Inline across -ffast-math boundary
Jan Hubicka
hubicka@ucw.cz
Thu Apr 21 11:45:00 GMT 2016
Hi,
this patch implements the long promised logic to inline across -ffast-math
boundary when eitehr caller or callee has no fp operations in it. This is
needed to resolve code quality regression on Firefox with LTO where
-O3/-O2/-Ofast flags are combined and we fail to inline a lot of comdats
otherwise.
Bootstrapped/regtested x86_64-linux. Ricahrd, I would like to know your opinion
on fp_expression_p predicate - it is bit ugly but I do not know how to implement
it better.
We still won't inline -O1 code into -O2+ because flag_strict_overflow differs.
I will implement similar logic for overflows incrementally. Similarly flag_errno_math
can be handled better, but I am not sure it matters - I think wast majority of time
users set errno_math in sync with other -ffast-math implied flags.
Honza
* ipa-inline-analysis.c (reset_inline_summary): Clear fp_expressions
(dump_inline_summary): Dump it.
(fp_expression_p): New predicate.
(estimate_function_body_sizes): Use it.
(inline_merge_summary): Merge fp_expressions.
(inline_read_section): Read fp_expressions.
(inline_write_summary): Write fp_expressions.
* ipa-inline.c (can_inline_edge_p): Permit inlining across fp math
codegen boundary if either caller or callee is !fp_expressions.
* ipa-inline.h (inline_summary): Add fp_expressions.
* ipa-inline-transform.c (inline_call): When inlining !fp_expressions
to fp_expressions be sure the fp generation flags are updated.
* gcc.dg/ipa/inline-8.c: New testcase.
Index: ipa-inline-analysis.c
===================================================================
--- ipa-inline-analysis.c (revision 235312)
+++ ipa-inline-analysis.c (working copy)
@@ -1069,6 +1069,7 @@ reset_inline_summary (struct cgraph_node
reset_inline_edge_summary (e);
for (e = node->indirect_calls; e; e = e->next_callee)
reset_inline_edge_summary (e);
+ info->fp_expressions = false;
}
/* Hook that is called by cgraph.c when a node is removed. */
@@ -1423,6 +1424,8 @@ dump_inline_summary (FILE *f, struct cgr
fprintf (f, " inlinable");
if (s->contains_cilk_spawn)
fprintf (f, " contains_cilk_spawn");
+ if (s->fp_expressions)
+ fprintf (f, " fp_expression");
fprintf (f, "\n self time: %i\n", s->self_time);
fprintf (f, " global time: %i\n", s->time);
fprintf (f, " self size: %i\n", s->self_size);
@@ -2459,6 +2462,42 @@ clobber_only_eh_bb_p (basic_block bb, bo
return true;
}
+/* Return true if STMT compute a floating point expression that may be affected
+ by -ffast-math and similar flags. */
+
+static bool
+fp_expression_p (gimple *stmt)
+{
+ tree fndecl;
+
+ if (gimple_code (stmt) == GIMPLE_ASSIGN
+ /* Even conversion to and from float are FP expressions. */
+ && (FLOAT_TYPE_P (TREE_TYPE (gimple_assign_lhs (stmt)))
+ || FLOAT_TYPE_P (TREE_TYPE (gimple_assign_rhs1 (stmt))))
+ /* Plain moves are safe. */
+ && (IS_EXPR_CODE_CLASS (TREE_CODE_CLASS (gimple_assign_rhs_code (stmt)))
+ || TREE_CODE_CLASS (gimple_assign_rhs_code (stmt)) == tcc_comparison))
+ return true;
+
+ /* Comparsions may be optimized with assumption that value is not NaN. */
+ if (gimple_code (stmt) == GIMPLE_COND
+ && (FLOAT_TYPE_P (TREE_TYPE (gimple_cond_lhs (stmt)))
+ || FLOAT_TYPE_P (TREE_TYPE (gimple_cond_rhs (stmt)))))
+ return true;
+
+ /* Builtins may be optimized depending on math mode. We don't really have
+ list of these, so just check that there are no FP arguments. */
+ if (gimple_code (stmt) == GIMPLE_CALL
+ && (fndecl = gimple_call_fndecl (stmt)) != NULL_TREE
+ && DECL_BUILT_IN_CLASS (fndecl) != NOT_BUILT_IN)
+ {
+ for (unsigned int i=0; i < gimple_call_num_args (stmt); i++)
+ if (FLOAT_TYPE_P (TREE_TYPE (gimple_call_arg (stmt, i))))
+ return true;
+ }
+ return false;
+}
+
/* Compute function body size parameters for NODE.
