[all-commits] [llvm/llvm-project] 637e81: Reland `[CodeGenPrepare] Convert `ctpop(X) ==/!= 1...

[Yingwei Zheng via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: 637e81f8adfe725c73aeafa4c2315d962be4770d
      https://github.com/llvm/llvm-project/commit/637e81f8adfe725c73aeafa4c2315d962be4770d
  Author: Yingwei Zheng <dtcxzyw2333 at gmail.com>
  Date:   2024-10-15 (Tue, 15 Oct 2024)

  Changed paths:
    M llvm/lib/CodeGen/CodeGenPrepare.cpp
    M llvm/test/CodeGen/AArch64/arm64-popcnt.ll
    M llvm/test/CodeGen/RISCV/rv32zbb.ll
    M llvm/test/CodeGen/RISCV/rv64zbb.ll
    M llvm/test/CodeGen/X86/ispow2.ll
    M llvm/test/CodeGen/X86/known-never-zero.ll

  Log Message:
  -----------
  Reland `[CodeGenPrepare] Convert `ctpop(X) ==/!= 1` into `ctpop(X) u</u> 2/1`  (#111284)` (#111998)

Relands #111284. Test failure with stage2 build has been fixed by
https://github.com/llvm/llvm-project/pull/111946.


Some targets have better codegen for `ctpop(X) u< 2` than `ctpop(X) ==
1`. After https://github.com/llvm/llvm-project/pull/100899, we set the
range of ctpop's return value to indicate the argument/result is
non-zero.

This patch converts `ctpop(X) ==/!= 1` into `ctpop(X) u</u> 2/1` in CGP
to fix https://github.com/llvm/llvm-project/issues/95255.



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