[PATCH] guard against calls with fewer arguments than the function type implies (PR 95581)

[Martin Sebor via Gcc-patches]

PR 95581 reports an ICE in a call to gimple_call_arg() with
an out-of-bounds argument number (2).  The attached patch avoids
the ICE but I'm not sure it's the right fix.  Other than verifying
the ICE is gone with a powerpc64 cross-compiler I couldn't come up
with a generic test cases to exercise this change.

The call, synthesized by the vectorizer, is

  vect__5.6_24 = __builtin_altivec_mask_for_load (vectp_a.5_8);

but the function is declared by the powerpc64 back end to take two
arguments: long and const void*.  Is it correct for the builtin to
be called with fewer arguments than their type indicates?  (If it
isn't the patch shouldn't be necessary but some other fix would
be needed.)

Martin

PR tree-optimization/95581 - ICE in gimple_call_arg for a call with fewer arguments than function type implies

gcc/ChangeLog:

	PR tree-optimization/95581
	* tree-ssa-uninit.c (maybe_warn_pass_by_reference): Guard against
	calls with fewer arguments than the called function type implies.

diff --git a/gcc/tree-ssa-uninit.c b/gcc/tree-ssa-uninit.c
index 2f0ff724cde..52f2de940c0 100644
--- a/gcc/tree-ssa-uninit.c
+++ b/gcc/tree-ssa-uninit.c
@@ -445,7 +445,7 @@ maybe_warn_pass_by_reference (gimple *stmt, wlimits &wlims)
   if (!wlims.wmaybe_uninit)
     return;
 
-  unsigned nargs = gimple_call_num_args (stmt);
+  const unsigned nargs = gimple_call_num_args (stmt);
   if (!nargs)
     return;
 
@@ -480,6 +480,11 @@ maybe_warn_pass_by_reference (gimple *stmt, wlimits &wlims)
 
   FOREACH_FUNCTION_ARGS (fntype, argtype, it)
     {
+      /* Guard against calls with fewer arguments than the function
+	 type implies.  See PR 95581.  */
+      if (nargs == argno)
+	break;
+
       ++argno;
 
       if (!POINTER_TYPE_P (argtype))