re PR c++/70001 (Infinity compilation time)

	PR c++/70001
	* constexpr.c (cxx_eval_vec_init_1): For pre_init case, reuse
	return value from cxx_eval_constant_expression from earlier
	elements if it is valid constant initializer requiring no
	relocations.

	* g++.dg/cpp0x/constexpr-70001-1.C: New test.
	* g++.dg/cpp0x/constexpr-70001-2.C: New test.
	* g++.dg/cpp0x/constexpr-70001-3.C: New test.

Co-Authored-By: Jakub Jelinek <jakub@redhat.com>

From-SVN: r234117

6 files changed, 88 insertions, 3 deletions

diff --git a/gcc/cp/ChangeLog b/gcc/cp/ChangeLog
index 6e69e77..46174cc 100644
--- a/gcc/cp/ChangeLog
+++ b/gcc/cp/ChangeLog
@@ -1,3 +1,12 @@
+2016-03-10  Patrick Palka  <ppalka@gcc.gnu.org>
+	    Jakub Jelinek  <jakub@redhat.com>
+
+	PR c++/70001
+	* constexpr.c (cxx_eval_vec_init_1): For pre_init case, reuse
+	return value from cxx_eval_constant_expression from earlier
+	elements if it is valid constant initializer requiring no
+	relocations.
+
 2016-03-10  Marek Polacek  <polacek@redhat.com>
 
 	PR c++/70153
diff --git a/gcc/cp/constexpr.c b/gcc/cp/constexpr.c
index 7f3edcf..5f97c9d 100644
--- a/gcc/cp/constexpr.c
+++ b/gcc/cp/constexpr.c
@@ -2340,6 +2340,7 @@ cxx_eval_vec_init_1 (const constexpr_ctx *ctx, tree atype, tree init,
   vec<constructor_elt, va_gc> **p = &CONSTRUCTOR_ELTS (ctx->ctor);
   vec_alloc (*p, max + 1);
   bool pre_init = false;
+  tree pre_init_elt = NULL_TREE;
   unsigned HOST_WIDE_INT i;
 
   /* For the default constructor, build up a call to the default
@@ -2389,9 +2390,18 @@ cxx_eval_vec_init_1 (const constexpr_ctx *ctx, tree atype, tree init,
 	{
 	  /* Initializing an element using value or default initialization
 	     we just pre-built above.  */
-	  eltinit = (cxx_eval_constant_expression
-		     (&new_ctx, init,
-		      lval, non_constant_p, overflow_p));
+	  if (pre_init_elt == NULL_TREE)
+	    pre_init_elt
+	      = cxx_eval_constant_expression (&new_ctx, init, lval,
+					      non_constant_p, overflow_p);
+	  eltinit = pre_init_elt;
+	  /* Don't reuse the result of cxx_eval_constant_expression
+	     call if it isn't a constant initializer or if it requires
+	     relocations.  */
+	  if (initializer_constant_valid_p (pre_init_elt,
+					    TREE_TYPE (pre_init_elt))
+	      != null_pointer_node)
+	    pre_init_elt = NULL_TREE;
 	}
       else
 	{
diff --git a/gcc/testsuite/ChangeLog b/gcc/testsuite/ChangeLog
index c6ffcf3..3043ab9 100644
--- a/gcc/testsuite/ChangeLog
+++ b/gcc/testsuite/ChangeLog
@@ -1,3 +1,11 @@
+2016-03-10  Patrick Palka  <ppalka@gcc.gnu.org>
+	    Jakub Jelinek  <jakub@redhat.com>
+
+	PR c++/70001
+	* g++.dg/cpp0x/constexpr-70001-1.C: New test.
+	* g++.dg/cpp0x/constexpr-70001-2.C: New test.
+	* g++.dg/cpp0x/constexpr-70001-3.C: New test.
+
 2016-03-10  Jan Hubicka  <hubicka@ucw.cz>
 
 	PR lto/69589
diff --git a/gcc/testsuite/g++.dg/cpp0x/constexpr-70001-1.C b/gcc/testsuite/g++.dg/cpp0x/constexpr-70001-1.C
new file mode 100644
index 0000000..e68ff0e
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp0x/constexpr-70001-1.C
@@ -0,0 +1,13 @@
+// PR c++/70001
+// { dg-do compile { target c++11 } }
+
+struct B
+{
+  int a;
+  constexpr B () : a (0) { }
+};
+
+struct A
+{
+  B b[1 << 19];
+} c;
diff --git a/gcc/testsuite/g++.dg/cpp0x/constexpr-70001-2.C b/gcc/testsuite/g++.dg/cpp0x/constexpr-70001-2.C
new file mode 100644
index 0000000..96f5ad4
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp0x/constexpr-70001-2.C
@@ -0,0 +1,19 @@
+// PR c++/70001
+// { dg-do run { target c++11 } }
+
+struct B
+{
+  struct B *a;
+  constexpr B () : a (this) { }
+};
+
+constexpr int N = 1 << 4;
+struct A { B c[N]; } d;
+
+int
+main ()
+{
+  for (int i = 0; i < N; ++i)
+    if (d.c[i].a != &d.c[i])
+      __builtin_abort ();
+}
diff --git a/gcc/testsuite/g++.dg/cpp0x/constexpr-70001-3.C b/gcc/testsuite/g++.dg/cpp0x/constexpr-70001-3.C
new file mode 100644
index 0000000..99d4c38
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp0x/constexpr-70001-3.C
@@ -0,0 +1,26 @@
+// PR c++/70001
+// { dg-do compile { target c++11 } }
+
+#include <array>
+#include <complex>
+
+typedef std::complex<double> cd;
+
+const int LOG = 17;
+const int N = (1 << LOG);
+
+std::array<cd, N> a;
+std::array<cd, N> b;
+
+void
+foo (std::array<cd, N> &arr)
+{
+  std::array<std::array<cd, N>, LOG + 1> f;
+}
+
+int
+main ()
+{
+  foo (a);
+  foo (b);
+}