This implements simple pattern matching for folding of
pointer subtraction GIMPLE IL which is performed in an
integer type. It handles the simple case, like the
others in associate_plusminus (cases involving cancellation).
Bootstrapped and tested on x86_64-unknown-linux-gnu, applied.
Richard.
2014-01-28 Richard Biener <rguent...@suse.de>
PR tree-optimization/58742
* tree-ssa-forwprop.c (associate_plusminus): Handle
pointer subtraction of the form (T)(P + A) - (T)P.
Index: gcc/tree-ssa-forwprop.c
===================================================================
*** gcc/tree-ssa-forwprop.c (revision 207180)
--- gcc/tree-ssa-forwprop.c (working copy)
*************** associate_plusminus (gimple_stmt_iterato
*** 2543,2548 ****
--- 2543,2549 ----
CST +- (CST +- A) -> CST +- A
CST +- (A +- CST) -> CST +- A
A + ~A -> -1
+ (T)(P + A) - (T)P -> (T)A
via commutating the addition and contracting operations to zero
by reassociation. */
*************** associate_plusminus (gimple_stmt_iterato
*** 2646,2651 ****
--- 2647,2701 ----
gimple_set_modified (stmt, true);
}
}
+ else if (CONVERT_EXPR_CODE_P (def_code) && code == MINUS_EXPR
+ && TREE_CODE (rhs2) == SSA_NAME)
+ {
+ /* (T)(ptr + adj) - (T)ptr -> (T)adj. */
+ gimple def_stmt2 = SSA_NAME_DEF_STMT (rhs2);
+ if (TREE_CODE (gimple_assign_rhs1 (def_stmt)) == SSA_NAME
+ && is_gimple_assign (def_stmt2)
+ && can_propagate_from (def_stmt2)
+ && CONVERT_EXPR_CODE_P (gimple_assign_rhs_code (def_stmt2))
+ && TREE_CODE (gimple_assign_rhs1 (def_stmt2)) == SSA_NAME)
+ {
+ /* Now we have (T)A - (T)ptr. */
+ tree ptr = gimple_assign_rhs1 (def_stmt2);
+ def_stmt2 = SSA_NAME_DEF_STMT (gimple_assign_rhs1 (def_stmt));
+ if (is_gimple_assign (def_stmt2)
+ && gimple_assign_rhs_code (def_stmt2) == POINTER_PLUS_EXPR
+ && gimple_assign_rhs1 (def_stmt2) == ptr)
+ {
+ /* And finally (T)(ptr + X) - (T)ptr. */
+ tree adj = gimple_assign_rhs2 (def_stmt2);
+ /* If the conversion of the pointer adjustment to the
+ final type requires a sign- or zero-extension we
+ have to punt - it is not defined which one is
+ correct. */
+ if (TYPE_PRECISION (TREE_TYPE (rhs1))
+ <= TYPE_PRECISION (TREE_TYPE (adj))
+ || (TREE_CODE (adj) == INTEGER_CST
+ && tree_int_cst_sign_bit (adj) == 0))
+ {
+ if (useless_type_conversion_p (TREE_TYPE (rhs1),
+ TREE_TYPE (adj)))
+ {
+ code = TREE_CODE (adj);
+ rhs1 = adj;
+ }
+ else
+ {
+ code = NOP_EXPR;
+ rhs1 = adj;
+ }
+ rhs2 = NULL_TREE;
+ gimple_assign_set_rhs_with_ops (gsi, code, rhs1,
+ NULL_TREE);
+ gcc_assert (gsi_stmt (*gsi) == stmt);
+ gimple_set_modified (stmt, true);
+ }
+ }
+ }
+ }
}
}
