[PATCH] D154805: [DAGCombiner] Fold IEEE `fmul`/`fdiv` by Pow2 to `add`/`sub` of exp

[Simon Pilgrim via Phabricator via llvm-commits]

RKSimon accepted this revision.
RKSimon added a comment.
This revision is now accepted and ready to land.

LGTM - please can you raise an issue describing the missing (fmul x, pow2_k) - > (ldexp x, (log2 pow2_k)) fold



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Comment at: llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp:27310
+  SDValue InexpensiveLogBase2 =
+      takeInexpensiveLog2(DAG, DL, VT, V, /*Depth*/ 0, KnownNonZero);
+  if (InexpensiveLogBase2 || InexpensiveOnly || !DAG.isKnownToBeAPowerOfTwo(V))
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(style) It'd be better to move the takeInexpensiveLog2 static implementation directly above BuildLogBase2 if that is its only user.


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