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Re: Reg Alloc Problem.
- From: Umesh Kalappa <umesh dot kalappa0 at gmail dot com>
- To: "gcc at gcc dot gnu dot org" <gcc at gcc dot gnu dot org>
- Date: Fri, 14 Mar 2014 20:30:14 +0530
- Subject: Re: Reg Alloc Problem.
- Authentication-results: sourceware.org; auth=none
- References: <CAGfacvTdD66MedugcV=g-rniTjZ=NurgTwKvLevMHai-scJQGw at mail dot gmail dot com>
To handle the below problem i.e making specific set of register as
base registers ,which is the subset of general registers set.
we see the *.c.208.ira logs as
Pass 0 for finding pseudo/allocno costs
r21: preferred BASE_REGS, alternative GENERAL_REGS, allocno GENERAL_REGS
a2 (r21,l0) best BASE_REGS, allocno GENERAL_REGS
r19: preferred GENERAL_REGS, alternative NO_REGS, allocno GENERAL_REGS
a0 (r19,l0) best GENERAL_REGS, allocno GENERAL_REGS
r18: preferred GENERAL_REGS, alternative NO_REGS, allocno GENERAL_REGS
a1 (r18,l0) best GENERAL_REGS, allocno GENERAL_REGS
a0(r19,l0) costs: LOW_8BIT_REGS:0 BASE_REGS:0 GENERAL_REGS:0 ALL_REGS:0 MEM:8
a1(r18,l0) costs: LOW_8BIT_REGS:0 BASE_REGS:0 GENERAL_REGS:0 ALL_REGS:0 MEM:8
a2(r21,l0) costs: LOW_8BIT_REGS:2 BASE_REGS:0 GENERAL_REGS:4 ALL_REGS:4 MEM:8
where IRA choose the GENERAL_REG over BASE (preferred) for the r21
pseudo,i'm looking for the cause in our backend,but mean while anyone
in the group can share there experience w.r.t that will help me to
solve issue asap.
On Wed, Mar 12, 2014 at 7:30 PM, Umesh Kalappa <email@example.com> wrote:
> Hi All,
> We are porting the gcc 4.8.1 to the new target and which has the pair
> 16 bit registers like AB or CD or EF and we modeled it in
> reg_class as AB,CD and DE 16 bit pair_regs and CD ,EF as 16 bit
> base_regs and A,B,C,D E and F as 8 bit as general_regs.
> We are stuck with below issues like
> 1)How do we modelled such that the register alloc to pick the
> respective base_regs i.e CD,DE instead of AB as show in the below
> LD AB ,_a; //invalid instead of it should be emit LD CD ,_a
> LD (AB),#100; // invalid instead of it should be emit LD (CD),#100
> Please note that we override the target hook like REGNO_REG_CLASS
> ,but still no luck here .
> 2)Current target enforce the restrictions on the pair register set
> usage for multiplication like
> MUL A,B or MUL C,D or MUL E,F
> But not MUL A,C or MUL B,C etc not across the pair_regs .
> Anyone can please shed some lights here ,will be appreciate and help
> us in the great way .
> Thank you for the patience