llvm/test/Transforms/InstCombine/trunc-demand.ll

; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
; RUN: opt < %s -instcombine -S | FileCheck %s

declare void @use6(i6)
declare void @use8(i8)

define i6 @trunc_lshr(i8 %x) {
; CHECK-LABEL: @trunc_lshr(
; CHECK-NEXT:    [[TMP1:%.*]] = trunc i8 [[X:%.*]] to i6
; CHECK-NEXT:    [[TMP2:%.*]] = lshr i6 [[TMP1]], 2
; CHECK-NEXT:    [[R:%.*]] = and i6 [[TMP2]], 14
; CHECK-NEXT:    ret i6 [[R]]
;
  %s = lshr i8 %x, 2
  %t = trunc i8 %s to i6
  %r = and i6 %t, 14
  ret i6 %r
}

; The 'and' is eliminated.

define i6 @trunc_lshr_exact_mask(i8 %x) {
; CHECK-LABEL: @trunc_lshr_exact_mask(
; CHECK-NEXT:    [[TMP1:%.*]] = trunc i8 [[X:%.*]] to i6
; CHECK-NEXT:    [[TMP2:%.*]] = lshr i6 [[TMP1]], 2
; CHECK-NEXT:    ret i6 [[TMP2]]
;
  %s = lshr i8 %x, 2
  %t = trunc i8 %s to i6
  %r = and i6 %t, 15
  ret i6 %r
}

; negative test - a high bit of x is in the result

define i6 @trunc_lshr_big_mask(i8 %x) {
; CHECK-LABEL: @trunc_lshr_big_mask(
; CHECK-NEXT:    [[S:%.*]] = lshr i8 [[X:%.*]], 2
; CHECK-NEXT:    [[T:%.*]] = trunc i8 [[S]] to i6
; CHECK-NEXT:    [[R:%.*]] = and i6 [[T]], 31
; CHECK-NEXT:    ret i6 [[R]]
;
  %s = lshr i8 %x, 2
  %t = trunc i8 %s to i6
  %r = and i6 %t, 31
  ret i6 %r
}

; negative test - too many uses

define i6 @trunc_lshr_use1(i8 %x) {
; CHECK-LABEL: @trunc_lshr_use1(
; CHECK-NEXT:    [[S:%.*]] = lshr i8 [[X:%.*]], 2
; CHECK-NEXT:    call void @use8(i8 [[S]])
; CHECK-NEXT:    [[T:%.*]] = trunc i8 [[S]] to i6
; CHECK-NEXT:    [[R:%.*]] = and i6 [[T]], 15
; CHECK-NEXT:    ret i6 [[R]]
;
  %s = lshr i8 %x, 2
  call void @use8(i8 %s)
  %t = trunc i8 %s to i6
  %r = and i6 %t, 15
  ret i6 %r
}

; negative test - too many uses

define i6 @trunc_lshr_use2(i8 %x) {
; CHECK-LABEL: @trunc_lshr_use2(
; CHECK-NEXT:    [[S:%.*]] = lshr i8 [[X:%.*]], 2
; CHECK-NEXT:    [[T:%.*]] = trunc i8 [[S]] to i6
; CHECK-NEXT:    call void @use6(i6 [[T]])
; CHECK-NEXT:    [[R:%.*]] = and i6 [[T]], 15
; CHECK-NEXT:    ret i6 [[R]]
;
  %s = lshr i8 %x, 2
  %t = trunc i8 %s to i6
  call void @use6(i6 %t)
  %r = and i6 %t, 15
  ret i6 %r
}

; Splat vectors are ok.

define <2 x i7> @trunc_lshr_vec_splat(<2 x i16> %x) {
; CHECK-LABEL: @trunc_lshr_vec_splat(
; CHECK-NEXT:    [[TMP1:%.*]] = trunc <2 x i16> [[X:%.*]] to <2 x i7>
; CHECK-NEXT:    [[TMP2:%.*]] = lshr <2 x i7> [[TMP1]], <i7 5, i7 5>
; CHECK-NEXT:    [[R:%.*]] = and <2 x i7> [[TMP2]], <i7 1, i7 1>
; CHECK-NEXT:    ret <2 x i7> [[R]]
;
  %s = lshr <2 x i16> %x, <i16 5, i16 5>
  %t = trunc <2 x i16> %s to <2 x i7>
  %r = and <2 x i7> %t, <i7 1, i7 1>
  ret <2 x i7> %r
}

