && clsy != FP_INFINITE)
     __set_errno (ERANGE);
 
   return r;
diff --git a/math/s_fdimf.c b/math/s_fdimf.c
index 03810b5728..86efe6ef2a 100644
--- a/math/s_fdimf.c
+++ b/math/s_fdimf.c
@@ -26,16 +26,16 @@ __fdimf (float x, float y)
   int clsx = fpclassify (x);
   int clsy = fpclassify (y);
 
-  if (clsx == FP_NAN || clsy == FP_NAN
-      || (y < 0 && clsx == FP_INFINITE && clsy == FP_INFINITE))
-    /* Raise invalid flag.  */
+  if (clsx == FP_NAN || clsy == FP_NAN)
+    /* Raise invalid flag for signaling but not quiet NaN.  */
     return x - y;
 
   if (x <= y)
     return 0.0f;
 
   float r = x - y;
-  if (fpclassify (r) == FP_INFINITE)
+  if (fpclassify (r) == FP_INFINITE
+      && clsx != FP_INFINITE && clsy != FP_INFINITE)
     __set_errno (ERANGE);
 
   return r;
diff --git a/math/s_fdiml.c b/math/s_fdiml.c
index 56045329af..030fcc22e6 100644
--- a/math/s_fdiml.c
+++ b/math/s_fdiml.c
@@ -26,16 +26,16 @@ __fdiml (long double x, long double y)
   int clsx = fpclassify (x);
   int clsy = fpclassify (y);
 
-  if (clsx == FP_NAN || clsy == FP_NAN
-      || (y < 0 && clsx == FP_INFINITE && clsy == FP_INFINITE))
-    /* Raise invalid flag.  */
+  if (clsx == FP_NAN || clsy == FP_NAN)
+    /* Raise invalid flag for signaling but not quiet NaN.  */
     return x - y;
 
   if (x <= y)
     return 0.0f;
 
   long double r = x - y;
-  if (fpclassify (r) == FP_INFINITE)
+  if (fpclassify (r) == FP_INFINITE
+      && clsx != FP_INFINITE && clsy != FP_INFINITE)
     __set_errno (ERANGE);
 
   return r;