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.

1 files changed, 54 insertions, 0 deletions

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