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* Support excess precision for integer / floating-point comparisons (PR c/87390)
@ 2018-09-26 21:16 Joseph Myers
  2018-09-27 19:24 ` Christophe Lyon
  0 siblings, 1 reply; 5+ messages in thread
From: Joseph Myers @ 2018-09-26 21:16 UTC (permalink / raw)
  To: gcc-patches

In C11, implicit conversions from integer to floating-point types
produce results with the range and precision of the corresponding
evaluation format rather than only those of the type implicitly
converted to.  This patch implements that case of C11 excess precision
semantics in the case of a comparison between integer and
floating-point types, previously missed when implementing other cases
of excess precision for such implicit conversions.  As with other such
fixes, this patch conservatively follows the reading of C99 where
conversions from integer to floating-point do not produce results with
excess precision and so the change is made for C11 mode only.

Bootstrapped with no regressions on x86_64-pc-linux-gnu.  Applied to 
mainline.

gcc/c:
2018-09-26  Joseph Myers  <joseph@codesourcery.com>

	PR c/87390
	* c-typeck.c (build_binary_op): Use excess precision for
	comparisons of integers and floating-point for C11 and later.

gcc/testsuite:
2018-09-26  Joseph Myers  <joseph@codesourcery.com>

	PR c/87390
	* gcc.target/i386/excess-precision-9.c,
	gcc.target/i386/excess-precision-10.c: New tests.

Index: gcc/c/c-typeck.c
===================================================================
--- gcc/c/c-typeck.c	(revision 264650)
+++ gcc/c/c-typeck.c	(working copy)
@@ -11249,6 +11249,20 @@ build_binary_op (location_t location, enum tree_co
     case EXACT_DIV_EXPR:
       may_need_excess_precision = true;
       break;
+
+    case EQ_EXPR:
+    case NE_EXPR:
+    case LE_EXPR:
+    case GE_EXPR:
+    case LT_EXPR:
+    case GT_EXPR:
+      /* Excess precision for implicit conversions of integers to
+	 floating point in C11 and later.  */
+      may_need_excess_precision = (flag_isoc11
+				   && (ANY_INTEGRAL_TYPE_P (type0)
+				       || ANY_INTEGRAL_TYPE_P (type1)));
+      break;
+
     default:
       may_need_excess_precision = false;
       break;
Index: gcc/testsuite/gcc.target/i386/excess-precision-10.c
===================================================================
--- gcc/testsuite/gcc.target/i386/excess-precision-10.c	(nonexistent)
+++ gcc/testsuite/gcc.target/i386/excess-precision-10.c	(working copy)
@@ -0,0 +1,52 @@
+/* Excess precision tests.  Test implicit conversions in comparisons:
+   excess precision in C11 mode.  */
+/* { dg-do run } */
+/* { dg-options "-std=c11 -mfpmath=387 -fexcess-precision=standard" } */
+
+extern void abort (void);
+extern void exit (int);
+
+int
+main (void)
+{
+  float f = 0x1p63f;
+  unsigned long long int u = (1ULL << 63) + 1;
+
+  if ((f == u) != 0)
+    abort ();
+
+  if ((u == f) != 0)
+    abort ();
+
+  if ((f != u) != 1)
+    abort ();
+
+  if ((u != f) != 1)
+    abort ();
+
+  if ((f < u) != 1)
+    abort ();
+
+  if ((u < f) != 0)
+    abort ();
+
+  if ((f <= u) != 1)
+    abort ();
+
+  if ((u <= f) != 0)
+    abort ();
+
+  if ((f > u) != 0)
+    abort ();
+
+  if ((u > f) != 1)
+    abort ();
+
+  if ((f >= u) != 0)
+    abort ();
+
+  if ((u >= f) != 1)
+    abort ();
+
+  exit (0);
+}
Index: gcc/testsuite/gcc.target/i386/excess-precision-9.c
===================================================================
--- gcc/testsuite/gcc.target/i386/excess-precision-9.c	(nonexistent)
+++ gcc/testsuite/gcc.target/i386/excess-precision-9.c	(working copy)
@@ -0,0 +1,52 @@
+/* Excess precision tests.  Test implicit conversions in comparisons:
+   no excess precision in C99 mode.  */
+/* { dg-do run } */
+/* { dg-options "-std=c99 -mfpmath=387 -fexcess-precision=standard" } */
+
+extern void abort (void);
+extern void exit (int);
+
+int
+main (void)
+{
+  float f = 0x1p63f;
+  unsigned long long int u = (1ULL << 63) + 1;
+
+  if ((f == u) != 1)
+    abort ();
+
+  if ((u == f) != 1)
+    abort ();
+
+  if ((f != u) != 0)
+    abort ();
+
+  if ((u != f) != 0)
+    abort ();
+
+  if ((f < u) != 0)
+    abort ();
+
+  if ((u < f) != 0)
+    abort ();
+
+  if ((f <= u) != 1)
+    abort ();
+
+  if ((u <= f) != 1)
+    abort ();
+
+  if ((f > u) != 0)
+    abort ();
+
+  if ((u > f) != 0)
+    abort ();
+
+  if ((f >= u) != 1)
+    abort ();
+
+  if ((u >= f) != 1)
+    abort ();
+
+  exit (0);
+}

-- 
Joseph S. Myers
joseph@codesourcery.com

^ permalink raw reply	[flat|nested] 5+ messages in thread
end of thread, other threads:[~2018-09-28 15:46 UTC | newest]

Thread overview: 5+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2018-09-26 21:16 Support excess precision for integer / floating-point comparisons (PR c/87390) Joseph Myers
2018-09-27 19:24 ` Christophe Lyon
2018-09-27 19:31   ` Joseph Myers
2018-09-28  8:11     ` Christophe Lyon
2018-09-28 15:48       ` Joseph Myers

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