While moving working on moving
cond_removal_in_builtin_zero_pattern to match, I noticed
that functions were not allowed to move as we reject all
non-assignments.
This changes to allowing a few calls which are known not
to throw/trap. Right now it is restricted to ones
which cond_removal_in_builtin_zero_pattern handles but
adding more is just adding it to the switch statement.
gcc/ChangeLog:
* tree-ssa-phiopt.cc (empty_bb_or_one_feeding_into_p):
Allow some builtin/internal function calls which
are known not to trap/throw.
(phiopt_worker::match_simplify_replacement):
Use name instead of getting the lhs again.
---
gcc/tree-ssa-phiopt.cc | 35 +++++++++++++++++++++++++++++++----
1 file changed, 31 insertions(+), 4 deletions(-)
diff --git a/gcc/tree-ssa-phiopt.cc b/gcc/tree-ssa-phiopt.cc
index 4b43f1abdbc..024a4362093 100644
--- a/gcc/tree-ssa-phiopt.cc
+++ b/gcc/tree-ssa-phiopt.cc
@@ -548,6 +548,7 @@ empty_bb_or_one_feeding_into_p (basic_block bb,
{
stmt = nullptr;
gimple *stmt_to_move = nullptr;
+ tree lhs;
if (empty_block_p (bb))
return true;
@@ -592,17 +593,43 @@ empty_bb_or_one_feeding_into_p (basic_block bb,
if (gimple_uses_undefined_value_p (stmt_to_move))
return false;
- /* Allow assignments and not no calls.
+ /* Allow assignments but allow some builtin/internal calls.
As const calls don't match any of the above, yet they could
still have some side-effects - they could contain
gimple_could_trap_p statements, like floating point
exceptions or integer division by zero. See PR70586.
FIXME: perhaps gimple_has_side_effects or gimple_could_trap_p
- should handle this. */
+ should handle this.
+ Allow some known builtin/internal calls that are known not to
+ trap: logical functions (e.g. bswap and bit counting). */
if (!is_gimple_assign (stmt_to_move))
- return false;
+ {
+ if (!is_gimple_call (stmt_to_move))
+ return false;
+ combined_fn cfn = gimple_call_combined_fn (stmt_to_move);
+ switch (cfn)
+ {
+ default:
+ return false;
+ case CFN_BUILT_IN_BSWAP16:
+ case CFN_BUILT_IN_BSWAP32:
+ case CFN_BUILT_IN_BSWAP64:
+ case CFN_BUILT_IN_BSWAP128:
+ CASE_CFN_FFS:
+ CASE_CFN_PARITY:
+ CASE_CFN_POPCOUNT:
+ CASE_CFN_CLZ:
+ CASE_CFN_CTZ:
+ case CFN_BUILT_IN_CLRSB:
+ case CFN_BUILT_IN_CLRSBL:
+ case CFN_BUILT_IN_CLRSBLL:
+ lhs = gimple_call_lhs (stmt_to_move);
+ break;
+ }
+ }
+ else
+ lhs = gimple_assign_lhs (stmt_to_move);
- tree lhs = gimple_assign_lhs (stmt_to_move);
gimple *use_stmt;
use_operand_p use_p;
--
2.39.1