When EARLY is true, we compute only simple summaries without
non-trivial predicates to drive the early inliner. */
@@ -2733,6 +2772,13 @@ estimate_function_body_sizes (struct cgr
this_time * (2 - prob), &p);
}
+ if (!info->fp_expressions && fp_expression_p (stmt))
+ {
+ info->fp_expressions = true;
+ if (dump_file)
+ fprintf (dump_file, " fp_expression set\n");
+ }
+
gcc_assert (time >= 0);
gcc_assert (size >= 0);
}
@@ -3577,6 +3623,8 @@ inline_merge_summary (struct cgraph_edge
else
toplev_predicate = true_predicate ();
+ info->fp_expressions |= callee_info->fp_expressions;
+
if (callee_info->conds)
evaluate_properties_for_edge (edge, true, &clause, NULL, NULL, NULL);
if (ipa_node_params_sum && callee_info->conds)
@@ -4229,6 +4277,7 @@ inline_read_section (struct lto_file_dec
bp = streamer_read_bitpack (&ib);
info->inlinable = bp_unpack_value (&bp, 1);
info->contains_cilk_spawn = bp_unpack_value (&bp, 1);
+ info->fp_expressions = bp_unpack_value (&bp, 1);
count2 = streamer_read_uhwi (&ib);
gcc_assert (!info->conds);
@@ -4395,6 +4444,7 @@ inline_write_summary (void)
bp = bitpack_create (ob->main_stream);
bp_pack_value (&bp, info->inlinable, 1);
bp_pack_value (&bp, info->contains_cilk_spawn, 1);
+ bp_pack_value (&bp, info->fp_expressions, 1);
streamer_write_bitpack (&bp);
streamer_write_uhwi (ob, vec_safe_length (info->conds));
for (i = 0; vec_safe_iterate (info->conds, i, &c); i++)
Index: ipa-inline.c
===================================================================
--- ipa-inline.c (revision 235319)
+++ ipa-inline.c (working copy)
@@ -396,6 +396,8 @@ can_inline_edge_p (struct cgraph_edge *e
(DECL_DISREGARD_INLINE_LIMITS (callee->decl)
&& lookup_attribute ("always_inline",
DECL_ATTRIBUTES (callee->decl)));
+ inline_summary *caller_info = inline_summaries->get (caller);
+ inline_summary *callee_info = inline_summaries->get (callee);
/* Until GCC 4.9 we did not check the semantics alterning flags
bellow and inline across optimization boundry.
@@ -417,16 +419,21 @@ can_inline_edge_p (struct cgraph_edge *e
== !opt_for_fn (callee->decl, optimize) || !always_inline))
|| check_match (flag_wrapv)
|| check_match (flag_trapv)
- /* Strictly speaking only when the callee uses FP math. */
- || check_maybe_up (flag_rounding_math)
- || check_maybe_up (flag_trapping_math)
- || check_maybe_down (flag_unsafe_math_optimizations)
- || check_maybe_down (flag_finite_math_only)
- || check_maybe_up (flag_signaling_nans)
- || check_maybe_down (flag_cx_limited_range)
- || check_maybe_up (flag_signed_zeros)
- || check_maybe_down (flag_associative_math)
- || check_maybe_down (flag_reciprocal_math)
+ /* When caller or callee does FP math, be sure FP codegen flags
+ compatible. */
+ || ((caller_info->fp_expressions && callee_info->fp_expressions)
+ && (check_maybe_up (flag_rounding_math)
+ || check_maybe_up (flag_trapping_math)
+ || check_maybe_down (flag_unsafe_math_optimizations)
+ || check_maybe_down (flag_finite_math_only)
+ || check_maybe_up (flag_signaling_nans)
+ || check_maybe_down (flag_cx_limited_range)
+ || check_maybe_up (flag_signed_zeros)
+ || check_maybe_down (flag_associative_math)
+ || check_maybe_down (flag_reciprocal_math)
+ /* Strictly speaking only when the callee contains function
+ calls that may end up setting errno. */
+ || check_maybe_up (flag_errno_math)))
/* We do not want to make code compiled with exceptions to be
brought into a non-EH function unless we know that the callee
does not throw.
@@ -435,9 +442,6 @@ can_inline_edge_p (struct cgraph_edge *e
&& DECL_FUNCTION_PERSONALITY (callee->decl))
|| (check_maybe_up (flag_exceptions)
&& DECL_FUNCTION_PERSONALITY (callee->decl))
- /* Strictly speaking only when the callee contains function
- calls that may end up setting errno. */
- || check_maybe_up (flag_errno_math)
/* When devirtualization is diabled for callee, it is not safe
to inline it as we possibly mangled the type info.
