Fix remquo spurious overflows (bug 17978).

Various remquo implementations, when computing the last three bits of
the quotient, have spurious overflows when 4 times the second argument
to remquo overflows.  These overflows can in turn cause bad results in
rounding modes where that overflow results in a finite value.  This
patch adds tests to avoid the problem multiplications in cases where
they would overflow, similar to those that control an earlier
multiplication by 8.

Tested for x86_64, x86, mips64 and powerpc.

	[BZ #17978]
	* sysdeps/ieee754/dbl-64/s_remquo.c (__remquo): Do not form
	products 4 * y and 2 * y where those would overflow.
	* sysdeps/ieee754/dbl-64/wordsize-64/s_remquo.c (__remquo):
	Likewise.
	* sysdeps/ieee754/flt-32/s_remquof.c (__remquof): Likewise.
	* sysdeps/ieee754/ldbl-128/s_remquol.c (__remquol): Likewise.
	* sysdeps/ieee754/ldbl-128ibm/s_remquol.c (__remquol): Likewise.
	* sysdeps/ieee754/ldbl-96/s_remquol.c (__remquol): Likewise.
	* math/libm-test.inc (remquo_test_data): Add more tests.

9 files changed, 78 insertions, 13 deletions

diff --git a/ChangeLog b/ChangeLog
index c09d9f8148..cde2c5ae1d 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,5 +1,16 @@
 2015-02-16  Joseph Myers  <joseph@codesourcery.com>
 
+	[BZ #17978]
+	* sysdeps/ieee754/dbl-64/s_remquo.c (__remquo): Do not form
+	products 4 * y and 2 * y where those would overflow.
+	* sysdeps/ieee754/dbl-64/wordsize-64/s_remquo.c (__remquo):
+	Likewise.
+	* sysdeps/ieee754/flt-32/s_remquof.c (__remquof): Likewise.
+	* sysdeps/ieee754/ldbl-128/s_remquol.c (__remquol): Likewise.
+	* sysdeps/ieee754/ldbl-128ibm/s_remquol.c (__remquol): Likewise.
+	* sysdeps/ieee754/ldbl-96/s_remquol.c (__remquol): Likewise.
+	* math/libm-test.inc (remquo_test_data): Add more tests.
+
 	* sysdeps/mips/sgidefs.h [!_ABIO64] (_ABIO64): New macro.
 
 	* sysdeps/mips/memcpy.S [_COMPILING_NEWLIB]: Change condition to
diff --git a/NEWS b/NEWS
index 781f7a7bf1..4f4f740af0 100644
--- a/NEWS
+++ b/NEWS
@@ -10,7 +10,7 @@ Version 2.22
 * The following bugs are resolved with this release:
 
   4719, 15467, 15790, 16560, 17569, 17792, 17912, 17932, 17944, 17949,
-  17964, 17965, 17967, 17969.
+  17964, 17965, 17967, 17969, 17978.
 
