introduce EH_ELSE tree and gimplifier
Alexandre Oliva
oliva@adacore.com
Thu Jul 4 08:19:00 GMT 2019
On Jul 1, 2019, Richard Biener <richard.guenther@gmail.com> wrote:
> On Fri, Jun 28, 2019 at 5:21 AM Alexandre Oliva <oliva@adacore.com> wrote:
>>
>> On Jun 27, 2019, Richard Biener <richard.guenther@gmail.com> wrote:
>>
>> > On Thu, Jun 27, 2019 at 10:18 AM Alexandre Oliva <oliva@adacore.com> wrote:
>>
>> >> @@ -909,6 +909,13 @@ DEFTREECODE (TRY_CATCH_EXPR, "try_catch_expr", tcc_statement, 2)
>> >> The second operand is a cleanup expression which is evaluated
>> >> on any exit (normal, exception, or jump out) from this expression. */
>> >> DEFTREECODE (TRY_FINALLY_EXPR, "try_finally", tcc_statement, 2)
>> >> +
>> >> +/* Evaluate either the normal or the exceptional cleanup. This must
>> >> + only be present as the cleanup expression in a TRY_FINALLY_EXPR.
>> >> + If the TRY_FINALLY_EXPR completes normally, the first operand of
>> >> + EH_ELSE is used as a cleanup, otherwise the second operand is
>> >> + used. */
>> >> +DEFTREECODE (EH_ELSE, "eh_else", tcc_statement, 2)
>>
>> > It's a bit weird that this is a tcc_statement as opposed to tcc_expression,
>> Erhm... What's weird about it? It is not something that belongs in an
>> arbitrary expr, it's a lot more like a top-level statement, like
>> try_finally, having side effects but no useful value.
> It's weird because it appears in a TRY_FINALLY statement operand.
The other operand could be a nested TRY_FINALLY, but that doesn't make
TRY_FINALLY a tcc_expression.
> But I guess the line between statements and expressions in GENERIC
> is muddy...
My understanding of the general rule is that tcc_expressions have
values, whereas tcc_statements don't.
>> > also I'd have called it EH_ELSE_EXPR for clarity.
>> Now *that* would be weird IMHO. No offense intended, but I'd have
>> dropped the _EXPR from TRY_FINALLY_EXPR to make it match the
>> "try_finally" string.
> OK, let me say for consistency then ...
Ok, I like that one ;-) I've adjusted the "try_finally" string, and
changed EH_ELSE to EH_ELSE_EXPR all over (but not in GIMPLE_EH_ELSE).
I've also changed the way TRY_FINALLY_EXPR/EH_ELSE_EXPR are output in
generic and gimple dumps, using the notation try/finally/else (this is
the notation I started using in my unfinished gimplefe attempt, to avoid
adding more keywords; more in another message). I've retained the
ability to dump GIMPLE_EH_EXPR separately, because I'm not entirely sure
it could never be separated from the enclosing TRY_FINALLY_EXPR.
introduce EH_ELSE_EXPR tree and gimplifier
I found GIMPLE_EH_ELSE offered exactly the semantics I needed for some
Ada changes yet to be contributed, but GIMPLE_EH_ELSE was only built
by GIMPLE passes, and I needed to build earlier something that
eventually became GIMPLE_EH_ELSE.
This patch does that, introducing an EH_ELSE_EXPR tree, and logic to
dump it and to gimplify it.
Regstrapped on x86_64-linux-gnu. Ok to install?
for gcc/ChangeLog
* doc/generic.texi (Cleanups): Document EH_ELSE_EXPR.
* except.c: Likewise.
* expr.c (expand_expr_real_1): Reject it.
* gimplify.c (gimplify_expr): Gimplify it, within
TRY_FINALLY_EXPR.
* tree-dump.c (dequeue_and_dump): Dump it.
* tree-pretty-print.c (dump_generic_node): Likewise.
* tree.c (block_may_fallthru): Handle it.
* tree.def (EH_ELSE_EXPR): Introduce it.
* gimple-pretty-print.c (dump_gimple_try): Dump TRY_FINALLY
with GIMPLE_EH_ELSE as try/finally/else.
