[llvm-dev] Register Allocation and Scheduling Issues

[hameeza ahmed via llvm-dev]

Actually my hardware is designed such that there are 32 lanes. each has 8
registers. the assembly code should be emitted keeping this fact.
I defined the registers as follows in .td in the following order;
L_0_R_0,
L_0_R_1,
L_0_R_2,
L_0_R_3,
L_0_R_4,
L_0_R_5,
L_0_R_6,
L_0_R_7,

L_1_R_0,
L_1_R_1,
L_1_R_2,
L_1_R_3,
L_1_R_4,
L_1_R_5,
L_1_R_6,
L_1_R_7,
...................

L_31_R_0,
L_31_R_1,
L_31_R_2,
L_31_R_3,
L_31_R_4,
L_31_R_5,
L_31_R_6,
L_31_R_7,

Now when i assemble the vec sum code by my implemented instructions and
default x86 scheduling & register allocation. it is only using L_0. But it
should use all the lanes? how to achieve this.

Something as follows:

currently it is emitting as follows:

P_2048B_LOAD_DWORD L_0_R_0, Pword ptr [rip + b]
P_2048B_LOAD_DWORD L_0_R_1, Pword ptr [rip + c]
P_2048B_VADD L_0_R_0, L_0_R_1, L_0_R_0
P_2048B_STORE_DWORD Pword ptr [rip + a], L_0_R_0
P_2048B_LOAD_DWORD L_0_R_0, Pword ptr [rip + b+2048]
P_2048B_LOAD_DWORD L_0_R_1, Pword ptr [rip + c+2048]
P_2048B_VADD L_0_R_0, L_0_R_1, L_0_R_0
P_2048B_STORE_DWORD Pword ptr [rip + a+2048], L_0_R_0
P_2048B_LOAD_DWORD L_0_R_0, Pword ptr [rip + b+4096]
P_2048B_LOAD_DWORD L_0_R_1, Pword ptr [rip + c+4096]
P_2048B_VADD L_0_R_0, L_0_R_1, L_0_R_0
P_2048B_STORE_DWORD Pword ptr [rip + a+4096], L_0_R_0
P_2048B_LOAD_DWORD L_0_R_0, Pword ptr [rip + b+6144]
P_2048B_LOAD_DWORD L_0_R_1, Pword ptr [rip + c+6144]
P_2048B_VADD L_0_R_0, L_0_R_1, L_0_R_0
P_2048B_STORE_DWORD Pword ptr [rip + a+6144], L_0_R_0

It should emit as follows:

P_2048B_LOAD_DWORD L_0_R_0, Pword ptr [rip + b]
P_2048B_LOAD_DWORD L_0_R_1, Pword ptr [rip + c]
P_2048B_VADD L_0_R_0, L_0_R_1, L_0_R_0
P_2048B_STORE_DWORD Pword ptr [rip + a], L_0_R_0
P_2048B_LOAD_DWORD L_1_R_0, Pword ptr [rip + b+2048]
P_2048B_LOAD_DWORD L_1_R_1, Pword ptr [rip + c+2048]
P_2048B_VADD L_1_R_0, L_1_R_1, L_1_R_0
P_2048B_STORE_DWORD Pword ptr [rip + a+2048], L_1_R_0
P_2048B_LOAD_DWORD L_2_R_0, Pword ptr [rip + b+4096]
P_2048B_LOAD_DWORD L_2_R_1, Pword ptr [rip + c+4096]
P_2048B_VADD L_2_R_0, L_2_R_1, L_2_R_0
P_2048B_STORE_DWORD Pword ptr [rip + a+4096], L_2_R_0
P_2048B_LOAD_DWORD L_3_R_0, Pword ptr [rip + b+6144]
P_2048B_LOAD_DWORD L_3_R_1, Pword ptr [rip + c+6144]
P_2048B_VADD L_3_R_0, L_3_R_1, L_3_R_0
P_2048B_STORE_DWORD Pword ptr [rip + a+6144], L_3_R_0

does it involve changing the register live intervals? or scheduling?

please help. i am trying hard but unable to solve this.






On Sun, Aug 27, 2017 at 12:31 AM, Tim Northover <t.p.northover at gmail.com>
wrote:

> On 26 August 2017 at 11:14, hameeza ahmed <hahmed2305 at gmail.com> wrote:
> > Hello,
> >
> > I have defined 8 registers in registerinfo.td file in the following
> order:
> > R_0, R_1, R_2, R_3, R_4, R_5, R_6, R_7
> >
> > But the generated assembly code only uses 2 registers. How to enable it
> to
> > use all 8?
>
> What are your thoughts on what might be the issue? Have you considered
> the advantages and disadvantages of using multiple registers for the
> code you're testing?
>
> Cheers.
>
> Tim.
>
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