[LLVMdev] scalar replacement of aggregates slower?

[Nick Lewycky]

I've patched SROA in a way that may have made it slower. Do you have a
testcase we can look at?

Nick

On 4 April 2012 16:19, Andrew Clinton <andrew at sidefx.com> wrote:

> I just upgraded our optimizer to LLVM 3.0 from 2.8 and noticed that the
> scalar replacement of aggregates pass takes a lot longer for some code.
> Has there been a performance regression in this pass, or does it do more
> work?
>
> LLVM 3.0:
>
>   Total Execution Time: 1.0600 seconds (1.0526 wall clock)
>
>    ---User Time---   --System Time--   --User+System--   ---Wall
> Time---  --- Name ---
>    0.5100 ( 49.5%)   0.0000 (  0.0%)   0.5100 ( 48.1%)   0.5099 (
> 48.4%)  Scalar Replacement of Aggregates (SSAUp)
>    0.1900 ( 18.4%)   0.0300 (100.0%)   0.2200 ( 20.8%)   0.2156 (
> 20.5%)  Scalar Replacement of Aggregates (DT)
>    0.1200 ( 11.7%)   0.0000 (  0.0%)   0.1200 ( 11.3%)   0.1158 (
> 11.0%)  VEX Constant Propagation
>    0.0200 (  1.9%)   0.0000 (  0.0%)   0.0200 (  1.9%)   0.0196 (
> 1.9%)  Simplify the CFG
>    0.0200 (  1.9%)   0.0000 (  0.0%)   0.0200 (  1.9%)   0.0181 (
> 1.7%)  Module Verifier
> ...
>
> LLVM 2.8:
>
>   Total Execution Time: 0.6500 seconds (0.6489 wall clock)
>
>    ---User Time---   --System Time--   --User+System--   ---Wall
> Time---  --- Name ---
>    0.1400 ( 21.9%)   0.0000 (  0.0%)   0.1400 ( 21.5%)   0.1379 (
> 21.3%)  Scalar Replacement of Aggregates
>    0.1200 ( 18.7%)   0.0000 (  0.0%)   0.1200 ( 18.5%)   0.1208 (
> 18.6%)  VEX Constant Propagation
>    0.1000 ( 15.6%)   0.0000 (  0.0%)   0.1000 ( 15.4%)   0.1050 (
> 16.2%)  Scalar Replacement of Aggregates
>    0.0400 (  6.3%)   0.0000 (  0.0%)   0.0400 (  6.2%)   0.0481 (
> 7.4%)  Combine redundant instructions
>    0.0200 (  3.1%)   0.0000 (  0.0%)   0.0200 (  3.1%)   0.0235 (
> 3.6%)  Preliminary module verification
> ...
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