[llvm-bugs] [Bug 42144] New: [X86] any_extend is pessimized by selection

[via llvm-bugs]

https://bugs.llvm.org/show_bug.cgi?id=42144

            Bug ID: 42144
           Summary: [X86] any_extend is pessimized by selection
           Product: libraries
           Version: trunk
          Hardware: PC
                OS: Linux
            Status: NEW
          Severity: enhancement
          Priority: P
         Component: Backend: X86
          Assignee: unassignedbugs at nondot.org
          Reporter: lebedev.ri at gmail.com
                CC: craig.topper at gmail.com, llvm-bugs at lists.llvm.org,
                    llvm-dev at redking.me.uk, spatel+llvm at rotateright.com

define dso_local zeroext i1 @_Z2t0jj(i32, i32) local_unnamed_addr #0 {
  %3 = add i32 %1, -1
  %4 = shl i32 1, %3
  %5 = and i32 %4, %0
  %6 = icmp ne i32 %5, 0
  ret i1 %6
}

results in:

# %bb.0:
        decb    %sil
        movzbl  %sil, %eax
        btl     %eax, %edi
        setb    %al
        retq

That movzbl shouldn't be there.

Combining: t0: ch = EntryToken
Optimized legalized selection DAG: %bb.0 '_Z2t0jj:'
SelectionDAG has 16 nodes:
  t0: ch = EntryToken
        t2: i32,ch = CopyFromReg t0, Register:i32 %0
              t4: i32,ch = CopyFromReg t0, Register:i32 %1
            t21: i8 = truncate t4
          t23: i8 = add t21, Constant:i8<-1>
        t27: i32 = any_extend t23
      t29: i32 = X86ISD::BT t2, t27
    t30: i8 = X86ISD::SETCC Constant:i8<2>, t29
  t17: ch,glue = CopyToReg t0, Register:i8 $al, t30
  t18: ch = X86ISD::RET_FLAG t17, TargetConstant:i32<0>, Register:i8 $al, t17:1

ISEL: Starting selection on root node: t27: i32 = any_extend t23
ISEL: Starting pattern match
  Initial Opcode index to 126894
  Match failed at index 126898
  Continuing at 127264
  TypeSwitch[i32] from 127267 to 127270
  Skipped scope entry (due to false predicate) at index 127276, continuing at
127285
  Morphed node: t27: i32 = MOVZX32rr8 t23
ISEL: Match complete!

===== Instruction selection ends:
Selected selection DAG: %bb.0 '_Z2t0jj:'
SelectionDAG has 18 nodes:
  t0: ch = EntryToken
          t2: i32,ch = CopyFromReg t0, Register:i32 %0
                t4: i32,ch = CopyFromReg t0, Register:i32 %1
              t21: i8 = EXTRACT_SUBREG t4, TargetConstant:i32<1>
            t23: i8,i32 = DEC8r t21
          t27: i32 = MOVZX32rr8 t23
        t29: i32 = BT32rr t2, t27
      t33: ch,glue = CopyToReg t0, Register:i32 $eflags, t29
    t30: i8 = SETCCr TargetConstant:i8<2>, t33:1
  t17: ch,glue = CopyToReg t0, Register:i8 $al, t30
  t18: ch = RET TargetConstant:i32<0>, Register:i8 $al, t17, t17:1

I'm not quite sure where to look though

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