Hi,
Here's version 2 of the patch to fix the missed SLSR PHI opportunities,
addressing Richard's comments. I've repeated regstrap and SPEC testing
on powerpc64le-unknown-linux-gnu, again showing the patch as neutral
with respect to performance. Is this ok for trunk?
Thanks for the review!
Bill
[gcc]
2016-06-23 Bill Schmidt <wschm...@linux.vnet.ibm.com>
* gimple-ssa-strength-reduction.c (uses_consumed_by_stmt): New
function.
(find_basis_for_candidate): Call uses_consumed_by_stmt rather than
has_single_use.
(slsr_process_phi): Likewise.
(replace_uncond_cands_and_profitable_phis): Don't replace a
multiply candidate with a stride of 1 (copy or cast).
(phi_incr_cost): Call uses_consumed_by_stmt rather than
has_single_use.
(lowest_cost_path): Likewise.
(total_savings): Likewise.
[gcc/testsuite]
2016-06-23 Bill Schmidt <wschm...@linux.vnet.ibm.com>
* gcc.dg/tree-ssa/slsr-35.c: Remove -fno-code-hoisting workaround.
* gcc.dg/tree-ssa/slsr-36.c: Likewise.
Index: gcc/gimple-ssa-strength-reduction.c
===================================================================
--- gcc/gimple-ssa-strength-reduction.c (revision 249223)
+++ gcc/gimple-ssa-strength-reduction.c (working copy)
@@ -482,6 +482,36 @@ find_phi_def (tree base)
return c->cand_num;
}
+/* Determine whether all uses of NAME are directly or indirectly
+ used by STMT. That is, we want to know whether if STMT goes
+ dead, the definition of NAME also goes dead. */
+static bool
+uses_consumed_by_stmt (tree name, gimple *stmt, unsigned recurse = 0)
+{
+ gimple *use_stmt;
+ imm_use_iterator iter;
+ bool retval = true;
+
+ FOR_EACH_IMM_USE_STMT (use_stmt, iter, name)
+ {
+ if (use_stmt == stmt || is_gimple_debug (use_stmt))
+ continue;
+
+ if (!is_gimple_assign (use_stmt)
+ || !gimple_get_lhs (use_stmt)
+ || !is_gimple_reg (gimple_get_lhs (use_stmt))
+ || recurse >= 10
+ || !uses_consumed_by_stmt (gimple_get_lhs (use_stmt), stmt,
+ recurse + 1))
+ {
+ retval = false;
+ BREAK_FROM_IMM_USE_STMT (iter);
+ }
+ }
+
+ return retval;
+}
+
/* Helper routine for find_basis_for_candidate. May be called twice:
once for the candidate's base expr, and optionally again either for
the candidate's phi definition or for a CAND_REF's alternative base
@@ -558,7 +588,8 @@ find_basis_for_candidate (slsr_cand_t c)
/* If we found a hidden basis, estimate additional dead-code
savings if the phi and its feeding statements can be removed. */
- if (basis && has_single_use (gimple_phi_result (phi_cand->cand_stmt)))
+ tree feeding_var = gimple_phi_result (phi_cand->cand_stmt);
+ if (basis && uses_consumed_by_stmt (feeding_var, c->cand_stmt))
c->dead_savings += phi_cand->dead_savings;
}
}
@@ -789,7 +820,7 @@ slsr_process_phi (gphi *phi, bool speed)
/* Gather potential dead code savings if the phi statement
can be removed later on. */
- if (has_single_use (arg))
+ if (uses_consumed_by_stmt (arg, phi))
{
if (gimple_code (arg_stmt) == GIMPLE_PHI)
savings += arg_cand->dead_savings;
@@ -2479,7 +2510,9 @@ replace_uncond_cands_and_profitable_phis (slsr_can
{
if (phi_dependent_cand_p (c))
{
- if (c->kind == CAND_MULT)
+ /* A multiply candidate with a stride of 1 is just an artifice
+ of a copy or cast; there is no value in replacing it. */
+ if (c->kind == CAND_MULT && wi::to_widest (c->stride) != 1)
{
/* A candidate dependent upon a phi will replace a multiply by
a constant with an add, and will insert at most one add for
@@ -2725,8 +2758,9 @@ phi_incr_cost (slsr_cand_t c, const widest_int &in
if (gimple_code (arg_def) == GIMPLE_PHI)
{
int feeding_savings = 0;
+ tree feeding_var = gimple_phi_result (arg_def);
cost += phi_incr_cost (c, incr, arg_def, &feeding_savings);
- if (has_single_use (gimple_phi_result (arg_def)))
+ if (uses_consumed_by_stmt (feeding_var, phi))
*savings += feeding_savings;
}
else
@@ -2739,7 +2773,7 @@ phi_incr_cost (slsr_cand_t c, const widest_int &in
tree basis_lhs = gimple_assign_lhs (basis->cand_stmt);
tree lhs = gimple_assign_lhs (arg_cand->cand_stmt);
cost += add_cost (true, TYPE_MODE (TREE_TYPE (basis_lhs)));
- if (has_single_use (lhs))
+ if (uses_consumed_by_stmt (lhs, phi))
*savings += stmt_cost (arg_cand->cand_stmt, true);
}
}
@@ -2816,7 +2850,7 @@ lowest_cost_path (int cost_in, int repl_savings, s
gimple *phi = lookup_cand (c->def_phi)->cand_stmt;
local_cost += phi_incr_cost (c, incr, phi, &savings);
- if (has_single_use (gimple_phi_result (phi)))
+ if (uses_consumed_by_stmt (gimple_phi_result (phi), c->cand_stmt))
local_cost -= savings;
}
@@ -2860,7 +2894,7 @@ total_savings (int repl_savings, slsr_cand_t c, co
gimple *phi = lookup_cand (c->def_phi)->cand_stmt;
savings -= phi_incr_cost (c, incr, phi, &phi_savings);
- if (has_single_use (gimple_phi_result (phi)))
+ if (uses_consumed_by_stmt (gimple_phi_result (phi), c->cand_stmt))
savings += phi_savings;
}
Index: gcc/testsuite/gcc.dg/tree-ssa/slsr-35.c
===================================================================
--- gcc/testsuite/gcc.dg/tree-ssa/slsr-35.c (revision 249223)
+++ gcc/testsuite/gcc.dg/tree-ssa/slsr-35.c (working copy)
@@ -3,7 +3,7 @@
phi has an argument which is a parameter. */
/* { dg-do compile } */
-/* { dg-options "-O3 -fno-code-hoisting -fdump-tree-optimized" } */
+/* { dg-options "-O3 -fdump-tree-optimized" } */
int
f (int c, int i)
Index: gcc/testsuite/gcc.dg/tree-ssa/slsr-36.c
===================================================================
--- gcc/testsuite/gcc.dg/tree-ssa/slsr-36.c (revision 249223)
+++ gcc/testsuite/gcc.dg/tree-ssa/slsr-36.c (working copy)
@@ -3,7 +3,7 @@
phi has an argument which is a parameter. */
/* { dg-do compile } */
-/* { dg-options "-O3 -fno-code-hoisting -fdump-tree-optimized" } */
+/* { dg-options "-O3 -fdump-tree-optimized" } */
int
f (int s, int c, int i)
