re PR middle-end/64182 (wide-int rounding division is broken)

gcc/
	PR middle-end/64182
	* wide-int.h (wi::div_round, wi::mod_round): Fix rounding of tied
	cases.
	* double-int.c (div_and_round_double): Fix handling of unsigned
	cases.  Use same rounding approach as wide-int.h.

gcc/testsuite/
2014-xx-xx  Richard Sandiford  <richard.sandiford@arm.com>
	    Joseph Myers  <joseph@codesourcery.com>

	PR middle-end/64182
	* gcc.dg/plugin/wide-int-test-1.c,
	gcc.dg/plugin/wide-int_plugin.c: New test.
	* gcc.dg/plugin/plugin.exp: Register it.
	* gnat.dg/round_div.adb: New test.

Co-Authored-By: Joseph Myers <joseph@codesourcery.com>

From-SVN: r218678

gcc/ChangeLog

+2014-12-12  Richard Sandiford  <richard.sandiford@arm.com>
+
+	PR middle-end/64182
+	* wide-int.h (wi::div_round, wi::mod_round): Fix rounding of tied
+	cases.
+	* double-int.c (div_and_round_double): Fix handling of unsigned
+	cases.  Use same rounding approach as wide-int.h.
+
 2014-12-12  Marek Polacek  <polacek@redhat.com>
 
 	PR middle-end/64274

gcc/double-int.c

@@ -569,24 +569,23 @@ div_and_round_double (unsigned code, int uns,
       {
 	unsigned HOST_WIDE_INT labs_rem = *lrem;
 	HOST_WIDE_INT habs_rem = *hrem;
-	unsigned HOST_WIDE_INT labs_den = lden, ltwice;
-	HOST_WIDE_INT habs_den = hden, htwice;
+	unsigned HOST_WIDE_INT labs_den = lden, lnegabs_rem, ldiff;
+	HOST_WIDE_INT habs_den = hden, hnegabs_rem, hdiff;
 
 	/* Get absolute values.  */
-	if (*hrem < 0)
+	if (!uns && *hrem < 0)
 	  neg_double (*lrem, *hrem, &labs_rem, &habs_rem);
-	if (hden < 0)
+	if (!uns && hden < 0)
 	  neg_double (lden, hden, &labs_den, &habs_den);
 
-	/* If (2 * abs (lrem) >= abs (lden)), adjust the quotient.  */
-	mul_double ((HOST_WIDE_INT) 2, (HOST_WIDE_INT) 0,
-		    labs_rem, habs_rem, &ltwice, &htwice);
+	/* If abs(rem) >= abs(den) - abs(rem), adjust the quotient.  */
+	neg_double (labs_rem, habs_rem, &lnegabs_rem, &hnegabs_rem);
+	add_double (labs_den, habs_den, lnegabs_rem, hnegabs_rem,
+		    &ldiff, &hdiff);
 
-	if (((unsigned HOST_WIDE_INT) habs_den
-	     < (unsigned HOST_WIDE_INT) htwice)
-	    || (((unsigned HOST_WIDE_INT) habs_den
-		 == (unsigned HOST_WIDE_INT) htwice)
-		&& (labs_den <= ltwice)))
+	if (((unsigned HOST_WIDE_INT) habs_rem
+	     > (unsigned HOST_WIDE_INT) hdiff)
+	    || (habs_rem == hdiff && labs_rem >= ldiff))
 	  {
 	    if (quo_neg)
 	      /* quo = quo - 1;  */

gcc/testsuite/ChangeLog

+2014-12-12  Richard Sandiford  <richard.sandiford@arm.com>
+	    Joseph Myers  <joseph@codesourcery.com>
+
+	PR middle-end/64182
+	* gcc.dg/plugin/wide-int-test-1.c,
+	gcc.dg/plugin/wide-int_plugin.c: New test.
+	* gcc.dg/plugin/plugin.exp: Register it.
+	* gnat.dg/round_div.adb: New test.
+
 2014-12-12  Jakub Jelinek  <jakub@redhat.com>
 
