The following adds more aggressive DCE to forwprop to clean up dead
stmts when folding a stmt leaves some operands unused. The patch
uses simple_dce_from_worklist for this purpose, queueing original
operands before substitution and folding, but only if we folded the
stmt.
This removes one dead stmt biasing threading costs in a later pass
but it doesn't resolve the optimization issue in the PR yet.
Bootstrapped and tested on x86_64-unknown-linux-gnu, pushed.
PR tree-optimization/111294
* tree-ssa-forwprop.cc (pass_forwprop::execute): Track
operands that eventually become dead and use simple_dce_from_worklist
to remove their definitions if they did so.
* gcc.dg/tree-ssa/evrp10.c: Adjust.
* gcc.dg/tree-ssa/evrp6.c: Likewise.
* gcc.dg/tree-ssa/forwprop-31.c: Likewise.
* gcc.dg/tree-ssa/neg-cast-3.c: Likewise.
---
gcc/testsuite/gcc.dg/tree-ssa/evrp10.c | 2 +-
gcc/testsuite/gcc.dg/tree-ssa/evrp6.c | 5 ++--
gcc/testsuite/gcc.dg/tree-ssa/forwprop-31.c | 3 +--
gcc/testsuite/gcc.dg/tree-ssa/neg-cast-3.c | 4 +--
gcc/tree-ssa-forwprop.cc | 27 +++++++++++++++++----
5 files changed, 28 insertions(+), 13 deletions(-)
diff --git a/gcc/testsuite/gcc.dg/tree-ssa/evrp10.c
b/gcc/testsuite/gcc.dg/tree-ssa/evrp10.c
index 6ca00e4adaa..776c80c684f 100644
--- a/gcc/testsuite/gcc.dg/tree-ssa/evrp10.c
+++ b/gcc/testsuite/gcc.dg/tree-ssa/evrp10.c
@@ -1,5 +1,5 @@
/* { dg-do compile } */
-/* { dg-options "-O2 -fdump-tree-evrp" }*/
+/* { dg-options "-O2 -fdump-tree-evrp -fno-tree-forwprop" }*/
typedef __INT32_TYPE__ int32_t;
diff --git a/gcc/testsuite/gcc.dg/tree-ssa/evrp6.c
b/gcc/testsuite/gcc.dg/tree-ssa/evrp6.c
index aaeec68866e..0f9561b6a72 100644
--- a/gcc/testsuite/gcc.dg/tree-ssa/evrp6.c
+++ b/gcc/testsuite/gcc.dg/tree-ssa/evrp6.c
@@ -1,5 +1,5 @@
/* { dg-do compile } */
-/* { dg-options "-O2 -fdump-tree-evrp-details" } */
+/* { dg-options "-O2 -fdump-tree-evrp-details -fdump-tree-mergephi1" } */
extern void abort (void);
@@ -18,4 +18,5 @@ foo (int k, int j)
return j;
}
-/* { dg-final { scan-tree-dump "\\\[12, \\+INF" "evrp" } } */
+/* { dg-final { scan-tree-dump "\\\[11, \\+INF" "evrp" } } */
+/* { dg-final { scan-tree-dump-not "abort" "mergephi1" } } */
diff --git a/gcc/testsuite/gcc.dg/tree-ssa/forwprop-31.c
b/gcc/testsuite/gcc.dg/tree-ssa/forwprop-31.c
index edf80264884..40cc86383fa 100644
--- a/gcc/testsuite/gcc.dg/tree-ssa/forwprop-31.c
+++ b/gcc/testsuite/gcc.dg/tree-ssa/forwprop-31.c
@@ -9,6 +9,5 @@ int foo (int x)
return w - z; /* becomes 0 */
}
-/* Only z = x + 1 is retained. */
-/* { dg-final { scan-tree-dump-times " = " 1 "forwprop1" } } */
+/* { dg-final { scan-tree-dump-times " = " 0 "forwprop1" } } */
/* { dg-final { scan-tree-dump "return 0;" "forwprop1" } } */
diff --git a/gcc/testsuite/gcc.dg/tree-ssa/neg-cast-3.c
b/gcc/testsuite/gcc.dg/tree-ssa/neg-cast-3.c
index 7b23ca85d1f..61b89403a93 100644
--- a/gcc/testsuite/gcc.dg/tree-ssa/neg-cast-3.c
+++ b/gcc/testsuite/gcc.dg/tree-ssa/neg-cast-3.c
