Hello,
The test case for this bug triggeres O(extern_delcs**2) behavior
because value_member traverses the pending_assemble_externals list
from start to end for every new extern decl.
The solution I've picked, is to add a pointer set, and while there I
made pending_assemble_externals a VEC instead of a TREE_LIST. I've
also added a FIXME to clarify that this whole situation of having
places calling assemble_external is not desirable.
On gcc110, the test case compiles in ~4s with the patch, and ~24s
without. If I add LIM5(Y) and LIM5(Z), the compile time is ~15s with
the patch, and ~372s without the patch. I am not sure what is
reasonable for this kind of test case, but on a smaller machine the
test case will probably blow up if I add those two extra LIM5s.
Anyway. Bootstrapped&tested on powerpc64-unknown-linux-gnu.
OK for trunk?
OK for all open release branches too?
Ciao!
Steven
gcc/
* varasm.c (pending_assemble_externals): Make a VEC.
(pending_assemble_externals_set): New pointer set.
(process_pending_assemble_externals): Traverse the VEC instead
of the TREE_LIST. Destroy the pointer set.
(assemble_external): See if decl is in pending_assemble_externals_set,
and add it to pending_assemble_externals if necessary.
(init_varasm_once): Allocate pending_assemble_externals and
pending_assemble_externals_set.
testsuite/
* gcc.c-torture/compile/limits-externdecl.c: New test for PR62640.
gcc/
* varasm.c (pending_assemble_externals): Make a VEC.
(pending_assemble_externals_set): New pointer set.
(process_pending_assemble_externals): Traverse the VEC instead
of the TREE_LIST. Destroy the pointer set.
(assemble_external): See if decl is in pending_assemble_externals_set,
and add it to pending_assemble_externals if necessary.
(init_varasm_once): Allocate pending_assemble_externals and
pending_assemble_externals_set.
testsuite/
* gcc.c-torture/compile/limits-externdecl.c: New test for PR62640.
Index: varasm.c
===================================================================
--- varasm.c (revision 185603)
+++ varasm.c (working copy)
@@ -2097,8 +2097,15 @@ contains_pointers_p (tree type)
the compilation unit is finalized. This is the best we can do for
right now (i.e. stage 3 of GCC 4.0) - the right thing is to delay
it all the way to final. See PR 17982 for further discussion. */
-static GTY(()) tree pending_assemble_externals;
+static GTY(()) VEC(tree,gc) *pending_assemble_externals;
+/* FIXME: Trunk is at GCC 4.8 now and the above problem still hasn't been
+ addressed properly. This caused PR 52640 due to O(external_decls**2)
+ lookups in the pending_assemble_externals queue in assemble_external.
+ Paper over with this pointer set. (And pending_assemble_externals even
+ was a TREE_LIST before?!) */
+static struct pointer_set_t *pending_assemble_externals_set;
+
#ifdef ASM_OUTPUT_EXTERNAL
/* True if DECL is a function decl for which no out-of-line copy exists.
It is assumed that DECL's assembler name has been set. */
@@ -2146,11 +2153,14 @@ void
process_pending_assemble_externals (void)
{
#ifdef ASM_OUTPUT_EXTERNAL
- tree list;
- for (list = pending_assemble_externals; list; list = TREE_CHAIN (list))
- assemble_external_real (TREE_VALUE (list));
+ size_t i;
+ tree decl;
- pending_assemble_externals = 0;
+ FOR_EACH_VEC_ELT (tree, pending_assemble_externals, i, decl)
