[all-commits] [llvm/llvm-project] 771fd1: [DAG] Extend input types if needed in combineShift...

[David Green via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: 771fd1ad2a988e8bb586c2165d6877f06e5ed19b
      https://github.com/llvm/llvm-project/commit/771fd1ad2a988e8bb586c2165d6877f06e5ed19b
  Author: David Green <david.green at arm.com>
  Date:   2024-01-03 (Wed, 03 Jan 2024)

  Changed paths:
    M llvm/lib/CodeGen/SelectionDAG/TargetLowering.cpp
    M llvm/test/CodeGen/AArch64/arm64-vhadd.ll

  Log Message:
  -----------
  [DAG] Extend input types if needed in combineShiftToAVG. (#76791)

This atempts to fix #76734 which is a crash in invalid TRUNC nodes types
from unoptimized input code in combineShiftToAVG. The NVT can be VT if
the larger type was legal and the adds will not overflow, in which case
the inputs should be extended.

>From what I can tell this appears to be valid (if not optimal for this
case): https://alive2.llvm.org/ce/z/fRieHR

The result has also been changed to getExtOrTrunc in case that VT==NVT,
which is not handled by SEXT/ZEXT.