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[PATCH] Fix ICE in default_use_anchors_for_symbol_p (PR middle-end/78201)


Hi!

On arm/aarch64 we ICE because some decls that make it here has non-NULL
DECL_SIZE, which is a VAR_DECL rather than CONST_INT (or DECL_SIZE that
doesn't fit into shwi would ICE similarly).  While it is arguably a FE bug
that it creates for VLA initialization from STRING_CST such a decl,
I believe we have some PRs about it already open.
I think it won't hurt to check for the large sizes properly even in this
function though, and punt on unexpected cases, or even extremely large ones.

Bootstrapped/regtested on x86_64-linux and i686-linux, Yvan said he is going
to test on arm and/or aarch64.  Ok for trunk if the testing there passes
too?

2016-11-10  Jakub Jelinek  <jakub@redhat.com>

	PR middle-end/78201
	* varasm.c (default_use_anchors_for_symbol_p): Fix a comment typo.
	Don't test decl != NULL.  Don't look at DECL_SIZE, but DECL_SIZE_UNIT
	instead, return false if it is NULL, or doesn't fit into uhwi, or
	is larger or equal to targetm.max_anchor_offset.

	* g++.dg/opt/pr78201.C: New test.

--- gcc/varasm.c.jj	2016-10-31 13:28:12.000000000 +0100
+++ gcc/varasm.c	2016-11-10 15:18:41.282886244 +0100
@@ -6804,11 +6804,12 @@ default_use_anchors_for_symbol_p (const_
 	return false;
 
       /* Don't use section anchors for decls that won't fit inside a single
-	 anchor range to reduce the amount of instructions require to refer
+	 anchor range to reduce the amount of instructions required to refer
 	 to the entire declaration.  */
-      if (decl && DECL_SIZE (decl)
-	 && tree_to_shwi (DECL_SIZE (decl))
-	    >= (targetm.max_anchor_offset * BITS_PER_UNIT))
+      if (DECL_SIZE_UNIT (decl) == NULL_TREE
+	  || !tree_fits_uhwi_p (DECL_SIZE_UNIT (decl))
+	  || (tree_to_uhwi (DECL_SIZE_UNIT (decl))
+	      >= (unsigned HOST_WIDE_INT) targetm.max_anchor_offset))
 	return false;
 
     }
--- gcc/testsuite/g++.dg/opt/pr78201.C.jj	2016-11-10 15:20:18.398660681 +0100
+++ gcc/testsuite/g++.dg/opt/pr78201.C	2016-11-10 15:19:58.000000000 +0100
@@ -0,0 +1,13 @@
+// PR middle-end/78201
+// { dg-do compile }
+// { dg-options "-O2" }
+
+struct B { long d (); } *c;
+long e;
+
+void
+foo ()
+{
+  char a[e] = "";
+  c && c->d();
+}

	Jakub


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