The following fixes a missed optimization in PRE which was over-cautionous
with rejecting simplifications to SSA names during phi-translation.
Bootstrapped on x86_64-unknown-linux-gnu, testing in progress.
Richard.
2016-08-12 Richard Biener <rguent...@suse.de>
PR tree-optimization/57326
* tree-ssa-pre.c (fully_constant_expression): Handle simplification
returning an SSA name.
(phi_translate_1): When fully_constant_expression returns a NAME
make sure we have a leader for it.
* gcc.dg/tree-ssa/ssa-pre-32.c: New testcase.
Index: gcc/tree-ssa-pre.c
===================================================================
*** gcc/tree-ssa-pre.c (revision 239361)
--- gcc/tree-ssa-pre.c (working copy)
*************** get_or_alloc_expr_for (tree t)
*** 1201,1207 ****
}
/* Return the folded version of T if T, when folded, is a gimple
! min_invariant. Otherwise, return T. */
static pre_expr
fully_constant_expression (pre_expr e)
--- 1201,1207 ----
}
/* Return the folded version of T if T, when folded, is a gimple
! min_invariant or an SSA name. Otherwise, return T. */
static pre_expr
fully_constant_expression (pre_expr e)
*************** fully_constant_expression (pre_expr e)
*** 1218,1227 ****
return e;
if (is_gimple_min_invariant (res))
return get_or_alloc_expr_for_constant (res);
! /* We might have simplified the expression to a
! SSA_NAME for example from x_1 * 1. But we cannot
! insert a PHI for x_1 unconditionally as x_1 might
! not be available readily. */
return e;
}
case REFERENCE:
--- 1218,1225 ----
return e;
if (is_gimple_min_invariant (res))
return get_or_alloc_expr_for_constant (res);
! if (TREE_CODE (res) == SSA_NAME)
! return get_or_alloc_expr_for_name (res);
return e;
}
case REFERENCE:
*************** phi_translate_1 (pre_expr expr, bitmap_s
*** 1464,1470 ****
constant = fully_constant_expression (expr);
PRE_EXPR_NARY (expr) = nary;
if (constant != expr)
! return constant;
tree result = vn_nary_op_lookup_pieces (newnary->length,
newnary->opcode,
--- 1462,1481 ----
constant = fully_constant_expression (expr);
PRE_EXPR_NARY (expr) = nary;
if (constant != expr)
! {
! /* For non-CONSTANTs we have to make sure we can eventually
! insert the expression. Which means we need to have a
! leader for it. */
! if (constant->kind != CONSTANT)
! {
! unsigned value_id = get_expr_value_id (constant);
! constant = find_leader_in_sets (value_id, set1, set2);
! if (constant)
! return constant;
! }
! else
! return constant;
! }
tree result = vn_nary_op_lookup_pieces (newnary->length,
newnary->opcode,
Index: gcc/testsuite/gcc.dg/tree-ssa/ssa-pre-32.c
===================================================================
*** gcc/testsuite/gcc.dg/tree-ssa/ssa-pre-32.c (revision 0)
--- gcc/testsuite/gcc.dg/tree-ssa/ssa-pre-32.c (working copy)
***************
*** 0 ****
--- 1,11 ----
+ /* { dg-do compile } */
+ /* { dg-options "-O2 -fdump-tree-pre" } */
+
+ unsigned f(unsigned x, unsigned y, _Bool b)
+ {
+ #define m (b?-1:0)
+ return (x&m)|(y&~m);
+ #undef m
+ }
+
+ /* { dg-final { scan-tree-dump "# prephitmp_\[0-9\]+ = PHI
<\[xy\]_\[0-9\]+\\(D\\)\[^,\]*, \[xy\]_\[0-9\]+\\(D\\)" "pre" } } */