; The 'and' is eliminated.

define <2 x i7> @trunc_lshr_vec_splat_exact_mask(<2 x i16> %x) {
; CHECK-LABEL: @trunc_lshr_vec_splat_exact_mask(
; CHECK-NEXT:    [[TMP1:%.*]] = trunc <2 x i16> [[X:%.*]] to <2 x i7>
; CHECK-NEXT:    [[TMP2:%.*]] = lshr <2 x i7> [[TMP1]], <i7 6, i7 6>
; CHECK-NEXT:    ret <2 x i7> [[TMP2]]
;
  %s = lshr <2 x i16> %x, <i16 6, i16 6>
  %t = trunc <2 x i16> %s to <2 x i7>
  %r = and <2 x i7> %t, <i7 1, i7 1>
  ret <2 x i7> %r
}

; negative test - the shift is too big for the narrow type

define <2 x i7> @trunc_lshr_big_shift(<2 x i16> %x) {
; CHECK-LABEL: @trunc_lshr_big_shift(
; CHECK-NEXT:    [[S:%.*]] = lshr <2 x i16> [[X:%.*]], <i16 7, i16 7>
; CHECK-NEXT:    [[T:%.*]] = trunc <2 x i16> [[S]] to <2 x i7>
; CHECK-NEXT:    [[R:%.*]] = and <2 x i7> [[T]], <i7 1, i7 1>
; CHECK-NEXT:    ret <2 x i7> [[R]]
;
  %s = lshr <2 x i16> %x, <i16 7, i16 7>
  %t = trunc <2 x i16> %s to <2 x i7>
  %r = and <2 x i7> %t, <i7 1, i7 1>
  ret <2 x i7> %r
}

; High bits could also be set rather than cleared.

define i6 @or_trunc_lshr(i8 %x) {
; CHECK-LABEL: @or_trunc_lshr(
; CHECK-NEXT:    [[TMP1:%.*]] = trunc i8 [[X:%.*]] to i6
; CHECK-NEXT:    [[TMP2:%.*]] = lshr i6 [[TMP1]], 1
; CHECK-NEXT:    [[R:%.*]] = or i6 [[TMP2]], -32
; CHECK-NEXT:    ret i6 [[R]]
;
  %s = lshr i8 %x, 1
  %t = trunc i8 %s to i6
  %r = or i6 %t, 32 ; 0b100000
  ret i6 %r
}

define i6 @or_trunc_lshr_more(i8 %x) {
; CHECK-LABEL: @or_trunc_lshr_more(
; CHECK-NEXT:    [[TMP1:%.*]] = trunc i8 [[X:%.*]] to i6
; CHECK-NEXT:    [[TMP2:%.*]] = lshr i6 [[TMP1]], 4
; CHECK-NEXT:    [[R:%.*]] = or i6 [[TMP2]], -4
; CHECK-NEXT:    ret i6 [[R]]
;
  %s = lshr i8 %x, 4
  %t = trunc i8 %s to i6
  %r = or i6 %t, 60 ; 0b111100
  ret i6 %r
}

; negative test - need all high bits to be undemanded

define i6 @or_trunc_lshr_small_mask(i8 %x) {
; CHECK-LABEL: @or_trunc_lshr_small_mask(
; CHECK-NEXT:    [[S:%.*]] = lshr i8 [[X:%.*]], 4
; CHECK-NEXT:    [[T:%.*]] = trunc i8 [[S]] to i6
; CHECK-NEXT:    [[R:%.*]] = or i6 [[T]], -8
; CHECK-NEXT:    ret i6 [[R]]
;
  %s = lshr i8 %x, 4
  %t = trunc i8 %s to i6
  %r = or i6 %t, 56 ; 0b111000
  ret i6 %r
}