similar to: [LLVMdev] induction variables

> Can you suggest a good way to use the loops and induction variable > passes to map loop exiting BasicBlocks to InductionVariables. That is, > can we use these tools to identify the loop condition. I can try. :) It looks like you're running into problems because we don't perform "Linear Function Test Replacement". This optimization would reduce the amount of code

LLVM, What is the status of the InductionVariable "semi-pass"? I have tested it out on spec benchmarks, and while it does correctly identify some of the variables, it fails to recognize most. Typically the following scenario arises a_loop: ... %tmp.19 = load int* %bsLive %tmp.20 = add int %tmp.19, -8 store int %tmp.20, int* %bsLive %tmp.5 = setgt int %tmp.20, 0 br bool %tmp.5, label

Hello, I've just downloaded the latest release of LLVM, and playing with the following simple example: int main() { int r(0); for (int i = 0; i < 100; ++i) r += i; ; return r; } I compile it and then run: analyze -indvars x.bc which prints: Printing analysis 'Induction Variable Analysis' for function 'main': and nothing else. It is a

I just subscribed this group. This is my first time to post a question (not sure if this is a right place for discussion) after I have a brief look at LLVM OPT (dev trunk). I would expect loop simplification and induction variable canonicalization pass (IndVarSimplify pass) should be able to convert the following loops into a simple canonical form, i.e., there is a canonical induction variable

But even for a very simple loop: int test1 (int *x, int *y, int *z, int k) { int sum = 0; for (int i = 10; i < k; i++) { z[i] = x[i] / y[i]; } return sum; } The initial value of induction variable is not zero after compiling with -O3 -mcpu=power8 x.cpp -S -c -emit-llvm -fno-unroll-loops (see bottom of the email for IR) Also I can write somewhat more complicated loop where step

On Wed, 31 Mar 2004, Vladimir Prus wrote: > I've just downloaded the latest release of LLVM, and playing with the > following simple example: > > int main() > { > int r(0); > for (int i = 0; i < 100; ++i) > r += i; > ; > return r; > } When I compiled it, I got the following LLVM code: int %main() { entry: call void %__main( )

Chris Lattner wrote: > > int main() > > { > > int r(0); > > for (int i = 0; i < 100; ++i) > > r += i; > > ; > > return r; > > } > > When I compiled it, I got the following LLVM code: The code I get is somewhat different: int %main() { entry: %tmp.1.i = load bool* %Initialized.0__ ; <bool> [#uses=1] br

Hi, I was looking at trying to get loop induction variable at IR level. LLVM documentation mentioned indvars pass and getCanonicalInductionVariable() to get them, I tried running the indvars pass and then a custom pass which iterates through loops and uses the function to obtain variable for a simple loop program. But the API returns null. I also read in similar posts that the indvars pass is not

On Jan 19, 2011, at 2:03 PM, Nick Lewycky wrote: > On 19 January 2011 13:01, Dan Gohman <gohman at apple.com> wrote: > > On Jan 18, 2011, at 12:32 AM, Nick Lewycky wrote: > > > Hi, > > > > I tracked down a bug in indvars where we weren't updating SCEV properly. The attached patch shows the fix to this bug with a testcase, but it also causes five new test

On 01/16/2012 01:19 PM, Pieter Custers wrote: > I am new to LLVM and I've a question about the optimization passes and > in particular about the loop transformation passes. I've setup the LLVM > tool-chain with Polly installed. > > The following example is causing problems with me: > http://llvm.org/docs/Passes.html#indvars > > The input is a .c file with the

Hello, Recently I've come across two instances where Induction Variable Simplification lead to noticable performance regressions. In one case, the removal of extra IV lead to the inability to reschedule instructions in a tight loop to reduce stalls. In that case, there were enough registers to spare, so using extra register for extra induction variable was preferable since it reduced

Hi Vesa, The pass IndVars changes the induction variables to allow SCEV to analyze them and enable other optimizations. This is the canonicalization phase. Later on, LSR lowers the canonicalized induction variables to induction variables that map nicely to the target's addressing modes. In many cases it can remove some of the induction variables. I suspect that the loop vectorizer does

This support was removed years ago from indvars. We don't need canonical induction variables any more as all analysis are done on SCEVs. The SCEV generator can transform them even without the need for explicit canonical induction variables. Best, Tobias On Wed, Aug 9, 2017, at 14:23, Anastasiya Ruzhanskaya via llvm-dev wrote: > The files of this strange pass are described here >

On 4 February 2013 18:25, Arnold Schwaighofer <aschwaighofer at apple.com>wrote: > For cases where this approach breaks really badly we could consider adding > a specialized api or parameters (like the type of a user/use). But we > should do so only as a last resort and backed by actual code that would > benefit from doing so. > Very sensible, more or less what I had in

Hi! By only two cases I mean , that in exiting block when computing the condition related to PHI node I can expect only icmp on one of incoming values or on phi node itself... I tried to come up with some more complex examples but I always receive only these two cases, that is why I am asking. This problem still relates to the problem of all induction, cumulative and so on variables in loop. SCEV

Hi all, It looks like the induction variable simplification pass prefers doing a zero-extension to compute the wider trip count of loops when extending the IV. This can sometimes result in loss of information making ScalarEvolution's analysis conservative which can lead to missed performance opportunities. For example, consider this loopnest- int i, j; for(i=0; i< 40; i++) for(j=0;

Hi Fellows, The goal is to find the induction variable for a loop, where the induction variable increments with the multiplication, division or shift operations, like this one: sz = 8; do { ... ... sz = sz / 2; } while (sz) Is SCEV capable of detecting the induction variable 'sz' in this case? The code snippet I am using to solve the problem is for each basic-block in a

Hello, I have this piece of code: int main() { int m = 0; // int i, j, k; // int N = f()%10; for (int l = 0; l < 1000; l+=4) printf("%d", l); I am sure, that llvm is capable to convert this into canonical induction variable, but even with O3 define i32 @main() #0 { br label %2 ; <label>:1 ; preds

Hi Hal, I see. So LSR could theoretically counteract undesirable Ind Var transformations but it's not implemented at the moment? I think I've managed to come up with a small reproducer that can also exhibit similar problem on x86, here it is: https://godbolt.org/z/_wxzut As you can see, when rewriteLoopExitValues is not disabled Clang generates worse code due to additional spills,

I've noticed that there was an attempt to mitigate ExitValues problem in https://reviews.llvm.org/D12494 that went nowhere. Were there particular issues with that approach? -- Danila From: Philip Reames [mailto:listmail at philipreames.com] Sent: Saturday, August 10, 2019 02:05 To: Danila Malyutin <Danila.Malyutin at synopsys.com>; Finkel, Hal J. <hfinkel at anl.gov> Cc: llvm-dev