similar to: [LLVMdev] register scavenger

Hello LLVMDev, I've encountered what looks like a bug in LLVM 2.9, it doesn't appear to be fixed in 3.0 either. The problem occurs in function ARMFrameLowering.cpp:processFunctionBeforeCalleeSavedScan. There's a circular dependency in setting the variable BigStack and AFI->setHashStackFrame(true). The expression which initializes BigStack calls estimateRSSStackSizeLimit which in

> That is irrelevant. The PEI code needs to know how much stack space is > required for each call to allocate and align the stack frame properly. It > gets this info from the ADJCALLSTACK instructions. I see. Looking at PEI::calculateCalleeSavedRegisters shows that the ADJCALLSTACK instructions is used to set up MaxCallFrameSize. Adding debug prints also show that in the example code

On my (out-of-tree) target I have 16 128-bit registers. Unaligned load/store are illegal. (must 16-bytes aligned) 8 of those registers are defined as callee-saved and 8 caller-saved. The default stack size is 4 bytes. The target implements dynamic stack realign to make sure the stack will always be aligned correctly when necessary. Yet I am still getting unaligned load/store when running this

The code has changed a lot over the years. Looks like at some point of time the assumption was broken. calculateCallsInformation() may have eliminated the pseudo set up instructions already. // If call frames are not being included as part of the stack frame, and

----- Original Message ----- > From: "Francois Pichet" <pichet2000 at gmail.com> > To: "LLVM Developers Mailing List" <llvmdev at cs.uiuc.edu> > Sent: Monday, November 18, 2013 2:26:30 PM > Subject: [LLVMdev] Unaligned load/store for callee-saved 128-bit registers > > > > On my (out-of-tree) target I have 16 128-bit registers. >

Thanks, I'll look into that. Still, the case where the function does not call anything remains---in such a situation there are no ADJCALLSTACK pseudos, so regardless of what that function you pointed at does, there won't be any target-independent information about the SP adjustment by the time the frame index elimination runs. Would it make sense to have ADJCALLSTACK pseudos every

CallFrameSetupOpcode is a pseudo opcode like X86::ADJCALLSTACKDOWN64. That means when the code is expected to be called before the pseudo instructions are eliminated. I don't know why it's not the case for you. A quick look at PEI code indicates the pseudo's should not have been removed at the time when replaceFrameIndices are run. Evan On Sep 25, 2013, at 8:57 AM, Krzysztof

Hi All, I'm dealing with a problem where the spill/restore instructions inserted during scavenging span an adjustment of the SP/FP register. The result is that despite the base register (SP/FP) being changed between the spill and the restore, both store and load use the same immediate offset. I see code in the PEI (replaceFrameIndices) that is supposed to track the SP/FP adjustment:

----- Original Message ----- > From: "Hal Finkel" <hfinkel at anl.gov> > To: "Francois Pichet" <pichet2000 at gmail.com> > Cc: "LLVM Developers Mailing List" <llvmdev at cs.uiuc.edu> > Sent: Monday, November 18, 2013 2:45:53 PM > Subject: Re: [LLVMdev] Unaligned load/store for callee-saved 128-bit registers > > ----- Original

BTW I managed to get around this problem by flagging all the 128-bit registers as caller saved only. On my system, vector registers are more likely to be used on leaf functions anyway. On Thu, Nov 21, 2013 at 3:24 PM, Hal Finkel <hfinkel at anl.gov> wrote: > ----- Original Message ----- > > From: "Hal Finkel" <hfinkel at anl.gov> > > To: "Francois

----- Original Message ----- > From: "Francois Pichet" <pichet2000 at gmail.com> > To: "Hal Finkel" <hfinkel at anl.gov> > Cc: "Chad Rosier" <mcrosier at codeaurora.org>, "Jakob Stoklund Olesen" <jolesen at apple.com>, "LLVM Developers Mailing > List" <llvmdev at cs.uiuc.edu> > Sent: Thursday, November

Consider this example: --- ex.ll --- declare void @bar() ; Function Attrs: nounwind optsize define void @main() { entry: %hin = alloca [256 x i32], align 4 %xin = alloca [256 x i32], align 4 call void @bar() ret void } ------------- Freshly built llc: llc -O2 -march=x86 < ex.ll -print-before-all # *** IR Dump Before Prologue/Epilogue Insertion & Frame Finalization ***: #

I ran into another issue with register scavenger. In my case, I don't need a place on the stack for an emergency spill slot. I have these free mips32 registers, that are not in general very useful for other things, for the emergency spill slot. I can move to and from mips16 (subset of mips32) registers and mips32 registers. I also have a situation where I need two free registers so then

In ARM the stack should be 8 bytes aligned during function calls. A function that has at least one function call then has a stack size of 8 bytes. PEI::calculateFrameObjectOffsets corretly computes this correctly. The problem is that the alignment is computed before adding space for the call frame size. This is done in emitProlog. Currently the ARM backend has a bug in that it doesn't align

You mean when I "explicity" use it by calling methods of register scavenger? Right now I'm just allocating virtual registers that will be resolved by the use of register scavenger and I'm also providing an override of the virtual method saveScavengerRegister. In Mips16, I have an extra mips 32 register (not usually very useful since it can only be used in a move instruction)

There is also the LivePhysReg facility that I would recomment if you just want to query for a free register and do not need the full feature set of the RegisterScavenger. - Matthias > On Jan 19, 2017, at 5:50 AM, Nemanja Ivanovic via llvm-dev <llvm-dev at lists.llvm.org> wrote: > > I believe what you're after is the register scavenger. > It's in:

I'm not sure exactly what you're after. I was under the impression that you want to know which register is live at a specific point (an instruction). If that's the case, how do one of the two suggested solutions not suffice? If a register is live-in to a block and not killed before your instruction or it has a def and no kill within the block, it is live. Otherwise it is dead and

Hi Alok, Echoing Anton's statements, please provide a testcase! :) Apart from that, looking at your patch and description I actually think that it is estimateRSStackSizeLimit that is wrong. It is performing a check for a Thumb2 addressing mode whether the target has a FP register. That's the main check - for some reason it is appending another check AFI->hasStackFrame() which seems

Hi, I am confused about the call to isPhyRegUsed in calculateCalleeSavedRegisters: if (Fn.getRegInfo().isPhysRegUsed(Reg)) { // If the reg is modified, save it! CSI.push_back(CalleeSavedInfo(Reg)); } It seems that isPhyRegUsed returns true if the register is read or written in the function. If this is right, why do we save a register if it is only read in the function ?? I would have

Hi! > According to the patch you send, the pass is not doing anything: > > +bool StackSegmenter::runOnMachineFunction(MachineFunction &MF) { > + return false; > +} > + It is, in the next patch. diff --git a/lib/CodeGen/StackSegmenter.cpp b/lib/CodeGen/StackSegmenter.cpp index 5ffb8f2..cc2ca87 100644 --- a/lib/CodeGen/StackSegmenter.cpp +++ b/lib/CodeGen/StackSegmenter.cpp