[all-commits] [llvm/llvm-project] 1712ae: [AArch64] Improve cost of umull from known bits

[David Green via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: 1712ae670915fc73ce136508497a727f1b9f4d85
      https://github.com/llvm/llvm-project/commit/1712ae670915fc73ce136508497a727f1b9f4d85
  Author: David Green <david.green at arm.com>
  Date:   2023-07-12 (Wed, 12 Jul 2023)

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

  Log Message:
  -----------
  [AArch64] Improve cost of umull from known bits

As in 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.

Differential Revision: https://reviews.llvm.org/D154936