[Bug target/49226] New: problematic _Complex long double argument passing

["ebotcazou at gcc dot gnu.org" <gcc-bugzilla at gcc dot gnu dot org>]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=49226

           Summary: problematic _Complex long double argument passing
           Product: gcc
           Version: 4.7.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: target
        AssignedTo: unassigned@gcc.gnu.org
        ReportedBy: ebotcazou@gcc.gnu.org
            Blocks: 48830
            Target: ia64-*-*


rtlanal.c:simplify_subreg_regno has these lines at the end:

  /* See whether (reg:YMODE YREGNO) is valid.

     ??? We allow invalid registers if (reg:XMODE XREGNO) is also invalid.
     This is a kludge to work around how float/complex arguments are passed
     on 32-bit SPARC and should be fixed.  */
  if (!HARD_REGNO_MODE_OK (yregno, ymode)
      && HARD_REGNO_MODE_OK (xregno, xmode))
    return -1;

It turns out that they are outdated, removing the kludge as follows:

  /* See whether (reg:YMODE YREGNO) is valid.  */
  if (!HARD_REGNO_MODE_OK (yregno, ymode))
    return -1;

works fine on the SPARC (both 32-bit and 64-bit).  Now there is a problem on
IA-64.  For the testcase to be attached, the function is invoked on:

#0  simplify_subreg_regno (xregno=122, xmode=XCmode, offset=0, ymode=XFmode)
    at /home/eric/svn/gcc/gcc/rtlanal.c:3461
3461      return (int) yregno;

and must return a valid regno, although everything is invalid according to the
HARD_REGNO_MODE_OK macro, otherwise wrong code is generated:

--- scalar-by-value-3_0.s       2011-05-29 15:26:12.174486000 -0400
+++ scalar-by-value-3.s 2011-05-29 15:26:29.694284000 -0400
@@ -453,10 +453,10 @@
        stfe [r14] = f6
        mov r14 = r34
        ;;
-       ld8 r40 = [r14]
+       ld8 r38 = [r14]
        adds r14 = 8, r34
        ;;
-       ld8 r41 = [r14]
+       ld8 r39 = [r14]
        br.call.sptk.many b0 = testvacld#
        mov r1 = r35
        mov r36 = r0

This is on the way of PR target/48830.