[Bug target/56560] [4.6/4.7 regression] vzeroupper clobbers argument with AVX

[hjl.tools at gmail dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=56560

--- Comment #4 from H.J. Lu <hjl.tools at gmail dot com> 2013-03-08 17:21:18 UTC ---
The caller info is lost by

(gdb) bt
#0  init_cumulative_args (cum=0x7fffffffc3f0, fntype=0x7ffff1472e70, 
    libname=0x0, fndecl=0x0, caller=1)
    at /export/gnu/import/git/gcc-release/gcc/config/i386/i386.c:5562
#1  0x0000000000640011 in block_move_libcall_safe_for_call_parm ()
    at /export/gnu/import/git/gcc-release/gcc/expr.c:1244
#2  0x000000000063fc07 in emit_block_move_hints (x=0x7ffff1470780, 
    y=0x7ffff1470750, size=0x7ffff133a530, method=BLOCK_OP_CALL_PARM, 
    expected_align=0, expected_size=-1)
    at /export/gnu/import/git/gcc-release/gcc/expr.c:1139
#3  0x000000000063ff3c in emit_block_move (x=0x7ffff1470780, y=0x7ffff1470750, 
    size=0x7ffff133a530, method=BLOCK_OP_CALL_PARM)
    at /export/gnu/import/git/gcc-release/gcc/expr.c:1206
#4  0x000000000064693a in emit_push_insn (x=0x7ffff1470750, mode=BLKmode, 
    type=0x7ffff1472690, size=0x7ffff133a530, align=64, partial=0, reg=0x0, 
    extra=4, args_addr=0x7ffff1334560, args_so_far=0x7ffff133a470, 
    reg_parm_stack_space=0, alignment_pad=0x7ffff133a470)
    at /export/gnu/import/git/gcc-release/gcc/expr.c:4116
#5  0x000000000056d1ad in store_one_arg (arg=0x7fffffffc760, 
    argblock=0x7ffff1334560, flags=0, variable_size=0, reg_parm_stack_space=0)
    at /export/gnu/import/git/gcc-release/gcc/calls.c:4646
#6  0x0000000000568b51 in expand_call (exp=0x7ffff1333cb0, 
    target=0x7ffff1461f00, ignore=0)
    at /export/gnu/import/git/gcc-release/gcc/calls.c:3023

when storing struct S on stack.  This patch:

diff --git a/gcc/config/i386/i386.c b/gcc/config/i386/i386.c
index c1f6c88..8005207 100644
--- a/gcc/config/i386/i386.c
+++ b/gcc/config/i386/i386.c
@@ -5562,7 +5562,7 @@ init_cumulative_args (CUMULATIVE_ARGS *cum,  /* Argument
info to initialize */
   memset (cum, 0, sizeof (*cum));

   /* Initialize for the current callee.  */
-  if (caller)
+  if (caller && fndecl)
     {
       cfun->machine->callee_pass_avx256_p = false;
       cfun->machine->callee_return_avx256_p = false;

fixes it.