+ assemble_external_real (decl);
+ VEC_free (tree, gc, pending_assemble_externals);
+
+ pointer_set_destroy (pending_assemble_externals_set);
#endif
}
@@ -2191,9 +2201,8 @@ assemble_external (tree decl ATTRIBUTE_UNUSED)
weak_decls = tree_cons (NULL, decl, weak_decls);
#ifdef ASM_OUTPUT_EXTERNAL
- if (value_member (decl, pending_assemble_externals) == NULL_TREE)
- pending_assemble_externals = tree_cons (NULL, decl,
- pending_assemble_externals);
+ if (! pointer_set_insert (pending_assemble_externals_set, decl))
+ VEC_safe_push (tree, gc, pending_assemble_externals, decl);
#endif
}
@@ -6168,6 +6177,11 @@ init_varasm_once (void)
if (readonly_data_section == NULL)
readonly_data_section = text_section;
+
+#ifdef ASM_OUTPUT_EXTERNAL
+ pending_assemble_externals = VEC_alloc (tree, gc, 12);
+ pending_assemble_externals_set = pointer_set_create ();
+#endif
}
enum tls_model
Index: testsuite/gcc.c-torture/compile/limits-externdecl.c
===================================================================
--- testsuite/gcc.c-torture/compile/limits-externdecl.c (revision 0)
+++ testsuite/gcc.c-torture/compile/limits-externdecl.c (revision 0)
@@ -0,0 +1,56 @@
+/* Inspired by the test case for PR middle-end/52640. */
+
+typedef struct
+{
+ char *value;
+} REFERENCE;
+
+/* Add a few "extern int Xxxxxx ();" declarations. */
+#undef DEF
+#undef LIM1
+#undef LIM2
+#undef LIM3
+#undef LIM4
+#undef LIM5
+#undef LIM6
+#define DEF(x) extern int x ()
+#define LIM1(x) DEF(x##0); DEF(x##1); DEF(x##2); DEF(x##3); DEF(x##4); \
+ DEF(x##5); DEF(x##6); DEF(x##7); DEF(x##8); DEF(x##9);
+#define LIM2(x) LIM1(x##0) LIM1(x##1) LIM1(x##2) LIM1(x##3) LIM1(x##4) \
+ LIM1(x##5) LIM1(x##6) LIM1(x##7) LIM1(x##8) LIM1(x##9)
+#define LIM3(x) LIM2(x##0) LIM2(x##1) LIM2(x##2) LIM2(x##3) LIM2(x##4) \
+ LIM2(x##5) LIM2(x##6) LIM2(x##7) LIM2(x##8) LIM2(x##9)
+#define LIM4(x) LIM3(x##0) LIM3(x##1) LIM3(x##2) LIM3(x##3) LIM3(x##4) \
+ LIM3(x##5) LIM3(x##6) LIM3(x##7) LIM3(x##8) LIM3(x##9)
+#define LIM5(x) LIM4(x##0) LIM4(x##1) LIM4(x##2) LIM4(x##3) LIM4(x##4) \
+ LIM4(x##5) LIM4(x##6) LIM4(x##7) LIM4(x##8) LIM4(x##9)
+#define LIM6(x) LIM5(x##0) LIM5(x##1) LIM5(x##2) LIM5(x##3) LIM5(x##4) \
+ LIM5(x##5) LIM5(x##6) LIM5(x##7) LIM5(x##8) LIM5(x##9)
+LIM5 (X);
+
+/* Add references to them, or GCC will simply ignore the extern decls. */
+#undef DEF
+#undef LIM1
+#undef LIM2
+#undef LIM3
+#undef LIM4
+#undef LIM5
+#undef LIM6
+#define DEF(x) (char *) x
+#define LIM1(x) DEF(x##0), DEF(x##1), DEF(x##2), DEF(x##3), DEF(x##4), \
+ DEF(x##5), DEF(x##6), DEF(x##7), DEF(x##8), DEF(x##9),
+#define LIM2(x) LIM1(x##0) LIM1(x##1) LIM1(x##2) LIM1(x##3) LIM1(x##4) \
+ LIM1(x##5) LIM1(x##6) LIM1(x##7) LIM1(x##8) LIM1(x##9)
+#define LIM3(x) LIM2(x##0) LIM2(x##1) LIM2(x##2) LIM2(x##3) LIM2(x##4) \
+ LIM2(x##5) LIM2(x##6) LIM2(x##7) LIM2(x##8) LIM2(x##9)
+#define LIM4(x) LIM3(x##0) LIM3(x##1) LIM3(x##2) LIM3(x##3) LIM3(x##4) \
+ LIM3(x##5) LIM3(x##6) LIM3(x##7) LIM3(x##8) LIM3(x##9)
+#define LIM5(x) LIM4(x##0) LIM4(x##1) LIM4(x##2) LIM4(x##3) LIM4(x##4) \
+ LIM4(x##5) LIM4(x##6) LIM4(x##7) LIM4(x##8) LIM4(x##9)
+#define LIM6(x) LIM5(x##0) LIM5(x##1) LIM5(x##2) LIM5(x##3) LIM5(x##4) \
+ LIM5(x##5) LIM5(x##6) LIM5(x##7) LIM5(x##8) LIM5(x##9)
+REFERENCE references[] = {
+ LIM5 (X)
+ 0
+};
+
