[Bug middle-end/55921] [4.6/4.7 Regression] Crash in verify_ssa for asm to side-steps complex pessimization

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

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=55921

--- Comment #9 from John David Anglin <danglin at gcc dot gnu.org> 2013-01-30 02:56:52 UTC ---
Return NULL_RTX in extract_bit_field_using_extv when it's not
possible to create pseudos just results in another similar error
a little further down the road:

#0  gen_reg_rtx (mode=DImode) at ../../gcc/gcc/emit-rtl.c:866
#1  0x40000000006242f4 in maybe_legitimize_operand (op=0x800003fffdff1ff8, 
    opno=0, icode=CODE_FOR_lshrdi3) at ../../gcc/gcc/optabs.c:8055
#2  maybe_legitimize_operands (icode=CODE_FOR_lshrdi3, opno=0, nops=3, 
    ops=<optimized out>) at ../../gcc/gcc/optabs.c:8128
#3  0x40000000006245a4 in maybe_gen_insn (icode=CODE_FOR_lshrdi3, 
    nops=<optimized out>, ops=0x800003fffdff1ff8)
    at ../../gcc/gcc/optabs.c:8146
#4  0x400000000062c9c4 in expand_binop_directly (mode=DImode, 
    binoptab=lshr_optab, op0=0x800003fffdebc260, op1=0x800003fffddbc670, 
    target=0x0, unsignedp=1, methods=OPTAB_DIRECT, last=0x0)
    at ../../gcc/gcc/optabs.c:1450
#5  0x4000000000626370 in expand_binop (mode=DImode, binoptab=lshr_optab, 
    op0=0x800003fffdebc260, op1=0x800003fffddbc670, target=0x0, unsignedp=1, 
    methods=OPTAB_DIRECT) at ../../gcc/gcc/optabs.c:1519
#6  0x400000000042e3bc in expand_shift_1 (code=RROTATE_EXPR, mode=BLKmode, 
    shifted=0x3e, amount=<optimized out>, target=0x0, unsignedp=-35928464)
    at ../../gcc/gcc/expmed.c:2210
#7  0x400000000043112c in expand_shift (code=RSHIFT_EXPR, mode=DImode, 
    shifted=<optimized out>, amount=<optimized out>, target=<optimized out>, 
    unsignedp=1) at ../../gcc/gcc/expmed.c:2254
#8  0x4000000000431688 in extract_fixed_bit_field (tmode=SImode, 
    op0=0x800003fffdebc260, bitsize=32, bitnum=32, target=0x0, unsignedp=1, 
    packedp=<optimized out>) at ../../gcc/gcc/expmed.c:1790
#9  0x40000000004322f4 in extract_bit_field_1 (str_rtx=<optimized out>, 
    bitsize=1, bitnum=32, unsignedp=1, packedp=<optimized out>, target=0x7, 
    mode=64, tmode=<optimized out>, fallback_p=false)
    at ../../gcc/gcc/expmed.c:1635

After ira, we have the following insns:

(insn 26 25 27 2 (set (reg:SC 85 [ cf ])        (asm_operands:SC ("") ("=r") 0
[
                (reg:DI 72 [ D.1406 ])
            ]
             [
                (asm_input:DI ("r") :0)            ]
             []
/test/gnu/gcc/gcc/gcc/testsuite/gcc.c-torture/compile/pr55921.c:
17)) /test/gnu/gcc/gcc/gcc/testsuite/gcc.c-torture/compile/pr55921.c:17 -1
     (expr_list:REG_DEAD (reg:DI 72 [ D.1406 ])
        (nil)))
(insn 27 26 29 2 (set (reg:DI 86)
        (subreg:DI (reg:SC 85 [ cf ]) 0))
/test/gnu/gcc/gcc/gcc/testsuite/gcc.c-
torture/compile/pr55921.c:17 121 {*pa.md:4189}
     (nil))

It seems insn 27 needs to expanded before reload as extraction of the SUBREG
needs an intermediate general register.