This fixes copy-propagation (in DOM in this case) which breaks
virtual SSA form by introducing overlapping life-ranges which
in turn breaks CFG transforms that rely on that property.
The patch disables copy-propagation of virtuals in general
(for all passes checking may_propagate_copy) because that
predicate cannot decide if the propagation would be valid.
Instead the patch special-cases propagation of virtual operands
across PHI nodes (the only relevant case of virtual operand
copy propagation) in phi_only_cprop.
Bootstrapped and tested on x86_64-unknown-linux-gnu, applied to trunk.
Richard.
2013-05-28 Richard Biener <rguent...@suse.de>
PR tree-optimization/57411
* tree-ssa-copy.c (may_propagate_copy): Cannot propagate
virtual operands.
* tree-ssa-dom.c (eliminate_const_or_copy): Special-case
virtual operand propagation.
* g++.dg/opt/pr57411.C: New testcase.
Index: gcc/tree-ssa-copy.c
===================================================================
*** gcc/tree-ssa-copy.c (revision 199356)
--- gcc/tree-ssa-copy.c (working copy)
*************** may_propagate_copy (tree dest, tree orig
*** 73,86 ****
if (!useless_type_conversion_p (type_d, type_o))
return false;
! /* Propagating virtual operands is always ok. */
if (TREE_CODE (dest) == SSA_NAME && virtual_operand_p (dest))
! {
! /* But only between virtual operands. */
! gcc_assert (TREE_CODE (orig) == SSA_NAME && virtual_operand_p (orig));
!
! return true;
! }
/* Anything else is OK. */
return true;
--- 73,82 ----
if (!useless_type_conversion_p (type_d, type_o))
return false;
! /* Generally propagating virtual operands is not ok as that may
! create overlapping life-ranges. */
if (TREE_CODE (dest) == SSA_NAME && virtual_operand_p (dest))
! return false;
/* Anything else is OK. */
return true;
Index: gcc/testsuite/g++.dg/opt/pr57411.C
===================================================================
*** gcc/testsuite/g++.dg/opt/pr57411.C (revision 0)
--- gcc/testsuite/g++.dg/opt/pr57411.C (working copy)
***************
*** 0 ****
--- 1,23 ----
+ // { dg-do compile }
+ // { dg-options "-O -fno-tree-dce -ftree-vectorize" }
+
+ static inline void
+ iota (int *__first, int *__last, int __value)
+ {
+ for (; __first != __last; ++__first)
+ {
+ *__first = __value;
+ }
+ }
+
+ void assert_fail ();
+
+ int A[] = { 0, 0, 0 };
+
+ void
+ test01 (int equal)
+ {
+ iota (A, A + 3, 1);
+ if (equal)
+ assert_fail ();
+ }
Index: gcc/tree-ssa-dom.c
===================================================================
*** gcc/tree-ssa-dom.c (revision 199355)
--- gcc/tree-ssa-dom.c (working copy)
*************** eliminate_const_or_copy (gimple stmt, bi
*** 2936,2942 ****
return;
}
! propagate_rhs_into_lhs (stmt, lhs, rhs, interesting_names);
/* Note that STMT may well have been deleted by now, so do
not access it, instead use the saved version # to clear
--- 2936,2957 ----
return;
}
! if (!virtual_operand_p (lhs))
! propagate_rhs_into_lhs (stmt, lhs, rhs, interesting_names);
! else
! {
! gimple use_stmt;
! imm_use_iterator iter;
! use_operand_p use_p;
! /* For virtual operands we have to propagate into all uses as
! otherwise we will create overlapping life-ranges. */
! FOR_EACH_IMM_USE_STMT (use_stmt, iter, lhs)
! FOR_EACH_IMM_USE_ON_STMT (use_p, iter)
! SET_USE (use_p, rhs);
! if (SSA_NAME_OCCURS_IN_ABNORMAL_PHI (lhs))
! SSA_NAME_OCCURS_IN_ABNORMAL_PHI (rhs) = 1;
! remove_stmt_or_phi (stmt);
! }
/* Note that STMT may well have been deleted by now, so do
not access it, instead use the saved version # to clear
