[PATCH] Fix RTL DSE (PR rtl-optimization/68955, take 2)

[Jakub Jelinek]

On Mon, Jan 18, 2016 at 11:40:23AM +0100, Eric Botcazou wrote:
> > So, do you suggest to tweak get_addr like the patch below, and remove the
> >   mem_addr = get_addr (mem_addr);
> > line above and the comment?
> 
> Yes, exactly.  And if that doesn't easily work, then go for your solution and 
> add a blurb to the comment explaining why get_addr cannot be easily changed.

Bootstrap/regtest passed on x86_64-linux and i686-linux, ok for trunk?

No changes in DSE locally_deleted/globally_deleted statistics from
x86_64-linux and i686-linux bootstraps/regtests seen (unpatched vs patched
compiler), other than in the testcase from this PR on i686-linux -O3 -g,
and varying number of compilations of struct-layout-1_generate.c (but always
the same number of DSE deleted insns in them) due to make -jN -k check
(the generator # of compilations/invocations depends on scheduling of
the make check tasks, unlike the number of actual testings).

2016-01-19  Jakub Jelinek  <jakub@redhat.com>

	PR rtl-optimization/68955
	PR rtl-optimization/64557
	* dse.c (record_store, check_mem_read_rtx): Don't call get_addr
	here.  Fix up formatting.
	* alias.c (get_addr): Handle VALUE + CONST_INT.

	* gcc.dg/torture/pr68955.c: New test.

--- gcc/dse.c.jj	2016-01-15 20:37:24.000000000 +0100
+++ gcc/dse.c	2016-01-18 12:18:04.115988214 +0100
@@ -1515,14 +1515,9 @@ record_store (rtx body, bb_info_t bb_inf
 	mem_addr = base->val_rtx;
       else
 	{
-	  group_info *group
-	    = rtx_group_vec[group_id];
+	  group_info *group = rtx_group_vec[group_id];
 	  mem_addr = group->canon_base_addr;
 	}
-      /* get_addr can only handle VALUE but cannot handle expr like:
-	 VALUE + OFFSET, so call get_addr to get original addr for
-	 mem_addr before plus_constant.  */
-      mem_addr = get_addr (mem_addr);
       if (offset)
 	mem_addr = plus_constant (get_address_mode (mem), mem_addr, offset);
     }
@@ -2128,14 +2123,9 @@ check_mem_read_rtx (rtx *loc, bb_info_t
 	mem_addr = base->val_rtx;
       else
 	{
-	  group_info *group
-	    = rtx_group_vec[group_id];
+	  group_info *group = rtx_group_vec[group_id];
 	  mem_addr = group->canon_base_addr;
 	}
-      /* get_addr can only handle VALUE but cannot handle expr like:
-	 VALUE + OFFSET, so call get_addr to get original addr for
-	 mem_addr before plus_constant.  */
-      mem_addr = get_addr (mem_addr);
       if (offset)
 	mem_addr = plus_constant (get_address_mode (mem), mem_addr, offset);
     }
--- gcc/alias.c.jj	2016-01-14 17:01:09.000000000 +0100
+++ gcc/alias.c	2016-01-18 10:30:46.780994699 +0100
@@ -2203,7 +2203,23 @@ get_addr (rtx x)
   struct elt_loc_list *l;
 
   if (GET_CODE (x) != VALUE)
-    return x;
+    {
+      if ((GET_CODE (x) == PLUS || GET_CODE (x) == MINUS)
+	  && GET_CODE (XEXP (x, 0)) == VALUE
+	  && CONST_SCALAR_INT_P (XEXP (x, 1)))
+	{
+	  rtx op0 = get_addr (XEXP (x, 0));
+	  if (op0 != XEXP (x, 0))
+	    {
+	      if (GET_CODE (x) == PLUS
+		  && GET_CODE (XEXP (x, 1)) == CONST_INT)
+		return plus_constant (GET_MODE (x), op0, INTVAL (XEXP (x, 1)));
+	      return simplify_gen_binary (GET_CODE (x), GET_MODE (x),
+					  op0, XEXP (x, 1));
+	    }
+	}
+      return x;
+    }
   v = CSELIB_VAL_PTR (x);
   if (v)
     {
--- gcc/testsuite/gcc.dg/torture/pr68955.c.jj	2016-01-18 12:18:31.254612960 +0100
+++ gcc/testsuite/gcc.dg/torture/pr68955.c	2016-01-18 12:18:31.254612960 +0100
@@ -0,0 +1,41 @@
+/* PR rtl-optimization/68955 */
+/* { dg-do run } */
+/* { dg-output "ONE1ONE" } */
+
+int a, b, c, d, g, m;
+int i[7][7][5] = { { { 5 } }, { { 5 } },
+		   { { 5 }, { 5 }, { 5 }, { 5 }, { 5 }, { -1 } } };
+static int j = 11;
+short e, f, h, k, l;
+
+static void
+foo ()
+{
+  for (; e < 5; e++)
+    for (h = 3; h; h--)
+      {
+	for (g = 1; g < 6; g++)
+	  {
+	    m = c == 0 ? b : b / c;
+	    i[e][1][e] = i[1][1][1] | (m & l) && f;
+	  }
+	for (k = 0; k < 6; k++)
+	  {
+	    for (d = 0; d < 6; d++)
+	      i[1][e][h] = i[h][k][e] >= l;
+	    i[e + 2][h + 3][e] = 6 & l;
+	    i[2][1][2] = a;
+	    for (; j < 5;)
+	      for (;;)
+		;
+	  }
+      }
+}
+
+int
+main ()
+{
+  foo ();
+  __builtin_printf ("ONE%dONE\n", i[1][0][2]);
+  return 0;
+}


	Jakub