This should optimize VEC_BASE that Jakub was patching by teaching
phiopt to handle some one-statement intermediate basic-blocks.
Bootstrapped and tested on x86_64-unknown-linux-gnu, any comments?
Thanks,
Richard.
2011-11-08 Richard Guenther <rguent...@suse.de>
PR tree-optimization/51030
* tree-ssa-phiopt.c (jump_function_from_stmt): New function.
(value_replacement): Use it to handle trivial non-empty
intermediate blocks.
* gcc.dg/tree-ssa/phi-opt-6.c: New testcase.
Index: gcc/tree-ssa-phiopt.c
===================================================================
*** gcc/tree-ssa-phiopt.c (revision 181154)
--- gcc/tree-ssa-phiopt.c (working copy)
*************** conditional_replacement (basic_block con
*** 591,596 ****
--- 591,628 ----
return true;
}
+ /* Update *ARG which is defined in STMT so that it contains the
+ computed value if that seems profitable. Return true if the
+ statement is made dead by that rewriting. */
+
+ static bool
+ jump_function_from_stmt (tree *arg, gimple stmt)
+ {
+ enum tree_code code = gimple_assign_rhs_code (stmt);
+ if (code == ADDR_EXPR)
+ {
+ /* For arg = &p->i transform it to p, if possible. */
+ tree rhs1 = gimple_assign_rhs1 (stmt);
+ HOST_WIDE_INT offset;
+ tree tem = get_addr_base_and_unit_offset (TREE_OPERAND (rhs1, 0),
+ &offset);
+ if (tem
+ && TREE_CODE (tem) == MEM_REF
+ && double_int_zero_p
+ (double_int_add (mem_ref_offset (tem),
+ shwi_to_double_int (offset))))
+ {
+ *arg = TREE_OPERAND (tem, 0);
+ return true;
+ }
+ }
+ /* TODO: Much like IPA-CP jump-functions we want to handle constant
+ additions symbolically here, and we'd need to update the comparison
+ code that compares the arg + cst tuples in our caller. For now the
+ code above exactly handles the VEC_BASE pattern from vec.h. */
+ return false;
+ }
+
/* The function value_replacement does the main work of doing the value
replacement. Return true if the replacement is done. Otherwise return
false.
*************** value_replacement (basic_block cond_bb,
*** 602,607 ****
--- 634,640 ----
edge e0, edge e1, gimple phi,
tree arg0, tree arg1)
{
+ gimple_stmt_iterator gsi;
gimple cond;
edge true_edge, false_edge;
enum tree_code code;
*************** value_replacement (basic_block cond_bb,
*** 611,618 ****
if (HONOR_SIGNED_ZEROS (TYPE_MODE (TREE_TYPE (arg1))))
return false;
! if (!empty_block_p (middle_bb))
! return false;
cond = last_stmt (cond_bb);
code = gimple_cond_code (cond);
--- 644,675 ----
if (HONOR_SIGNED_ZEROS (TYPE_MODE (TREE_TYPE (arg1))))
return false;
! /* Allow a single statement in MIDDLE_BB that defines one of the PHI
! arguments. */
! gsi = gsi_after_labels (middle_bb);
! if (!gsi_end_p (gsi))
! {
! if (is_gimple_debug (gsi_stmt (gsi)))
! gsi_next_nondebug (&gsi);
! if (!gsi_end_p (gsi))
! {
! gimple stmt = gsi_stmt (gsi);
! tree lhs;
! gsi_next_nondebug (&gsi);
! if (!gsi_end_p (gsi))
! return false;
! if (!is_gimple_assign (stmt))
! return false;
! /* Now try to adjust arg0 or arg1 according to the computation
! in the single statement. */
! lhs = gimple_assign_lhs (stmt);
! if (!((lhs == arg0
! && jump_function_from_stmt (&arg0, stmt))
! || (lhs == arg1
! && jump_function_from_stmt (&arg1, stmt))))
! return false;
! }
! }
cond = last_stmt (cond_bb);
code = gimple_cond_code (cond);
Index: gcc/testsuite/gcc.dg/tree-ssa/phi-opt-6.c
===================================================================
*** gcc/testsuite/gcc.dg/tree-ssa/phi-opt-6.c (revision 0)
--- gcc/testsuite/gcc.dg/tree-ssa/phi-opt-6.c (revision 0)
***************
*** 0 ****
--- 1,13 ----
+ /* { dg-do compile } */
+ /* { dg-options "-O -fdump-tree-phiopt1" } */
+
+ struct C { int i; };
+ int *g(struct C *p)
+ {
+ if (p)
+ return &p->i;
+ return (int *)0;
+ }
+
+ /* { dg-final { scan-tree-dump-not "if" "phiopt1" } } */
+ /* { dg-final { cleanup-tree-dump "phiopt1" } } */
