[PATCH] D154936: [AArch64] Improve cost of umull from known bits

[Dave Green via Phabricator via llvm-commits]

dmgreen created this revision.
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As in D140287 <https://reviews.llvm.org/D140287>, we can now generate `umull` from `mul(zext(x), y)` in cases where we know that the top bits of `y` are zero. This teaches that to the cost model, adjusting how isWideningInstruction detects mul operations that can extend both operands. This helps for constants and other cases where the operands of the mul are known to be extended, but not directly extends.


https://reviews.llvm.org/D154936

Files:
  llvm/lib/Target/AArch64/AArch64TargetTransformInfo.cpp
  llvm/lib/Target/AArch64/AArch64TargetTransformInfo.h
  llvm/test/Analysis/CostModel/AArch64/arith-widening.ll

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