From: Georg-Johann Lay <avr@gjlay.de>
Date: Tue, 22 Aug 2017 10:07:51 +0000 (+0000)
Subject: backport: re PR rtl-optimization/75964 (insn combiner removes comparison after ABS)
X-Git-Tag: releases/gcc-5.5.0~105
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=5568877d2c9ae00ea677fab426cf301ae7bbab79;p=thirdparty%2Fgcc.git

backport: re PR rtl-optimization/75964 (insn combiner removes comparison after ABS)

gcc/
	Backport from 2017-05-06 trunk r247719.
	PR rtl-optimization/75964
	* simplify-rtx.c (simplify_const_relational_operation): Remove
	invalid handling of comparisons of integer ABS.
gcc/testsuite/
	Backport from 2017-05-06 trunk r247719.
	PR rtl-optimization/75964
	* gcc.dg/torture/pr75964.c: New test.

From-SVN: r251271
---

diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index bf7af04a3417..fc3d5a57e5e8 100644
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,3 +1,12 @@
+2017-08-22  Georg-Johann Lay  <avr@gjlay.de>
+
+	Backport from trunk r247719.
+	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.
+
 2017-08-22  Georg-Johann Lay  <avr@gjlay.de>
 
 	Backport from 2017-07-05 trunk r249995.
diff --git a/gcc/simplify-rtx.c b/gcc/simplify-rtx.c
index 5f732b279c8c..2388fd0e0b98 100644
--- a/gcc/simplify-rtx.c
+++ b/gcc/simplify-rtx.c
@@ -5117,34 +5117,14 @@ 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 && flag_strict_overflow)))
-	    {
-	      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 && flag_strict_overflow)))
-	    {
-	      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:
diff --git a/gcc/testsuite/ChangeLog b/gcc/testsuite/ChangeLog
index 139ea0c5e3b0..d437045a9373 100644
--- a/gcc/testsuite/ChangeLog
+++ b/gcc/testsuite/ChangeLog
@@ -1,3 +1,11 @@
+2017-08-22  Georg-Johann Lay  <avr@gjlay.de>
+
+	Backport from trunk r247719.
+	2017-05-06  Richard Sandiford  <richard.sandiford@linaro.org>
+
+	PR rtl-optimization/75964
+	* gcc.dg/torture/pr75964.c: New test.
+
 2017-08-22  Georg-Johann Lay  <avr@gjlay.de>
 
 	Backport from 2017-07-05 trunk r249995, r249996.
diff --git a/gcc/testsuite/gcc.dg/torture/pr75964.c b/gcc/testsuite/gcc.dg/torture/pr75964.c
new file mode 100644
index 000000000000..3b895ba7085c
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/torture/pr75964.c
@@ -0,0 +1,28 @@
+/* { 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;
+}