Jakub noticed that we don't forward &a[i] into a dereference of said
pointer when the resulting struct is partially accessed. I suppose
I just didn't implement that initially because I was lazy. It turns
out to be comparatively easy to do though.
Bootstrapped and tested on x86_64-unknown-linux-gnu, applied to trunk.
Richard.
2013-09-12 Richard Biener <rguent...@suse.de>
PR tree-optimization/58404
* tree-ssa-forwprop.c (forward_propagate_addr_expr_1): Also
propagate non-invariant addresses into dereferences wrapped
in component references.
* g++.dg/tree-ssa/pr58404.C: New testcase.
Index: gcc/tree-ssa-forwprop.c
===================================================================
*** gcc/tree-ssa-forwprop.c (revision 202515)
--- gcc/tree-ssa-forwprop.c (working copy)
*************** forward_propagate_addr_expr_1 (tree name
*** 786,794 ****
/* Now strip away any outer COMPONENT_REF/ARRAY_REF nodes from the LHS.
ADDR_EXPR will not appear on the LHS. */
! lhs = gimple_assign_lhs (use_stmt);
! while (handled_component_p (lhs))
! lhs = TREE_OPERAND (lhs, 0);
/* Now see if the LHS node is a MEM_REF using NAME. If so,
propagate the ADDR_EXPR into the use of NAME and fold the result. */
--- 786,795 ----
/* Now strip away any outer COMPONENT_REF/ARRAY_REF nodes from the LHS.
ADDR_EXPR will not appear on the LHS. */
! tree *lhsp = gimple_assign_lhs_ptr (use_stmt);
! while (handled_component_p (*lhsp))
! lhsp = &TREE_OPERAND (*lhsp, 0);
! lhs = *lhsp;
/* Now see if the LHS node is a MEM_REF using NAME. If so,
propagate the ADDR_EXPR into the use of NAME and fold the result. */
*************** forward_propagate_addr_expr_1 (tree name
*** 822,832 ****
/* If the LHS is a plain dereference and the value type is the same as
that of the pointed-to type of the address we can put the
dereferenced address on the LHS preserving the original alias-type. */
! else if (gimple_assign_lhs (use_stmt) == lhs
! && integer_zerop (TREE_OPERAND (lhs, 1))
! && useless_type_conversion_p
! (TREE_TYPE (TREE_OPERAND (def_rhs, 0)),
! TREE_TYPE (gimple_assign_rhs1 (use_stmt)))
/* Don't forward anything into clobber stmts if it would result
in the lhs no longer being a MEM_REF. */
&& (!gimple_clobber_p (use_stmt)
--- 823,835 ----
/* If the LHS is a plain dereference and the value type is the same as
that of the pointed-to type of the address we can put the
dereferenced address on the LHS preserving the original alias-type. */
! else if (integer_zerop (TREE_OPERAND (lhs, 1))
! && ((gimple_assign_lhs (use_stmt) == lhs
! && useless_type_conversion_p
! (TREE_TYPE (TREE_OPERAND (def_rhs, 0)),
! TREE_TYPE (gimple_assign_rhs1 (use_stmt))))
! || types_compatible_p (TREE_TYPE (lhs),
! TREE_TYPE (TREE_OPERAND (def_rhs,
0))))
/* Don't forward anything into clobber stmts if it would result
in the lhs no longer being a MEM_REF. */
&& (!gimple_clobber_p (use_stmt)
*************** forward_propagate_addr_expr_1 (tree name
*** 854,860 ****
TREE_SIDE_EFFECTS (*def_rhs_basep) = TREE_SIDE_EFFECTS (lhs);
TREE_THIS_NOTRAP (*def_rhs_basep) = TREE_THIS_NOTRAP (lhs);
new_lhs = unshare_expr (TREE_OPERAND (def_rhs, 0));
! gimple_assign_set_lhs (use_stmt, new_lhs);
TREE_THIS_VOLATILE (new_lhs) = TREE_THIS_VOLATILE (lhs);
TREE_SIDE_EFFECTS (new_lhs) = TREE_SIDE_EFFECTS (lhs);
*def_rhs_basep = saved;
--- 857,863 ----
TREE_SIDE_EFFECTS (*def_rhs_basep) = TREE_SIDE_EFFECTS (lhs);
TREE_THIS_NOTRAP (*def_rhs_basep) = TREE_THIS_NOTRAP (lhs);
new_lhs = unshare_expr (TREE_OPERAND (def_rhs, 0));
! *lhsp = new_lhs;
TREE_THIS_VOLATILE (new_lhs) = TREE_THIS_VOLATILE (lhs);
TREE_SIDE_EFFECTS (new_lhs) = TREE_SIDE_EFFECTS (lhs);
