introduce EH_ELSE tree and gimplifier
Alexandre Oliva
oliva@adacore.com
Thu Jun 27 08:17:00 GMT 2019
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 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.
* 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): Introduce.
---
gcc/doc/generic.texi | 5 +++++
gcc/except.c | 12 ++++++------
gcc/expr.c | 1 +
gcc/gimplify.c | 18 +++++++++++++++++-
gcc/tree-dump.c | 1 +
gcc/tree-pretty-print.c | 11 +++++++++++
gcc/tree.c | 3 +++
gcc/tree.def | 7 +++++++
8 files changed, 51 insertions(+), 7 deletions(-)
diff --git a/gcc/doc/generic.texi b/gcc/doc/generic.texi
index 67f7ad53af6b..1d0e3cfec1d6 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} 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..76cd099749f3 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, 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 c78bc74c0d9f..70fb721a9621 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:
/* Lowered by tree-eh.c. */
gcc_unreachable ();
diff --git a/gcc/gimplify.c b/gcc/gimplify.c
index 0b25e7100cde..de4cb66e2b65 100644
--- a/gcc/gimplify.c
+++ b/gcc/gimplify.c
@@ -13074,7 +13074,22 @@ 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)
+ {
+ 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))
{
@@ -13632,6 +13647,7 @@ 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
&& code != OACC_PARALLEL
&& code != OACC_KERNELS
&& code != OACC_DATA
diff --git a/gcc/tree-dump.c b/gcc/tree-dump.c
index 58cb1ee5a729..f7c89c3374ff 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:
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 329cc6fceeb2..663616d0a0f3 100644
--- a/gcc/tree-pretty-print.c
+++ b/gcc/tree-pretty-print.c
@@ -2823,6 +2823,17 @@ dump_generic_node (pretty_printer *pp, tree node, int spc, dump_flags_t flags,
is_expr = false;
break;
+ case EH_ELSE:
+ pp_string (pp, "<<normal>>:");
+ newline_and_indent (pp, spc+2);
+ dump_generic_node (pp, TREE_OPERAND (node, 0), spc+2, flags, true);
+ newline_and_indent (pp, spc);
+ pp_string (pp, "<<except>>:");
+ newline_and_indent (pp, spc+2);
+ dump_generic_node (pp, TREE_OPERAND (node, 1), spc+2, flags, true);
+ is_expr = false;
+ break;
+
case CATCH_EXPR:
pp_string (pp, "catch (");
dump_generic_node (pp, CATCH_TYPES (node), spc+2, flags, false);
diff --git a/gcc/tree.c b/gcc/tree.c
index c97facd7ce50..8f6f6c43b6ce 100644
--- a/gcc/tree.c
+++ b/gcc/tree.c
@@ -13408,6 +13408,9 @@ block_may_fallthru (const_tree block)
return (block_may_fallthru (TREE_OPERAND (stmt, 0))
&& block_may_fallthru (TREE_OPERAND (stmt, 1)));
+ case EH_ELSE:
+ 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..9cf53964f8eb 100644
--- a/gcc/tree.def
+++ b/gcc/tree.def
@@ -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)
/* 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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