PR 75964: Invalid integer ABS handling in simplify-rtx.c

RTL has no distinction between signed and unsigned values, so it
doesn't make sense to test for signed overflow.

2017-05-06  Richard Sandiford  <richard.sandiford@linaro.org>

gcc/
	PR rtl-optimization/75964
	* simplify-rtx.c (simplify_const_relational_operation): Remove
	invalid handling of comparisons of integer ABS.

gcc/testsuite/
	PR rtl-optimization/75964
	* gcc.dg/torture/pr75964.c: New test.

From-SVN: r247719

gcc/ChangeLog

+2017-05-06  Richard Sandiford  <richard.sandiford@linaro.org>
+
+	PR rtl-optimization/75964
+	* simplify-rtx.c (simplify_const_relational_operation): Remove
+	invalid handling of comparisons of integer ABS.
+
 2017-05-06  Uros Bizjak  <ubizjak@gmail.com>
 
 	* config/i386/i386.c (ext_80387_constant_init): Do not explicitly

gcc/simplify-rtx.c

@@ -5316,34 +5316,14 @@ simplify_const_relational_operation (enum rtx_code code,
 	{
 	case LT:
 	  /* Optimize abs(x) < 0.0.  */
-	  if (!HONOR_SNANS (mode)
-	      && (!INTEGRAL_MODE_P (mode)
-		  || (!flag_wrapv && !flag_trapv)))
-	    {
-	      if (INTEGRAL_MODE_P (mode)
-		  && (issue_strict_overflow_warning
-		      (WARN_STRICT_OVERFLOW_CONDITIONAL)))
-		warning (OPT_Wstrict_overflow,
-			 ("assuming signed overflow does not occur when "
-			  "assuming abs (x) < 0 is false"));
-	       return const0_rtx;
-	    }
+	  if (!INTEGRAL_MODE_P (mode) && !HONOR_SNANS (mode))
+	    return const0_rtx;
 	  break;
 
 	case GE:
 	  /* Optimize abs(x) >= 0.0.  */
-	  if (!HONOR_NANS (mode)
-	      && (!INTEGRAL_MODE_P (mode)
-		  || (!flag_wrapv && !flag_trapv)))
-	    {
-	      if (INTEGRAL_MODE_P (mode)
-	          && (issue_strict_overflow_warning
-	    	  (WARN_STRICT_OVERFLOW_CONDITIONAL)))
-	        warning (OPT_Wstrict_overflow,
-			 ("assuming signed overflow does not occur when "
-			  "assuming abs (x) >= 0 is true"));
-	      return const_true_rtx;
-	    }
+	  if (!INTEGRAL_MODE_P (mode) && !HONOR_NANS (mode))
+	    return const_true_rtx;
 	  break;
 
 	case UNGE:

gcc/testsuite/ChangeLog

+2017-05-06  Richard Sandiford  <richard.sandiford@linaro.org>
+
+	PR rtl-optimization/75964
+	* gcc.dg/torture/pr75964.c: New test.
+
 2017-05-06  Tom de Vries  <tom@codesourcery.com>
 
 	PR testsuite/80606

gcc/testsuite/gcc.dg/torture/pr75964.c

+/* { dg-do run } */
+
+typedef __UINT8_TYPE__ uint8_t;
+
+uint8_t __attribute__ ((noinline, noclone))
+abs8 (uint8_t x)
+{
+  if (x & 0x80)
+    x = -x;
+
+  if (x & 0x80)
+    x = 0x7f;
+
+  return x;
+}
+
+int
+main (void)
+{
+  if (abs8 (0) != 0
+      || abs8 (1) != 1
+      || abs8 (127) != 127
+      || abs8 (128) != 127
+      || abs8 (129) != 127
+      || abs8 (255) != 1)
+    __builtin_abort ();
+  return 0;
+}