Patchwork Use get_range_info during number of iterations analysis

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Submitter Jakub Jelinek
Date Nov. 7, 2013, 2:32 p.m.
Message ID <20131107143237.GC27813@tucnak.zalov.cz>
Download mbox | patch
Permalink /patch/289369/
State New
Headers show

Comments

Jakub Jelinek - Nov. 7, 2013, 2:32 p.m.
On Wed, Nov 06, 2013 at 03:21:04PM -0700, Jeff Law wrote:
> >2013-11-06  Jakub Jelinek  <jakub@redhat.com>
> >
> >	* tree-ssa-loop-niter.c: Include tree-ssanames.h.
> >	(determine_value_range): Add loop argument.  Use get_range_info to
> >	improve range.
> >	(bound_difference): Adjust caller.
> Clever, using the range from the PHI in the loop header.  While it
> may be too wide, it's likely going to be a lot better than nothing.
> 
> Add a testcase and this is OK.

Ok, thanks, here is what I've committed after another bootstrap/regtest.

2013-11-07  Jakub Jelinek  <jakub@redhat.com>

	* tree-ssa-loop-niter.c: Include tree-ssanames.h.
	(determine_value_range): Add loop argument.  Use get_range_info to
	improve range.
	(bound_difference): Adjust caller.

	* gcc.dg/tree-ssa/loop-39.c: New test.


	Jakub

Patch

--- gcc/tree-ssa-loop-niter.c.jj	2013-10-24 10:19:21.000000000 +0200
+++ gcc/tree-ssa-loop-niter.c	2013-11-07 11:49:37.568083138 +0100
@@ -45,6 +45,7 @@  along with GCC; see the file COPYING3.
 #include "diagnostic-core.h"
 #include "tree-inline.h"
 #include "tree-pass.h"
+#include "tree-ssanames.h"
 
 
 #define SWAP(X, Y) do { affine_iv *tmp = (X); (X) = (Y); (Y) = tmp; } while (0)
@@ -119,9 +120,12 @@  split_to_var_and_offset (tree expr, tree
    in TYPE to MIN and MAX.  */
 
 static void
-determine_value_range (tree type, tree var, mpz_t off,
+determine_value_range (struct loop *loop, tree type, tree var, mpz_t off,
 		       mpz_t min, mpz_t max)
 {
+  double_int minv, maxv;
+  enum value_range_type rtype = VR_VARYING;
+
   /* If the expression is a constant, we know its value exactly.  */
   if (integer_zerop (var))
     {
@@ -130,9 +134,73 @@  determine_value_range (tree type, tree v
       return;
     }
 
+  get_type_static_bounds (type, min, max);
+
+  /* See if we have some range info from VRP.  */
+  if (TREE_CODE (var) == SSA_NAME && INTEGRAL_TYPE_P (type))
+    {
+      edge e = loop_preheader_edge (loop);
+      gimple_stmt_iterator gsi;
+
+      /* Either for VAR itself...  */
+      rtype = get_range_info (var, &minv, &maxv);
+      /* Or for PHI results in loop->header where VAR is used as
+	 PHI argument from the loop preheader edge.  */
+      for (gsi = gsi_start_phis (loop->header); !gsi_end_p (gsi); gsi_next (&gsi))
+	{
+	  gimple phi = gsi_stmt (gsi);
+	  double_int minc, maxc;
+	  if (PHI_ARG_DEF_FROM_EDGE (phi, e) == var
+	      && (get_range_info (gimple_phi_result (phi), &minc, &maxc)
+		  == VR_RANGE))
+	    {
+	      if (rtype != VR_RANGE)
+		{
+		  rtype = VR_RANGE;
+		  minv = minc;
+		  maxv = maxc;
+		}
+	      else
+		{
+		  minv = minv.max (minc, TYPE_UNSIGNED (type));
+		  maxv = maxv.min (maxc, TYPE_UNSIGNED (type));
+		  gcc_assert (minv.cmp (maxv, TYPE_UNSIGNED (type)) <= 0);
+		}
+	    }
+	}
+      if (rtype == VR_RANGE)
+	{
+	  mpz_t minm, maxm;
+	  gcc_assert (minv.cmp (maxv, TYPE_UNSIGNED (type)) <= 0);
+	  mpz_init (minm);
+	  mpz_init (maxm);
+	  mpz_set_double_int (minm, minv, TYPE_UNSIGNED (type));
+	  mpz_set_double_int (maxm, maxv, TYPE_UNSIGNED (type));
+	  mpz_add (minm, minm, off);
+	  mpz_add (maxm, maxm, off);
+	  /* If the computation may not wrap or off is zero, then this
+	     is always fine.  If off is negative and minv + off isn't
+	     smaller than type's minimum, or off is positive and
+	     maxv + off isn't bigger than type's maximum, use the more
+	     precise range too.  */
+	  if (nowrap_type_p (type)
+	      || mpz_sgn (off) == 0
+	      || (mpz_sgn (off) < 0 && mpz_cmp (minm, min) >= 0)
+	      || (mpz_sgn (off) > 0 && mpz_cmp (maxm, max) <= 0))
+	    {
+	      mpz_set (min, minm);
+	      mpz_set (max, maxm);
+	      mpz_clear (minm);
+	      mpz_clear (maxm);
+	      return;
+	    }
+	  mpz_clear (minm);
+	  mpz_clear (maxm);
+	}
+    }
+
   /* If the computation may wrap, we know nothing about the value, except for
      the range of the type.  */
-  get_type_static_bounds (type, min, max);
   if (!nowrap_type_p (type))
     return;
 
@@ -405,8 +473,8 @@  bound_difference (struct loop *loop, tre
       mpz_init (maxx);
       mpz_init (miny);
       mpz_init (maxy);
-      determine_value_range (type, varx, offx, minx, maxx);
-      determine_value_range (type, vary, offy, miny, maxy);
+      determine_value_range (loop, type, varx, offx, minx, maxx);
+      determine_value_range (loop, type, vary, offy, miny, maxy);
 
       mpz_sub (bnds->below, minx, maxy);
       mpz_sub (bnds->up, maxx, miny);
--- gcc/testsuite/gcc.dg/tree-ssa/loop-39.c.jj	2013-11-07 11:52:01.871309995 +0100
+++ gcc/testsuite/gcc.dg/tree-ssa/loop-39.c	2013-11-07 11:54:30.549496152 +0100
@@ -0,0 +1,26 @@ 
+/* { dg-do compile } */
+/* { dg-options "-O2 -fdump-tree-sccp-details" } */
+
+int
+foo (unsigned int n)
+{
+  int i, r = 1;
+  if (n > 0)
+    {
+      asm ("");
+      if (n < 10)
+	{
+	  asm ("");
+	  do
+	    {
+	      --n;
+	      r *= 2;
+	    }
+	  while (n > 0);
+	}
+    }
+  return r + n;
+}
+
+/* { dg-final { scan-tree-dump "# of iterations \[^\n\r]*, bounded by 8" "sccp" } } */
+/* { dg-final { cleanup-tree-dump "sccp" } } */