[LLVMdev] Opt pass 'Canonicalize Induction Variables' not working

[Pieter Custers]

Hello Tobi,

Thank you for the quick reply.

I updated my complete build suite with your script (http://polly.grosser.es/polly.sh). The make-test fails with some errors, the rest went smoothly;

--
Exit Code: 1
Command Output (stderr):
--
LLVM ERROR: Could not resolve external global address: stdout
--

********************
Testing Time: 10.01s
********************
Failing Tests (3):
    Polly :: CodeGen/do_pluto_matmult.ll
    Polly :: CodeGen/single_do_loop_int_max_iterations.ll
    Polly :: CodeGen/single_do_loop_scev_replace.ll

  Expected Passes    : 104
  Expected Failures  : 29
  Unexpected Failures: 3
make: *** [polly-test] Error 1

When I try your command 'clang -Xclang -load ${POLLY_DLIB} ${FILE}.c -o ${FILE}.ll -S -emit-llvm -mllvm -polly -O0' if fails with the following errors:

--------------------------------------
clang: warning: /Developer/llvm_build/tools/polly/Debug+Asserts/lib/LLVMPolly.dylib: 'linker' input unused when '-S' is present
clang: warning: argument unused during compilation: '-mllvm'
clang: warning: argument unused during compilation: '-polly'
Error opening '-o': dlopen(-o, 9): image not found
  -load request ignored.
error: error reading 'indvar.ll'
--------------------------------------

I tried a different order of arguments to no avail. My CLang version is 1.0.2

Also the '-enable-iv-rewrite' has no effect.

Any ideas?

Thanks in advance,

Pieter

On 16 jan 2012, at 15:01, Tobias Grosser wrote:

> 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 following loops:
>> 
>> # 01 Standard, N=100
>> for (i=0; i<N; i++)
>> b[i] = a[i] + 5;
>> 
>> # 02 Example loop -indvars
>> for (i = 7; i*i < 1000; ++i)
>> b[i] = 4;
>> 
>> # 03 Start at 1 instead of 0
>> for (i = 1; i<10; i++)
>> b[i] = 3;
>> 
>> I have the latest LLVM build installed on Mac OSX 10.6.8.
>> 
>> A script with (among others) the following lines is used:
>> 
>> -----------------------------------------------------------------------------------------------------
>> POLLY_DLIB=/Developer/llvm_build/tools/polly/Debug+Asserts/lib/LLVMPolly.dylib
>> alias opt="/Developer/llvm_build/Debug+Asserts/bin/opt -load ${POLLY_DLIB}"
>> alias llvm-as="/Developer/llvm_build/Debug+Asserts/bin/llvm-as"
>> 
>> # Set input filename
>> FILE="indvar"
>> 
>> # Run clang to generate LLVM-IR
>> clang -S -emit-llvm ${FILE}.c -o ${FILE}.s
>> 
>> # Make the human readable format into bitcode format
>> llvm-as ${FILE}.s -o ${FILE}.bc
>> 
>> # Prepare the LLVM-Bytecode into canonical form
>> opt -S -mem2reg -loop-simplify -indvars ${FILE}.bc > ${FILE}.ll
>> -----------------------------------------------------------------------------------------------------
>> 
>> 
>> What I want (and what is not working) is that loop 2 and loop 3 are
>> transformed into a loop starting at 0 with stride 1 (natural loop).
>> Subsequent passes need this to output information to form a Polyhedral
>> model (PHM).
>> 
>> Up to now, only the first loop is recognized as natural loop (as it
>> already is one) and information about the loop is outputted as PHM. The
>> other two loops aren't changed.
>> 
>> Can somebody give me some advise? Maybe I'm using the wrong passes or in
>> the wrong order?
> 
> Hi Pieter,
> 
> the -indvars pass does by default not generate canonical induction variables. Most LLVM passes where converted to work without canonical induction variables. For Polly those induction variables are (still) required. You can enable the relevant conversion by adding
> -enable-iv-rewrite to the opt flags.
> 
> In general, the to code for Polly a larger set of canonicalization passes is required. They can be run from clang with
> 
> clang -Xclang -load ${POLLY_DLIB} ${FILE}.c -o ${FILE}.ll -S -emit-llvm -mllvm -polly -O0
> 
> You need to make sure that Polly, LLVM and clang are compiled from the same source version.
> 
> Cheers
> Tobi