---
gcc/doc/generic.texi | 5 +++++
gcc/except.c | 12 ++++++------
gcc/expr.c | 1 +
gcc/gimple-pretty-print.c | 20 +++++++++++++++++++-
gcc/gimplify.c | 18 +++++++++++++++++-
gcc/tree-dump.c | 1 +
gcc/tree-pretty-print.c | 28 +++++++++++++++++++++++++---
gcc/tree.c | 3 +++
gcc/tree.def | 9 ++++++++-
9 files changed, 85 insertions(+), 12 deletions(-)
diff --git a/gcc/doc/generic.texi b/gcc/doc/generic.texi
index 67f7ad53af6b..8901d5f357e2 100644
--- a/gcc/doc/generic.texi
+++ b/gcc/doc/generic.texi
@@ -2180,6 +2180,11 @@ After the second sequence is executed, if it completes normally by
falling off the end, execution continues wherever the first sequence
would have continued, by falling off the end, or doing a goto, etc.
+If the second sequence is an @code{EH_ELSE_EXPR} selector, then the
+sequence in its first operand is used when the first sequence completes
+normally, and that in its second operand is used for exceptional
+cleanups, i.e., when an exception propagates out of the first sequence.
+
@code{TRY_FINALLY_EXPR} complicates the flow graph, since the cleanup
needs to appear on every edge out of the controlled block; this
reduces the freedom to move code across these edges. Therefore, the
diff --git a/gcc/except.c b/gcc/except.c
index edaeeb4cfd1b..29f333912d15 100644
--- a/gcc/except.c
+++ b/gcc/except.c
@@ -27,14 +27,14 @@ along with GCC; see the file COPYING3. If not see
the compilation process:
In the beginning, in the front end, we have the GENERIC trees
- TRY_CATCH_EXPR, TRY_FINALLY_EXPR, WITH_CLEANUP_EXPR,
+ TRY_CATCH_EXPR, TRY_FINALLY_EXPR, EH_ELSE_EXPR, WITH_CLEANUP_EXPR,
CLEANUP_POINT_EXPR, CATCH_EXPR, and EH_FILTER_EXPR.
- During initial gimplification (gimplify.c) these are lowered
- to the GIMPLE_TRY, GIMPLE_CATCH, and GIMPLE_EH_FILTER nodes.
- The WITH_CLEANUP_EXPR and CLEANUP_POINT_EXPR nodes are converted
- into GIMPLE_TRY_FINALLY nodes; the others are a more direct 1-1
- conversion.
+ During initial gimplification (gimplify.c) these are lowered to the
+ GIMPLE_TRY, GIMPLE_CATCH, GIMPLE_EH_ELSE, and GIMPLE_EH_FILTER
+ nodes. The WITH_CLEANUP_EXPR and CLEANUP_POINT_EXPR nodes are
+ converted into GIMPLE_TRY_FINALLY nodes; the others are a more
+ direct 1-1 conversion.
During pass_lower_eh (tree-eh.c) we record the nested structure
of the TRY nodes in EH_REGION nodes in CFUN->EH->REGION_TREE.
