[all-commits] [llvm/llvm-project] 331eb8: [X86][CodeGen] Support lowering for CCMP/CTEST (#9...

[Shengchen Kan via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: 331eb8a0047504f3ae2cdf2d6c60b93e5d0543f1
      https://github.com/llvm/llvm-project/commit/331eb8a0047504f3ae2cdf2d6c60b93e5d0543f1
  Author: Shengchen Kan <shengchen.kan at intel.com>
  Date:   2024-05-26 (Sun, 26 May 2024)

  Changed paths:
    M llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
    M llvm/lib/Target/X86/X86ISelDAGToDAG.cpp
    M llvm/lib/Target/X86/X86ISelLowering.cpp
    M llvm/lib/Target/X86/X86ISelLowering.h
    M llvm/lib/Target/X86/X86InstrConditionalCompare.td
    M llvm/lib/Target/X86/X86InstrFragments.td
    M llvm/lib/Target/X86/X86InstrInfo.cpp
    M llvm/lib/Target/X86/X86InstrInfo.h
    A llvm/test/CodeGen/X86/apx/ccmp.ll
    A llvm/test/CodeGen/X86/apx/ctest.ll

  Log Message:
  -----------
  [X86][CodeGen] Support lowering for CCMP/CTEST (#91747)

DAG combine for `CCMP` and `CTESTrr`:

```
and/or(setcc(cc0, flag0), setcc(cc1, sub (X, Y)))
->
setcc(cc1, ccmp(X, Y, ~cflags/cflags, cc0/~cc0, flag0))

and/or(setcc(cc0, flag0), setcc(cc1, cmp (X, 0)))
 ->
setcc(cc1, ctest(X, X, ~cflags/cflags, cc0/~cc0, flag0))
```
 where `cflags` is determined by `cc1`.

Generic DAG combine:
```
cmp(setcc(cc, X), 0)
brcond ne
->
X
brcond cc

sub(setcc(cc, X), 1)
brcond ne
->
X
brcond ~cc
```

Post DAG transform:  `ANDrr/rm + CTESTrr -> CTESTrr/CTESTmr`


Pattern match for `CTESTri`:
```
X= and A, B
ctest(X, X, cflags, cc0/, flag0)
->
ctest(A, B, cflags, cc0/, flag0)
```

`CTESTmi` is already handled by the memory folding mechanism in MIR.



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