similar to: [LLVMdev] Prevent DAG combiner from changing "store ConstFP, addr" to integer store

Hello, I am new to LLVM and I am not sure whether I am writing to the right distribution list or not. Please let me know if this is not the right distribution list. Question: - I am having hard time lowering ADD instructions for different purposes. Basically, I want to have different machine instruction for pointer addition vs scalar addition. I am having hard time mapping LLVM add to my machine

Hello, I'm new to LLVM and I'm using it to translate from LLVM to another language rather than emitting actual machine code. The target language has instructions that operate on pointers which aren't naturally exposed in LLVM. Here's what I've done to add pointer support for an instruction called PADD that takes a pointers and an offset and returns the new pointer value:

Are there any other patterns in your TD file? If so, then one of the ones before this pattern will match everything, and this pattern will never be matched. -bw On Jul 3, 2009, at 8:27 PM, Javier Martinez wrote: > Hello, > > I'm new to LLVM and I'm using it to translate from LLVM to another > language rather than emitting actual machine code. The target language > has

Hi Bill, Yes, there are other patterns. I tried commenting out all the other instructions definitions and I still get this error. After debugging TblGen I found that the second pattern is being generated as a variant of the first. I think the reason is that the PADD instruction is inheriting the commutative property from ADD defined inTargetSelectionDAG.td. The variant ends up being the same

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

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

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,

> I expected that this optimization would be picked > up in a cse, gvn, machine-cse or even peepholing pass. > > Comments? At the LLVM IR level this is represented as define i64 @caller() #0 { entry: store i64* @val, i64** @p, align 8, !tbaa !0 store i64 12345123400, i64* @val, align 8, !tbaa !3 %call = tail call i64 @xtr(i64 12345123400) #2 ret i64 %call } Which is

On Aug 2, 2013, at 1:37 PM, Rafael Espíndola <rafael.espindola at gmail.com> wrote: >> I expected that this optimization would be picked >> up in a cse, gvn, machine-cse or even peepholing pass. >> >> Comments? > > > At the LLVM IR level this is represented as > > define i64 @caller() #0 { > entry: > store i64* @val, i64** @p, align 8, !tbaa

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

Hi, I've been looking at the Machine Scheduler on Power PC. I am looking only at the pre-RA machine scheduler and I am running it in the default bi-directional mode (so, both top down and bottom up queues are considered). I've come across an example where the scheduler picks a poor ordering for the instructions which results in very high register pressure which results in spills.

Ok, after a long detour I am back to where I have started. I think there is a problem at dep DAG construction. Let me try to convince you. Here is the C code we are dealing with: push () { struct xx_stack *stack, *top; for (stack = xx_stack; stack; stack = stack->next) top = stack; yy_instr = top->first; } If the loop never iterates, "top" will have

Hi, We recently found a testcase showing that simplifications in instcombine sometimes change the instruction without reducing the instruction cost, but causing problems in TwoAddressInstruction pass. And it looks like the problem is generic and other simplification may have the same issue. I want to get some ideas about what is the best way to fix such kind of problem. The testcase:

Sergei, Absolutely right, the copy/ldriw should not be reordered. I was attempting to explain that I consider it a phi-elimination bug, not a DAG builder bug. Liveness will also have problems with this code in the long run. To avoid confusion, I filed PR13112: Phi elimination generates uninitialized vreg uses, and disabled the SSA check until its fixes in r158461. However, your C code is also

Hi, I am working on a simple copy propagation pass for the R600 backend that propagates immediates rather than registers. For example, I want to transform: ... %vreg1 = V_MOV_B32 1 %vreg2 = V_ADD_I32 %vreg1, %vreg0 ... into: %vreg1 = V_MOV_B32 1 ; <- Only delete this if it is dead %vreg2 = V_ADD_I32 1, %vreg0 For best results, I am trying to run this pass after the TwoAddressInstruction

On Jun 13, 2012, at 1:15 PM, Sergei Larin <slarin at codeaurora.org> wrote: > Andy, > > You are probably right here – look at this – before phi elimination this code looks much more sane: > > # *** IR Dump After Live Variable Analysis ***: > # Machine code for function push: SSA > Function Live Outs: %R0 > > BB#0: derived from LLVM BB %entry >

On Wed, Aug 2, 2017 at 3:36 PM, Matthias Braun <mbraun at apple.com> wrote: > So to write this in a more condensed form, you have: > > %v0 = ... > %v1 = and %v0, 255 > %v2 = and %v1, 31 > use %v1 > use %v2 > > and transform this to > %v0 = ... > %v1 = and %v0, 255 > %v2 = and %v0, 31 > ... > > This is a classical problem with instruction

Andy, You are probably right here - look at this - before phi elimination this code looks much more sane: # *** IR Dump After Live Variable Analysis ***: # Machine code for function push: SSA Function Live Outs: %R0 BB#0: derived from LLVM BB %entry %vreg5<def> = IMPLICIT_DEF; IntRegs:%vreg5 %vreg4<def> = TFRI_V4 <ga:@xx_stack>; IntRegs:%vreg4

Thanks for spelling it out, now I understand. On Jun 5, 2011, at 6:11 AM, Galanov, Sergey wrote: > Well, the point is CMOV_GR* are marked clobbering EFLAGS conservatively just in case they turn out to be lowered into a sequence containing XOR %reg,%reg which indeed clobbers EFLAGS. This means there might not be any instruction which actually uses this EFLAGS value. This actually looks like a

Hi, All, I'm trying to build a customized backend and I need to lower the formal arguments like this: There are several specific registers just for storing formal arguments. And also there are several general purpose registers for computation. If there is an instruction which uses parameters, I should first use a move instruction, which moves the value to general purpose register. For