c: Fix ICE with cast to VLA [93576]

The following testcase ICEs, because the PR84305 changes try to evaluate
the size earlier.  If size has side-effects, that is desirable, and the
side-effects will actually be wrapped in a SAVE_EXPR.  The problem on this
testcase is that there are no side-effects, and c_fully_fold doesn't fold
those COMPOUND_EXPRs to constant, and while before gimplification we unshare
trees found in the expressions, the unsharing doesn't involve TYPE_SIZE etc.
of used types.  Gimplification is destructive though, so when we gimplify
the two nested COMPOUND_EXPRs and then try to gimplify it the second time
for the TYPE_SIZEs, we ICE.
Now, we could use unshare_expr in what we push to *expr, SAVE_EXPRs and
their operands in there aren't unshared, but I really don't see a point of
evaluating expressions that don't have side-effects before, so instead
this just pushes there expressions that do have side-effects.

2020-02-13  Jakub Jelinek  <jakub@redhat.com>

	PR c/93576
	* c-decl.c (grokdeclarator): If this_size_varies, only push size into
	*expr if it has side effects.

	* gcc.dg/pr93576.c: New test.

diff --git a/gcc/c/ChangeLog b/gcc/c/ChangeLog
index 995f315..e88337b 100644 (file)
--- a/gcc/c/ChangeLog
+++ b/gcc/c/ChangeLog
@@ -1,3 +1,9 @@
+2020-02-13  Jakub Jelinek  <jakub@redhat.com>
+
+       PR c/93576
+       * c-decl.c (grokdeclarator): If this_size_varies, only push size into
+       *expr if it has side effects.
+
 2020-01-30  Jeff Law  <law@redhat.com>
 
        PR c/88660

diff --git a/gcc/c/c-decl.c b/gcc/c/c-decl.c
index 8281af7..1aa410d 100644 (file)
--- a/gcc/c/c-decl.c
+++ b/gcc/c/c-decl.c
@@ -6512,11 +6512,14 @@ grokdeclarator (const struct c_declarator *declarator,
                  }
                if (this_size_varies)
                  {
-                   if (*expr)
-                     *expr = build2 (COMPOUND_EXPR, TREE_TYPE (size),
-                                     *expr, size);
-                   else
-                     *expr = size;
+                   if (TREE_SIDE_EFFECTS (size))
+                     {
+                       if (*expr)
+                         *expr = build2 (COMPOUND_EXPR, TREE_TYPE (size),
+                                         *expr, size);
+                       else
+                         *expr = size;
+                     }
                    *expr_const_operands &= size_maybe_const;
                  }
              }

diff --git a/gcc/testsuite/ChangeLog b/gcc/testsuite/ChangeLog
index 560187c..a262bdd 100644 (file)
--- a/gcc/testsuite/ChangeLog
+++ b/gcc/testsuite/ChangeLog
@@ -1,3 +1,8 @@
+2020-02-13  Jakub Jelinek  <jakub@redhat.com>
+
+       PR c/93576
+       * gcc.dg/pr93576.c: New test.
+
 2020-02-13  Sandra Loosemore  <sandra@codesourcery.com>
 
        * g++.dg/cpp0x/constexpr-static13.C:

diff --git a/gcc/testsuite/gcc.dg/pr93576.c b/gcc/testsuite/gcc.dg/pr93576.c
new file mode 100644 (file)
index 0000000..13c34f3
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/pr93576.c
@@ -0,0 +1,10 @@
+/* PR c/93576 */
+/* { dg-do compile } */
+/* { dg-options "" } */
+
+void
+foo (void)
+{
+  int b[] = { 0 };
+  (char (*)[(1, 7, 2)]) 0;
+}