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[Bug rtl-optimization/33552] New: wrong code for multiple output asm, wrong df?


On x86_64, the following function (extracted from gmp, the asms are from
its longlong.h)

void
mul_basecase (unsigned long * wp, unsigned long * up, long un,
              unsigned long * vp, long vn)
{
  long j;
  unsigned long prod_low, prod_high;
  unsigned long cy_dig;
  unsigned long v_limb;

  v_limb = vp[0];
  cy_dig = 0;
  for (j = un; j > 0; j--)
    {
      unsigned long u_limb, w_limb;
      u_limb = *up++;
      __asm__ ("mulq %3" : "=a" (prod_low), "=d" (prod_high)
                         : "%0" (u_limb), "rm" (v_limb));
      __asm__ ("addq %5,%q1\n"
             "\tadcq %3,%q0" : "=r" (cy_dig), "=&r" (w_limb)
                             : "0" (prod_high), "rme" (0), "%1" (prod_low),
"rme" (cy_dig));
      *wp++ = w_limb;
    }
}

produces with optimization:

#APP
# 16 "t.c" 1
        mulq %rcx
# 0 "" 2
# 18 "t.c" 1
        addq %rdx,%rax
        adcq $0,%rdx
# 0 "" 2
#NO_APP

where you can see that cy_dig is allocated to the upper half of the mulq
result.  It looks like that we are confused by rest_of_match_asm_constraints
which inserts

(insn 44 25 26 4 t.c:18 (set (reg/v:DI 67 [ cy_dig ])
        (reg/v:DI 68 [ prod_high ])) -1 (nil))

after the mulq asm.


-- 
           Summary: wrong code for multiple output asm, wrong df?
           Product: gcc
           Version: 4.3.0
            Status: UNCONFIRMED
          Keywords: wrong-code
          Severity: major
          Priority: P3
         Component: rtl-optimization
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: rguenth at gcc dot gnu dot org
GCC target triplet: x86_64-*-*


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=33552


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