Re: PROPOSAL: Extend inline asm syntax with size spec

Segher Boessenkool
2018-10-09T16:12:18Z

On Mon, Oct 08, 2018 at 11:07:46AM +0200, Richard Biener wrote:
> On Mon, 8 Oct 2018, Segher Boessenkool wrote:
> > On Sun, Oct 07, 2018 at 03:53:26PM +0000, Michael Matz wrote:
> > > On Sun, 7 Oct 2018, Segher Boessenkool wrote:
> > > > On Sun, Oct 07, 2018 at 11:18:06AM +0200, Borislav Petkov wrote:
> > > > > Now, Richard suggested doing something like:
> > > > >
> > > > > 1) inline asm ("...")
> > > >
> > > > What would the semantics of this be?
> > >
> > > The size of the inline asm wouldn't be counted towards the inliner size
> > > limits (or be counted as "1").
> >
> > That sounds like a good option.
>
> Yes, I also like it for simplicity. It also avoids the requirement
> of translating the number (in bytes?) given by the user to
> "number of GIMPLE instructions" as needed by the inliner.

This patch implements this, for C only so far. And the syntax is
"asm inline", which is more in line with other syntax.

How does this look?

Segher

diff --git a/gcc/c/c-parser.c b/gcc/c/c-parser.c
index 1f173fc..94b1d41 100644
--- a/gcc/c/c-parser.c
+++ b/gcc/c/c-parser.c
@@ -6287,7 +6287,7 @@ static tree
c_parser_asm_statement (c_parser *parser)
{
tree quals, str, outputs, inputs, clobbers, labels, ret;
- bool simple, is_goto;
+ bool simple, is_goto, is_inline;
location_t asm_loc = c_parser_peek_token (parser)->location;
int section, nsections;

@@ -6318,6 +6318,13 @@ c_parser_asm_statement (c_parser *parser)
is_goto = true;
}

+ is_inline = false;
+ if (c_parser_next_token_is_keyword (parser, RID_INLINE))
+ {
+ c_parser_consume_token (parser);
+ is_inline = true;
+ }
+
/* ??? Follow the C++ parser rather than using the
lex_untranslated_string kludge. */
parser->lex_untranslated_string = true;
@@ -6393,7 +6400,8 @@ c_parser_asm_statement (c_parser *parser)
c_parser_skip_to_end_of_block_or_statement (parser);

ret = build_asm_stmt (quals, build_asm_expr (asm_loc, str, outputs, inputs,
- clobbers, labels, simple));
+ clobbers, labels, simple,
+ is_inline));

error:
parser->lex_untranslated_string = false;
diff --git a/gcc/c/c-tree.h b/gcc/c/c-tree.h
index 017c01c..f5629300 100644
--- a/gcc/c/c-tree.h
+++ b/gcc/c/c-tree.h
@@ -677,7 +677,8 @@ extern tree build_compound_literal (location_t, tree, tree, bool,
extern void check_compound_literal_type (location_t, struct c_type_name *);
extern tree c_start_case (location_t, location_t, tree, bool);
extern void c_finish_case (tree, tree);
-extern tree build_asm_expr (location_t, tree, tree, tree, tree, tree, bool);
+extern tree build_asm_expr (location_t, tree, tree, tree, tree, tree, bool,
+ bool);
extern tree build_asm_stmt (tree, tree);
extern int c_types_compatible_p (tree, tree);
extern tree c_begin_compound_stmt (bool);
diff --git a/gcc/c/c-typeck.c b/gcc/c/c-typeck.c
index 9d09b8d..e013100 100644
--- a/gcc/c/c-typeck.c
+++ b/gcc/c/c-typeck.c
@@ -10064,7 +10064,7 @@ build_asm_stmt (tree cv_qualifier, tree args)
are subtly different. We use a ASM_EXPR node to represent this. */
tree
build_asm_expr (location_t loc, tree string, tree outputs, tree inputs,
- tree clobbers, tree labels, bool simple)
+ tree clobbers, tree labels, bool simple, bool is_inline)
{
tree tail;
tree args;
@@ -10182,6 +10182,7 @@ build_asm_expr (location_t loc, tree string, tree outputs, tree inputs,
as volatile. */
ASM_INPUT_P (args) = simple;
ASM_VOLATILE_P (args) = (noutputs == 0);
+ ASM_INLINE_P (args) = is_inline;