*def_rhs_basep = saved;
*************** forward_propagate_addr_expr_1 (tree name
*** 873,883 ****
/* Strip away any outer COMPONENT_REF, ARRAY_REF or ADDR_EXPR
nodes from the RHS. */
! rhs = gimple_assign_rhs1 (use_stmt);
! if (TREE_CODE (rhs) == ADDR_EXPR)
! rhs = TREE_OPERAND (rhs, 0);
! while (handled_component_p (rhs))
! rhs = TREE_OPERAND (rhs, 0);
/* Now see if the RHS node is a MEM_REF using NAME. If so,
propagate the ADDR_EXPR into the use of NAME and fold the result. */
--- 876,887 ----
/* Strip away any outer COMPONENT_REF, ARRAY_REF or ADDR_EXPR
nodes from the RHS. */
! tree *rhsp = gimple_assign_rhs1_ptr (use_stmt);
! if (TREE_CODE (*rhsp) == ADDR_EXPR)
! rhsp = &TREE_OPERAND (*rhsp, 0);
! while (handled_component_p (*rhsp))
! rhsp = &TREE_OPERAND (*rhsp, 0);
! rhs = *rhsp;
/* Now see if the RHS node is a MEM_REF using NAME. If so,
propagate the ADDR_EXPR into the use of NAME and fold the result. */
*************** forward_propagate_addr_expr_1 (tree name
*** 909,919 ****
/* If the RHS is a plain dereference and the value type is the same as
that of the pointed-to type of the address we can put the
dereferenced address on the RHS preserving the original alias-type. */
! else if (gimple_assign_rhs1 (use_stmt) == rhs
! && integer_zerop (TREE_OPERAND (rhs, 1))
! && useless_type_conversion_p
! (TREE_TYPE (gimple_assign_lhs (use_stmt)),
! TREE_TYPE (TREE_OPERAND (def_rhs, 0))))
{
tree *def_rhs_basep = &TREE_OPERAND (def_rhs, 0);
tree new_offset, new_base, saved, new_rhs;
--- 913,925 ----
/* If the RHS is a plain dereference and the value type is the same as
that of the pointed-to type of the address we can put the
dereferenced address on the RHS preserving the original alias-type. */
! else if (integer_zerop (TREE_OPERAND (rhs, 1))
! && ((gimple_assign_rhs1 (use_stmt) == rhs
! && useless_type_conversion_p
! (TREE_TYPE (gimple_assign_lhs (use_stmt)),
! TREE_TYPE (TREE_OPERAND (def_rhs, 0))))
! || types_compatible_p (TREE_TYPE (rhs),
! TREE_TYPE (TREE_OPERAND (def_rhs,
0)))))
{
tree *def_rhs_basep = &TREE_OPERAND (def_rhs, 0);
tree new_offset, new_base, saved, new_rhs;
*************** forward_propagate_addr_expr_1 (tree name
*** 937,943 ****
TREE_SIDE_EFFECTS (*def_rhs_basep) = TREE_SIDE_EFFECTS (rhs);
TREE_THIS_NOTRAP (*def_rhs_basep) = TREE_THIS_NOTRAP (rhs);
new_rhs = unshare_expr (TREE_OPERAND (def_rhs, 0));
! gimple_assign_set_rhs1 (use_stmt, new_rhs);
TREE_THIS_VOLATILE (new_rhs) = TREE_THIS_VOLATILE (rhs);
TREE_SIDE_EFFECTS (new_rhs) = TREE_SIDE_EFFECTS (rhs);
*def_rhs_basep = saved;
--- 943,949 ----
TREE_SIDE_EFFECTS (*def_rhs_basep) = TREE_SIDE_EFFECTS (rhs);
TREE_THIS_NOTRAP (*def_rhs_basep) = TREE_THIS_NOTRAP (rhs);
new_rhs = unshare_expr (TREE_OPERAND (def_rhs, 0));
! *rhsp = new_rhs;
TREE_THIS_VOLATILE (new_rhs) = TREE_THIS_VOLATILE (rhs);
TREE_SIDE_EFFECTS (new_rhs) = TREE_SIDE_EFFECTS (rhs);
*def_rhs_basep = saved;
Index: gcc/testsuite/g++.dg/tree-ssa/pr58404.C
===================================================================
*** gcc/testsuite/g++.dg/tree-ssa/pr58404.C (revision 0)
--- gcc/testsuite/g++.dg/tree-ssa/pr58404.C (working copy)
***************
*** 0 ****
--- 1,20 ----
+ // { dg-do compile }
+ // { dg-options "-O -fdump-tree-cddce1" }
+
+ struct S { int s; };
+ S a[1024];
+
+ void
+ foo ()
+ {
+ for (int i = 0; i < 1024; i++)
+ {
+ S &r = a[i];
+ r.s++;
+ }
+ }
+
+ // We should propagate the reference into both memory accesses
+ // during the first forwprop pass
+ // { dg-final { scan-tree-dump-times "= &a" 0 "cddce1" } }
+ // { dg-final { cleanup-tree-dump "cddce1" } }
