From: Steven Bosscher <steven@gcc.gnu.org>
Date: Sat, 24 Mar 2012 13:46:33 +0000 (+0000)
Subject: re PR middle-end/52640 (performance bottleneck: gcc/tree.c;value_member)
X-Git-Tag: releases/gcc-4.5.4~171
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=935387e29346b4287bde112f33780b9ed9bb84ff;p=thirdparty%2Fgcc.git

re PR middle-end/52640 (performance bottleneck: gcc/tree.c;value_member)

gcc/
	PR middle-end/52640
	* varasm.c: Include pointer-set.h.
	(pending_assemble_externals_set): New pointer set.
	(process_pending_assemble_externals): 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_set.

testsuite/
	PR middle-end/52640
	* gcc.c-torture/compile/limits-externdecl.c: New test.

From-SVN: r185757
---

diff --git a/gcc/testsuite/gcc.c-torture/compile/limits-externdecl.c b/gcc/testsuite/gcc.c-torture/compile/limits-externdecl.c
new file mode 100644
index 000000000000..c484becb85f5
--- /dev/null
+++ b/gcc/testsuite/gcc.c-torture/compile/limits-externdecl.c
@@ -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
+};
+
diff --git a/gcc/varasm.c b/gcc/varasm.c
index 0d6ecb314d66..e18606a3e22e 100644
--- a/gcc/varasm.c
+++ b/gcc/varasm.c
@@ -30,6 +30,7 @@ along with GCC; see the file COPYING3.  If not see
 #include "config.h"
 #include "system.h"
 #include "coretypes.h"
+#include "pointer-set.h"
 #include "tm.h"
 #include "rtl.h"
 #include "tree.h"
@@ -2302,6 +2303,14 @@ contains_pointers_p (tree type)
    it all the way to final.  See PR 17982 for further discussion.  */
 static GTY(()) tree 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 TREE_LIST in assemble_external.
+   Paper over with this pointer set, which we use to see if we have already
+   added a decl to pending_assemble_externals without first traversing
+   the entire pending_assemble_externals list.  See assemble_external().  */
+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.  */
@@ -2351,6 +2360,7 @@ process_pending_assemble_externals (void)
     assemble_external_real (TREE_VALUE (list));
 
   pending_assemble_externals = 0;
+  pointer_set_destroy (pending_assemble_externals_set);
 #endif
 }
 
@@ -2391,7 +2401,7 @@ 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)
+  if (! pointer_set_insert (pending_assemble_externals_set, decl))
     pending_assemble_externals = tree_cons (NULL, decl,
 					    pending_assemble_externals);
 #endif
@@ -5952,6 +5962,10 @@ init_varasm_once (void)
 
   if (readonly_data_section == NULL)
     readonly_data_section = text_section;
+
+#ifdef ASM_OUTPUT_EXTERNAL
+  pending_assemble_externals_set = pointer_set_create ();
+#endif
 }
 
 enum tls_model