 	PR tree-optimization/64269

gcc/testsuite/gcc.dg/plugin/plugin.exp

@@ -62,6 +62,7 @@ set plugin_test_list [list \
     { sreal_plugin.c sreal-test-1.c } \
     { start_unit_plugin.c start_unit-test-1.c } \
     { finish_unit_plugin.c finish_unit-test-1.c } \
+    { wide-int_plugin.c wide-int-test-1.c } \
 ]
 
 foreach plugin_test $plugin_test_list {

gcc/testsuite/gcc.dg/plugin/wide-int-test-1.c

+/* Test that pass is inserted and invoked once. */
+/* { dg-do compile } */
+/* { dg-options "-O" } */
+
+int
+main (int argc, char **argv)
+{
+  return 0;
+}

gcc/testsuite/gcc.dg/plugin/wide-int_plugin.c

+#include "config.h"
+#include "gcc-plugin.h"
+#include "system.h"
+#include "coretypes.h"
+#include "tree.h"
+
+int plugin_is_GPL_compatible;
+
+static void
+test_double_int_round_udiv (void)
+{
+  double_int dmin = { 0, HOST_WIDE_INT_MIN };
+  double_int dmax = { -1, HOST_WIDE_INT_MAX };
+  double_int dnegone = { -1, -1 };
+  double_int mod, div;
+  div = dmin.udivmod (dnegone, ROUND_DIV_EXPR, &mod);
+  if (div.low != 1 || div.high != 0
+      || mod.low != 1 || mod.high != HOST_WIDE_INT_MIN)
+    abort ();
+  div = dmax.udivmod (dnegone, ROUND_DIV_EXPR, &mod);
+  if (div.low != 0 || div.high != 0
+      || mod.low != dmax.low || mod.high != dmax.high)
+    abort ();
+}
+
+static void
+test_wide_int_round_sdiv (void)
+{
+  if (wi::ne_p (wi::div_round (2, 3, SIGNED), 1))
+    abort ();
+  if (wi::ne_p (wi::div_round (1, 3, SIGNED), 0))
+    abort ();
+  if (wi::ne_p (wi::mod_round (2, 3, SIGNED), -1))
+    abort ();
+  if (wi::ne_p (wi::mod_round (1, 3, SIGNED), 1))
+    abort ();
+}
+
+int
+plugin_init (struct plugin_name_args *plugin_info,
+	     struct plugin_gcc_version *version)
+{
+  test_double_int_round_udiv ();
+  test_wide_int_round_sdiv ();
+  return 0;
+}

gcc/testsuite/gnat.dg/round_div.adb

+-- { dg-do run }
+-- { dg-options "-O3" }
+procedure Round_Div is
+   type Fixed is delta 1.0 range -2147483648.0 .. 2147483647.0;
+   A : Fixed := 1.0;
+   B : Fixed := 3.0;
+   C : Integer;
+   function Divide (X, Y : Fixed) return Integer is
+   begin
+      return Integer (X / Y);
+   end;
+begin
+   C := Divide (A, B);
+   if C /= 0 then
+      raise Program_Error;
+   end if;
+end Round_Div;

gcc/wide-int.h

@@ -2616,8 +2616,8 @@ wi::div_round (const T1 &x, const T2 &y, signop sgn, bool *overflow)
     {
       if (sgn == SIGNED)
 	{
-	  if (wi::ges_p (wi::abs (remainder),
-			 wi::lrshift (wi::abs (y), 1)))
+	  WI_BINARY_RESULT (T1, T2) abs_remainder = wi::abs (remainder);
+	  if (wi::geu_p (abs_remainder, wi::sub (wi::abs (y), abs_remainder)))
 	    {
 	      if (wi::neg_p (x, sgn) != wi::neg_p (y, sgn))
 		return quotient - 1;
@@ -2627,7 +2627,7 @@ wi::div_round (const T1 &x, const T2 &y, signop sgn, bool *overflow)
 	}
       else
 	{
-	  if (wi::geu_p (remainder, wi::lrshift (y, 1)))
+	  if (wi::geu_p (remainder, wi::sub (y, remainder)))
 	    return quotient + 1;
 	}
     }
@@ -2784,8 +2784,8 @@ wi::mod_round (const T1 &x, const T2 &y, signop sgn, bool *overflow)
     {
       if (sgn == SIGNED)
 	{
-	  if (wi::ges_p (wi::abs (remainder),
-			 wi::lrshift (wi::abs (y), 1)))
+	  WI_BINARY_RESULT (T1, T2) abs_remainder = wi::abs (remainder);
+	  if (wi::geu_p (abs_remainder, wi::sub (wi::abs (y), abs_remainder)))
 	    {
 	      if (wi::neg_p (x, sgn) != wi::neg_p (y, sgn))
 		return remainder + y;
@@ -2795,7 +2795,7 @@ wi::mod_round (const T1 &x, const T2 &y, signop sgn, bool *overflow)
 	}
       else
 	{
-	  if (wi::geu_p (remainder, wi::lrshift (y, 1)))
+	  if (wi::geu_p (remainder, wi::sub (y, remainder)))
 	    return remainder - y;
 	}
     }