Handle folded nonconstant array bounds [PR101702]

PR c/101702 - ICE: in handle_argspec_attribute, at c-family/c-attribs.c:3623

gcc/c/ChangeLog:

	PR c/101702
	* c-decl.c (get_parm_array_spec): Strip casts earlier and fold array
	bounds before deciding if they're constant.

gcc/testsuite/ChangeLog:

	PR c/101702
	* gcc.dg/Warray-parameter-11.c: New test.

diff --git a/gcc/c/c-decl.c b/gcc/c/c-decl.c
index 186fa1692c1..63d806a84c9 100644
--- a/gcc/c/c-decl.c
+++ b/gcc/c/c-decl.c
@@ -5866,6 +5866,12 @@ get_parm_array_spec (const struct c_parm *parm, tree attrs)
       if (pd->u.array.static_p)
 	spec += 's';
 
+      if (!INTEGRAL_TYPE_P (TREE_TYPE (nelts)))
+	/* Avoid invalid NELTS.  */
+	return attrs;
+
+      STRIP_NOPS (nelts);
+      nelts = c_fully_fold (nelts, false, nullptr);
       if (TREE_CODE (nelts) == INTEGER_CST)
 	{
 	  /* Skip all constant bounds except the most significant one.
@@ -5883,13 +5889,9 @@ get_parm_array_spec (const struct c_parm *parm, tree attrs)
 	  spec += buf;
 	  break;
 	}
-      else if (!INTEGRAL_TYPE_P (TREE_TYPE (nelts)))
-	/* Avoid invalid NELTS.  */
-	return attrs;
 
       /* Each variable VLA bound is represented by a dollar sign.  */
       spec += "$";
-      STRIP_NOPS (nelts);
       vbchain = tree_cons (NULL_TREE, nelts, vbchain);
     }
 
diff --git a/gcc/testsuite/gcc.dg/Warray-parameter-11.c b/gcc/testsuite/gcc.dg/Warray-parameter-11.c
new file mode 100644
index 00000000000..8ca1b55bd28
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/Warray-parameter-11.c
@@ -0,0 +1,24 @@
+/* PR c/101702 - ICE on invalid function redeclaration
+   { dg-do compile }
+   { dg-options "-Wall" } */
+
+typedef __INTPTR_TYPE__ intptr_t;
+
+#define copysign(x, y) __builtin_copysign (x, y)
+
+void f0 (double[!copysign (~2, 3)]);
+
+void f1 (double[!copysign (~2, 3)]);
+void f1 (double[1]);                    // { dg-warning "-Warray-parameter" }
+
+void f2 (int[(int)+1.0]);
+void f2 (int[(int)+1.1]);
+
+/* Also verify that equivalent expressions don't needlessly cause false
+   positives or negatives.  */
+struct S { int a[1]; };
+extern struct S *sp;
+
+void f3 (int[(intptr_t)((char*)sp->a - (char*)sp)]);
+void f3 (int[(intptr_t)((char*)&sp->a[0] - (char*)sp)]);
+void f3 (int[(intptr_t)((char*)&sp->a[1] - (char*)sp)]);   // { dg-warning "-Warray-parameter" }