[all-commits] [llvm/llvm-project] 0f6859: Pre-commit test cases for DAG combine folds of SSH...

[Björn Pettersson via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: 0f685976057e2ea27b35b609f4d1653d24ab6694
      https://github.com/llvm/llvm-project/commit/0f685976057e2ea27b35b609f4d1653d24ab6694
  Author: Bjorn Pettersson <bjorn.a.pettersson at ericsson.com>
  Date:   2022-02-06 (Sun, 06 Feb 2022)

  Changed paths:
    M llvm/test/CodeGen/AArch64/sshl_sat.ll
    M llvm/test/CodeGen/AArch64/ushl_sat.ll

  Log Message:
  -----------
  Pre-commit test cases for DAG combine folds of SSHLSAT/USHLSAT -> SHL

It should be possible to replace SSHLSAT and USHLSAT with SHL when
it is known that no saturation will take place (e.g. by analysing
known sign bits in the first shift operand).

Differential Revision: https://reviews.llvm.org/D118764


  Commit: cecf11c31544ec17b16843297246e93618cd56cd
      https://github.com/llvm/llvm-project/commit/cecf11c31544ec17b16843297246e93618cd56cd
  Author: Bjorn Pettersson <bjorn.a.pettersson at ericsson.com>
  Date:   2022-02-06 (Sun, 06 Feb 2022)

  Changed paths:
    M llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
    M llvm/test/CodeGen/AArch64/sshl_sat.ll
    M llvm/test/CodeGen/AArch64/ushl_sat.ll

  Log Message:
  -----------
  [DAGCombiner] Fold SSHLSAT/USHLSAT to SHL when no saturation will occur

When the shift amount is known and a known sign bit analysis of
the shiftee indicates that no saturation will occur, then we can
replace SSHLSAT/USHLSAT by SHL.

Differential Revision: https://reviews.llvm.org/D118765


Compare: https://github.com/llvm/llvm-project/compare/1b27940a112c...cecf11c31544