The following adds a fold_builtins pass at -O0, keying off some
unwanted optimization and setting pointer alignment of the result
of __builtin_assume_alignment before removing the call. This
allows libatomic calls to be elided at -O0 on s390 for
__uint128_t foo(__uint128_t *p)
{
return __atomic_load_n((__uint128_t *)__builtin_assume_aligned (p, 16), 0);
}
not sure how to reliably test this though.
Thoughts?
Thanks,
Richard.
PR tree-optimization/107389
* tree-pass.h (pass_fold_builtins_O0): Declare.
* passes.def (pass_fold_builtins_O0): Schedule.
* tree-ssa-ccp.cc (pass_fold_builtins_O0): Define.
(pass_fold_builtins): Template, add gate.
(pass_fold_builtins::execute): Apply alignment to the
target of __builtin_assume_aligned at -O0. Disable most
optimizations for the -O0 pass instance.
---
gcc/passes.def | 1 +
gcc/tree-pass.h | 1 +
gcc/tree-ssa-ccp.cc | 52 +++++++++++++++++++++++++++++++++++++--------
3 files changed, 45 insertions(+), 9 deletions(-)
diff --git a/gcc/passes.def b/gcc/passes.def
index 193b5794749..4cc7c8acfcb 100644
--- a/gcc/passes.def
+++ b/gcc/passes.def
@@ -419,6 +419,7 @@ along with GCC; see the file COPYING3. If not see
NEXT_PASS (pass_lower_vaarg);
NEXT_PASS (pass_lower_vector);
NEXT_PASS (pass_lower_complex_O0);
+ NEXT_PASS (pass_fold_builtins_O0);
NEXT_PASS (pass_sancov_O0);
NEXT_PASS (pass_lower_switch_O0);
NEXT_PASS (pass_asan_O0);
diff --git a/gcc/tree-pass.h b/gcc/tree-pass.h
index 8480d41384b..43a4811128b 100644
--- a/gcc/tree-pass.h
+++ b/gcc/tree-pass.h
@@ -441,6 +441,7 @@ extern gimple_opt_pass *make_pass_warn_printf (gcc::context
*ctxt);
extern gimple_opt_pass *make_pass_warn_recursion (gcc::context *ctxt);
extern gimple_opt_pass *make_pass_strlen (gcc::context *ctxt);
extern gimple_opt_pass *make_pass_fold_builtins (gcc::context *ctxt);
+extern gimple_opt_pass *make_pass_fold_builtins_O0 (gcc::context *ctxt);
extern gimple_opt_pass *make_pass_post_ipa_warn (gcc::context *ctxt);
extern gimple_opt_pass *make_pass_stdarg (gcc::context *ctxt);
extern gimple_opt_pass *make_pass_early_warn_uninitialized (gcc::context
*ctxt);
diff --git a/gcc/tree-ssa-ccp.cc b/gcc/tree-ssa-ccp.cc
index 9778e776cf2..adb1e351e15 100644
--- a/gcc/tree-ssa-ccp.cc
+++ b/gcc/tree-ssa-ccp.cc
@@ -4197,6 +4197,7 @@ const pass_data pass_data_fold_builtins =
TODO_update_ssa, /* todo_flags_finish */
};
+template <bool O0>
class pass_fold_builtins : public gimple_opt_pass
{
public:
@@ -4204,14 +4205,17 @@ public:
: gimple_opt_pass (pass_data_fold_builtins, ctxt)
{}
+ bool gate (function *) final override { return O0 == !optimize; }
+
/* opt_pass methods: */
opt_pass * clone () final override { return new pass_fold_builtins (m_ctxt);
}
unsigned int execute (function *) final override;
}; // class pass_fold_builtins
+template <bool O0>
unsigned int
-pass_fold_builtins::execute (function *fun)
+pass_fold_builtins<O0>::execute (function *fun)
{
bool cfg_changed = false;