@@ -10,6 +10,4 @@ unsigned f(_Bool a)
}
/* There should be no cast to int at all. */
-/* Forwprop1 does not remove all of the statements. */
-/* { dg-final { scan-tree-dump-not "\\\(int\\\)" "forwprop1" { xfail *-*-* } }
} */
-/* { dg-final { scan-tree-dump-not "\\\(int\\\)" "optimized" } } */
+/* { dg-final { scan-tree-dump-not "\\\(int\\\)" "forwprop1" } } */
diff --git a/gcc/tree-ssa-forwprop.cc b/gcc/tree-ssa-forwprop.cc
index 94ca47a9726..d4e9202a2d4 100644
--- a/gcc/tree-ssa-forwprop.cc
+++ b/gcc/tree-ssa-forwprop.cc
@@ -53,6 +53,7 @@ along with GCC; see the file COPYING3. If not see
#include "cgraph.h"
#include "tree-ssa.h"
#include "gimple-range.h"
+#include "tree-ssa-dce.h"
/* This pass propagates the RHS of assignment statements into use
sites of the LHS of the assignment. It's basically a specialized
@@ -3502,8 +3503,9 @@ pass_forwprop::execute (function *fun)
|= EDGE_EXECUTABLE;
auto_vec<gimple *, 4> to_fixup;
auto_vec<gimple *, 32> to_remove;
+ auto_bitmap simple_dce_worklist;
+ auto_bitmap need_ab_cleanup;
to_purge = BITMAP_ALLOC (NULL);
- bitmap need_ab_cleanup = BITMAP_ALLOC (NULL);
for (int i = 0; i < postorder_num; ++i)
{
gimple_stmt_iterator gsi;
@@ -3902,10 +3904,14 @@ pass_forwprop::execute (function *fun)
{
tree use = USE_FROM_PTR (usep);
tree val = fwprop_ssa_val (use);
- if (val && val != use && may_propagate_copy (use, val))
+ if (val && val != use)
{
- propagate_value (usep, val);
- substituted_p = true;
+ bitmap_set_bit (simple_dce_worklist, SSA_NAME_VERSION (use));
+ if (may_propagate_copy (use, val))
+ {
+ propagate_value (usep, val);
+ substituted_p = true;
+ }
}
}
if (substituted_p
@@ -3925,6 +3931,11 @@ pass_forwprop::execute (function *fun)
&& gimple_call_noreturn_p (stmt));
changed = false;
+ auto_vec<tree, 8> uses;
+ FOR_EACH_SSA_USE_OPERAND (usep, stmt, iter, SSA_OP_USE)
+ if (uses.space (1))
+ uses.quick_push (USE_FROM_PTR (usep));
+
if (fold_stmt (&gsi, fwprop_ssa_val))
{
changed = true;
@@ -3935,6 +3946,12 @@ pass_forwprop::execute (function *fun)
if (gimple_cond_true_p (cond)
|| gimple_cond_false_p (cond))
cfg_changed = true;
+ /* Queue old uses for simple DCE. */
+ for (tree use : uses)
+ if (TREE_CODE (use) == SSA_NAME
+ && !SSA_NAME_IS_DEFAULT_DEF (use))
+ bitmap_set_bit (simple_dce_worklist,
+ SSA_NAME_VERSION (use));
}
if (changed || substituted_p)
@@ -4115,6 +4132,7 @@ pass_forwprop::execute (function *fun)
release_defs (stmt);
}
}
+ simple_dce_from_worklist (simple_dce_worklist, to_purge);
/* Fixup stmts that became noreturn calls. This may require splitting
blocks and thus isn't possible during the walk. Do this
@@ -4135,7 +4153,6 @@ pass_forwprop::execute (function *fun)
cfg_changed |= gimple_purge_all_dead_eh_edges (to_purge);
cfg_changed |= gimple_purge_all_dead_abnormal_call_edges (need_ab_cleanup);
BITMAP_FREE (to_purge);
- BITMAP_FREE (need_ab_cleanup);
if (get_range_query (fun) != get_global_range_query ())
disable_ranger (fun);
--
2.35.3
