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isel: Small cleanup of duplicating comparisons

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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_apinski@quicinc.com>
This commit is contained in:
Andrew Pinski 2024-07-25 17:07:28 -07:00
parent 9e7b2ad4ab
commit db74887097
1 changed files with 24 additions and 14 deletions
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38
gcc/gimple-isel.cc
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@ -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);
}
}