[llvm-bugs] [Bug 50172] New: Missing fold cttz(zext(x)) -> zext(cttz(x))

[via llvm-bugs]

https://bugs.llvm.org/show_bug.cgi?id=50172

            Bug ID: 50172
           Summary: Missing fold cttz(zext(x)) -> zext(cttz(x))
           Product: libraries
           Version: trunk
          Hardware: PC
                OS: Linux
            Status: NEW
          Severity: enhancement
          Priority: P
         Component: Scalar Optimizations
          Assignee: unassignedbugs at nondot.org
          Reporter: david.bolvansky at gmail.com
                CC: llvm-bugs at lists.llvm.org

define i32 @src(i16 %x) {

  %z = zext i16 %x to i32
  %p = call i32 @llvm.cttz.i32(i32 %z, i1 true)
  ret i32 %p
}

define i32 @tgt(i16 %x) {

  %p = call i16 @llvm.cttz.i16(i16 %x, i1 true)
  %z = zext i16 %p to i32
  ret i32 %z
}


declare i32 @llvm.cttz.i32(i32, i1)
declare i16 @llvm.cttz.i16(i16, i1)

----------------------------------------
define i32 @src(i16 %x) {
%0:
  %z = zext i16 %x to i32
  %p = cttz i32 %z, 1
  ret i32 %p
}
=>
define i32 @tgt(i16 %x) {
%0:
  %p = cttz i16 %x, 0
  %z = zext i16 %p to i32
  ret i32 %z
}
Transformation seems to be correct!


src:                                    # @src
        movzx   eax, di
        bsf     eax, eax
        ret
tgt:                                    # @tgt
        bsf     ax, di
        movzx   eax, ax
        ret

-- 
You are receiving this mail because:
You are on the CC list for the bug.
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.llvm.org/pipermail/llvm-bugs/attachments/20210429/819877ca/attachment.html>