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Hi, Intel Advanced Matrix Extensions (Intel AMX) is a new programming paradigm consisting of two components: a set of 2-dimensional registers (tiles) representing sub-arrays from a larger 2-dimensional memory image, and accelerators able to operate on tiles. Capability of Intel AMX implementation is enumerated by palettes. Two palettes are supported: palette 0 represents the initialized state and

[Yuanke] AMX register is special. It needs to be configured before use and the config instruction is expensive. To avoid unnecessary tile configure, we collect the tile shape information as much as possible and combine them into one ldtilecfg instruction. The ldtilecfg instruction should dominate any AMX instruction that access tile register. On the other side, the ldtilecfg should post-dominated

The AMX registers are complicated. The single configuration register (which is mostly used implicitly, similar to MXCSR for floating point) controls the shape of all the tile registers, and if you change the tile configuration every single tile register is cleared. In practice, if we have to change the the configuration while any of the tile registers are live, performance is going to be terrible.

Hi Hal, There is 3 aspect to be solved. 1. The HW support max shape 16x16, so there are many register classes from 1x1 to 16x16. We need 256 register classes. 2. We want to support variable shape, so compiler don't know what register class to fit tile shape as it is only known in runtime. 3. The tile configure is to configure physical tile register, so we need to allocate

There is no problem to have 256 register classes. Just a lot of register classes to me. We don't assume the shape of each physical register be 16x16, it is defined by user. For variable shape, I mean the shape is known in runtime and in compile time the shape is unknown. Take below code as an example, the %row and %col are variable instead of constant. Compiler recognizes llvm.x86.tileloadd64

Hi Philip, Your idea make sense to me in my first thought. Thank you for the idea. I will take more time to think it over to see it can help to reduce the complexity of tile register allocation. Yuanke From: Philip Reames <listmail at philipreames.com> Sent: Saturday, August 15, 2020 11:29 AM To: Luo, Yuanke <yuanke.luo at intel.com>; llvm-dev at lists.llvm.org; florian_hahn at

> When the tile shape is unknown at compile time, how do you plan to do the register allocation of the tiles? My question is: do you do the allocation for this case in the same way as you would if you knew the size was 16x16 (i.e., conservatively assume the largest size)? I think what will happen is that the registers are allocated based on a number of runtime values that are assumed to be

From: Hal Finkel <hfinkel at anl.gov> Sent: Friday, August 14, 2020 11:27 PM To: Luo, Yuanke <yuanke.luo at intel.com>; llvm-dev at lists.llvm.org; florian_hahn at apple.com; Kaylor, Andrew <andrew.kaylor at intel.com>; Topper, Craig <craig.topper at intel.com>; Lu, Hongjiu <hongjiu.lu at intel.com> Subject: Re: [llvm-dev] Intel AMX programming model discussion. On

The width and height can be runtime values that we would just copy into 64 byte configuration block we pass to ldtilecfg. So the code doesn't need to be multiversioned. The user code would also use those values to update pointers in the loops they write using the tiles. If we can't determine that two tiles were defined with the same width and height we need to assume the shape is different

On 8/20/20 2:47 PM, Topper, Craig wrote: > > I think I’m still missing something here. The configuration is per > tile. The multiply instructions take a MxK tile and multiply it by a > KxN tile and accumulate into an MxN tile. So the configuration needs > to know how many of each size of tile it needs to avoid a spill. > Wouldn’t the register allocator then need to know which

Hi Hal, The proposal is attractive to me, but there is something I still can't figure out. Let's take below MIR as an example. We assume we have 256 register classes (vtile1x1, vtile1x2, ..., tile16x16). 1. After instruction selection, the pseudo AMX instruction is generated. The name of pseudo instructions have 'P' prefix. Now all the AMX pseudo instruction take vtile as