re PR tree-optimization/88074 (g++ hangs on math expression)

	PR middle-end/88074
	PR middle-end/89415
	* toplev.c (do_compile): Double the emin/emax exponents to workaround
	buggy mpc_norm.

	* gcc.dg/pr88074-2.c: New test.

From-SVN: r269055

gcc/ChangeLog

+2019-02-20  Jakub Jelinek  <jakub@redhat.com>
+
+	PR middle-end/88074
+	PR middle-end/89415
+	* toplev.c (do_compile): Double the emin/emax exponents to workaround
+	buggy mpc_norm.
+
 2019-02-20  Uroš Bizjak  <ubizjak@gmail.com>
 
 	PR target/89397

gcc/testsuite/ChangeLog

 2019-02-20  Jakub Jelinek  <jakub@redhat.com>
 
+	PR middle-end/88074
+	PR middle-end/89415
+	* gcc.dg/pr88074-2.c: New test.
+
 	PR c++/89336
 	* g++.dg/cpp1y/constexpr-89336-3.C: New test.
 

gcc/testsuite/gcc.dg/pr88074-2.c

+/* PR middle-end/88074 */
+/* { dg-do compile } */
+/* { dg-options "-O2 -fdump-tree-optimized" } */
+/* { dg-add-options float128 } */
+/* { dg-require-effective-target float128 } */
+/* { dg-final { scan-tree-dump-not "link_error " "optimized" } } */
+
+extern void link_error (void);
+int
+main ()
+{
+  if (((__FLT128_MAX__ * 0.5 + __FLT128_MAX__ * 0.5i)
+       / (__FLT128_MAX__ * 0.25 + __FLT128_MAX__ * 0.25i))
+      != (_Complex _Float128) 2)
+    link_error ();
+  return 0;
+}

gcc/toplev.c

@@ -2173,8 +2173,12 @@ do_compile ()
 		  max_exp = fmt->emax;
 	      }
 	  }
-      if (mpfr_set_emin (min_exp)
-	  || mpfr_set_emax (max_exp))
+      /* E.g. mpc_norm assumes it can square a number without bothering with
+	 with range scaling, so until that is fixed, double the minimum
+	 and maximum exponents, plus add some buffer for arithmetics
+	 on the squared numbers.  */
+      if (mpfr_set_emin (2 * (min_exp - 1))
+	  || mpfr_set_emax (2 * (max_exp + 1)))
 	sorry ("mpfr not configured to handle all float modes");
 
       /* Set up the back-end if requested.  */