 Version 2.21
 
diff --git a/math/libm-test.inc b/math/libm-test.inc
index 2f3902a445..1cf80e3379 100644
--- a/math/libm-test.inc
+++ b/math/libm-test.inc
@@ -8764,6 +8764,60 @@ static const struct test_ffI_f1_data remquo_test_data[] =
     TEST_ffI_f1 (remquo, -3419, 360, -179, -1, NO_INEXACT_EXCEPTION),
     TEST_ffI_f1 (remquo, 3419, -360, 179, -1, NO_INEXACT_EXCEPTION),
     TEST_ffI_f1 (remquo, -3419, -360, -179, 1, NO_INEXACT_EXCEPTION),
+
+    TEST_ffI_f1 (remquo, max_value, max_value, plus_zero, 1, NO_INEXACT_EXCEPTION),
+    TEST_ffI_f1 (remquo, max_value, -max_value, plus_zero, -1, NO_INEXACT_EXCEPTION),
+    TEST_ffI_f1 (remquo, max_value, min_value, plus_zero, 0, NO_INEXACT_EXCEPTION),
+    TEST_ffI_f1 (remquo, max_value, -min_value, plus_zero, 0, NO_INEXACT_EXCEPTION),
+    TEST_ffI_f1 (remquo, max_value, min_subnorm_value, plus_zero, 0, NO_INEXACT_EXCEPTION),
+    TEST_ffI_f1 (remquo, max_value, -min_subnorm_value, plus_zero, 0, NO_INEXACT_EXCEPTION),
+    TEST_ffI_f1 (remquo, -max_value, max_value, minus_zero, -1, NO_INEXACT_EXCEPTION),
+    TEST_ffI_f1 (remquo, -max_value, -max_value, minus_zero, 1, NO_INEXACT_EXCEPTION),
+    TEST_ffI_f1 (remquo, -max_value, min_value, minus_zero, 0, NO_INEXACT_EXCEPTION),
+    TEST_ffI_f1 (remquo, -max_value, -min_value, minus_zero, 0, NO_INEXACT_EXCEPTION),
+    TEST_ffI_f1 (remquo, -max_value, min_subnorm_value, minus_zero, 0, NO_INEXACT_EXCEPTION),
+    TEST_ffI_f1 (remquo, -max_value, -min_subnorm_value, minus_zero, 0, NO_INEXACT_EXCEPTION),
+    TEST_ffI_f1 (remquo, min_value, max_value, min_value, 0, NO_INEXACT_EXCEPTION),
+    TEST_ffI_f1 (remquo, min_value, -max_value, min_value, 0, NO_INEXACT_EXCEPTION),
+    TEST_ffI_f1 (remquo, min_value, min_value, plus_zero, 1, NO_INEXACT_EXCEPTION),
+    TEST_ffI_f1 (remquo, min_value, -min_value, plus_zero, -1, NO_INEXACT_EXCEPTION),
+    TEST_ffI_f1 (remquo, min_value, min_subnorm_value, plus_zero, 0, NO_INEXACT_EXCEPTION),
+    TEST_ffI_f1 (remquo, min_value, -min_subnorm_value, plus_zero, 0, NO_INEXACT_EXCEPTION),
+    TEST_ffI_f1 (remquo, -min_value, max_value, -min_value, 0, NO_INEXACT_EXCEPTION),
+    TEST_ffI_f1 (remquo, -min_value, -max_value, -min_value, 0, NO_INEXACT_EXCEPTION),
+    TEST_ffI_f1 (remquo, -min_value, min_value, minus_zero, -1, NO_INEXACT_EXCEPTION),
+    TEST_ffI_f1 (remquo, -min_value, -min_value, minus_zero, 1, NO_INEXACT_EXCEPTION),
+    TEST_ffI_f1 (remquo, -min_value, min_subnorm_value, minus_zero, 0, NO_INEXACT_EXCEPTION),
+    TEST_ffI_f1 (remquo, -min_value, -min_subnorm_value, minus_zero, 0, NO_INEXACT_EXCEPTION),
+    TEST_ffI_f1 (remquo, min_subnorm_value, max_value, min_subnorm_value, 0, NO_INEXACT_EXCEPTION),
+    TEST_ffI_f1 (remquo, min_subnorm_value, -max_value, min_subnorm_value, 0, NO_INEXACT_EXCEPTION),
+    TEST_ffI_f1 (remquo, min_subnorm_value, min_value, min_subnorm_value, 0, NO_INEXACT_EXCEPTION),
+    TEST_ffI_f1 (remquo, min_subnorm_value, -min_value, min_subnorm_value, 0, NO_INEXACT_EXCEPTION),
+    TEST_ffI_f1 (remquo, min_subnorm_value, min_subnorm_value, plus_zero, 1, NO_INEXACT_EXCEPTION),
+    TEST_ffI_f1 (remquo, min_subnorm_value, -min_subnorm_value, plus_zero, -1, NO_INEXACT_EXCEPTION),
+    TEST_ffI_f1 (remquo, -min_subnorm_value, max_value, -min_subnorm_value, 0, NO_INEXACT_EXCEPTION),
+    TEST_ffI_f1 (remquo, -min_subnorm_value, -max_value, -min_subnorm_value, 0, NO_INEXACT_EXCEPTION),
+    TEST_ffI_f1 (remquo, -min_subnorm_value, min_value, -min_subnorm_value, 0, NO_INEXACT_EXCEPTION),
+    TEST_ffI_f1 (remquo, -min_subnorm_value, -min_value, -min_subnorm_value, 0, NO_INEXACT_EXCEPTION),
+    TEST_ffI_f1 (remquo, -min_subnorm_value, min_subnorm_value, minus_zero, -1, NO_INEXACT_EXCEPTION),
+    TEST_ffI_f1 (remquo, -min_subnorm_value, -min_subnorm_value, minus_zero, 1, NO_INEXACT_EXCEPTION),
+
+    TEST_ffI_f1 (remquo, 1, max_value, 1, 0, NO_INEXACT_EXCEPTION),
+    TEST_ffI_f1 (remquo, 1, -max_value, 1, 0, NO_INEXACT_EXCEPTION),
+    TEST_ffI_f1 (remquo, 1, max_value / 2, 1, 0, NO_INEXACT_EXCEPTION),
+    TEST_ffI_f1 (remquo, 1, -max_value / 2, 1, 0, NO_INEXACT_EXCEPTION),
+    TEST_ffI_f1 (remquo, 1, max_value / 4, 1, 0, NO_INEXACT_EXCEPTION),
+    TEST_ffI_f1 (remquo, 1, -max_value / 4, 1, 0, NO_INEXACT_EXCEPTION),
+    TEST_ffI_f1 (remquo, 1, max_value / 8, 1, 0, NO_INEXACT_EXCEPTION),
+    TEST_ffI_f1 (remquo, 1, -max_value / 8, 1, 0, NO_INEXACT_EXCEPTION),
+    TEST_ffI_f1 (remquo, -1, max_value, -1, 0, NO_INEXACT_EXCEPTION),
+    TEST_ffI_f1 (remquo, -1, -max_value, -1, 0, NO_INEXACT_EXCEPTION),
+    TEST_ffI_f1 (remquo, -1, max_value / 2, -1, 0, NO_INEXACT_EXCEPTION),
+    TEST_ffI_f1 (remquo, -1, -max_value / 2, -1, 0, NO_INEXACT_EXCEPTION),
+    TEST_ffI_f1 (remquo, -1, max_value / 4, -1, 0, NO_INEXACT_EXCEPTION),
+    TEST_ffI_f1 (remquo, -1, -max_value / 4, -1, 0, NO_INEXACT_EXCEPTION),
+    TEST_ffI_f1 (remquo, -1, max_value / 8, -1, 0, NO_INEXACT_EXCEPTION),
+    TEST_ffI_f1 (remquo, -1, -max_value / 8, -1, 0, NO_INEXACT_EXCEPTION),
   };
 
