similar to: [LLVMdev] Inserting stack spilling code that modifies globally visible state

I start my porting for picoblaze,the soft cpu for fpga ,which is designed by XILINX from MSP430 porting . After some day's work , somethinig looks good , for it can generate for some simple C program: eg : int f1(int a) { return a+1; } but it failed with this : char f() { char a; a++; a++; a++; a++; a++; a++; a++; a++; a++; a++; a++; a++; a++; a++; a++;

To make my point clear, I believe an implementation of storeRegToStackSlot()/loadRegFromStackSlot() is not sufficient (as it received the physical register already). Does this make sense? On 2018-01-30 13:33, ahmede wrote: > Right Matthias, I am aware that an implementation for > storeRegToStackSlot()/loadRegFromStackSlot() is necessary. But these > functions receive the physical

Right Matthias, I am aware that an implementation for storeRegToStackSlot()/loadRegFromStackSlot() is necessary. But these functions receive the physical register that need to be spilled, they might receive the sub-register. In this case, using the super-register naively is unsafe (e.g., one might overwrite parts of it). Thus, I think the register allocator/spillar need to be aware of the

I still think my answer applies that you have to modify storeRegToStackSlot()/loadRegFromStackSlot(). They decide how registers are spilled and reloaded. Nobody is stopping you from using super registers spills/reloads to implement spilling/reloading smaller registers there. - Matthias > On Jan 30, 2018, at 10:21 AM, ahmede <ahmede at ece.ubc.ca> wrote: > > Hi Quentin, > >

Hi Quentin, Let me clarify if I understood this correctly. If the accesses (writes and reads) to sub-registers are expressed always as sub-registers of the super-register register class (e.g., SuperReg.sub1;), then the spilling decision is for the super register. But, if the accesses are in terms of the register class of the sub-registers directly (SubReg;), then the spilling decision will

> On Jan 29, 2018, at 1:20 PM, ahmede via llvm-dev <llvm-dev at lists.llvm.org> wrote: > > Hi, > > > I wonder if there is a way in LLVM to disable spilling a register-class while still enabling the super-registers of this register-class to be spilled. What would you have the register allocator do when it runs out of register and you have spilling disabled? Abort the

Hi, I wonder if there is a way in LLVM to disable spilling a register-class while still enabling the super-registers of this register-class to be spilled. If not, how can we implement spilling for sub-registers when stack load/stores can only operate on the super registers? Is there a way even if it is suboptimal? Thanks, Ahmed

Hi Matthias, No. I want the register allocator to spill the super-register (the large one e.g., 64-bit) and not just the sub-register (e.g., the 32-bit that is a piece of of the 64-bit register) because the stack loads/store width is 64-bit in this example. RegClass1 (sub-registers): sub_registers (32-bit) --> can be natively used in arithmetic operations but no stack

Hi Ahmed, If you access your values with sub-registers indices, IIRC the inline spiller will spill the super register. If you access your values directly (via sub-regclass), then the spiller uses this class. Basically what I am saying is the spiller spills the value that contains the accesses. E.g., = v; will spill v = v.sub1; will spill v too, but v is a super register in that case. Cheers,

Does anybody have any tips for generating spills/reloads for large non-vector registers? I'm working on a back end for a DSP architecture that has accumulator registers that are too large to be spilled or reloaded with a single instruction. All of their bits can be accessed in word-size chunks via three sub-registers (low, high, and ext). So loading or storing one requires three instructions:

On Jul 20, 2010, at 10:57 AM, Ken Dyck wrote: > Does anybody have any tips for generating spills/reloads for large > non-vector registers? > > I'm working on a back end for a DSP architecture that has accumulator > registers that are too large to be spilled or reloaded with a single > instruction. All of their bits can be accessed in word-size chunks via > three

Hello, I have a compiler in LLVM 2.9 for the KCPM3 processor. I'd like to create a subtarget for the new cpu version called KCPSM6. Besides a couple of new instructions which are not important at the moment, the KCPSM6 cpu has different instruction opcodes. Semantically the instructions are the same, hence I'd like to keep all the lowering and pattern matching stuff unmodified For

Hi Brian, +1 on what Nemanja said: specifying large register classes is the key. More details here: http://lists.llvm.org/pipermail/llvm-dev/2019-December/137700.html <http://lists.llvm.org/pipermail/llvm-dev/2019-December/137700.html> Cheers, -Quentin > On Sep 9, 2020, at 11:13 AM, Nemanja Ivanovic via llvm-dev <llvm-dev at lists.llvm.org> wrote: > > On PowerPC, we

> I am not sure extending the scavenger is the right way to go about this. > > There are two different situations where we might need extra registers to > spill something: > > 1. When spilling a weird register class like predicate registers, we > already known during register allocation that we will need a scratch GPR > to assist with the spill. > > 2. When spilling

Hi folks, I am interesting in creating an LLVM backend for a very small stack machine. Before I start in on the actual implementation, I'd like to make sure that I'm on the right track. Any comments, suggestions, warnings, tips, etc would be greatly appreciated. Background ---------- There are a number of small as other embedded microprocessors that are often used in FPGAs such as

Hi, right now, LLVM does register spilling by: 1. Creating stack object 2. Passing index of that stack object to MRegisterInfo::storeRegToStackSlot 3. At later stage, frame indices are replaced by calling to MRegisterInfo::eliminateFrameIndex. This works for me, but there's slight problem. The target does not have "register + contant" addressing mode, so accessing frame index

s/llvm-commits/llvmdev/ On Dec 9, 2011, at 12:58 PM, Arnold Schwaighofer wrote: > >> As Jakob pointed out to me, the core problem is that the current >> register scavenger implementation will only give you one register; for >> the PowerPC case, and it looks like for your case as well, we might >> really need two registers. In the short term, a reasonable solution

On Tue, 23 May 2006, Vladimir Prus wrote: > right now, LLVM does register spilling by: > > 1. Creating stack object > 2. Passing index of that stack object to MRegisterInfo::storeRegToStackSlot > 3. At later stage, frame indices are replaced by calling to > MRegisterInfo::eliminateFrameIndex. > > This works for me, but there's slight problem. The target does not have

Given an architecture with two classes of registers: A is general purpose and has an "adequate" number of registers, and C which is special purpose and has very few (e.g. one) register. There are cheap instructions that directly copy from C to A and vice versa. If we need another C register and they are all live, we need to spill one. Currently as far as I can tell, the only way to

Hi folks, I'm running into this weird issue where the register spills appear to be missing for an "if" block for some reason. For example, the original if/else blocks: --- if reg0 // storeRegToStackSlot for reg1 // do something - missing a load for reg1? else // storeRegToStackSlot for reg1 // do something // loadRegFromStackSlot for reg1 end ---- I tried looking in the LLVM