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.

6 files changed, 12 insertions, 12 deletions

diff --git a/sysdeps/ieee754/dbl-64/s_remquo.c b/sysdeps/ieee754/dbl-64/s_remquo.c
index 2724902..e07efa8 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 5b71425..ab56178 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 a9cdf8f..04944fd 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 8543265..da175a1 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 e36af52..ac22879 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 6b3499d..1462b54 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;