[llvm-dev] Issues with using scalar evolution with newer versions of LLVM IR

[hameeza ahmed via llvm-dev]

Hello,

I am trying to use scalar evolution pass using following command;

opt -analyze -mem2reg -indvars -loop-simplify -scalar-evolution < vec.bc
when vec.bc is generated using newer version of LLVM i.e LLVM 6 and 7 i get
following message in the end;
Determining loop execution counts for: @main
Loop %8: Unpredictable backedge-taken count.
Loop %8: Unpredictable max backedge-taken count.
Loop %8: Unpredictable predicated backedge-taken count.
which means it is unable to compute iteration count.

However, when .bc file is generated using LLVM 4.0 i am getting following;

Determining loop execution counts for: @main
Loop %4: backedge-taken count is 512
Loop %4: max backedge-taken count is 512
Loop %4: Predicated backedge-taken count is 512
 Predicates:

Loop %4: Trip multiple is 513

means correct computation of loop count...
Why is that happening with newer version of LLVM?

Please help.
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