similar to: [LLVMdev] How to determine the a use reference is the last reference of a virtual Register through current path

Hello llvmers: I'm study Fast register allocation in codegen. I get confused with isKill flag in MachineOperand. I thin "isKill" flag the last Use Reference. But, Fast Register doesn't require LiveVariable Analysis which will mark isKill Flag for global virtual Register. So during Fast RegisterAllocation, Faster Register Allocation procedure can't determine

I am observing poor instruction scheduling in my out-of-tree target. The problem is an over-constrained scheduling DAG. In particular, the DAG includes spurious output dependencies on physical, non-register-allocatable registers. MISched already includes code to avoid this problem. However that code relies on information clobbered by the earlier pass LiveVariables. I wonder whether this is a

On Thu, May 26, 2011 at 15:07:24 +0200, Jonas Paulsson wrote: > In order to get a pre-RA scheduling, I would need something like: > - LiveVars > - PhiElim > - TwoAddr > - LiveIntervals > - Coalescing > - Scheduler (new) > - SlotIndexing > - LiveIntervals2 (new) > - RegAlloc > My qeustion then is, is it really so difficult to create the live intervals

This seems a very natural approach but I probably am having a trouble with the iterator invalidation. However, looking at other peephole optimizers passes, I couldn't see how to do this: #define BUILD_INS(opcode, new_reg, i) \ BuildMI(*MBB, MBBI, MBBI->getDebugLoc(), TII->get(X86::opcode)) \ .addReg(X86::new_reg, kill).addImm(i) for

Thanks. I saw the header comments but it wasn’t clear to me what the difference between those concepts is? My slightly vague understanding is IsDef means that the register specified by this operand is set by the machine instruction. So I understand that to mean the MO will override that register? Also things like early clobber, perhaps there is another document that clarifies some of these

Hi all, I am using the fast register allocator on a partially allocated machine function. I have noticed reserved registers (i.e. liveins) are marked as free after first use (in usePhysReg(..) method). This seems an error to me as a livein might be still used later in the basic block. As I understand this should check for isKill() before marking it as free, but I see it even *sets* the kill

Hi Sergei, our use of target flags will be on immediate register operands if I am not mistaken (and if not we can always encode it as such)? I guess you are refering to the hexagon backend needing to distinguish between instances of an instruction that uses a constant value that can fit into the 4 byte of the instruction and one that encodes the immediate in an extra instruction slot (what we

Jakob and anyone else who might be interested... Base on this patch back in August, I sense some need to double check with you whether it is OK to start making a heavy use of MachineOperand TargetFlags? We do seem to have a compelling reason for it in Hexagon, and I wanted to make sure that it is OK with everyone. I plan to use it for attributing target specific info to MOs and in more general

The isKill must be correct if present, but a vreg may still be killed even if the operand has no Kill flag. The isDead and isUndef flags however are required to be correct. We need further details to say anything about your problem, a LiveIntervals::dump() dump for example would be helpful to assess whether the liveness data is correct in your case. - Matthias > On Jul 28, 2016, at 1:42 PM,

Hi all, I am attempting to implement the "reaching definitions" data-flow algorithm on (X86) MachineBasicBlocks for an analysis pass. To do this, I need to compute gen/kill sets for machine basic blocks. To start with, I am only considering the general-purpose registers, RAX-R15 and their sub-registers. Thus, I need to examine each MachineInstr to determine which register(s) it

Arnold, I wanted to hear from Jacob is the original patch in question still needed, since our use of this field could surpass const extenders and could potentially include MO_Register. Jacob, Can you please comment? Thanks. Sergei --- Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum, hosted by The Linux Foundation > -----Original Message----- > From: Arnold

Hi All, Currently, changing register assignments of definitions after register allocation is not safe because there is no way to know which register definitions were physical registers before RA (e.g. to meet ABI or ISA constraints) and thus should not be changed. I'd like to propose adding a bit to MachineOperand (by overloading the meaning of the IsKill bit for defs, so no extra

Hi all, I noticed that the x86 backend tends to emit unnecessary vector insert instructions immediately after sse scalar fp instructions like addss/mulss. For example: ///////////////////////////////// __m128 foo(__m128 A, __m128 B) { _mm_add_ss(A, B); } ///////////////////////////////// produces the sequence: addss %xmm0, %xmm1 movss %xmm1, %xmm0 which could be easily optimized into

On Wednesday 11 July 2007 15:07, Christopher Lamb wrote: > Could it be possible for there to be a harness type interface that > would allow coalescers that support both modes to be hooked into the > pass registration, and those that depend on the allocator not be > registered as passes? I have a patch for this kind of thing attached. Please take a look and let me know if it looks

I just finished coding up a change to how code generation builds machine instructions. The change is in include/llvm/CodeGen/MachineInstrBuilder.h, where when you want to add a register, you have to specify a long list of booleans indicating if it's defined, implicit, killed, dead, or early clobbered. I don't know about you, but it was hard for me to read the source and understand what was

sorry ! I have re-corrected the title. ------------------ 原始邮件 ------------------ 发件人: "Sheng Wang"<wansheg at gmail.com>; 发送时间: 2009年9月4日(星期五) 下午3:23 收件人: "LLVMdev"<LLVMdev at cs.uiuc.edu>; 主题: [LLVMdev] Dose I need to build llvm-gcc front-end from sourceresolve this error? /* mm.cpp */ #include<iostream> using namespace std; struct xx{ int x;

Hi, I wondered whether the AggressiveAntiDepBreaker can properly handle predicated instructions. At the end of PrescanInstruction the "DefIndices" array is updated with the destination register without checking whether the instruction is predicated. That shortens the live range: Later on, in HandleLastUse we check whether the register IsLive, which considers only

Ok, i'm having a problem with understanding the allocating of registers. I've written in the "addPassesToEmitAssembly()" the passes to create the assembly code, as in the PowerPC example. I'ved tried filling up as much of the code in <Target>RegisterInfo.cpp (Register/Frame code) to handle writing and reading from stack. The allocation method I used was

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++;

On Jan 14, 2010, at 6:39 PM, 任坤 wrote: > But I want do some optimization after register alloction by adjusting > register using. I scan MachineBasicBlock to analyze operand's IsKill, IsDead , IsDef attribute to get a physical register's liverange. But I get a strange case at MBB.jpg. You can also look at RegisterScavenging.cpp and MachineVerifier.cpp. They are doing the same