Allow early inlining of always inlines. */
Index: ipa-inline.h
===================================================================
--- ipa-inline.h (revision 235312)
+++ ipa-inline.h (working copy)
@@ -132,6 +132,8 @@ struct GTY(()) inline_summary
/* True wen there is only one caller of the function before small function
inlining. */
unsigned int single_caller : 1;
+ /* True if function contains any floating point expressions. */
+ unsigned int fp_expressions : 1;
/* Information about function that will result after applying all the
inline decisions present in the callgraph. Generally kept up to
Index: ipa-inline-transform.c
===================================================================
--- ipa-inline-transform.c (revision 235312)
+++ ipa-inline-transform.c (working copy)
@@ -338,6 +338,63 @@ inline_call (struct cgraph_edge *e, bool
DECL_FUNCTION_SPECIFIC_OPTIMIZATION (to->decl)
= build_optimization_node (&opts);
}
+ inline_summary *caller_info = inline_summaries->get (to);
+ inline_summary *callee_info = inline_summaries->get (callee);
+ if (!caller_info->fp_expressions && callee_info->fp_expressions)
+ {
+ caller_info->fp_expressions = true;
+ if (opt_for_fn (callee->decl, flag_rounding_math)
+ != opt_for_fn (to->decl, flag_rounding_math)
+ || opt_for_fn (callee->decl, flag_trapping_math)
+ != opt_for_fn (to->decl, flag_trapping_math)
+ || opt_for_fn (callee->decl, flag_unsafe_math_optimizations)
+ != opt_for_fn (to->decl, flag_unsafe_math_optimizations)
+ || opt_for_fn (callee->decl, flag_finite_math_only)
+ != opt_for_fn (to->decl, flag_finite_math_only)
+ || opt_for_fn (callee->decl, flag_signaling_nans)
+ != opt_for_fn (to->decl, flag_signaling_nans)
+ || opt_for_fn (callee->decl, flag_cx_limited_range)
+ != opt_for_fn (to->decl, flag_cx_limited_range)
+ || opt_for_fn (callee->decl, flag_signed_zeros)
+ != opt_for_fn (to->decl, flag_signed_zeros)
+ || opt_for_fn (callee->decl, flag_associative_math)
+ != opt_for_fn (to->decl, flag_associative_math)
+ || opt_for_fn (callee->decl, flag_reciprocal_math)
+ != opt_for_fn (to->decl, flag_reciprocal_math)
+ || opt_for_fn (callee->decl, flag_errno_math)
+ != opt_for_fn (to->decl, flag_errno_math))
+ {
+ struct gcc_options opts = global_options;
+
+ cl_optimization_restore (&opts, opts_for_fn (to->decl));
+ opts.x_flag_rounding_math
+ = opt_for_fn (callee->decl, flag_rounding_math);
+ opts.x_flag_trapping_math
+ = opt_for_fn (callee->decl, flag_trapping_math);
+ opts.x_flag_unsafe_math_optimizations
+ = opt_for_fn (callee->decl, flag_unsafe_math_optimizations);
+ opts.x_flag_finite_math_only
+ = opt_for_fn (callee->decl, flag_finite_math_only);
+ opts.x_flag_signaling_nans
+ = opt_for_fn (callee->decl, flag_signaling_nans);
+ opts.x_flag_cx_limited_range
+ = opt_for_fn (callee->decl, flag_cx_limited_range);
+ opts.x_flag_signed_zeros
+ = opt_for_fn (callee->decl, flag_signed_zeros);
+ opts.x_flag_associative_math
+ = opt_for_fn (callee->decl, flag_associative_math);
+ opts.x_flag_reciprocal_math
+ = opt_for_fn (callee->decl, flag_reciprocal_math);
+ opts.x_flag_errno_math
+ = opt_for_fn (callee->decl, flag_errno_math);
+ if (dump_file)
+ fprintf (dump_file, "Copying FP flags from %s:%i to %s:%i\n",
+ callee->name (), callee->order, to->name (), to->order);
+ build_optimization_node (&opts);
+ DECL_FUNCTION_SPECIFIC_OPTIMIZATION (to->decl)
+ = build_optimization_node (&opts);
+ }
+ }
/* If aliases are involved, redirect edge to the actual destination and
possibly remove the aliases. */
Index: testsuite/gcc.dg/ipa/inline-8.c
===================================================================
--- testsuite/gcc.dg/ipa/inline-8.c (revision 0)
+++ testsuite/gcc.dg/ipa/inline-8.c (working copy)
@@ -0,0 +1,36 @@
+/* Verify that we do not inline isnanf test info -ffast-math code but that we
+ do inline trivial functions across -Ofast boundary. */
+/* { dg-do run } */
+/* { dg-options "-O2" } */
+#include <math.h>
+/* Can't be inlined because isnanf will be optimized out. */
+int
+cmp (float a)
+{
+ return isnanf (a);
+}
+/* Can be inlined. */
+float
+move (float a)
+{
+ return a;
+}
+float a;
+void
+set ()
+{
+ a=nan("");
+}
+float b;
+__attribute__ ((optimize("Ofast")))
+int
+main()
+{
+ b++;
+ if (cmp(a))
+ __builtin_abort ();
+ float a = move (1);
+ if (!__builtin_constant_p (a))
+ __builtin_abort ();
+ return 0;
+}
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