similar to: extending liveness of 'this' pointer via FAKE_USE opcode

Oops, forgot to reply-all (& adding a few other people to the 'to' line) ---------- Forwarded message ---------- From: David Blaikie <dblaikie at gmail.com> Date: Mon, Sep 21, 2015 at 11:22 AM Subject: Re: [llvm-dev] extending liveness of 'this' pointer via FAKE_USE opcode To: "Pieb, Wolfgang" <Wolfgang_Pieb at playstation.sony.com> On Mon, Sep 21,

We thought about putting the 'this' pointer into memory but that would mean that even small member functions would acquire a stack frame (on architectures where leaf routines can get away without one), which may degrade performance considerably. You could apply some heuristics and determine when a store is unnecessary, but inlining may complicate things. A fake_use operation would be

I have code along the lines of: void foo(struct A *a) { struct B *b = a->m_B; /* do a whole bunch of things with b */ } When LLVM generates code for this, it sees that after initializing b, a is no longer used, so it is optimized out. Unfortunately, for debug, I'd like the value for a to be kept around, if only so that I can determine the value of b and go from there. I

On Aug 13, 2012, at 8:34 AM, Sergei Larin <slarin at codeaurora.org> wrote: > Andy, > > Yes, this is what Arnold has suggested also, and from this point it looks > like it should work, but it will require parsing the bundle every time we > care to know whether this is a real use or a conditional def. This might > become awkward... but I guess I should provide a better

On Thursday 17 January 2008 13:03, Evan Cheng wrote: > > So why does the live range extend throughout the entire basic block? > > > > %reg1055 doesn't appear anywhere else in the program so it shouldn't > > be > > live-in to the block. > > It could be a bug. Can you get me a test case? I'll see if I can whittle it down. It's a pretty huge

I had been assuming that give a LiveRange a, a.valno->def, if valid, would be the same as a.start. But this is apparently not always the case. For example: Predecessors according to CFG: 0x839d130 (#3) 0x8462780 (#35) 308 %reg1051 = MOV64rr %reg1227<kill> 312 %reg1052 = MOV64rr %reg1228<kill> 316 %reg1053 = MOV64rr %reg1229<kill> 320 %reg1054 = MOV64rr

On Jan 16, 2008, at 11:49 AM, David Greene wrote: > I had been assuming that give a LiveRange a, a.valno->def, if > valid, would be the same as a.start. But this is apparently not > always the case. For example: > > Predecessors according to CFG: 0x839d130 (#3) 0x8462780 (#35) > 308 %reg1051 = MOV64rr %reg1227<kill> > 312 %reg1052 = MOV64rr %reg1228<kill>

I've been working on patches to improve subregister liveness tracking on llvm and I wanted to inform the llvm community about the overal design/motivation for them. I will send the patches to llvm-commits later today. Greetings Matthias Braun Subregisters in llvm ==================== Some targets can access registers in different ways resulting in wider or narrower accesses. For

Currently it will always spill / restore the whole vreg but only spilling the parts that are actually live would be a nice addition in the future. Looking at r192119': if "mtlo" writes to $LO and sets $HI to an unpredictable value, then it should just have an additional (dead) def operand for $hi, shouldn't it? Greetings Matthias Am 10/8/13, 11:03 AM, schrieb Akira

On Sun, Aug 8, 2010 at 8:20 PM, Jakob Stoklund Olesen <stoklund at 2pi.dk> wrote: > > On Aug 7, 2010, at 7:05 PM, Steven Noonan wrote: >> I've been doing work on memory reduction in Unladen Swallow, and >> during testing, LiveRanges seemed to be consuming one of the largest >> chunks of memory. > > That's interesting. How did you measure this? I'd

What I didn't mention in r192119 is that mthi/lo clobbers the other sub-register only if the contents of hi and lo are produced by mult or other arithmetic instructions (div, madd, etc.) It doesn't have this side-effect if it is produced by another mthi/lo. So I don't think making mthi/lo clobber the other half would work. For example, this is an illegal sequence of instructions,

Hello Wolfgang and team, I see that you are working on support of .debug_rnglists, I am interested in the feature too, could you please point me out what else left to be done so that I could help you? -- Best Regards, Victor Leschuk | Software Engineer | Access Softek

On Oct 8, 2013, at 2:06 PM, Akira Hatanaka <ahatanak at gmail.com> wrote: > What I didn't mention in r192119 is that mthi/lo clobbers the other sub-register only if the contents of hi and lo are produced by mult or other arithmetic instructions (div, madd, etc.) It doesn't have this side-effect if it is produced by another mthi/lo. So I don't think making mthi/lo clobber the

On Sun, Aug 8, 2010 at 9:20 PM, Reid Kleckner <reid.kleckner at gmail.com>wrote: > On Sun, Aug 8, 2010 at 8:20 PM, Jakob Stoklund Olesen <stoklund at 2pi.dk> > wrote: > > > > On Aug 7, 2010, at 7:05 PM, Steven Noonan wrote: > >> I've been doing work on memory reduction in Unladen Swallow, and > >> during testing, LiveRanges seemed to be

Andy, Jacob, I have ported Hexagon MI scheduler to use the new scheduler infrastructure, but one of my tests triggers an assert in LiveInterval update. On the surface it does not make much sense to me, so I wonder if this is something you readily recognize, before I try to prop it open... The assert is: lib/CodeGen/LiveInterval.cpp:266: llvm::LiveRange*

Hi Victor, The work Wolfgang is doing should get us to the "minimum syntactically correct DWARF v5" stage, which we really wanted to have for LLVM 7.0. That is, once we have .debug_rnglists and .debug_loclists done, you can ask for DWARF 5 and get something that conforms to the spec. However, it won't conform if you ask for type units (I'm working on that) or split DWARF. If

On Aug 7, 2010, at 7:05 PM, Steven Noonan wrote: > I've been doing work on memory reduction in Unladen Swallow, and > during testing, LiveRanges seemed to be consuming one of the largest > chunks of memory. That's interesting. How did you measure this? I'd love to see your data. Note that the LiveRange struct is allocated by a plain std::vector, and your patch doesn't

Hello all, I've found an old post (November 2016) http://lists.llvm.org/pipermail/llvm-dev/2016-November/107006.html which discussed debug information for optimized code. At the end of that discussion, Adrian broached the interest in making -O1 only enable optimizations. I see in the code ( *clang/lib/Frontend/CompilerInvocation.cpp*, in function *getOptimizationLevel*) that *-Og* option is

Say I want to find all LLVM Value*-es that a live on exit from a basic block. What's the best way? - The 'LiveRange', 'LiveVariables' and 'LiveIntervals' classes seem to be tied to register allocation. - The ./lib/Target/SparcV9/LiveVar/FunctionLiveVarInfo.h file seem to provide what I need, but it's no a public header. - Volodya

In other compilers I've worked on there were special pseudo instructions (or similar mechanisms like adding extra source operands to returns) that allowed you to artificially extend lifetimes of values. For instance we might have a requirement that a certain local (say the 'this pointer') remain live throughout the method. Is there anything like this in LLVM? -------------- next part