similar to: [LLVMdev] How to avoid register reuse in machine instructions?

Hello, > I'm guessing that the right way to do this would be to kill the operand > registers after the given machine instruction rather than before it, but > I don't see a way to mark it this way. Right now the only way is to mark output reg as earlyclobber (see ARM backend for examples). Note that post-RA scheduler is not yet aware about earlyclobber operands and thus can break

Hi, I'd like to define a pseudo-instruction whose expansion will, as a side-effect, overwrite an input register's value: the pseudo-instruction ldw r1:r2, P to load 2 bytes from memory address P is to be expaneded to ld r1, P+ ld r2, P where "ld _, P+" is an instruction that loads a single byte from P, and post-increments P by one. How can I represent this behaviour in

Hi, To fix this bug(http://llvm.org/bugs/show_bug.cgi?id=18881), we need to add more register constraints that for STLXR , Ws and Wt should not be the same register. Because these unpredictable instructions are valid instructions in MC layer, we couldn't just simply treat them as unallocated encoding. I suppose to add some extra rules on register allocator to avoid it allocating register

Hi Kevin, I concur Tim’s advice, you should use the @earlyclobber. Cheers, -Quentin On Feb 19, 2014, at 3:27 AM, Tim Northover <t.p.northover at gmail.com> wrote: > Hi Kevin, > >> I suppose to add some extra rules on register allocator to avoid it >> allocating register causing any unpredictable behavior, but I don't have >> experience to this part. Can

Hi, I've been giving a look at the archives of the mailing list and I've seen that you have rewritten a lot of functions using mmx to make them faster. I'm currently trying to optimize some code, but I'm have some problems, because I work with 16 bit per component and not 8 like theora. I know that it is off topic, but I'm posting to ask you a little help. I've got

Hi all, I'm working on a target whose registers have equal-sized subregisters and all of those subregisters can be named (or the other way round: registers can be grouped into super registers). So for instance we've got 16 registers W (as in wide) W0..W15 and 32 registers N (as in narrow) N0..N31. This way, W0 is made by grouping N0 and N1, W1 is N2 and N3, W2 is N4 and N5, ..., W15 is

On Sun, 28 May 2017, David Chisnall wrote: >> let Constraints = "@earlyclobber $reg" in >> def LDWRdPtr : Pseudo<(outs DREGS:$reg), >> (ins PTRREGS:$ptrreg), >> "ldw\t$reg, $ptrreg", >> [(set i16:$reg, (load i16:$ptrreg))]>, >>

Hello, I'm getting a machine verifier error after introducing the earlyclobber constraint to some instructions where the src and dest regs can't be the same. The offending instruction pattern is this one: let canFoldAsLoad = 1, isReMaterializable = 1, Constraints = "@earlyclobber $dst" in def LDDWRdPtrQ : Inst<(outs DREGS:$dst), (ins memri:$src),

On Jul 14, 2012, at 10:09 AM, Borja Ferrer <borja.ferav at gmail.com> wrote: > Hello, > > I'm getting a machine verifier error after introducing the earlyclobber constraint to some instructions where the src and dest regs can't be the same. The offending instruction pattern is this one: > > let canFoldAsLoad = 1, > isReMaterializable = 1, > Constraints =

Hello Jakob, I'm still getting the error, I can give you any other debug info you need. I haven't pasted the regalloc debug info here because it is quite huge, but if you tell me what specific details you need I will include them. Thanks for your help! 2012/7/14 Jakob Stoklund Olesen <stoklund at 2pi.dk> > > On Jul 14, 2012, at 10:09 AM, Borja Ferrer <borja.ferav at

For any instruction, a list of constraints can be specified, like: let Constraints = "$dst = $lhs" in ... I checked the existing backends and I didn't notice any complex constraints: basically "Constraints" keyword is used to force 1 operand register to be the same as another one. I am wondering if there is any way to express more complicated constraints like for

Hi Guys, In LLVM codegen, a typical binary operation instruction is defined something like below: " def _rr: NVPTXInst<(outs Int1Regs:$dst), (ins Int1Regs:$a, Int1Regs:$b), "xor.pred \t$dst, $a, $b;", [(set Int1Regs:$dst, (OpNode Int1Regs:$a, Int1Regs:$b))]>; “ which takes two inputs and write the result to the $dst register. Then how to define a binary

Hi Quentin, > It sounds like you only need the earlyclobber description for the N, N > variant. > In other words, as long as you use different opcodes for widen-op NN and > widen-op WN, you model exactly what you want. > > What am I missing? > we are using different opcodes for widen-op NN and widen-op WN. My understanding is that not setting earlyclobber to the W, N

On Jul 15, 2012, at 9:20 AM, Borja Ferrer <borja.ferav at gmail.com> wrote: > Jakob, one more hint, I've placed some asserts around the code you added and noticed that the InlineSpiller::insertReload() function is not being called. > > 2012/7/14 Borja Ferrer <borja.ferav at gmail.com> > Hello Jakob, > > I'm still getting the error, I can give you any other

On Dec 15, 2009, at 5:08 PM, David Greene wrote: > On Tuesday 15 December 2009 18:01, Jim Grosbach wrote: > >> For a usage example, I've included in the patch the modification to >> use the constraint for the STREX ARM instruction. > > Your example is: > > constraints = "@early $success" > > Why not spell it as: > > constraints =

Hi, I am planning to expanding the pseudo instructions in XXXTargetLowering::EmitInstrWithCustomInserter(), and use temporary virtual registers as operands. If I use virtual registers, do I need to mark them as "early clobber"? I saw that sometimes they marked virtual register as "early clobber" in EmitInstrWithCustomInserter() in MIPS backend. What is the effect of marking a

Hi, How can I specify in a .td file that source and destination should not use the same register? Thanks. - Elena --------------------------------------------------------------------- Intel Israel (74) Limited This e-mail and any attachments may contain confidential material for the sole use of the intended recipient(s). Any review or distribution by others is strictly prohibited. If

On Tuesday 15 December 2009 19:52, Jim Grosbach wrote: > Do you have specific examples in mind that would be expressible with > something more complicated that aren't handleable via an early-clobber > constraint? Not offhand, no. I'm mostly concerned about the readability of .td files. > Perhaps spelling it out more fully with "earlyclobber" rather than >

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One other minor thing: I notice that in the inline assembly the result (rd) is constrained as an earlyclobber operand. What was the reason for that?