 static void
diff --git a/sysdeps/ieee754/dbl-64/s_remquo.c b/sysdeps/ieee754/dbl-64/s_remquo.c
index 2724902908..e07efa89f8 100644
--- a/sysdeps/ieee754/dbl-64/s_remquo.c
+++ b/sysdeps/ieee754/dbl-64/s_remquo.c
@@ -60,12 +60,12 @@ __remquo (double x, double y, int *quo)
   y = fabs (y);
   cquo = 0;
 
-  if (x >= 4 * y)
+  if (hy <= 0x7fcfffff && x >= 4 * y)
     {
       x -= 4 * y;
       cquo += 4;
     }
-  if (x >= 2 * y)
+  if (hy <= 0x7fdfffff && x >= 2 * y)
     {
       x -= 2 * y;
       cquo += 2;
diff --git a/sysdeps/ieee754/dbl-64/wordsize-64/s_remquo.c b/sysdeps/ieee754/dbl-64/wordsize-64/s_remquo.c
index 5b7142576a..ab561780c8 100644
--- a/sysdeps/ieee754/dbl-64/wordsize-64/s_remquo.c
+++ b/sysdeps/ieee754/dbl-64/wordsize-64/s_remquo.c
@@ -59,12 +59,12 @@ __remquo (double x, double y, int *quo)
   INSERT_WORDS64 (y, hy);
   cquo = 0;
 
