similar to: [LLVMdev] Possible missed optimization?

Hello > and as the return value. Is this a missed optimization from LLVM or did i > miss something out? > Changing the register allocation order didnt work. What are the patterns for xor / mov ? -- With best regards, Anton Korobeynikov Faculty of Mathematics and Mechanics, Saint Petersburg State University

Indeed, i've marked it as commutable: let isCommutable = 1, isTwoAddress = 1 in def XORRdRr : FRdRr<0b0010, 0b01, (outs GPR8:$dst), (ins GPR8:$src1, GPR8:$src2), "xor\t$dst, $src2", [(set GPR8:$dst, (xor GPR8:$src1, GPR8:$src2))]>; -------------- next part -------------- An HTML

On Sep 4, 2010, at 11:21 AM, Borja Ferrer wrote: > I've noticed this pattern happening with other operators aswell, but used xor in this example. As i said before, i tried with different register allocation orders, but it will produce always the same result. GCC is emitting longer code, but since LLVM is so nearer to the optimal code sequence i wanted to reach it. In LLVM, copies are

Hello everbody, This is my first email to the list, and hope to write more as i get more involved in LLVM. I'm currently writing a backend for a 8 bit microcontroller, and i have arrived to a point where i need to take a design decision in order to continue the development. Some background information: The microcontroller only has 8bit registers, however it has some special instructions that

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) {

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, 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.

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

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 all, I am writing a custom backend. Doing more testing i notice that for some reason something like: int test(int x) { return x - 1; } is being turned into this IR: ; Function Attrs: nounwind define i32 @test(i32 %n) #0 { entry: %n.addr = alloca i32, align 4 store i32 %n, i32* %n.addr, align 4 %0 = load i32* %n.addr, align 4 %sub = sub nsw i32 %0, 1 ret i32 %sub } But finally in

TableGen, as a DSL language, is made up of records. Every def corresponds to a record. For example, TableGen has a class Register, and your backend will define records by def GPR8 : Register<...>. You are correct in saying that the record definition is one of the SDNode values. These correspond 1:1 to llvm::ISD::NodeType

I'm attempting to implement codegen support for the AVR ST/LD <http://www.atmel.com/webdoc/avrassembler/avrassembler.wb_ST.html> family of instructions. The binary encoding is not particularly consistent -- take a look at this table of variants of LD, along with their machine code representation: # load 8 bits from pointer register X into general purpose Rd ld Rd, X `1001 000d dddd

On Fri, Jan 29, 2016 at 11:39 AM, Rail Shafigulin <rail at esenciatech.com> wrote: > > > On Thu, Jan 28, 2016 at 8:34 PM, Dylan McKay <dylanmckay34 at gmail.com> > wrote: > >> Try visualising the DAG like this. >> >> ``` >> ---- GPR:$rA >> / >> set GPR:$rd ---- add >>

Hello Jim thanks for the reply, For normal additions with immediates I've done the same as ARM does, basically transforming add(x, imm) nodes to sub(x, -imm) with a pattern in the .td file like this: def : Pat<(add DLDREGS:$src1, imm:$src2), (SUBIWRdK DLDREGS:$src1, (imm16_neg_XFORM imm:$src2))>; Now, the typical pattern concerning additions with global addresses looks

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.

Thanks Jim, I've implemented the negation part successfully :) maybe the second part could be a possible feature request so others could use it aswell? 2011/4/27 Jim Grosbach <grosbach at apple.com> > > On Apr 26, 2011, at 1:27 PM, Borja Ferrer wrote: > > > Hello Jim thanks for the reply, > > > > For normal additions with immediates I've done the same as

Hi Leslie, On 20 December 2017 at 10:51, Leslie Zhai via llvm-dev <llvm-dev at lists.llvm.org> wrote: > Sorry, I am apprentice of lowRISC, and meet new bug when porting GlobalISel > to RISCV target > https://github.com/xiangzhai/llvm/commit/b3f91ea54d9fee0ef7e73a32c6b8456bbe252811 > > > In file included from >

I've noticed this pattern happening with other operators aswell, but used xor in this example. As i said before, i tried with different register allocation orders, but it will produce always the same result. GCC is emitting longer code, but since LLVM is so nearer to the optimal code sequence i wanted to reach it. -------------- next part -------------- An HTML attachment was scrubbed... URL:

Thank You. I have seen the opcode is 8 bits and all the combinations are already used in llvm x86. Now what to do? On Sat, Jul 8, 2017 at 10:57 AM, Craig Topper <craig.topper at gmail.com> wrote: > Yes its an opcode conflict. You'll have to look through Intel documents > and find an unused opcode. I've only added instructions based on a real > spec so I don't know