[PATCH] D43769: [TTI] rename getArithmeticInstructionCost() to getUnitThroughput(); NFC

Sanjay Patel via Phabricator via llvm-commits llvm-commits at lists.llvm.org
Tue Feb 27 10:59:58 PST 2018

spatel added a comment.

> This just needs to be fixed somehow, e.g by introducing some multiplier.

Now I'm even more confused.

The cost model is approximating the throughput of the entire target, not a single pipeline/execution unit.
But https://reviews.llvm.org/D43733 did the opposite of that. We said that FP ops after Pentium4 have the lowest possible reciprocal throughput value which means they have the same throughput as an integer add.
Did we purposely introduce wrong costs because we acknowledge that the cost-based calculations in the vectorizers are broken? And this is how we are working around that?


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