Opt pass 'Canonicalize Induction Variables' not working

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:

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

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;

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

That is interesting. Can you send me the individual error messages? Are you using a 32bit platform?

   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:

The command to prepare the code for Polly was incorrect. I missed a '-Xclang' option. The correct one is:

clang -Xclang -load -Xclang ${POLLY_DLIB} ${FILE}.c -o ${FILE}.ll -S -emit-llvm -mllvm -polly -O0

to also enable -enable-iv-rewrite you need:

clang -Xclang -load -Xclang ${POLLY_DLIB} ${FILE}.c -o ${FILE}.ll -S -emit-llvm -mllvm -polly -O0 -mllvm -enable-iv-rewrite.

I just tried to detect the scops myself. I used for this the following command:

alias pollycc='~/Projekte/polly/build_clang/bin/clang -Xclang -load \
                -Xclang ~/Projekte/polly/build_clang/lib/LLVMPolly.so'

pollycc -mllvm -polly-show test.c -c -mllvm -enable-iv-rewrite -mllvm -polly -O3

It detects all three loops. Can you reproduce this?

Cheers
Tobi

test.c (188 Bytes)

Hey Tobi,

My CLang version is very old (1.0.2), I have manually installed the latest version from SVN and I am compiling LLVM again right now. Is it right that CLang is not in the standard LLVM repos (svn checkout http://llvm.org/svn/llvm-project/llvm/trunk) as indicated on http://polly.grosser.es/get_started.html? This are the instructions I followed to install my tools.

I will get back to you when I’ve results.

Cheers, Pieter

The instructions did not yet include how to (optionally) install the corresponding clang version. I updated them. The only additional step is checking out clang into tools/clang.

Cheers
Tobi