[PATCH] Fix PR71984

[Richard Biener]

The following should fix PR71984 which stems from a bogus (but harmless
for CONCAT) use of GET_MODE_UNIT_SIZE vs. GET_MODE_SIZE (where the
former is really really badly named...).  In the process of fixing it
I also hardened it against VOIDmode which might have occured for
CONCAT as well given we have CSImode.

Bootstrap / regtest running on x86_64-unknown-linux-gnu.

I don't have AVX512 HW to check but by inspection the testcase is fixed.
(and the issue is obvious once you analyzed it)

It was Honza who sneaked in this GET_MODE_UNIT_SIZE use, the bad
name exists since the initial repository version.

Ok for trunk?

Thanks,
Richard.

2016-07-25  Richard Biener  <rguenther@suse.de>

	PR rtl-optimization/71984
	* simplify-rtx.c (simplify_subreg): Use GET_MODE_SIZE and prepare
	for VOIDmode.

	* gcc.dg/torture/pr71984.c: New testcase.

Index: gcc/simplify-rtx.c
===================================================================
*** gcc/simplify-rtx.c	(revision 238710)
--- gcc/simplify-rtx.c	(working copy)
*************** simplify_subreg (machine_mode outermode,
*** 6116,6122 ****
        unsigned int part_size, final_offset;
        rtx part, res;
  
!       part_size = GET_MODE_UNIT_SIZE (GET_MODE (XEXP (op, 0)));
        if (byte < part_size)
  	{
  	  part = XEXP (op, 0);
--- 6116,6125 ----
        unsigned int part_size, final_offset;
        rtx part, res;
  
!       enum machine_mode part_mode = GET_MODE (XEXP (op, 0));
!       if (part_mode == VOIDmode)
! 	part_mode = GET_MODE_INNER (GET_MODE (op));
!       part_size = GET_MODE_SIZE (part_mode);
        if (byte < part_size)
  	{
  	  part = XEXP (op, 0);
*************** simplify_subreg (machine_mode outermode,
*** 6131,6137 ****
        if (final_offset + GET_MODE_SIZE (outermode) > part_size)
  	return NULL_RTX;
  
!       enum machine_mode part_mode = GET_MODE (part);
        if (part_mode == VOIDmode)
  	part_mode = GET_MODE_INNER (GET_MODE (op));
        res = simplify_subreg (outermode, part, part_mode, final_offset);
--- 6134,6140 ----
        if (final_offset + GET_MODE_SIZE (outermode) > part_size)
  	return NULL_RTX;
  
!       part_mode = GET_MODE (part);
        if (part_mode == VOIDmode)
  	part_mode = GET_MODE_INNER (GET_MODE (op));
        res = simplify_subreg (outermode, part, part_mode, final_offset);
Index: gcc/testsuite/gcc.dg/torture/pr71984.c
===================================================================
*** gcc/testsuite/gcc.dg/torture/pr71984.c	(revision 0)
--- gcc/testsuite/gcc.dg/torture/pr71984.c	(working copy)
***************
*** 0 ****
--- 1,21 ----
+ /* { dg-do run { target lp64 } } */
+ /* { dg-additional-options "-w -Wno-psabi" } */
+ 
+ typedef unsigned char v64u8 __attribute__((vector_size(64)));
+ typedef unsigned long v64u64 __attribute__((vector_size(64)));
+ typedef unsigned char u8;
+ 
+ static u8 __attribute__ ((noinline, noclone))
+ foo (v64u64 v64u64_0)
+ {
+   return ((v64u8)(v64u64){0, v64u64_0[0]})[13];
+ }
+ 
+ int
+ main ()
+ {
+   u8 x = foo((v64u64){0x0706050403020100UL});
+   if (x != 5)
+     __builtin_abort ();
+   return 0;
+ }