[all-commits] [llvm/llvm-project] f6ae0d: [CodeGen] Pre-commit test case related to ComputeN...

[Björn Pettersson via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: f6ae0d302f09f62b852a29f6dbfdbb4b9c2affb7
      https://github.com/llvm/llvm-project/commit/f6ae0d302f09f62b852a29f6dbfdbb4b9c2affb7
  Author: Bjorn Pettersson <bjorn.a.pettersson at ericsson.com>
  Date:   2024-07-05 (Fri, 05 Jul 2024)

  Changed paths:
    A llvm/test/CodeGen/X86/computenumsignbits-shl.ll

  Log Message:
  -----------
  [CodeGen] Pre-commit test case related to ComputeNumSignBits for SHL (#97695)

Adding test cases aiming at showing possibility to look through
ZERO_EXTEND/ANY_EXTEND when computing number of sign bits for an
SHL node. If all extended bits are shifted out we can analyze the
operand that is extended.


  Commit: c2fbc701aaf826e2015a5dcab36e3ba792e7da7f
      https://github.com/llvm/llvm-project/commit/c2fbc701aaf826e2015a5dcab36e3ba792e7da7f
  Author: Bjorn Pettersson <bjorn.a.pettersson at ericsson.com>
  Date:   2024-07-05 (Fri, 05 Jul 2024)

  Changed paths:
    M llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
    R llvm/test/CodeGen/X86/computenumsignbits-shl.ll
    A llvm/test/CodeGen/X86/known-signbits-shl.ll

  Log Message:
  -----------
  [SelectionDAG] Let ComputeKnownSignBits handle (shl (ext X), C) (#97695)

Add simple support for looking through ZEXT/ANYEXT/SEXT when doing
ComputeKnownSignBits for SHL. This is valid for the case when all
extended bits are shifted out, because then the number of sign bits
can be found by analysing the EXT operand.

A future improvement could be to pass along the "shifted left by"
information in the recursive calls to ComputeKnownSignBits. Allowing
us to handle this more generically.


Compare: https://github.com/llvm/llvm-project/compare/e70f376b25ea...c2fbc701aaf8

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