https://gcc.gnu.org/g:db74887097272a8390e33eba47c6fb8f50b64f5c
commit r15-2342-gdb74887097272a8390e33eba47c6fb8f50b64f5c
Author: Andrew Pinski <quic_apin...@quicinc.com>
Date: Thu Jul 25 17:07:28 2024 -0700
isel: Small cleanup of duplicating comparisons
This is a small cleanup of the duplicating comparison code.
There is code generation difference but only for -O0 and -fno-tree-ter
(both of which will be fixed in a later patch).
The difference is instead of skipping the first use if the
comparison uses are only in cond_expr we skip the last use.
Also we go through the uses list in the opposite order now too.
The cleanups are the following:
* Don't call has_single_use as we will do the loop anyways
* Change the order of the checks slightly, it is better
to check for cond_expr earlier
* Use cond_exprs as a stack and pop from it.
Skipping the top if the use is only from cond_expr.
Bootstrapped and tested on x86_64-linux-gnu with no regressions.
gcc/ChangeLog:
* gimple-isel.cc (duplicate_comparison): Rename to ...
(maybe_duplicate_comparison): This. Add check for use here
rather than in its caller.
(pass_gimple_isel::execute): Don't check how many uses the
comparison had and call maybe_duplicate_comparison instead of
duplicate_comparison.
Signed-off-by: Andrew Pinski <quic_apin...@quicinc.com>
Diff:
---
gcc/gimple-isel.cc | 38 ++++++++++++++++++++++++--------------
1 file changed, 24 insertions(+), 14 deletions(-)
diff --git a/gcc/gimple-isel.cc b/gcc/gimple-isel.cc
index 327a78ea408e..99bfc937bd55 100644
--- a/gcc/gimple-isel.cc
+++ b/gcc/gimple-isel.cc
@@ -399,34 +399,46 @@ gimple_expand_vec_cond_expr (struct function *fun,
gimple_stmt_iterator *gsi,
comparisons so RTL expansion with the help of TER
can perform better if conversion. */
static void
-duplicate_comparison (gassign *stmt, basic_block bb)
+maybe_duplicate_comparison (gassign *stmt, basic_block bb)
{
imm_use_iterator imm_iter;
use_operand_p use_p;
auto_vec<gassign *, 4> cond_exprs;
- unsigned cnt = 0;
tree lhs = gimple_assign_lhs (stmt);
+ unsigned cnt = 0;
+
FOR_EACH_IMM_USE_FAST (use_p, imm_iter, lhs)
{
if (is_gimple_debug (USE_STMT (use_p)))
continue;
cnt++;
+ /* Add the use statement if it was a cond_expr. */
if (gimple_bb (USE_STMT (use_p)) == bb
&& is_gimple_assign (USE_STMT (use_p))
- && gimple_assign_rhs1_ptr (USE_STMT (use_p)) == use_p->use
- && gimple_assign_rhs_code (USE_STMT (use_p)) == COND_EXPR)
+ && gimple_assign_rhs_code (USE_STMT (use_p)) == COND_EXPR
+ && gimple_assign_rhs1_ptr (USE_STMT (use_p)) == use_p->use)
cond_exprs.safe_push (as_a <gassign *> (USE_STMT (use_p)));
- }
- for (unsigned i = cond_exprs.length () == cnt ? 1 : 0;
- i < cond_exprs.length (); ++i)
+ }
+
+ /* If the comparison has 0 or 1 uses, no reason to do anything. */
+ if (cnt <= 1)
+ return;
+
+ /* If we only use the expression inside cond_exprs in that BB, we don't
+ need to duplicate for one of them so pop the top. */
+ if (cond_exprs.length () == cnt)
+ cond_exprs.pop();
+
+ while (!cond_exprs.is_empty())
{
+ auto old_top = cond_exprs.pop();
gassign *copy = as_a <gassign *> (gimple_copy (stmt));
tree new_def = duplicate_ssa_name (lhs, copy);
gimple_assign_set_lhs (copy, new_def);
- auto gsi2 = gsi_for_stmt (cond_exprs[i]);
+ auto gsi2 = gsi_for_stmt (old_top);
gsi_insert_before (&gsi2, copy, GSI_SAME_STMT);
- gimple_assign_set_rhs1 (cond_exprs[i], new_def);
- update_stmt (cond_exprs[i]);
+ gimple_assign_set_rhs1 (old_top, new_def);
+ update_stmt (old_top);
}
}
@@ -500,10 +512,8 @@ pass_gimple_isel::execute (struct function *fun)
continue;
tree_code code = gimple_assign_rhs_code (stmt);
- tree lhs = gimple_assign_lhs (stmt);
- if (TREE_CODE_CLASS (code) == tcc_comparison
- && !has_single_use (lhs))
- duplicate_comparison (stmt, bb);
+ if (TREE_CODE_CLASS (code) == tcc_comparison)
+ maybe_duplicate_comparison (stmt, bb);
}
}
