similar to: Marking a register as reserved midway through register allocation

Sorry, forgot to Reply-All. Begin forwarded message: > From: Steve Montgomery <stephen.montgomery3 at btinternet.com> > Subject: Re: [LLVMdev] Prevention register promotion at the isel codegen phase > Date: 24 November 2012 17:09:58 GMT > To: Joseph Pusdesris <joe at pusdesris.com> > > I had a similar problem trying to implement reg-mem operations. The solution I

Yes, this is very helpful! Thank you! How does this work when exiting a variable's liveness range? Will it automatically know to free the stack slot for reuse? -Joe On Sat, Nov 24, 2012 at 12:23 PM, Steve Montgomery < stephen.montgomery3 at btinternet.com> wrote: > Sorry, forgot to Reply-All. > > Begin forwarded message: > > *From: *Steve Montgomery

Chris Lattner wrote: > On Thu, 12 Apr 2007, Fernando Magno Quintao Pereira wrote: >>> I'm definitely interested in improving coalescing and it sounds like >>> this would fall under that work. Do you have references to papers >>> that talk about the various algorithms? >> Some suggestions: >> >> @InProceedings{Budimlic02, >> AUTHOR =

On Thu, 12 Apr 2007, Fernando Magno Quintao Pereira wrote: >> I'm definitely interested in improving coalescing and it sounds like >> this would fall under that work. Do you have references to papers >> that talk about the various algorithms? > > Some suggestions: > > @InProceedings{Budimlic02, > AUTHOR = {Zoran Budimlic and Keith D. Cooper and Timothy

Hi Matthias, Thanks for your hint! It is just for learning and practicing for me, just like migrate DragonEgg http://lists.llvm.org/pipermail/llvm-dev/2017-September/117201.html the motivating is for learning from GCC and LLVM developers. 在 2017年12月19日 10:07, Matthias Braun 写道: > > >> On Dec 18, 2017, at 9:52 AM, Leslie Zhai via llvm-dev >> <llvm-dev at lists.llvm.org

Here are 2 patches, which are independent of each other. The first splits PrologEpilogInserter into 2 parts : http://reviews.llvm.org/D16481 After looking at the code I thought it made more sense for the major split to include whether callee-saved register spills are supported. So for non-virtual targets, virtual registers are not supported and scavenging is optionally supported, and vice versa

Can someone explain the theory behind the spillers in VirtRegMap.cpp? It seems as though the spillers do triple duty: - Insert load/store operations and/or fold instructions as necessary to carry out spills - Rewrite the spilled virtual registers to use machine registers (mapping given by the caller in the VRM). - Rewrite machine code to change virtual registers to physical registers

We had some additional discussion on this. There is a lot of concern generally about post-RA passes which do not expect to have to handle virtual registers; specifically if they unexpectedly start seeing virtual registers, or if they work today but start making assumptions in the future. We discussed considering a mechanism that would require MachineFunctionPasses to "opt-in" and declare

Hi GCC and LLVM developers, I am learning Register Allocation algorithms and I am clear that: * Unlimited VirtReg (pseudo) -> limited or fixed or alias[1] PhysReg (hard) * Memory (20 - 100 cycles) is expensive than Register (1 cycle), but it has to spill code when PhysReg is unavailable * Folding spill code into instructions, handling register coallescing, splitting live ranges, doing

> On Jan 22, 2016, at 1:23 PM, Matthias Braun <mbraun at apple.com> wrote: > >> >> On Jan 22, 2016, at 12:29 PM, Derek Schuff <dschuff at google.com <mailto:dschuff at google.com>> wrote: >> >> Here are 2 patches, which are independent of each other. >> >> The first splits PrologEpilogInserter into 2 parts :

Ok, thanks. Except the question was meant slightly different. Less w.r.t. organizing the register classes, and more w.r.t. implementation. I've noticed for instance that when trying to model this straight forwardly by writing a vreg from spills and reading this from fills (not further elaborated here), that the spiller can't handle vreg def-use pairs: there are assertions making sure a

On Monday 06 August 2007 12:15, Anton Vayvod wrote: > Spill intervals must be precolored because they can't be spilled once more. > They are the shortest intervals precisely over each def/use of the original > interval. That is why they also have their weights set to #INF. Yes, that's true. But I wonder if we shouldn't be smarter about which register we pick to color it.

>It should be possible to get llvm to produce very good code for the Z80... Yes, I was thinking that too. These techniques didn't exist back then, so I'm really looking forward to the point where the first regular C sources can be compiled and see the magic happening in action live :) ------------------------------------------------------------------------ *From:* Bruce Hoult

I have an issue that I've been wrestling with for quite some time and I'm hoping that someone with a deeper understanding of the register allocator can help me with. Namely, I am trying to teach RA to split a live range rather than allocating a CSR. I've attempted a very large number of tweaks to the costs (both existing and experimental ones that I've added). However, despite all

Hello, for an architecture that doesn't have a good way to load/store a given register class to memory, is it instead easy to spill/fill from another register class instead? e.g. - storeRegToStack/loadRegFromStack use a pseudo instruction and add virtual register operand is not supported (spill optimization doesn't seem to like this). - AMDGPU backend seems to do sth. similar? The only

On Mon, 16 Apr 2007, David Greene wrote: >> Yep, this is the one I was thinking of. It is available online here: >> http://www.cs.rice.edu/~keith/LACSI/pldi02.pdf > > I was just looking at this today. One thing that strikes me about > all these papers I've read on the topic is that no one seems to > consider the interaction of coalescing with spilling. By definition

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

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

On 2017-10-27 19:50, Hal Finkel wrote: > On 10/27/2017 03:32 PM, Jun Lim via llvm-dev wrote: > >> When compiling C code below for AArach64, I saw that shrink-wrapping >> didn't happen due to the very early uses of CSRs in the entry block. >> So CSR spills/reloads are executed even when the early exit block is >> taken. >> >> int getI(int i); >>

On 2017-11-14 17:22, Quentin Colombet wrote: > Hi, > > I think it is kind of artificial to tie the CSRCost with the presence > of calls. > I think I’ve already mentioned it in one of the review, but I > believe it would be better to differentiate when we want to use a CSR > to avoid spilling or to avoid splitting. CSR instead of spilling is > good, CSR instead of