diff --git a/gcc/expr.c b/gcc/expr.c
index 4acf250dd3ce..c922aaa45b9b 100644
--- a/gcc/expr.c
+++ b/gcc/expr.c
@@ -11292,6 +11292,7 @@ expand_expr_real_1 (tree exp, rtx target, machine_mode tmode,
case CATCH_EXPR:
case EH_FILTER_EXPR:
case TRY_FINALLY_EXPR:
+ case EH_ELSE_EXPR:
/* Lowered by tree-eh.c. */
gcc_unreachable ();
diff --git a/gcc/gimple-pretty-print.c b/gcc/gimple-pretty-print.c
index 0ccbd6c63527..ea845492b0be 100644
--- a/gcc/gimple-pretty-print.c
+++ b/gcc/gimple-pretty-print.c
@@ -1228,6 +1228,8 @@ dump_gimple_try (pretty_printer *buffer, gtry *gs, int spc,
newline_and_indent (buffer, spc + 2);
pp_right_brace (buffer);
+ gimple_seq seq = gimple_try_cleanup (gs);
+
if (gimple_try_kind (gs) == GIMPLE_TRY_CATCH)
{
newline_and_indent (buffer, spc);
@@ -1241,12 +1243,28 @@ dump_gimple_try (pretty_printer *buffer, gtry *gs, int spc,
pp_string (buffer, "finally");
newline_and_indent (buffer, spc + 2);
pp_left_brace (buffer);
+
+ if (seq && is_a <geh_else *> (gimple_seq_first_stmt (seq))
+ && gimple_seq_nondebug_singleton_p (seq))
+ {
+ geh_else *stmt = as_a <geh_else *> (gimple_seq_first_stmt (seq));
+ seq = gimple_eh_else_n_body (stmt);
+ pp_newline (buffer);
+ dump_gimple_seq (buffer, seq, spc + 4, flags);
+ newline_and_indent (buffer, spc + 2);
+ pp_right_brace (buffer);
+ seq = gimple_eh_else_e_body (stmt);
+ newline_and_indent (buffer, spc);
+ pp_string (buffer, "else");
+ newline_and_indent (buffer, spc + 2);
+ pp_left_brace (buffer);
+ }
}
else
pp_string (buffer, " <UNKNOWN GIMPLE_TRY> {");
pp_newline (buffer);
- dump_gimple_seq (buffer, gimple_try_cleanup (gs), spc + 4, flags);
+ dump_gimple_seq (buffer, seq, spc + 4, flags);
newline_and_indent (buffer, spc + 2);
pp_right_brace (buffer);
}
diff --git a/gcc/gimplify.c b/gcc/gimplify.c
index 9e5e42309412..a3792d16742e 100644
--- a/gcc/gimplify.c
+++ b/gcc/gimplify.c
@@ -13079,7 +13079,22 @@ gimplify_expr (tree *expr_p, gimple_seq *pre_p, gimple_seq *post_p,
input_location = UNKNOWN_LOCATION;
eval = cleanup = NULL;
gimplify_and_add (TREE_OPERAND (*expr_p, 0), &eval);
- gimplify_and_add (TREE_OPERAND (*expr_p, 1), &cleanup);
+ if (TREE_CODE (*expr_p) == TRY_FINALLY_EXPR
+ && TREE_CODE (TREE_OPERAND (*expr_p, 1)) == EH_ELSE_EXPR)
+ {
+ gimple_seq n = NULL, e = NULL;
+ gimplify_and_add (TREE_OPERAND (TREE_OPERAND (*expr_p, 1),
+ 0), &n);
+ gimplify_and_add (TREE_OPERAND (TREE_OPERAND (*expr_p, 1),
+ 1), &e);
+ if (!gimple_seq_empty_p (n) && !gimple_seq_empty_p (e))
+ {
+ geh_else *stmt = gimple_build_eh_else (n, e);
+ gimple_seq_add_stmt (&cleanup, stmt);
+ }
+ }
+ else
+ gimplify_and_add (TREE_OPERAND (*expr_p, 1), &cleanup);
/* Don't create bogus GIMPLE_TRY with empty cleanup. */
if (gimple_seq_empty_p (cleanup))
{
@@ -13637,6 +13652,7 @@ gimplify_expr (tree *expr_p, gimple_seq *pre_p, gimple_seq *post_p,
&& code != LOOP_EXPR
&& code != SWITCH_EXPR
&& code != TRY_FINALLY_EXPR
+ && code != EH_ELSE_EXPR
&& code != OACC_PARALLEL
&& code != OACC_KERNELS
&& code != OACC_DATA
diff --git a/gcc/tree-dump.c b/gcc/tree-dump.c
index 58cb1ee5a729..51c0965861f8 100644
--- a/gcc/tree-dump.c
+++ b/gcc/tree-dump.c
@@ -604,6 +604,7 @@ dequeue_and_dump (dump_info_p di)
