[PATCH] D68789: [LoopNest]: Analysis to discover properties of a loop nest.

[Bardia Mahjour via Phabricator via llvm-commits]

bmahjour added inline comments.


================
Comment at: llvm/lib/Analysis/LoopNestAnalysis.cpp:92-94
+      bool isAllowed = isa<BinaryOperator>(I) || isa<CmpInst>(I) ||
+                       isa<PHINode>(I) || isa<BranchInst>(I) ||
+                       isa<CastInst>(I);
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Meinersbur wrote:
> [serious] Should this just use `llvm::isSafeToSpeculativelyExecute`? It basically contains anything that could just be moved into the innermost loop such that it is executed multiple times.
`isSafeToSpeculativelyExecute` returns false for phi nodes, branches and most integer divisions.
We need to allow phi and branches due to inner loop induction and control.
As far as I know integer divisions are safe to speculate most of the time, except on some platforms where zero-division generate a trap. 
It puzzles me why `isSafeToSpeculativelyExecute` checks for integer division but completely ignores floating-point division which would have visible side-effects on more platforms!



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