basic_block bb;
@@ -4245,7 +4249,7 @@ pass_fold_builtins::execute (function *fun)
continue;
}
}
- else if (gimple_assign_load_p (stmt) && gimple_store_p (stmt))
+ else if (!O0 && gimple_assign_load_p (stmt) && gimple_store_p
(stmt))
optimize_memcpy (&i, gimple_assign_lhs (stmt),
gimple_assign_rhs1 (stmt), NULL_TREE);
gsi_next (&i);
@@ -4266,7 +4270,7 @@ pass_fold_builtins::execute (function *fun)
}
fcode = DECL_FUNCTION_CODE (callee);
- if (fold_stmt (&i))
+ if (!O0 && fold_stmt (&i))
;
else
{
@@ -4281,7 +4285,29 @@ pass_fold_builtins::execute (function *fun)
break;
case BUILT_IN_ASSUME_ALIGNED:
- /* Remove __builtin_assume_aligned. */
+ /* Remove __builtin_assume_aligned. At -O0 preserve
+ the alignment info in the result. */
+ if (O0)
+ {
+ tree align = gimple_call_arg (stmt, 1);
+ tree misalign = (gimple_call_num_args (stmt) > 2
+ ? gimple_call_arg (stmt, 2) : NULL_TREE);
+ tree lhs = gimple_call_lhs (stmt);
+ if (lhs
+ && POINTER_TYPE_P (TREE_TYPE (lhs))
+ && tree_fits_uhwi_p (align)
+ && (!misalign || tree_fits_uhwi_p (misalign)))
+ {
+ ptr_info_def *pi = get_ptr_info (lhs);
+ unsigned aligni = TREE_INT_CST_LOW (align);
+ unsigned misaligni
+ = misalign ? TREE_INT_CST_LOW (misalign) : 0;
+ if (aligni > 1
+ && (aligni & (aligni - 1)) == 0
+ && (misaligni & ~(aligni - 1)) == 0)
+ set_ptr_info_alignment (pi, aligni, misaligni);
+ }
+ }
result = gimple_call_arg (stmt, 0);
break;
@@ -4293,7 +4319,7 @@ pass_fold_builtins::execute (function *fun)
continue;
case BUILT_IN_UNREACHABLE:
- if (optimize_unreachable (i))
+ if (!O0 && optimize_unreachable (i))
cfg_changed = true;
break;
@@ -4454,7 +4480,8 @@ pass_fold_builtins::execute (function *fun)
break;
case BUILT_IN_MEMCPY:
- if (gimple_call_builtin_p (stmt, BUILT_IN_NORMAL)
+ if (!O0
+ && gimple_call_builtin_p (stmt, BUILT_IN_NORMAL)
&& TREE_CODE (gimple_call_arg (stmt, 0)) == ADDR_EXPR
&& TREE_CODE (gimple_call_arg (stmt, 1)) == ADDR_EXPR
&& TREE_CODE (gimple_call_arg (stmt, 2)) == INTEGER_CST)
@@ -4470,7 +4497,8 @@ pass_fold_builtins::execute (function *fun)
case BUILT_IN_VA_END:
case BUILT_IN_VA_COPY:
/* These shouldn't be folded before pass_stdarg. */
- result = optimize_stdarg_builtin (stmt);
+ if (!O0)
+ result = optimize_stdarg_builtin (stmt);
break;
default:;
@@ -4534,7 +4562,13 @@ pass_fold_builtins::execute (function *fun)
gimple_opt_pass *
make_pass_fold_builtins (gcc::context *ctxt)
{
- return new pass_fold_builtins (ctxt);
+ return new pass_fold_builtins<false> (ctxt);
+}
+
+gimple_opt_pass *
+make_pass_fold_builtins_O0 (gcc::context *ctxt)
+{
+ return new pass_fold_builtins<true> (ctxt);
}
/* A simple pass that emits some warnings post IPA. */
@@ -4566,7 +4600,7 @@ public:
bool gate (function *) final override { return warn_nonnull != 0; }
unsigned int execute (function *) final override;
-}; // class pass_fold_builtins
+}; // class pass_post_ipa_warn
unsigned int
pass_post_ipa_warn::execute (function *fun)
--
2.35.3
