similar to: [LLVMdev] Register design decision for backend

Hi, I don't know if anyone else has responded to your question, but I am currently in development of a register allocator. Thank you for bringing up the fact that sub-register classes may be larger than their super-register. If this remains the case, I for one will write a transform for my allocator which will make the 16 bit register the super-register with the 8bit as the sub. At least for

Hello Jeff, you're the first one to reply to my question :) I got a bit confused with the fact you said that the subregister class is larger than the superregister class. As far as i understood or what i tried to do with my code is to define a register pair composed of two 8 bit registers the way i described in my previous message. So R1R0 in WDREGS is directly mapped into R0 and R1 of GPR8.

Hello, some months ago i wrote to the mailing list asking some questions about register pairing, i've been experimenting several things with the help i got back then. Some background first: this issue is for a backend for an 8bit microcontroller with only 8bit regs, however it has a few 16bit instructions that only work with fixed register pairs, so it doesnt allow all combinations of regs.

Hello Jakob and everyone, I am observing an issue with MCRegUnitIterator in my back end, and trying to reverse engineer some of the table gen magic around it, but if you or someone readily knows the answer, I would highly appreciate it. Here is the problem. In my back end we have a rather simple int register file structure: // Integer registers. def R0 : Ri< 0, "r0">,

I’m hitting TableGen errors trying to match the smullohi <lhs> <rhs> node in TableGen. smullohi returns two results, which is the problem. I am not sure how to match against multiple results. The only other nodes to return two operands are umullohi, udivrem, and sdivrem. There are no examples of these in TableGen in tree. The closest I can get is this: set (R1, R0, (umullohi

Hello LLVMDevs, I am looking for an example for how to lower LLVM IR to mulsu kind of instruction. I found that AVR back end have such instruction but AVRInstrInfo.td does not define any DAG pattern for which this instruction gets emitted. def MULSURdRr : FMUL2RdRr<1, (outs), (ins GPR8:$lhs, GPR8:$rhs), "mulsu\t$lhs, $rhs", []>, Requires<[SupportsMultiplication]>; Also

Mark, did you get anywhere with this? We have a similar issue, where a family of otherwise-identical instructions operates on different register classes depending on a non-static property -- functional unit selection in our case. I started to head down the path of using multidefs but quickly abandoned that. I had envisioned a MachineOperand that would hold the functional unit assignment, and

Hi Sergei, Register units != sub registers. Register units are an abstraction to describe overlapping of registers effectively. You probably wanted to use MCSubRegIterator. On Thu, Aug 30, 2012 at 2:30 PM, Sergei Larin <slarin at codeaurora.org> wrote: > Hello Jakob and everyone, > > I am observing an issue with MCRegUnitIterator in my back end, and trying > to reverse

Andy, Lang, Thanks for the suggestion. I have spent more time with it today, and I do see some strange things in liveness update. I am not at the actual cause yet, but here is what I got so far: I have the following live ranges when I start scheduling a region: R2 = [0B,48r:0)[352r,416r:5)... R3 = [0B,48r:0)[368r,416r:5)... R4 = [0B,32r:0)[384r,416r:4)... R5 = [0B,32r:0)[400r,416r:4)...

On Mar 15, 2009, at 2:02 PM, Jakob Stoklund Olesen wrote: > Hi, > > I am writing a backend for the Blackfin processor from Analog > Devices. I > just started so I still have a lot to learn about the code > generator. So > far, I can compile test/CodeGen/Generic/BasicInstrs.ll correctly, but > that is about it. > > The Blackfin 32-bit registers divide naturally

Thanks Dylan, I am working on a backend which has mulhsu instruction that performs multiplication between signed and unsigned number and returns upper 32 bits into result register. I think I also need to write some code probably as you indicated to check signedness of the operands and based on that lower to mulhsu instruction. -Vivek On Mon, Feb 27, 2017 at 11:13 AM, Dylan McKay <me at

Hi, I am writing a backend for the Blackfin processor from Analog Devices. I just started so I still have a lot to learn about the code generator. So far, I can compile test/CodeGen/Generic/BasicInstrs.ll correctly, but that is about it. The Blackfin 32-bit registers divide naturally into several classes. I have modelled these register classes without knowing anything about what the code

On 9/28/2016 7:30 PM, Quentin Colombet wrote: > Out of curiosity, could describe why this is useful to have such precision in the liveness tracking? RDF is meant to allow optimizations across the whole function. As a result, registers may change between basic blocks, and there is code to recalculate it. Accuracy is required to avoid unnecessary block live-ins. For example, calculate live-ins

Dan Gohman <gohman at apple.com> writes: > On Mar 15, 2009, at 2:02 PM, Jakob Stoklund Olesen wrote: >> Am I misusing register classes, or is this simply functionality that >> has not been written yet? The existing backends seem to have only one >> register class per machine value type. > > The x86 backend has an example of a partial solution. The GR32 >

Hello, I am working on a AVR backend and have a version up and running that will convert LLVM IR code to assembly code for my target. I have written a bunch of instructions from the AVR Instruction Set in AVRInstrInfo.td and not much else. In a simple test case I am attempting to compile (if that is the word you are supposed to use for this operation) test.ll: define i8 @foo(i8 %a, i8 %b) {

While beginning to add vector registers to a back end I came across the following problem: as soon as I define two sets of registers that have a many-to-one mapping the live interval pass appears to double- kill the mapped-onto register. I have the following excerpts from my RegisterInfo.td. def V4R0 : R4v<0 , "V4R0 ", []>, DwarfRegNum<0>; def R0 : Rg<0 ,

On 6 Dec 2012, at 07:46, 陳韋任 (Wei-Ren Chen) wrote: > The code below in lib/Target/ARM/ARMRegisterInfo.td is where you > should look into, > > // Integer registers > def R0 : ARMReg< 0, "r0">, DwarfRegNum<[0]>; > def R1 : ARMReg< 1, "r1">, DwarfRegNum<[1]>; > > ... That's the easy part. ARM (AArch32) has 16 registers

Hi, I want to increase the number of integer registers in the ARM machine. I don't have any idea how/where I can start. Can anybody help me? By the way, what are the following line in the ARMRegisterInfo.td specify: def qsub_0 def qsub_1 .... Thanks Best Regards, A. Yazdanbakhsh

On Mar 25, 2007, at 7:12 AM, Christopher Lamb wrote: > While beginning to add vector registers to a back end I came across > the following problem: as soon as I define two sets of registers > that have a many-to-one mapping the live interval pass appears to > double-kill the mapped-onto register. I have the following excerpts > from my RegisterInfo.td. > > def V4R0

> This isn't really my area of expertise, but I think you're messing up > your RegisterClass definition. Look at how ARM defines DTriple. DTriple is untyped :) , because we do not have any valut type which defines 3xi64. However, the paired register needs to have type. Fabian, what are the definitions of ER and DR register classes? -- With best regards, Anton Korobeynikov Faculty