In some cases (usually dealing with bools only), there could be some statements
left behind which are considered trivial dead.
An example is:
```
bool f(bool a, bool b)
{
if (!a && !b)
return 0;
if (!a && b)
return 0;
if (a && !b)
return 0;
return 1;
}
```
Where during phiopt2, the IR had:
```
_3 = ~b_7(D);
_4 = _3 & a_6(D);
_4 != 0 ? 0 : 1
```
match-and-simplify would transform that into:
```
_11 = ~a_6(D);
_12 = b_7(D) | _11;
```
But phiopt would leave around the statements defining _4 and _3.
This helps by marking the conditional's lhs and rhs to see if they are
trivial dead.
OK? Bootstrapped and tested on x86_64-linux-gnu.
gcc/ChangeLog:
* tree-ssa-phiopt.cc (match_simplify_replacement): Mark's cond
statement's lhs and rhs to check if trivial dead.
Rename inserted_exprs to exprs_maybe_dce; also move it so
bitmap is not allocated if not needed.
---
gcc/tree-ssa-phiopt.cc | 21 ++++++++++++++++-----
1 file changed, 16 insertions(+), 5 deletions(-)
diff --git a/gcc/tree-ssa-phiopt.cc b/gcc/tree-ssa-phiopt.cc
index cb4e2da023d..ff36bb0119b 100644
--- a/gcc/tree-ssa-phiopt.cc
+++ b/gcc/tree-ssa-phiopt.cc
@@ -767,7 +767,6 @@ match_simplify_replacement (basic_block cond_bb,
basic_block middle_bb,
tree result;
gimple *stmt_to_move = NULL;
gimple *stmt_to_move_alt = NULL;
- auto_bitmap inserted_exprs;
tree arg_true, arg_false;
/* Special case A ? B : B as this will always simplify to B. */
@@ -844,6 +843,18 @@ match_simplify_replacement (basic_block cond_bb,
basic_block middle_bb,
if (!result)
return false;
+ auto_bitmap exprs_maybe_dce;
+
+ /* Mark the cond statements' lhs/rhs as maybe dce. */
+ if (TREE_CODE (gimple_cond_lhs (stmt)) == SSA_NAME
+ && !SSA_NAME_IS_DEFAULT_DEF (gimple_cond_lhs (stmt)))
+ bitmap_set_bit (exprs_maybe_dce,
+ SSA_NAME_VERSION (gimple_cond_lhs (stmt)));
+ if (TREE_CODE (gimple_cond_rhs (stmt)) == SSA_NAME
+ && !SSA_NAME_IS_DEFAULT_DEF (gimple_cond_rhs (stmt)))
+ bitmap_set_bit (exprs_maybe_dce,
+ SSA_NAME_VERSION (gimple_cond_rhs (stmt)));
+
gsi = gsi_last_bb (cond_bb);
/* Insert the sequence generated from gimple_simplify_phiopt. */
if (seq)
@@ -855,7 +866,7 @@ match_simplify_replacement (basic_block cond_bb,
basic_block middle_bb,
gimple *stmt = gsi_stmt (gsi1);
tree name = gimple_get_lhs (stmt);
if (name && TREE_CODE (name) == SSA_NAME)
- bitmap_set_bit (inserted_exprs, SSA_NAME_VERSION (name));
+ bitmap_set_bit (exprs_maybe_dce, SSA_NAME_VERSION (name));
}
if (dump_file && (dump_flags & TDF_FOLDING))
{
@@ -867,10 +878,10 @@ match_simplify_replacement (basic_block cond_bb,
basic_block middle_bb,
/* If there was a statement to move, move it to right before
the original conditional. */
- move_stmt (stmt_to_move, &gsi, inserted_exprs);
- move_stmt (stmt_to_move_alt, &gsi, inserted_exprs);
+ move_stmt (stmt_to_move, &gsi, exprs_maybe_dce);
+ move_stmt (stmt_to_move_alt, &gsi, exprs_maybe_dce);
- replace_phi_edge_with_variable (cond_bb, e1, phi, result, inserted_exprs);
+ replace_phi_edge_with_variable (cond_bb, e1, phi, result, exprs_maybe_dce);
/* Add Statistic here even though replace_phi_edge_with_variable already
does it as we want to be able to count when match-simplify happens vs
--
2.31.1
