[all-commits] [llvm/llvm-project] b3cd44: Use SETNE directly rather than SUB/SETNE 0 for sta...

[James Clarke via All-commits]

  Branch: refs/heads/master
  Home:   https://github.com/llvm/llvm-project
  Commit: b3cd44f80b8d6de76d41f1c78241d782c77cd193
      https://github.com/llvm/llvm-project/commit/b3cd44f80b8d6de76d41f1c78241d782c77cd193
  Author: James Clarke <jrtc27 at jrtc27.com>
  Date:   2020-02-18 (Tue, 18 Feb 2020)

  Changed paths:
    M llvm/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
    M llvm/test/CodeGen/SystemZ/stack-guard.ll
    M llvm/test/CodeGen/Thumb/stack_guard_remat.ll
    M llvm/test/CodeGen/WebAssembly/stack-protector.ll

  Log Message:
  -----------
  Use SETNE directly rather than SUB/SETNE 0 for stack guard check

Summary:
Backends should fold the subtraction into the comparison, but not all
seem to. Moreover, on targets where pointers are not integers, such as
CHERI, an integer subtraction is not appropriate. Instead we should just
compare the two pointers directly, as this should work everywhere and
potentially generate more efficient code.

Reviewers: bogner, lebedev.ri, efriedma, t.p.northover, uweigand, sunfish

Reviewed By: lebedev.ri

Subscribers: dschuff, sbc100, arichardson, jgravelle-google, hiraditya, aheejin, llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D74454