re PR rtl-optimization/89679 (wrong code with -Og -frerun-cse-after-loop -fno-tree-fre)

	PR rtl-optimization/89679
	* expmed.c (expand_mult_const): Don't add a REG_EQUAL note if it
	would contain a paradoxical SUBREG.

	* gcc.dg/pr89679.c: New test.

From-SVN: r269680

gcc/ChangeLog

+2019-03-14  Jakub Jelinek  <jakub@redhat.com>
+
+	PR rtl-optimization/89679
+	* expmed.c (expand_mult_const): Don't add a REG_EQUAL note if it
+	would contain a paradoxical SUBREG.
+
 2019-03-14  Richard Biener  <rguenther@suse.de>
 
 	PR tree-optimization/89710

gcc/expmed.c

@@ -3356,13 +3356,20 @@ expand_mult_const (machine_mode mode, rtx op0, HOST_WIDE_INT val,
 	      tem = gen_lowpart (nmode, op0);
 	    }
 
-	  insn = get_last_insn ();
-	  wide_int wval_so_far
-	    = wi::uhwi (val_so_far,
-			GET_MODE_PRECISION (as_a <scalar_mode> (nmode)));
-	  rtx c = immed_wide_int_const (wval_so_far, nmode);
-	  set_dst_reg_note (insn, REG_EQUAL, gen_rtx_MULT (nmode, tem, c),
-			    accum_inner);
+	  /* Don't add a REG_EQUAL note if tem is a paradoxical SUBREG.
+	     In that case, only the low bits of accum would be guaranteed to
+	     be equal to the content of the REG_EQUAL note, the upper bits
+	     can be anything.  */
+	  if (!paradoxical_subreg_p (tem))
+	    {
+	      insn = get_last_insn ();
+	      wide_int wval_so_far
+		= wi::uhwi (val_so_far,
+			    GET_MODE_PRECISION (as_a <scalar_mode> (nmode)));
+	      rtx c = immed_wide_int_const (wval_so_far, nmode);
+	      set_dst_reg_note (insn, REG_EQUAL, gen_rtx_MULT (nmode, tem, c),
+				accum_inner);
+	    }
 	}
     }
 

gcc/testsuite/ChangeLog

+2019-03-14  Jakub Jelinek  <jakub@redhat.com>
+
+	PR rtl-optimization/89679
+	* gcc.dg/pr89679.c: New test.
+
 2019-03-14  Richard Biener  <rguenther@suse.de>
 
 	PR tree-optimization/89710

gcc/testsuite/gcc.dg/pr89679.c

+/* PR rtl-optimization/89679 */
+/* { dg-do run } */
+/* { dg-options "-Og -frerun-cse-after-loop -fno-tree-fre" } */
+
+unsigned short g;
+
+void
+foo (unsigned long long x)
+{
+  if (x != 0xffff)
+    __builtin_abort ();
+}
+
+int
+main ()
+{
+#if __SIZEOF_SHORT__ == 2 && __SIZEOF_INT__ == 4 && __CHAR_BIT__ == 8
+  unsigned short d = 0;
+  unsigned long long x, c = ~0;
+  c = c >> d;
+  __builtin_memset (&d, c, 2);
+  x = d + g;
+  foo (x);
+#endif
+  return 0;
+}