[LLVMdev] llc is taking a long time at -O1 to convert *.bc to *.s
mcrosier at apple.com
Fri Feb 3 10:08:45 PST 2012
Without a test case, we really can't determine if this is expected behavior. Certainly, we'd prefer -O1 compile-times to be relatively fast. Have you tried this with a ToT clang? If you're still seeing such poor performance then I suggest filing a bug (http://llvm.org/bugs). Please include a test case and the command line arguments to reproduce the problem. I believe ToT is compatible with 3.0 bitcode files, so you could just submit your bitcode file.
On Feb 2, 2012, at 11:03 PM, "Kodakara, Sreekumar V" <sreekumar.v.kodakara at intel.com> wrote:
> Hi All,
> I am using llvm-3.0 release version for compiling some files. I have a cpp file on which I did a few custom passes. After that I used llc to convert the *.bc file to *.s file at –O1 optimization level. llc took ~2630 seconds to perform this conversion. I timed llc and these are the top three passes that is taking most of the time.
> ---User Time--- --System Time-- --User+System-- ---Wall Time--- --- Name ---
> 1816.1735 ( 77.8%) 23.3215 ( 69.7%) 1839.4950 ( 77.6%) 1839.4132 ( 77.6%) Simple Register Coalescing
> 493.5948 ( 21.1%) 9.1846 ( 27.4%) 502.7794 ( 21.2%) 502.7681 ( 21.2%) X86 DAG->DAG Instruction Selection
> 5.7244 ( 0.2%) 0.0000 ( 0.0%) 5.7244 ( 0.2%) 5.7204 ( 0.2%) Machine Instruction LICM
> I am running this in a fairly new Xeon server. Furthermore, at –O0, llc takes less than 20 seconds to complete. Is this behavior expected and is there a way to disable Simple Register Coalescing pass without switching to –O0 optimization level to get around this problem?
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