-  if (x >= 4 * y)
+  if (hy <= UINT64_C(0x7fcfffffffffffff) && x >= 4 * y)
     {
       x -= 4 * y;
       cquo += 4;
     }
-  if (x >= 2 * y)
+  if (hy <= UINT64_C(0x7fdfffffffffffff) && x >= 2 * y)
     {
       x -= 2 * y;
       cquo += 2;
diff --git a/sysdeps/ieee754/flt-32/s_remquof.c b/sysdeps/ieee754/flt-32/s_remquof.c
index a9cdf8fb98..04944fdcd3 100644
--- a/sysdeps/ieee754/flt-32/s_remquof.c
+++ b/sysdeps/ieee754/flt-32/s_remquof.c
@@ -59,12 +59,12 @@ __remquof (float x, float y, int *quo)
   y  = fabsf (y);
   cquo = 0;
 
-  if (x >= 4 * y)
+  if (hy <= 0x7e7fffff && x >= 4 * y)
     {
       x -= 4 * y;
       cquo += 4;
     }
-  if (x >= 2 * y)
+  if (hy <= 0x7effffff && x >= 2 * y)
     {
       x -= 2 * y;
       cquo += 2;
diff --git a/sysdeps/ieee754/ldbl-128/s_remquol.c b/sysdeps/ieee754/ldbl-128/s_remquol.c
index 8543265f1a..da175a14f6 100644
--- a/sysdeps/ieee754/ldbl-128/s_remquol.c
+++ b/sysdeps/ieee754/ldbl-128/s_remquol.c
@@ -61,12 +61,12 @@ __remquol (long double x, long double y, int *quo)
   y  = fabsl (y);
   cquo = 0;
 
-  if (x >= 4 * y)
+  if (hy <= 0x7ffcffffffffffffLL && x >= 4 * y)
     {
       x -= 4 * y;
       cquo += 4;
     }
-  if (x >= 2 * y)
+  if (hy <= 0x7ffdffffffffffffLL && x >= 2 * y)
     {
       x -= 2 * y;
       cquo += 2;
diff --git a/sysdeps/ieee754/ldbl-128ibm/s_remquol.c b/sysdeps/ieee754/ldbl-128ibm/s_remquol.c
index e36af52d77..ac228796b0 100644
--- a/sysdeps/ieee754/ldbl-128ibm/s_remquol.c
+++ b/sysdeps/ieee754/ldbl-128ibm/s_remquol.c
@@ -66,12 +66,12 @@ __remquol (long double x, long double y, int *quo)
   y  = fabsl (y);
   cquo = 0;
 
-  if (x >= 4 * y)
+  if (hy <= 0x7fcfffffffffffffLL && x >= 4 * y)
     {
       x -= 4 * y;
       cquo += 4;
     }
-  if (x >= 2 * y)
+  if (hy <= 0x7fdfffffffffffffLL && x >= 2 * y)
     {
       x -= 2 * y;
       cquo += 2;
diff --git a/sysdeps/ieee754/ldbl-96/s_remquol.c b/sysdeps/ieee754/ldbl-96/s_remquol.c
index 6b3499d257..1462b54456 100644
--- a/sysdeps/ieee754/ldbl-96/s_remquol.c
+++ b/sysdeps/ieee754/ldbl-96/s_remquol.c
@@ -60,12 +60,12 @@ __remquol (long double x, long double p, int *quo)
   p  = fabsl (p);
   cquo = 0;
 
-  if (x >= 4 * p)
+  if (ep <= 0x7ffc && x >= 4 * p)
     {
       x -= 4 * p;
       cquo += 4;
     }
-  if (x >= 2 * p)
+  if (ep <= 0x7ffd && x >= 2 * p)
     {
       x -= 2 * p;
       cquo += 2;