Fix UBSAN in postreload-gcse.c (PR rtl-optimization/87868).

2018-11-07  Martin Liska  <mliska@suse.cz>

	PR rtl-optimization/87868
	* postreload-gcse.c (eliminate_partially_redundant_load): Set
	threshold to max_count if we would overflow.
	* profile-count.h: Make max_count a public constant.

From-SVN: r265869

gcc/ChangeLog

 2018-11-07  Martin Liska  <mliska@suse.cz>
 
+	PR rtl-optimization/87868
+	* postreload-gcse.c (eliminate_partially_redundant_load): Set
+	threshold to max_count if we would overflow.
+	* profile-count.h: Make max_count a public constant.
+
+2018-11-07  Martin Liska  <mliska@suse.cz>
+
 	* mem-stats.h: Fix GNU coding style.
 
 2018-11-07  Chenghua Xu  <paul.hua.gm@gmail.com>

gcc/postreload-gcse.c

@@ -1170,8 +1170,18 @@ eliminate_partially_redundant_load (basic_block bb, rtx_insn *insn,
   if (ok_count.to_gcov_type ()
       < GCSE_AFTER_RELOAD_PARTIAL_FRACTION * not_ok_count.to_gcov_type ())
     goto cleanup;
-  if (ok_count.to_gcov_type ()
-      < GCSE_AFTER_RELOAD_CRITICAL_FRACTION * critical_count.to_gcov_type ())
+
+  gcov_type threshold;
+#if (GCC_VERSION >= 5000)
+  if (__builtin_mul_overflow (GCSE_AFTER_RELOAD_CRITICAL_FRACTION,
+			      critical_count.to_gcov_type (), &threshold))
+    threshold = profile_count::max_count;
+#else
+  threshold
+    = GCSE_AFTER_RELOAD_CRITICAL_FRACTION * critical_count.to_gcov_type ();
+#endif
+
+  if (ok_count.to_gcov_type () < threshold)
     goto cleanup;
 
   /* Generate moves to the loaded register from where

gcc/profile-count.h

@@ -641,8 +641,8 @@ public:
      type to hold various extra stages.  */
 
   static const int n_bits = 61;
-private:
   static const uint64_t max_count = ((uint64_t) 1 << n_bits) - 2;
+private:
   static const uint64_t uninitialized_count = ((uint64_t) 1 << n_bits) - 1;
 
   uint64_t m_val : n_bits;