Re: [PATCH] Break false dependence for vpternlog by inserting vpxor.

[simonaytes.yan--- via Gcc-patches]

+; False dependency happens on destination register which is not really
+; used when moving all ones to vector register
+(define_split
+  [(set (match_operand:VMOVE 0 "register_operand")
+       (match_operand:VMOVE 1 "int_float_vector_all_ones_operand"))]
+  "TARGET_AVX512F && reload_completed
+  && (<MODE_SIZE> == 64 || EXT_REX_SSE_REG_P (operands[0]))"
+  [(set (match_dup 0) (match_dup 2))
+   (parallel
+     [(set (match_dup 0) (match_dup 1))
+      (unspec [(match_dup 0)] UNSPEC_INSN_FALSE_DEP)])]
+  "operands[2] = CONST0_RTX (<MODE>mode);")

I think we shouldnt emit PXOR when optimizing for size. So should change 
define_split:
define_split
  [(set (match_operand:VMOVE 0 "register_operand")
        (match_operand:VMOVE 1 "int_float_vector_all_ones_operand"))]
  "TARGET_AVX512F && reload_completed
  && (<MODE_SIZE> == 64 || EXT_REX_SSE_REG_P (operands[0]))
  && optimize_insn_for_speed_p ()"
  [(set (match_dup 0) (match_dup 2))
   (parallel
     [(set (match_dup 0) (match_dup 1))
      (unspec [(match_dup 0)] UNSPEC_INSN_FALSE_DEP)])]
  "operands[2] = CONST0_RTX (<MODE>mode);")