[Bug rtl-optimization/54342] New: [4.8 Regression] Wrong mode of call argument

[vbyakovl23 at gmail dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=54342

             Bug #: 54342
           Summary: [4.8 Regression] Wrong mode of call argument
    Classification: Unclassified
           Product: gcc
           Version: 4.8.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: rtl-optimization
        AssignedTo: unassig...@gcc.gnu.org
        ReportedBy: vbyakov...@gmail.com


The argument of call has mode OI rather than V8SF. Test case

-------------------------------------------------
#include <immintrin.h>

typedef union un1
{
    __m256 x;
    float f;
} UN1;
UN1 u;
extern __m256 y;
extern int bar2(UN1);

int foo2 ()
{
    u.x = y;
    return bar2(u);
}
----------------------------------------------

Dump after expand

(note 4 2 5 3 [bb 3] NOTE_INSN_BASIC_BLOCK) 

(insn 5 4 6 3 (set (reg/f:DI 62) 
        (symbol_ref:DI ("u")  <var_decl 0x7f312f270a00 u>)) er.c:13 -1 
     (nil)) 

(insn 6 5 7 3 (set (reg:V8SF 63) 
        (mem/c:V8SF (symbol_ref:DI ("y") [flags 0x40]  <var_decl 0x7f312f270aa0
y>) [2 y+0 S32 A256])) er.c:13 -1 
     (nil)) 

(insn 7 6 8 3 (set (mem/c:V8SF (reg/f:DI 62) [0 u.x+0 S32 A256]) 
        (reg:V8SF 63)) er.c:13 -1 
     (nil)) 

(insn 8 7 9 3 (set (reg/f:DI 65) 
        (symbol_ref:DI ("u")  <var_decl 0x7f312f270a00 u>)) er.c:14 -1 
     (nil)) 

(insn 9 8 10 3 (set (reg:OI 64) 
        (mem/c:OI (reg/f:DI 65) [3 u+0 S32 A256])) er.c:14 -1 
     (nil)) 

(insn 10 9 11 3 (set (reg:OI 21 xmm0) 
        (reg:OI 64)) er.c:14 -1 
     (nil)) 

(call_insn/j 11 10 12 3 (parallel [ 
            (set (reg:SI 0 ax) 
                (call (mem:QI (symbol_ref:DI ("bar2") [flags 0x41] 
<function_decl 0x7f312f27b300 bar2>) [0 bar2 S1 A8]) 
                    (const_int 0 [0]))) 
            (unspec [ 
                    (const_int 1 [0x1]) 
                ] UNSPEC_CALL_NEEDS_VZEROUPPER) 
        ]) er.c:14 -1 
     (nil) 
    (expr_list:REG_DEP_TRUE (use (reg:OI 21 xmm0)) 
        (nil)))

Following patch fixes that.

diff --git a/gcc/stor-layout.c b/gcc/stor-layout.c
index 53554a9..bb39e7f 100644
--- a/gcc/stor-layout.c
+++ b/gcc/stor-layout.c
@@ -1639,7 +1639,8 @@ compute_record_mode (tree type)
   /* If we only have one real field; use its mode if that mode's size
      matches the type's size.  This only applies to RECORD_TYPE.  This
      does not apply to unions.  */
-  if (TREE_CODE (type) == RECORD_TYPE && mode != VOIDmode
+  if ((TREE_CODE (type) == RECORD_TYPE || TREE_CODE (type) == UNION_TYPE)
+      && mode != VOIDmode
       && host_integerp (TYPE_SIZE (type), 1)
       && GET_MODE_BITSIZE (mode) == TREE_INT_CST_LOW (TYPE_SIZE (type)))
     SET_TYPE_MODE (type, mode);