search for: ragreedi

Compile times increased by roughly 20X after upgrading the Radian compiler project from LLVM 3.1 to 3.3. I am curious whether this is considered normal. If it is not, I would appreciate some help figuring out what it is about the Radian compiler's output which is causing LLVM to spend so much time compiling such small programs. I recorded these times with Apple's Xcode Instruments

enableAdvancedRASplitCost() does the same thing as ConsiderLocalIntervalCost, but as a subtarget option instead of a command-line option, and as I’ve said it doesn’t help because it’s a non-local interval causing the eviction chain (RAGreedy::splitCanCauseEvictionChain only considers the local interval for a single block, and it’s unclear to me how to make it handle a non-local interval). John

Preamble -------- While working on an IR-level optimisation completely unrelated to register allocation I happened to trigger some really strange register allocator behaviour causing a large regression in bzip2 in spec2006. I've been trying to fix that regression before getting the optimisation patch committed, because I don't want to regress spec2006, but I'm basically fumbling in

Hi, so just to verify the obvious: these are both the same type of build (Release-Asserts, or whatever) rather than an optimized 3.1 vs a 3.3 debug build? (I know this is unlikely, but I've managed to mix-up my configurations in the past so it is worth checking before trying more involved options). A 20x slow-down that looks to be on everything (rather than one component) is a strong symptom

Hi Quentin, Jonas, Splitting fits in with PBQP reasonably well, at least conceptually. The PBQP graph is designed to be mutable, so there is no problem with updating it when splitting. As I see it, there are two logical places to integrate splitting into PBQP: 1) Split during spilling -- If a PBQP solution selects the spill option for a node, rather than spill immediately, split the interval

Hi, I have worked a little on the PBQP register allocator, and it is quite clear (at least to me) that it is not even a serious alternative to RegAllocGreedy at the moment, due to the poor handling of spilling. As Arnaud wrote below, it is not optimizing spilling at all, but rather just spills anything that does not get an assignment. The result is a lot more spill/reload instructions than

On Nov 16, 2011, at 10:23 AM, David A. Greene wrote: > Jakob Stoklund Olesen <stoklund at 2pi.dk> writes: >> You want LiveRangeEdit::allUsesAvailableAt() which performs the same >> check today. > > But not in 3.0, right? Yes, 3.0 defaults to RAGreedy which uses the new spilling framework. It is ignoring the -spiller=... command line option. Also note that SplitKit

Both approaches are not exclusive. I would even think it makes sense to have a pre-split pass to prepare the graph, with a global view, and later on use use trySplit (or an equivalent) to handle the local coloring issues. From: Quentin Colombet [mailto:qcolombet at apple.com] Sent: 09 March 2015 23:08 To: Lang Hames Cc: Jonas Paulsson; llvmdev at cs.uiuc.edu; Arnaud De Grandmaison Subject:

On Nov 29, 2011, at 10:24 AM, Borja Ferrer wrote: > Yes, I want the register to be allocatable when there are no stack frames used in the function so it can be used for other purposes. In fact, I looked at how other backends solve this problem, but they are all too conservative by always reserving the register which in my case it is not a good solution because of the performance impact of not

Jakob Stoklund Olesen <stoklund at 2pi.dk> writes: > On Nov 16, 2011, at 9:15 AM, David Greene wrote: > >> I'm working on some enhancements to rematerialization that I hope to >> contribute. > > What do you have in mind? Rematting more types of loads. >> /// getReMatImplicitUse - If the remat definition MI has one (for now, we only >> /// allow one)

Jakob I've just noticed that I'm getting false positives about spills when there are actually none. What is happening is that although execution reaches to the line spiller().spill(LRE); inside RAGreedy::selectOrSplit() the insertion of the spill is avoided because the register gets rematted. This is the debug output I'm getting to show what I mean: Inline spilling

On Dec 17, 2012, at 8:38 AM, Borja Ferrer <borja.ferav at gmail.com> wrote: > Hello, > > I'm getting the "LLVM ERROR: ran out of registers during register allocation" error message for an out of tree target I'm developing. This is happening for the following piece of C code: > > struct ss > { > int a; > int b; > int c; > }; > void

Yes, I want the register to be allocatable when there are no stack frames used in the function so it can be used for other purposes. In fact, I looked at how other backends solve this problem, but they are all too conservative by always reserving the register which in my case it is not a good solution because of the performance impact of not having this register available. I find very interesting

I will be removing RegAllocLinearScan and VirtRegRewriter from trunk shortly after we cut the 3.0 release branch. LLVM 3.0 will still ship with the linear scan register allocator, but the default will be the new greedy allocator. Linear scan can be enabled by passing '-regalloc=linearscan -join-physregs' to llc. RegAllocLinearScan and VirtRegRewriter need to go away soon because they

Hello, I'm getting the "LLVM ERROR: ran out of registers during register allocation" error message for an out of tree target I'm developing. This is happening for the following piece of C code: struct ss { int a; int b; int c; }; void loop(struct ss *x, struct ss **y, int z) { int i; for (i=0; i<z; ++i) { x->c += y[i]->b; } } The problem relies in

Hal's advice helps me a lot to understand the implementation much better. Thanks so much! So, now I am able to state my problem more clearly: 1) There are two kinds of locals, i.e., the local variables originated from the source code (like C/C++), and the compilation generated temporaries. After instruction selection phase, the former is seen as frame indexes, while the latter is seen as

Hello Jakob, > Those are some severe constraints on register allocation, but it ought to > be possible anyway. > Indeed, these constraints aren't playing very well with the register allocator :\ > > You may wan't to investigate how RAGreedy::canEvictInterference() is > behaving. > Ok, this is what I've noticed, not sure if it makes sense at all but, regalloc

Hi, Can anyone help me with the stack slot coloring optimization? This corresponding file is /lib/codegen/stackslotcoloring.cpp. It is said this optimization was for stack slot overlay for frame size reduction, after register allocation phase. And this transformation pass relies on the LiveStack analysis pass. How, when checking the source code, it seems the LiveStack analysis has not been

Hi All, I am observing something i suspect is a misbehaviour of the register allocator which impacts the performance of patchpoints. This occurs in the context of an abstract machine which in some places uses inline caches. The problematic code looks like this: entry: ; Initialize the abstract machine %db = call create_big_seldom_used_database() ; do a lot of things which increases register

Hi all, I've come across a problem with register allocation which I have been unable to track down the root cause of. 6728B %vreg304<def> = COPY %vreg278; VRF128:%vreg304,%vreg278 6736B %vreg302<def> = COPY %vreg278; VRF128:%vreg302,%vreg278 6752B %vreg278<def,tied1> = foo %vreg278<tied0>, %vreg277, 14, pred:1, pred:%noreg, 5; VRF128:%vreg278 VRF64_l:%vreg277 * bar