[Bug c/31385] New: gcc fails to find spill register for decimal arithmetic

[beebe at math dot utah dot edu]

In compilation of a large library of code for decimal floating-point
arithmetic, I found that compilations with -g would succeed, but most
would fail with -O1, -O2, or -O3 on IA-32.  I've taken a single example
and chopped away extraneous code to produce a standalone file
that exhibits the compiler error:

% cat bug002.c
typedef _Decimal32 fp_t;

extern fp_t g(fp_t);

fp_t
bug(fp_t x)
{
    fp_t result;
    int n;
    fp_t f, f3, y, z;

    n = 0;
    y = 1.DF;
    f = g(x);

    if (f < 0.DF)
        f = -f;

    f3 = 2.DF;

    z = (y + y + f / (y * y));
    y = (z + z) / (9.DF) + f3 / (z * z);

    result = y;

    return (result);
}

% gcc --version
gcc (GCC) 4.3.0 20070316 (experimental)

% gcc -c -O1 bug002.c
bug002.c: In function 'bug':
bug002.c:27: error: unable to find a register to spill in class 'GENERAL_REGS'
bug002.c:27: error: this is the insn:
(insn 25 24 26 3 (set (subreg:SI (reg/v:SD 59 [ f ]) 0)
        (plus:SI (subreg:SI (reg/v:SD 59 [ f ]) 0)
            (const_int -2147483648 [0x80000000]))) 144 {*lea_1} (nil)
    (nil))
bug002.c:27: internal compiler error: in spill_failure, at reload1.c:1944


-- 
           Summary: gcc fails to find spill register for decimal arithmetic
           Product: gcc
           Version: 4.3.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: beebe at math dot utah dot edu
 GCC build triplet: i686-pc-linux-gnu
  GCC host triplet: i686-pc-linux-gnu
GCC target triplet: i686-pc-linux-gnu


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=31385