break;
case TRY_FINALLY_EXPR:
+ case EH_ELSE_EXPR:
dump_child ("op 0", TREE_OPERAND (t, 0));
dump_child ("op 1", TREE_OPERAND (t, 1));
break;
diff --git a/gcc/tree-pretty-print.c b/gcc/tree-pretty-print.c
index dacda7bd0534..742c2840cd53 100644
--- a/gcc/tree-pretty-print.c
+++ b/gcc/tree-pretty-print.c
@@ -2815,12 +2815,34 @@ dump_generic_node (pretty_printer *pp, tree node, int spc, dump_flags_t flags,
newline_and_indent (pp, spc+2);
pp_right_brace (pp);
newline_and_indent (pp, spc);
- pp_string (pp,
- (TREE_CODE (node) == TRY_CATCH_EXPR) ? "catch" : "finally");
+ if (TREE_CODE (node) == TRY_CATCH_EXPR)
+ {
+ node = TREE_OPERAND (node, 1);
+ pp_string (pp, "catch");
+ }
+ else
+ {
+ gcc_assert (TREE_CODE (node) == TRY_FINALLY_EXPR);
+ node = TREE_OPERAND (node, 1);
+ pp_string (pp, "finally");
+ if (TREE_CODE (node) == EH_ELSE_EXPR)
+ {
+ newline_and_indent (pp, spc+2);
+ pp_left_brace (pp);
+ newline_and_indent (pp, spc+4);
+ dump_generic_node (pp, TREE_OPERAND (node, 0), spc+4,
+ flags, true);
+ newline_and_indent (pp, spc+2);
+ pp_right_brace (pp);
+ newline_and_indent (pp, spc);
+ node = TREE_OPERAND (node, 1);
+ pp_string (pp, "else");
+ }
+ }
newline_and_indent (pp, spc+2);
pp_left_brace (pp);
newline_and_indent (pp, spc+4);
- dump_generic_node (pp, TREE_OPERAND (node, 1), spc+4, flags, true);
+ dump_generic_node (pp, node, spc+4, flags, true);
newline_and_indent (pp, spc+2);
pp_right_brace (pp);
is_expr = false;
diff --git a/gcc/tree.c b/gcc/tree.c
index 76d94c6578a5..563af6fbdda6 100644
--- a/gcc/tree.c
+++ b/gcc/tree.c
@@ -13415,6 +13415,9 @@ block_may_fallthru (const_tree block)
return (block_may_fallthru (TREE_OPERAND (stmt, 0))
&& block_may_fallthru (TREE_OPERAND (stmt, 1)));
+ case EH_ELSE_EXPR:
+ return block_may_fallthru (TREE_OPERAND (stmt, 0));
+
case MODIFY_EXPR:
if (TREE_CODE (TREE_OPERAND (stmt, 1)) == CALL_EXPR)
stmt = TREE_OPERAND (stmt, 1);
diff --git a/gcc/tree.def b/gcc/tree.def
index 10a14fc23b0c..d2e693892cd6 100644
--- a/gcc/tree.def
+++ b/gcc/tree.def
@@ -908,7 +908,14 @@ DEFTREECODE (TRY_CATCH_EXPR, "try_catch_expr", tcc_statement, 2)
/* Evaluate the first operand.
The second operand is a cleanup expression which is evaluated
on any exit (normal, exception, or jump out) from this expression. */
-DEFTREECODE (TRY_FINALLY_EXPR, "try_finally", tcc_statement, 2)
+DEFTREECODE (TRY_FINALLY_EXPR, "try_finally_expr", tcc_statement, 2)
+
+/* Evaluate either the normal or the exceptional cleanup. This must
+ only be present as the cleanup expression in a TRY_FINALLY_EXPR.
+ If the TRY_FINALLY_EXPR completes normally, the first operand of
+ EH_ELSE_EXPR is used as a cleanup, otherwise the second operand is
+ used. */
+DEFTREECODE (EH_ELSE_EXPR, "eh_else_expr", tcc_statement, 2)
/* These types of expressions have no useful value,
and always have side effects. */
--
Alexandre Oliva, freedom fighter he/him https://FSFLA.org/blogs/lxo
Be the change, be Free! FSF Latin America board member
GNU Toolchain Engineer Free Software Evangelist
Hay que enGNUrecerse, pero sin perder la terGNUra jamás - Che GNUevara
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