[RTL-ifcvt] PR rtl-optimization/67465: Handle pairs of complex+simple blocks and…

[RTL-ifcvt] PR rtl-optimization/67465: Handle pairs of complex+simple blocks and empty blocks more gracefully

        PR rtl-optimization/67456
        PR rtl-optimization/67464
        PR rtl-optimization/67465
        * ifcvt.c (noce_try_cmove_arith): Bail out if cannot conditionally
        move in the mode of x.  Handle combination of complex and simple
        block pairs as well as the case when one is empty.

        * gcc.dg/pr67465.c: New test.

From-SVN: r228194

gcc/ChangeLog

+2015-09-28  Kyrylo Tkachov  <kyrylo.tkachov@arm.com>
+
+	PR rtl-optimization/67456
+	PR rtl-optimization/67464
+	PR rtl-optimization/67465
+	* ifcvt.c (noce_try_cmove_arith): Bail out if cannot conditionally
+	move in the mode of x.  Handle combination of complex and simple
+	block pairs as well as the case when one is empty.
+
 2015-09-28  Trevor Saunders  <tbsaunde+gcc@tbsaunde.org>
 
 	* doc/gimple.texi: Update references to gimple_statement_base.

gcc/ifcvt.c

@@ -1961,6 +1961,11 @@ noce_try_cmove_arith (struct noce_if_info *if_info)
   insn_a = if_info->insn_a;
   insn_b = if_info->insn_b;
 
+  machine_mode x_mode = GET_MODE (x);
+
+  if (!can_conditionally_move_p (x_mode))
+    return FALSE;
+
   unsigned int then_cost;
   unsigned int else_cost;
   if (insn_a)
@@ -1997,13 +2002,38 @@ noce_try_cmove_arith (struct noce_if_info *if_info)
 	}
     }
 
-  if (!a_simple && then_bb && !b_simple && else_bb
+  if (then_bb && else_bb && !a_simple && !b_simple
       && (!bbs_ok_for_cmove_arith (then_bb, else_bb)
 	  || !bbs_ok_for_cmove_arith (else_bb, then_bb)))
     return FALSE;
 
   start_sequence ();
 
+  /* If one of the blocks is empty then the corresponding B or A value
+     came from the test block.  The non-empty complex block that we will
+     emit might clobber the register used by B or A, so move it to a pseudo
+     first.  */
+
+  if (b_simple || !else_bb)
+    {
+      rtx tmp_b = gen_reg_rtx (x_mode);
+      /* Perform the simplest kind of set.  The register allocator
+	 should remove it if it's not actually needed.  If this set is not
+	 a valid insn (can happen on the is_mem path) then end_ifcvt_sequence
+	 will cancel the whole sequence.  Don't try any of the fallback paths
+	 from noce_emit_move_insn since we want this to be the simplest kind
+	 of move.  */
+      emit_insn (gen_rtx_SET (tmp_b, b));
+      b = tmp_b;
+    }
+
+  if (a_simple || !then_bb)
+    {
+      rtx tmp_a = gen_reg_rtx (x_mode);
+      emit_insn (gen_rtx_SET (tmp_a, a));
+      a = tmp_a;
+    }
+
   orig_a = a;
   orig_b = b;
 

gcc/testsuite/ChangeLog

+2015-09-28  Kyrylo Tkachov  <kyrylo.tkachov@arm.com>
+
+	PR rtl-optimization/67456
+	PR rtl-optimization/67464
+	PR rtl-optimization/67465
+	* gcc.dg/pr67465.c: New test.
+
 2015-09-28  Tom de Vries  <tom@codesourcery.com>
 
 	* gcc.dg/vect/pr62171.c: New test.

gcc/testsuite/gcc.dg/pr67465.c

+/* { dg-do run } */
+/* { dg-options "-O3 -std=gnu99" } */
+
+int a, b, c, d, e, h;
+
+int
+fn1 (int p1)
+{
+  {
+    int g[2];
+    for (int i = 0; i < 1; i++)
+      g[i] = 0;
+    if (g[0] < c)
+      {
+	a = (unsigned) (1 ^ p1) % 2;
+	return 0;
+      }
+  }
+  return 0;
+}
+
+void
+fn2 ()
+{
+  for (h = 0; h < 1; h++)
+    {
+      for (int j = 0; j < 2; j++)
+	{
+	  for (b = 1; b; b = 0)
+	    a = 1;
+	  for (; b < 1; b++)
+	    ;
+	  if (e)
+	    continue;
+	  a = 2;
+	}
+      fn1 (h);
+      short k = -16;
+      d = k > a;
+    }
+}
+
+int
+main ()
+{
+  fn2 ();
+
+  if (a != 2)
+    __builtin_abort ();
+
+  return 0;
+}
+