third_party/llvm-7.0/llvm/test/Transforms/InstCombine/bitreverse-known-bits.ll

; RUN: opt < %s -S -instcombine | FileCheck %s

declare i8 @llvm.bitreverse.i8(i8)
declare i32 @llvm.bitreverse.i32(i32)

; CHECK-LABEL: @test1
; CHECK: ret i1 true
define i1 @test1(i32 %arg) {
  %a = or i32 %arg, 4294901760
  %b = call i32 @llvm.bitreverse.i32(i32 %a)
  %and = and i32 %b, 65535
  %res = icmp eq i32 %and, 65535
  ret i1 %res
}

; CHECK-LABEL: @test2
; CHECK: ret i1 true
define i1 @test2(i32 %arg) {
  %a = or i32 %arg, 1
  %b = call i32 @llvm.bitreverse.i32(i32 %a)
  %c = and i32 %b, 2147483648
  %d = call i32 @llvm.bitreverse.i32(i32 %c)
  %res = icmp eq i32 %d, 1
  ret i1 %res
}

; CHECK-LABEL: @test3
; CHECK: ret i1 false
define i1 @test3(i32 %arg) {
  %a = or i32 %arg, 65536
  %b = call i32 @llvm.bitreverse.i32(i32 %a)
  %and = and i32 %b, 32768
  %res = icmp eq i32 %and, 0
  ret i1 %res
}

; CHECK-LABEL: @add_bitreverse
; Make sure we process range metadata on bitreverse
define i8 @add_bitreverse(i8 %a) {
  %b = and i8 %a, 252
  ; known bits for the bitreverse will say the result is in the range [0, 64)
  ; but the metadata says [0, 16). So make sure the range metadata wins.
  ;    add %reverse, 1111 0000
  ; should become
  ;    or  %reverse, 1111 0000
  %reverse = call i8 @llvm.bitreverse.i8(i8 %b), !range !1
  %c = add i8 %reverse, -16
; CHECK: or i8 %reverse, -16
  ret i8 %c
}
!1 = !{i8 0, i8 16}