Steven Bosscher <stevenb....@gmail.com> wrote: >Hello, > >This patch is necessary to make ARM pass the test suite with LRA >enabled. The symptom is recog failing to recognize a store_minmaxsi >insn, see: > http://gcc.gnu.org/ml/gcc-patches/2013-11/msg00725.html > >But I am not sure if that's also the root cause of the problem, or >whether the ARM back end should not let recognition of insn patterns >be dependent on the state of the profile flags. > >The pattern for store_minmaxsi (in arm.md) is: > >(define_insn "*store_minmaxsi" > [(set (match_operand:SI 0 "memory_operand" "=m") > (match_operator:SI 3 "minmax_operator" > [(match_operand:SI 1 "s_register_operand" "r") > (match_operand:SI 2 "s_register_operand" "r")])) > (clobber (reg:CC CC_REGNUM))] > "TARGET_32BIT && optimize_insn_for_size_p()" > "* > operands[3] = gen_rtx_fmt_ee (minmax_code (operands[3]), SImode, > operands[1], operands[2]); > output_asm_insn (\"cmp\\t%1, %2\", operands); > if (TARGET_THUMB2) > output_asm_insn (\"ite\t%d3\", operands); > output_asm_insn (\"str%d3\\t%1, %0\", operands); > output_asm_insn (\"str%D3\\t%2, %0\", operands); > return \"\"; > " > [(set_attr "conds" "clob") > (set (attr "length") > (if_then_else (eq_attr "is_thumb" "yes") > (const_int 14) > (const_int 12))) > (set_attr "type" "store1")] >) > > >Note the insn condition uses optimize_insn_for_size_p(). This means >the pattern can be valid or invalid dependent on the context where the >insn appears: in hot or cold code. IMHO this behavior should not be >allowed. The back end cannot expect the middle end to know at all >times the context that the insn appears in, and more importantly >whether a pattern is valid or not is independent of where the insn >appears: That is a *cost* issue! > >It seems to me that the ARM back end should be fixed here, not LRA's >check_rtl. > >Comments&thoughts?
The intent is to allow this also to control combine and split, but certainly making insns invalid after the fact is bad. think of sinking a previously hot insn into a cold path... Honza, how was this supposed to work? Richard. >Ciao! >Steven
