[PATCH] Fix PR40460, exponential behavior in SCEV
Richard Guenther
rguenther@suse.de
Tue Jun 16 15:05:00 GMT 2009
This fixes another exponential behavior in SCEV. The issue is that
we create arbitrarily complex exponential CHRECs during
chrec_fold_multiply_poly_poly because we do not bail out from
build_polynomial_chrec with the no_evolution_in_loop_p test if
that cannot compute its property.
Maybe the following is then the correct fix.
Bootstrapped on x86_64-unknown-linux-gnu, tests still running.
Sebastian, does this look like the correct approach? (See the PR
for more details).
Thanks,
Richard.
2009-06-16 Richard Guenther <rguenther@suse.de>
PR middle-end/40460
* tree-chrec.h (build_polynomial_chrec): If we cannot determine
if there is no evolution of left in the loop bail out.
* tree-chrec.c (chrec_fold_multiply_poly_poly): CSE one
chrec_fold_multiply.
* g++.dg/torture/pr40460.C: New testcase.
Index: gcc/tree-chrec.h
===================================================================
*** gcc/tree-chrec.h (revision 148523)
--- gcc/tree-chrec.h (working copy)
*************** build_polynomial_chrec (unsigned loop_nu
*** 132,138 ****
|| right == chrec_dont_know)
return chrec_dont_know;
! if (no_evolution_in_loop_p (left, loop_num, &val) && !val)
return chrec_dont_know;
/* Pointer types should occur only on the left hand side, i.e. in
--- 132,139 ----
|| right == chrec_dont_know)
return chrec_dont_know;
! if (!no_evolution_in_loop_p (left, loop_num, &val)
! || !val)
return chrec_dont_know;
/* Pointer types should occur only on the left hand side, i.e. in
Index: gcc/tree-chrec.c
===================================================================
*** gcc/tree-chrec.c (revision 148523)
--- gcc/tree-chrec.c (working copy)
*************** chrec_fold_multiply_poly_poly (tree type
*** 220,235 ****
/* "a*c". */
t0 = chrec_fold_multiply (type, CHREC_LEFT (poly0), CHREC_LEFT (poly1));
! /* "a*d + b*c + b*d". */
t1 = chrec_fold_multiply (type, CHREC_LEFT (poly0), CHREC_RIGHT (poly1));
t1 = chrec_fold_plus (type, t1, chrec_fold_multiply (type,
CHREC_RIGHT (poly0),
CHREC_LEFT (poly1)));
! t1 = chrec_fold_plus (type, t1, chrec_fold_multiply (type,
! CHREC_RIGHT (poly0),
! CHREC_RIGHT (poly1)));
! /* "2*b*d". */
t2 = chrec_fold_multiply (type, CHREC_RIGHT (poly0), CHREC_RIGHT (poly1));
t2 = chrec_fold_multiply (type, SCALAR_FLOAT_TYPE_P (type)
? build_real (type, dconst2)
: build_int_cst (type, 2), t2);
--- 220,235 ----
/* "a*c". */
t0 = chrec_fold_multiply (type, CHREC_LEFT (poly0), CHREC_LEFT (poly1));
! /* "a*d + b*c". */
t1 = chrec_fold_multiply (type, CHREC_LEFT (poly0), CHREC_RIGHT (poly1));
t1 = chrec_fold_plus (type, t1, chrec_fold_multiply (type,
CHREC_RIGHT (poly0),
CHREC_LEFT (poly1)));
! /* "b*d". */
t2 = chrec_fold_multiply (type, CHREC_RIGHT (poly0), CHREC_RIGHT (poly1));
+ /* "a*d + b*c + b*d". */
+ t1 = chrec_fold_plus (type, t1, t2);
+ /* "2*b*d". */
t2 = chrec_fold_multiply (type, SCALAR_FLOAT_TYPE_P (type)
? build_real (type, dconst2)
: build_int_cst (type, 2), t2);
Index: gcc/testsuite/g++.dg/torture/pr40460.C
===================================================================
*** gcc/testsuite/g++.dg/torture/pr40460.C (revision 0)
--- gcc/testsuite/g++.dg/torture/pr40460.C (revision 0)
***************
*** 0 ****
--- 1,9 ----
+ /* { dg-do compile } */
+
+ void bar(int);
+ void foo(void)
+ {
+ for (int i = 0; i<1; ++i)
+ bar (i*i*i*i*i*i*i*i*i*i*i*i*i*i*i*i*i*i*i*i*i*i*i*i*i*i*i*i*i*i*i*i*i);
+ }
+
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