[PATCH] ceil, floor: avoid spurious failure with icc

[Eric Blake]

* tests/test-ceilf2.c (ceilf_reference): Avoid icc's use of DAZ
[denormals-as-zero] when optimizing without -mieee-fp option.
* tests/test-floorf2.c (floorf_reference): Likewise.

Signed-off-by: Eric Blake <address@hidden>
---

This fixes failures of icc without -mieee-fp on test-{ceil,floor}f2.c.
However, it does not fix test-{ceil,floor}f1.c, where my recent testsuite
improvements flushed out the following compiler quirk:

icc -mieee-fp, as well as icc -O0 (which is also implied by icc -g),
emit a call to ceilf(); therefore, if -lm has a working
implementation, then configure detects that it is working, lib/ceil.c
is never compiled, and the test passes.  But icc -O2 (which is the
default with plain icc) recognizes ceilf and inlines it into assembly
code that unfortunately turns -0.0f into 0.0.  Technically, this is
not a bug, since POSIX is explicit that compliance of -0.0f is an
optional feature, if you are not compliant with the <MX> option.

And, since I'm still not sure I want to force -mieee-fp onto all
gnulib projects, that means I'm still scratching my head for a way
to either defeat icc's insistence on inlining ceilf, or I'll have
to tighten m4/ceilf.m4 to detect when icc is being used without full
IEEE compliance.

 ChangeLog            |    5 +++++
 tests/test-ceilf2.c  |    3 +++
 tests/test-floorf2.c |    3 +++
 3 files changed, 11 insertions(+), 0 deletions(-)

diff --git a/ChangeLog b/ChangeLog
index cce182c..b853aad 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,5 +1,10 @@
 2010-11-05  Eric Blake  <address@hidden>

+       ceil, floor: avoid spurious failure with icc
+       * tests/test-ceilf2.c (ceilf_reference): Avoid icc's use of DAZ
+       [denormals-as-zero] when optimizing without -mieee-fp option.
+       * tests/test-floorf2.c (floorf_reference): Likewise.
+
        tests: require working signbit
        * modules/ceilf-tests (Depends-on): Add signbit.
        * modules/ceill-tests (Depends-on): Likewise.
diff --git a/tests/test-ceilf2.c b/tests/test-ceilf2.c
index 705c19a..3455cbf 100644
--- a/tests/test-ceilf2.c
+++ b/tests/test-ceilf2.c
@@ -63,6 +63,9 @@ ceilf_reference (DOUBLE x)

   if (z > L_(0.0))
     {
+      /* Work around ICC's desire to optimize denormal floats to 0.  */
+      if (z < FLT_MIN)
+        return L_(1.0);
       /* Avoid rounding errors for values near 2^k, where k >= MANT_DIG-1.  */
       if (z < TWO_MANT_DIG)
         {
diff --git a/tests/test-floorf2.c b/tests/test-floorf2.c
index b26a508..6811728 100644
--- a/tests/test-floorf2.c
+++ b/tests/test-floorf2.c
@@ -76,6 +76,9 @@ floorf_reference (DOUBLE x)
     }
   else if (z < L_(0.0))
     {
+      /* Work around ICC's desire to optimize denormal floats to 0.  */
+      if (z > -FLT_MIN)
+        return L_(-1.0);
       /* Avoid rounding errors for values near -2^k, where k >= MANT_DIG-1.  */
       if (z > - TWO_MANT_DIG)
         {
-- 
1.7.3.2