return args;
}
diff --git a/gcc/gimple-pretty-print.c b/gcc/gimple-pretty-print.c
index 83e2273..1a00fa3 100644
--- a/gcc/gimple-pretty-print.c
+++ b/gcc/gimple-pretty-print.c
@@ -2019,6 +2019,8 @@ dump_gimple_asm (pretty_printer *buffer, gasm *gs, int spc, dump_flags_t flags)
pp_string (buffer, "__asm__");
if (gimple_asm_volatile_p (gs))
pp_string (buffer, " __volatile__");
+ if (gimple_asm_inline_p (gs))
+ pp_string (buffer, " __inline__");
if (gimple_asm_nlabels (gs))
pp_string (buffer, " goto");
pp_string (buffer, "(\"");
diff --git a/gcc/gimple.h b/gcc/gimple.h
index a5dda93..8a58e07 100644
--- a/gcc/gimple.h
+++ b/gcc/gimple.h
@@ -137,6 +137,7 @@ enum gimple_rhs_class
enum gf_mask {
GF_ASM_INPUT = 1 << 0,
GF_ASM_VOLATILE = 1 << 1,
+ GF_ASM_INLINE = 1 << 2,
GF_CALL_FROM_THUNK = 1 << 0,
GF_CALL_RETURN_SLOT_OPT = 1 << 1,
GF_CALL_TAILCALL = 1 << 2,
@@ -3911,7 +3912,7 @@ gimple_asm_volatile_p (const gasm *asm_stmt)
}

-/* If VOLATLE_P is true, mark asm statement ASM_STMT as volatile. */
+/* If VOLATILE_P is true, mark asm statement ASM_STMT as volatile. */

static inline void
gimple_asm_set_volatile (gasm *asm_stmt, bool volatile_p)
@@ -3923,6 +3924,27 @@ gimple_asm_set_volatile (gasm *asm_stmt, bool volatile_p)
}

+/* Return true ASM_STMT ASM_STMT is an asm statement marked inline. */
+
+static inline bool
+gimple_asm_inline_p (const gasm *asm_stmt)
+{
+ return (asm_stmt->subcode & GF_ASM_INLINE) != 0;
+}
+
+
+/* If INLINE_P is true, mark asm statement ASM_STMT as inline. */
+
+static inline void
+gimple_asm_set_inline (gasm *asm_stmt, bool inline_p)
+{
+ if (inline_p)
+ asm_stmt->subcode |= GF_ASM_INLINE;
+ else
+ asm_stmt->subcode &= ~GF_ASM_INLINE;
+}
+
+
/* If INPUT_P is true, mark asm ASM_STMT as an ASM_INPUT. */

static inline void
diff --git a/gcc/gimplify.c b/gcc/gimplify.c
index 509fc2f..10b80f2 100644
--- a/gcc/gimplify.c
+++ b/gcc/gimplify.c
@@ -6315,6 +6315,7 @@ gimplify_asm_expr (tree *expr_p, gimple_seq *pre_p, gimple_seq *post_p)

gimple_asm_set_volatile (stmt, ASM_VOLATILE_P (expr) || noutputs == 0);
gimple_asm_set_input (stmt, ASM_INPUT_P (expr));
+ gimple_asm_set_inline (stmt, ASM_INLINE_P (expr));

gimplify_seq_add_stmt (pre_p, stmt);
}
diff --git a/gcc/ipa-icf-gimple.c b/gcc/ipa-icf-gimple.c
index ba39ea3..5361139 100644
--- a/gcc/ipa-icf-gimple.c
+++ b/gcc/ipa-icf-gimple.c
@@ -993,6 +993,9 @@ func_checker::compare_gimple_asm (const gasm *g1, const gasm *g2)
if (gimple_asm_input_p (g1) != gimple_asm_input_p (g2))
return false;

+ if (gimple_asm_inline_p (g1) != gimple_asm_inline_p (g2))
+ return false;
+
if (gimple_asm_ninputs (g1) != gimple_asm_ninputs (g2))
return false;

diff --git a/gcc/tree-inline.c b/gcc/tree-inline.c
index 9134253..6b1d2ea 100644
--- a/gcc/tree-inline.c
+++ b/gcc/tree-inline.c
@@ -4108,6 +4108,8 @@ estimate_num_insns (gimple *stmt, eni_weights *weights)
with very long asm statements. */
if (count > 1000)
count = 1000;
+ if (gimple_asm_inline_p (as_a <gasm *> (stmt)))
+ count = !!count;
return MAX (1, count);
}

diff --git a/gcc/tree.h b/gcc/tree.h
index 2e45f9d..160b3a7 100644
--- a/gcc/tree.h
+++ b/gcc/tree.h
@@ -1245,6 +1245,9 @@ extern tree maybe_wrap_with_location (tree, location_t);
ASM_OPERAND with no operands. */
#define ASM_INPUT_P(NODE) (ASM_EXPR_CHECK (NODE)->base.static_flag)
#define ASM_VOLATILE_P(NODE) (ASM_EXPR_CHECK (NODE)->base.public_flag)
+/* Nonzero if we want to consider this asm as minimum length and cost
+ for inlining decisions. */
+#define ASM_INLINE_P(NODE) (ASM_EXPR_CHECK (NODE)->base.protected_flag)

/* COND_EXPR accessors. */
#define COND_EXPR_COND(NODE) (TREE_OPERAND (COND_EXPR_CHECK (NODE), 0))