[PATCH] Improve inlining heuristics via estimate_num_insns

[Richard Guenther <rguenth at tat dot physik dot uni-tuebingen dot de>]

Hi!

This patch improves inlining heuristics by tweaking estimate_num_insns 
to return numbers that
  1. are more close to those of gcc 3.4
  2. do not penaltize abstraction.  I.e. the size estimate results in
       inline int foo(int x) { return x*x; }
       int bar(int x) { return foo(x); }
     having the same sizes (actually 1) if foo is inlined in bar.

See http://gcc.gnu.org/ml/gcc/2005-02/msg00981.html for more comparisons
with gcc 3.4 and unpatched gcc 4.0.

The patch needs to tweak gcc.dg/winline-6.c because the size estimate
for t changed from 13 to 10 and we now happily inline q into t because
we use q for the large function growth limit, and 10-10+100 == 100 which
is exactly the size of q.  Fixed by increasing the size of t by one 
which will result in a inlined size of 101 and so we emit the warning.

Bootstrapped and tested on x86_64-unknown-linux-gnu with no regressions.

Ok for 4.0 (suppose it opens)?  Ok for mainline?

Anyone willing to throw their favorite benchmark or SPEC against it?

Thanks,
Richard.


2005-Feb-24  Richard Guenther  <rguenth@gcc.gnu.org>

        * tree-inline.c (estimate_num_insns_1): Ignore stores to decls
	with ignored flag set.

        * gcc.dg/winline-6.c (t): Adjust function body size for changed
        size estimate.

Index: tree-inline.c
===================================================================
RCS file: /cvs/gcc/gcc/gcc/tree-inline.c,v
retrieving revision 1.170
diff -c -3 -p -r1.170 tree-inline.c
*** tree-inline.c	27 Jan 2005 14:36:17 -0000	1.170
--- tree-inline.c	24 Feb 2005 20:07:40 -0000
*************** estimate_num_insns_1 (tree *tp, int *wal
*** 1247,1255 ****
         big arrays.  */
      case INIT_EXPR:
      case MODIFY_EXPR:
        x = TREE_OPERAND (x, 0);
        /* FALLTHRU */
-     case TARGET_EXPR:
      case CONSTRUCTOR:
        {
  	HOST_WIDE_INT size;
--- 1247,1257 ----
         big arrays.  */
      case INIT_EXPR:
      case MODIFY_EXPR:
+     case TARGET_EXPR:
        x = TREE_OPERAND (x, 0);
+       if (DECL_P (x) && DECL_IGNORED_P (x))
+ 	break;
        /* FALLTHRU */
      case CONSTRUCTOR:
        {
  	HOST_WIDE_INT size;
Index: testsuite/gcc.dg/winline-6.c
===================================================================
RCS file: /cvs/gcc/gcc/gcc/testsuite/gcc.dg/winline-6.c,v
retrieving revision 1.1
diff -c -3 -p -r1.1 winline-6.c
*** testsuite/gcc.dg/winline-6.c	4 Jan 2004 14:39:13 -0000	1.1
--- testsuite/gcc.dg/winline-6.c	24 Feb 2005 22:36:08 -0000
*************** inline int q(void)
*** 17,21 ****
  }
  inline int t (void)
  {
! 	return q ();		 /* { dg-warning "called from here" } */
  }
--- 17,21 ----
  }
  inline int t (void)
  {
! 	return q () + 1;	 /* { dg-warning "called from here" } */
  }