Hi!
If memcpy is folded into an assignment, that assignment can be for C++
folded into nothing (if it is copying of 1 byte from or to empty C++ class).
gimple-fold.c was changed to handle that case in some spots, but not all,
particularly if that memcpy is the last stmt in a basic block (which can
happen e.g. during inlining), gsi_stmt (*gsi) in fold_stmt_1 will ICE.
The gimple-fold.c hunks fix this (and also make sure that even when it
isn't the last stmt in a bb, we won't try to fold lhs of next stmt
if it folded/gimplified into nothing). With that fix the testcase ICEs
shortly afterwards, the tree-inline.c hunk is supposed to fix that.
I'd use cgraph_remove_edge there, but I'd have to handle all clones too,
so I'm calling cgraph_update_edges_for_call_stmt with a dummy stmt
instead (perhaps NULL could be used instead with adjustment of the
cgraph_update_edges_for_call_stmt{,_node} routines?).
The cgraph.c change is just in case the edge isn't there, we'd do useless
work and crash while doing that.
Bootstrapped/regtested on x86_64-linux and i686-linux, ok for trunk/4.6?
2011-06-03 Jakub Jelinek <ja...@redhat.com>
PR c++/49264
* gimple-fold.c (fold_stmt_1): Don't try to fold *& on the lhs
if stmt folded into nothing.
* tree-inline.c (fold_marked_statements): If a builtin at the
end of a bb folded into nothing, just update cgraph edges
and move to next bb.
* cgraph.c (cgraph_update_edges_for_call_stmt_node): Don't compute
count and frequency if new_call is NULL.
* g++.dg/opt/pr49264.C: New test.
--- gcc/gimple-fold.c.jj 2011-05-24 23:34:28.000000000 +0200
+++ gcc/gimple-fold.c 2011-06-03 09:13:34.000000000 +0200
@@ -1577,6 +1577,11 @@ fold_stmt_1 (gimple_stmt_iterator *gsi,
bool changed = false;
gimple stmt = gsi_stmt (*gsi);
unsigned i;
+ gimple_stmt_iterator gsinext = *gsi;
+ gimple next_stmt;
+
+ gsi_next (&gsinext);
+ next_stmt = gsi_end_p (gsinext) ? NULL : gsi_stmt (gsinext);
/* Fold the main computation performed by the statement. */
switch (gimple_code (stmt))
@@ -1665,10 +1670,19 @@ fold_stmt_1 (gimple_stmt_iterator *gsi,
default:;
}
+ /* If stmt folds into nothing and it was the last stmt in a bb,
+ don't call gsi_stmt. */
+ if (gsi_end_p (*gsi))
+ {
+ gcc_assert (next_stmt == NULL);
+ return changed;
+ }
+
stmt = gsi_stmt (*gsi);
- /* Fold *& on the lhs. */
- if (gimple_has_lhs (stmt))
+ /* Fold *& on the lhs. Don't do this if stmt folded into nothing,
+ as we'd changing the next stmt. */
+ if (gimple_has_lhs (stmt) && stmt != next_stmt)
{
tree lhs = gimple_get_lhs (stmt);
if (lhs && REFERENCE_CLASS_P (lhs))
--- gcc/tree-inline.c.jj 2011-06-02 10:15:20.000000000 +0200
+++ gcc/tree-inline.c 2011-06-03 09:29:15.000000000 +0200
@@ -4108,6 +4108,14 @@ fold_marked_statements (int first, struc
if (fold_stmt (&gsi))
{
gimple new_stmt;
+ /* If a builtin at the end of a bb folded into nothing,
+ the following loop won't work. */
+ if (gsi_end_p (gsi))
+ {
+ cgraph_update_edges_for_call_stmt (old_stmt, old_decl,
+ gimple_build_nop
());
+ break;
+ }
if (gsi_end_p (i2))
i2 = gsi_start_bb (BASIC_BLOCK (first));
else
--- gcc/cgraph.c.jj 2011-05-11 19:39:03.000000000 +0200
+++ gcc/cgraph.c 2011-06-03 09:40:02.000000000 +0200
@@ -1277,7 +1277,7 @@ cgraph_update_edges_for_call_stmt_node (
frequency = e->frequency;
cgraph_remove_edge (e);
}
- else
+ else if (new_call)
{
/* We are seeing new direct call; compute profile info based on BB.
*/
basic_block bb = gimple_bb (new_stmt);
--- gcc/testsuite/g++.dg/opt/pr49264.C.jj 2011-06-03 09:35:50.000000000
+0200
+++ gcc/testsuite/g++.dg/opt/pr49264.C 2011-06-03 08:50:33.000000000 +0200
@@ -0,0 +1,19 @@
+// PR c++/49264
+// { dg-do compile }
+// { dg-options "-O2" }
+
+struct B { };
+struct A { char a[sizeof (B) + 1]; } a;
+
+static inline void
+foo (const B &b)
+{
+ __builtin_memcpy (&a, &b, sizeof (b));
+}
+
+void
+bar ()
+{
+ B c;
+ foo (c);
+}
Jakub
