From: Jakub Jelinek <jakub@redhat.com>
Date: Wed, 7 Feb 2018 08:29:58 +0000 (+0100)
Subject: re PR tree-optimization/84235 (Miscompilation of floating point code by dom2)
X-Git-Url: https://git.libre-soc.org/?a=commitdiff_plain;h=40ff1a2d1dd5ab23649e2df91a11534f3e654ace;p=gcc.git

re PR tree-optimization/84235 (Miscompilation of floating point code by dom2)

	PR tree-optimization/84235
	* tree-ssa-scopedtables.c
	(avail_exprs_stack::simplify_binary_operation): Fir MINUS_EXPR, punt
	if the subtraction is performed in floating point type where NaNs are
	honored.  For *DIV_EXPR, punt for ALL_FRACT_MODE_Ps where we can't
	build 1.  Formatting fix.

	* gcc.c-torture/execute/ieee/pr84235.c: New test.

From-SVN: r257437
---

diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index 8edc8cc84a1..088aa477574 100644
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,3 +1,12 @@
+2018-02-07  Jakub Jelinek  <jakub@redhat.com>
+
+	PR tree-optimization/84235
+	* tree-ssa-scopedtables.c
+	(avail_exprs_stack::simplify_binary_operation): Fir MINUS_EXPR, punt
+	if the subtraction is performed in floating point type where NaNs are
+	honored.  For *DIV_EXPR, punt for ALL_FRACT_MODE_Ps where we can't
+	build 1.  Formatting fix.
+
 2018-02-06  Jakub Jelinek  <jakub@redhat.com>
 
 	PR target/84146
diff --git a/gcc/testsuite/ChangeLog b/gcc/testsuite/ChangeLog
index a32ef377294..ac3949a3b02 100644
--- a/gcc/testsuite/ChangeLog
+++ b/gcc/testsuite/ChangeLog
@@ -1,3 +1,8 @@
+2018-02-07  Jakub Jelinek  <jakub@redhat.com>
+
+	PR tree-optimization/84235
+	* gcc.c-torture/execute/ieee/pr84235.c: New test.
+
 2018-02-07  Rainer Orth  <ro@CeBiTec.Uni-Bielefeld.DE>
 
 	PR testsuite/84243
diff --git a/gcc/testsuite/gcc.c-torture/execute/ieee/pr84235.c b/gcc/testsuite/gcc.c-torture/execute/ieee/pr84235.c
new file mode 100644
index 00000000000..479b2b0f6ab
--- /dev/null
+++ b/gcc/testsuite/gcc.c-torture/execute/ieee/pr84235.c
@@ -0,0 +1,11 @@
+/* PR tree-optimization/84235 */
+
+int
+main ()
+{
+  double d = 1.0 / 0.0;
+  _Bool b = d == d && (d - d) != (d - d);
+  if (!b)
+    __builtin_abort ();
+  return 0;
+}
diff --git a/gcc/tree-ssa-scopedtables.c b/gcc/tree-ssa-scopedtables.c
index 47cca782595..2a40fdae0a2 100644
--- a/gcc/tree-ssa-scopedtables.c
+++ b/gcc/tree-ssa-scopedtables.c
@@ -182,8 +182,15 @@ avail_exprs_stack::simplify_binary_operation (gimple *stmt,
 		      case BIT_AND_EXPR:
 			return gimple_assign_rhs1 (stmt);
 
-		      case BIT_XOR_EXPR:
 		      case MINUS_EXPR:
+			/* This is unsafe for certain floats even in non-IEEE
+			   formats.  In IEEE, it is unsafe because it does
+			   wrong for NaNs.  */
+			if (FLOAT_TYPE_P (result_type)
+			    && HONOR_NANS (result_type))
+			  break;
+			/* FALLTHRU */
+		      case BIT_XOR_EXPR:
 		      case TRUNC_MOD_EXPR:
 		      case CEIL_MOD_EXPR:
 		      case FLOOR_MOD_EXPR:
@@ -195,6 +202,9 @@ avail_exprs_stack::simplify_binary_operation (gimple *stmt,
 		      case FLOOR_DIV_EXPR:
 		      case ROUND_DIV_EXPR:
 		      case EXACT_DIV_EXPR:
+			/* Avoid _Fract types where we can't build 1.  */
+			if (ALL_FRACT_MODE_P (TYPE_MODE (result_type)))
+			  break;
 			return build_one_cst (result_type);
 
 		      default:
@@ -204,8 +214,8 @@ avail_exprs_stack::simplify_binary_operation (gimple *stmt,
 		break;
 	      }
 
-	      default:
-		break;
+	    default:
+	      break;
 	    }
 	}
     }