similar to: Question about register allocation

Hi, ABCRegister.td : def SGPR32 : RegisterClass<"ABC", [i32], 16, (add S0, S1, S2, S3, S4, S5, S6, S7, S8, S9, S10, S11, S12, S13, S14, S15 )>; def SFGPR32 : RegisterClass<"ABC", [f32], 16, (add S0, S1, S2, S3, S4, S5, S6, S7, S8, S9, S10, S11, S12, S13, S14, S15 )>; ===== Instruction selection ends: ... t8: i32 = ADDrr t37, t32

Yes, immediately after branch folding the code would still behave the same as the original. At the same time, any subsequent optimization may "exploit" the incorrect liveness information to do something bad. If you add -run-pass if-converter, you'll get: # After If Converter # Machine code for function fred: IsSSA, NoPHIs, TracksLiveness, NoVRegs BB#0: %R0<def>

Hi Venu, > On Sep 11, 2017, at 11:00 PM, Raghavan, Venugopal via llvm-dev <llvm-dev at lists.llvm.org> wrote: > > Hi Krzysztof, > > Thanks for your reply. > > I agree that adding extra register units for x86 would be the right way to fix this. Do you know if there is a plan to fix this? No concrete plan, no. We've been thinking about for quite some time now, but

Hi Venu, FWIW, I have a pass that does copy propagation after RA [1] (currently only within a basic block) that should be enabled some time in the not-too-distant future. It has been reviewed and accepted, but I'm currently working on getting a slight change to the MachineOperand representation [2] that should make the copy propagation change much simpler. I believe this change to

Hi Geoff/Krzyssztof, Wouldn't the isRenamable() change be required even for the RDF based copy propagation? Maybe Hexagon does not impose ABI/ISA restrictions which require specific registers to be used in specific contexts. Also, if Geoff's copy propagation pass is invoked post-RA wouldn't it need to handle the x86 ISA feature which allows 8 bit/16 bit values to be moved into a

Hi Tim, >That C++ function is probably what looks for an FrameIndex node and >has been taught that it can be folded into the load. How do you teach a function that a node can be folded into an instruction? ________________________________ From: Tim Northover <t.p.northover at gmail.com> Sent: Monday, January 21, 2019 11:52 PM To: Josh Sharp Cc: via llvm-dev Subject: Re: [llvm-dev]

The comment in test/CodeGen/X86/branchfolding-undef.mir states that such merging is legal, however doing so can actually generate wrong code: Consider this (valid code): --- name: fred tracksRegLiveness: true body: | bb.0: successors: %bb.1, %bb.2 J2_jumpt undef %p0, %bb.2, implicit-def %pc J2_jump %bb.1, implicit-def %pc bb.1: successors: %bb.3 %r0 =

Hello, Im (trying) to write a backend for a simple 32bit processor architecture, with a single instruction format having no condition code registers. www.docm.mmu.ac.uk/STAFF/A.Nisbet/Sabre.pdf is the short 15 page document describing the architecture of Sabre. It is a Celoxica developed research/teaching processor, pages 5-8 contain relevant information for targetting it from a new compiler

I've looked into that and it's not going to be simple, unfortunately. Here's the original example again: --- name: fred tracksRegLiveness: true body: | bb.0: successors: %bb.1, %bb.2 J2_jumpt undef %p0, %bb.2, implicit-def %pc J2_jump %bb.1, implicit-def %pc bb.1: successors: %bb.3 %r0 = L2_loadruh_io undef %r0, 0 PS_storerhabs 0, killed

Hi, I’m hitting a machine verifier error in a trivial testcase which I don’t understand. There are 2 dead defs of the same register: --- name: multiple_connected_compnents_dead tracksRegLiveness: true body: | bb.0: dead %0:vgpr_32 = V_MOV_B32_e32 0, implicit $exec dead %0:vgpr_32 = V_MOV_B32_e32 1, implicit $exec ... The live intervals look OK to me with 1 valno

Hi, I'm looking for some suggestions on a problem related to the Hexagon backend. Hexagon architecture allows instructions in various formats. For example, we have 3 variations of the add instruction as defined below: ADDrr : r1 = add(r2, r3) --> add 2 32-bit registers ADDrr_p : if(p0) r1 = add(r2, r3) --> predicated version of ADDrr instruction, executed when p0 is true ADDrr_np :

Hi Venu, This is happening because there is an implicit def of ECX on the COPY instruction. This was an issue on Hexagon as well. Let me give you some background. There are two kinds of implicit defs (and implicit uses, but I'll refer only to defs for brevity): (1) Those that indicate that some physical register (that is not an operand) is modified by a given instruction (EFLAGS is a good

Hi Krzysztof, In one of your earlier emails in this thread you mentioned that you had some changes which add extra aliases for subregisters. Did you mean for X86? And is it extra register units that you added or aliases? I tried adding extra register units for X86 through some changes in CodeGenRegisters.cpp in TableGen but I am seeing a runtime error in one of my test cases possibly due to the

On Aug 1, 2012, at 1:53 PM, Jyotsna Verma <jverma at codeaurora.org> wrote: > > Currently, we rely on switch tables to transform between formats. However, > we would like to have a different mechanism to represent these relationships > instead of switch tables. I am thinking of modeling these relations in > HexagonInstrInfo.td file and use TableGen to generate a table with

Hi Everyone, After some more thoughts to the Jacob's suggestion of using multiclasses for Opcode mapping, this is what I have come up with. Please take a look at the design below and let me know if you have any suggestions/questions. I have tried to keep the design target independent so that other targets could benefit from it. 1) The idea is to add 3 new classes into

Hello all, I am at the adding Instruction Set stage of adding new target support into LLVM. There is a single instruction op mnemonic with multiple operand forms. For example: Add R1, R2 & Add @R1, R2. I found that there is similar case in x86 instruction set, such like ADD reg, reg & ADD mem, reg. However, the solution of x86 is adding suffix of instruction and translating instruction op

Hi! I'm making a strange observation in my backend, that ends in illegal code: Version 1: - I lower FrameIndex to TargetFrameIndex (nothing special) - I generate a special address-register ADD instruction in eliminateFrameIndex() to write FramePointer + offset into a new address-register - I use explicit load and store and address-registers in my target instruction patterns: eg (store

I have this same problem in our backend. I solve it by adding a pseudo instruction at instruction selection that transforms @R1 into R1, so only a single pattern is required. I then can propogate the pseudo instruction after instruction selection. Micah From: llvmdev-bounces at cs.uiuc.edu [mailto:llvmdev-bounces at cs.uiuc.edu] On Behalf Of Lu Mitnick Sent: Tuesday, January 18, 2011 10:29 AM

Hello Villmow, Is it your backend EFI Byte Code Virtual Machine?? Would you mind to give me an example about what pseudo instruction you add?? thanks a lot yi-hong 2011/1/19 Villmow, Micah <Micah.Villmow at amd.com> > I have this same problem in our backend. I solve it by adding a pseudo > instruction at instruction selection that transforms @R1 into R1, so only a > single

Hi, Is there a kind of scope mechanism in the instruction lowering pattern language in order to control where instructions are inserted or how they are later reordered during the SelectionDiag linearization? I know the glue chain that stick instructions together. But such mechanism in not provided in instruction lowering pattern. I'm facing many situations where some patterns are lowered into