[llvm-dev] Issues with using scalar evolution with newer versions of LLVM IR (original) (raw)
hameeza ahmed via llvm-dev llvm-dev at lists.llvm.org
Tue Jan 15 13:41:41 PST 2019
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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?
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