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

	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

diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index 329954b..fb9a555 100644 (file)
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,3 +1,9 @@
+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

diff --git a/gcc/expmed.c b/gcc/expmed.c
index b7f55a7..d7f8e9a 100644 (file)
--- a/gcc/expmed.c
+++ b/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);
+           }
        }
     }
 

diff --git a/gcc/testsuite/ChangeLog b/gcc/testsuite/ChangeLog
index 3536cf1..19c319e 100644 (file)
--- a/gcc/testsuite/ChangeLog
+++ b/gcc/testsuite/ChangeLog
@@ -1,3 +1,8 @@
+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

diff --git a/gcc/testsuite/gcc.dg/pr89679.c b/gcc/testsuite/gcc.dg/pr89679.c
new file mode 100644 (file)
index 0000000..0d6e2d2
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/pr89679.c
@@ -0,0 +1,26 @@
+/* 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;
+}