[Bug rtl-optimization/99930] Failure to optimize floating point -abs(x) in nontrivial code at -O2/3

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

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=99930

Richard Biener <rguenth at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |segher at gcc dot gnu.org

--- Comment #2 from Richard Biener <rguenth at gcc dot gnu.org> ---
Seems because of r93 being live:

insn_cost 8 for     9: r93:V4SF=[`*.LC0']
      REG_EQUAL const_vector
insn_cost 4 for    10: {r91:SF=abs(r92:SF);use r93:V4SF;clobber flags:CC;}
      REG_DEAD r92:SF
      REG_UNUSED flags:CC
insn_cost 8 for    11: r95:V4SF=[`*.LC1']
      REG_EQUAL const_vector
insn_cost 4 for    12: {r94:SF=-r91:SF;use r95:V4SF;clobber flags:CC;}
      REG_DEAD r91:SF
      REG_UNUSED flags:CC
insn_cost 4 for    13: flags:CCFP=cmp(r90:SF,r94:SF)
      REG_DEAD r94:SF
insn_cost 12 for    14: pc={(flags:CCFP>0)?L35:pc}
      REG_DEAD flags:CCFP
      REG_BR_PROB 59055804
insn_cost 8 for    16: r97:SF=[r89:DI+0x4]
      REG_DEAD r89:DI
insn_cost 4 for    18: {r96:SF=abs(r97:SF);use r93:V4SF;clobber flags:CC;}
      REG_DEAD r97:SF
      REG_DEAD r93:V4SF
      REG_UNUSED flags:CC
insn_cost 4 for    20: {r99:SF=-r96:SF;use r95:V4SF;clobber flags:CC;}
      REG_DEAD r96:SF
      REG_DEAD r95:V4SF
      REG_UNUSED flags:CC

while at -O1 we have two loads of LC0 and r93 is dead after insn 10.