[all-commits] [llvm/llvm-project] 48a21e: [RISCV] Fix a correctness issue in optimizeCondBra...

[Craig Topper via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: 48a21e69159a7e6698cde380f6d64274c6569f29
      https://github.com/llvm/llvm-project/commit/48a21e69159a7e6698cde380f6d64274c6569f29
  Author: Craig Topper <craig.topper at sifive.com>
  Date:   2025-06-24 (Tue, 24 Jun 2025)

  Changed paths:
    M llvm/lib/Target/RISCV/RISCVInstrInfo.cpp
    M llvm/test/CodeGen/RISCV/branch-opt.mir

  Log Message:
  -----------
  [RISCV] Fix a correctness issue in optimizeCondBranch. Prevent optimizing compare with x0. NFC (#145440)

We were incorrectly changing -1 to 0 for unsigned compares in case 1.
The comment incorrectly said UINT64_MAX is bigger than INT64_MAX, but
we were doing a signed compare and UINT64_MAX is smaller than INT64_MAX
in signed space.

Prevent changing 0 constants since we can use x0. The test cases
for these are contrived to use addi rd, x0, 0. We're more likely
to have a COPY from x0 which we already don't optimize for other
reasons.

Check if registers are virtual before calling hasOneUse. The use count
for physical registers is meaningless.



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