https://gcc.gnu.org/bugzilla/show_bug.cgi?id=110170
--- Comment #10 from Hongtao.liu <crazylht at gmail dot com> ---
There're couple of other issues.
1. rtx_cost for and/ior/xor:SF/DF is not right, it actually generate vector
instructions.
2. branch_cost is COSTS_N_INSN(1) instead of BRANCH_COST ().
which make noce more conservative to eliminate condition.
w/ sse2, backend tries
(insn 34 0 36 (set (reg:DF 86 [ _1 ])
(reg:DF 82 [ _1 ])) 151 {*movdf_internal}
(nil))
(insn 36 34 37 (set (reg:DF 92)
(unspec:DF [
(reg:DF 83 [ _2 ])
(reg:DF 82 [ _1 ])
] UNSPEC_IEEE_MAX)) -1
(nil))
(insn 37 36 38 (set (reg:DF 93)
(lt:DF (reg:DF 82 [ _1 ])
(reg:DF 83 [ _2 ]))) -1
(nil))
(insn 38 37 39 (set (reg:DF 94)
(and:DF (reg:DF 86 [ _1 ])
(reg:DF 93))) -1
(nil))
(insn 39 38 40 (set (reg:DF 95)
(and:DF (not:DF (reg:DF 93))
(reg:DF 83 [ _2 ]))) -1
(nil))
(insn 40 39 41 (set (reg:DF 83 [ _2 ])
(ior:DF (reg:DF 95)
(reg:DF 94))) -1
(nil))
(insn 41 40 0 (set (reg:DF 82 [ _1 ])
(reg:DF 92)) 151 {*movdf_internal}
(nil))
which is cost is 28, and original cost is 12 (3 moves + 1 branch).(needs also
conside comparison? since it's counted in cmov seq), if use ix86_branch_cost +
count comparison cost in the orginal seq, then the cost should be 28 vs 28.)
(insn 5 17 6 3 (set (reg:DF 86 [ _1 ])
(reg:DF 82 [ _1 ]))
"/export/users/liuhongt/tools-build/build_intel-innersource_pr110170_debug/test.c":5:23
151 {*movdf_internal}
(expr_list:REG_DEAD (reg:DF 82 [ _1 ])
(nil)))
(insn 6 5 7 3 (set (reg:DF 82 [ _1 ])
(reg:DF 83 [ _2 ]))
"/export/users/liuhongt/tools-build/build_intel-innersource_pr110170_debug/test.c":6:15
discrim 1 151 {*movdf_internal}
(expr_list:REG_DEAD (reg:DF 83 [ _2 ])
(nil)))
(insn 7 6 18 3 (set (reg:DF 83 [ _2 ])
(reg:DF 86 [ _1 ]))
"/export/users/liuhongt/tools-build/build_intel-innersource_pr110170_debug/test.c":5:23
discrim 1 151 {*movdf_internal}
(expr_list:REG_DEAD (reg:DF 86 [ _1 ])
(nil)))
