Thanks .. your reply is really helpful ... Btw, I checked the MIPS backend at MIPS.c, but I can't find the definition of some functions such as:
get_attr_hazard(), gen_hazard_nop (), etc. Anyone know where those functions defined? Ian Lance Taylor-3 wrote: > > petruk_gile <[EMAIL PROTECTED]> writes: > >> I'm a pure beginner in GCC, and currently working on a project to >> implement >> instruction scheduling for a new DSP processor. This processor doesn't >> have >> pipeline interlock, so the compiler HAVE to schedule the instruction >> without >> relying on hardware help anymore .... >> >> The problem is, I'm a very beginner in GCC. I think the scheduling in GCC >> is >> activated by INSN_SCHEDULING variable (in automatically generated file: >> insn-attr.h), but I don't even know how to activate this variable. > > INSN_SCHEDULING will automatically be turned on if you have any > define_insn_reservation clauses in your CPU.md file. See the > "Processor pipeline description" documentation in the gcc internals > manual. > > That said, the gcc scheduler unfortunately does not work very well for > processors which do not have hardware interlocks. The scheduler will > lay out the instructions more or less optimally. But the scheduler > has no ability to insert nops when they are required to satisfy > interlock constraints. > > I know of two workable approachs. You can either insert the required > nops in the TARGET_MACHINE_DEPENDENT_REORG pass or in the > TARGET_ASM_FUNCTION_PROLOGUE hook. I personally prefer the latter > approach, as it takes effect after all other instruction rearrangement > is complete, but there are existing backends which use the former. > > For an example of inserting nops in TARGET_MACHINE_DEPENDENT_REORG, > see the MIPS backend, specifically mips_avoid_hazards. For an example > of inserting nops in TARGET_ASM_FUNCTION_PROLOGUE, see the FRV > backend, specifically frv_pack_insns. > > Ian > > -- View this message in context: http://www.nabble.com/How-to-activate-instruction-scheduling-in-GCC--tf4167590.html#a11940780 Sent from the gcc - Dev mailing list archive at Nabble.com.
