[C++ PATCH] Fix ICE with offsetof-like initializer (PR c++/88410)

[Jakub Jelinek <jakub@redhat.com>]

Hi!

The following testcase ICEs starting with my change to move offsetof-like
expression handling from the parsing to cp_fold - if the base expression
is not INTEGER_CST, but a constant VAR_DECL initialized with INTEGER_CST,
then we don't fold it as offsetof-like expression and as we use recursive
cp_fold only on functions, not initializers, we don't fold that VAR_DECL in
there into INTEGER_CST and the middle-end ICEs on it trying to fold it.

Fixed thusly, bootstrapped/regtested on x86_64-linux and i686-linux, ok for
trunk?

2018-12-09  Jakub Jelinek  <jakub@redhat.com>

	PR c++/88410
	* cp-gimplify.c (cp_fold) <case ADDR_EXPR>: For offsetof-like folding,
	call maybe_constant_value on val to see if it is INTEGER_CST.

	* g++.dg/cpp0x/pr88410.C: New test.

--- gcc/cp/cp-gimplify.c.jj	2018-11-23 20:00:26.603273556 +0100
+++ gcc/cp/cp-gimplify.c	2018-12-08 11:39:03.983985326 +0100
@@ -2317,6 +2317,7 @@ cp_fold (tree x)
 	    {
 	      val = TREE_OPERAND (val, 0);
 	      STRIP_NOPS (val);
+	      val = maybe_constant_value (val);
 	      if (TREE_CODE (val) == INTEGER_CST)
 		return fold_offsetof (op0, TREE_TYPE (x));
 	    }
--- gcc/testsuite/g++.dg/cpp0x/pr88410.C.jj	2018-12-08 11:41:10.946927148 +0100
+++ gcc/testsuite/g++.dg/cpp0x/pr88410.C	2018-12-08 11:40:48.476291414 +0100
@@ -0,0 +1,7 @@
+// PR c++/88410
+// { dg-do compile { target c++11 } }
+
+typedef __UINTPTR_TYPE__ uintptr_t;
+const uintptr_t a = 32;
+struct C { int b; int c; };
+uintptr_t d { uintptr_t (&reinterpret_cast<C *>(a)->c) - a };

	Jakub