llvm-project/llvm/test/Transforms/InstCombine/unsigned_saturated_sub.ll

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

; Transforms for unsigned saturated subtraction idioms are tested here.
; In all cases, we want to form a canonical min/max op (the compare and
; select operands are the same), so that is recognized by the backend.
; The backend recognition is tested in test/CodeGen/X86/psubus.ll.

declare void @use(i64)

; (a > b) ? a - b : 0 -> ((a > b) ? a : b) - b)

define i64 @max_sub_ugt(i64 %a, i64 %b) {
; CHECK-LABEL: @max_sub_ugt(
; CHECK-NEXT:    [[CMP:%.*]] = icmp ugt i64 [[A:%.*]], [[B:%.*]]
; CHECK-NEXT:    [[SUB:%.*]] = sub i64 [[A]], [[B]]
; CHECK-NEXT:    [[SEL:%.*]] = select i1 [[CMP]], i64 [[SUB]], i64 0
; CHECK-NEXT:    ret i64 [[SEL]]
;
  %cmp = icmp ugt i64 %a, %b
  %sub = sub i64 %a, %b
  %sel = select i1 %cmp, i64 %sub ,i64 0
  ret i64 %sel
}

; Again, with vectors:
; (a > b) ? a - b : 0 -> ((a > b) ? a : b) - b)

define <4 x i32> @max_sub_ugt_vec(<4 x i32> %a, <4 x i32> %b) {
; CHECK-LABEL: @max_sub_ugt_vec(
; CHECK-NEXT:    [[CMP:%.*]] = icmp ugt <4 x i32> [[A:%.*]], [[B:%.*]]
; CHECK-NEXT:    [[SUB:%.*]] = sub <4 x i32> [[A]], [[B]]
; CHECK-NEXT:    [[SEL:%.*]] = select <4 x i1> [[CMP]], <4 x i32> [[SUB]], <4 x i32> zeroinitializer
; CHECK-NEXT:    ret <4 x i32> [[SEL]]
;
  %cmp = icmp ugt <4 x i32> %a, %b
  %sub = sub <4 x i32> %a, %b
  %sel = select <4 x i1> %cmp, <4 x i32> %sub, <4 x i32> zeroinitializer
  ret <4 x i32> %sel
}

; Use extra ops to thwart icmp swapping canonicalization.
; (b < a) ? a - b : 0 -> ((a > b) ? a : b) - b)

define i64 @max_sub_ult(i64 %a, i64 %b) {
; CHECK-LABEL: @max_sub_ult(
; CHECK-NEXT:    [[CMP:%.*]] = icmp ult i64 [[B:%.*]], [[A:%.*]]
; CHECK-NEXT:    [[SUB:%.*]] = sub i64 [[A]], [[B]]
; CHECK-NEXT:    [[SEL:%.*]] = select i1 [[CMP]], i64 [[SUB]], i64 0
; CHECK-NEXT:    [[EXTRASUB:%.*]] = sub i64 [[B]], [[A]]
; CHECK-NEXT:    call void @use(i64 [[EXTRASUB]])
; CHECK-NEXT:    ret i64 [[SEL]]
;
  %cmp = icmp ult i64 %b, %a
  %sub = sub i64 %a, %b
  %sel = select i1 %cmp, i64 %sub ,i64 0
  %extrasub = sub i64 %b, %a
  call void @use(i64 %extrasub)
  ret i64 %sel
}

; (b > a) ? 0 : a - b -> ((a > b) ? a : b) - b)

define i64 @max_sub_ugt_sel_swapped(i64 %a, i64 %b) {
; CHECK-LABEL: @max_sub_ugt_sel_swapped(
; CHECK-NEXT:    [[CMP:%.*]] = icmp ugt i64 [[B:%.*]], [[A:%.*]]
; CHECK-NEXT:    [[SUB:%.*]] = sub i64 [[A]], [[B]]
; CHECK-NEXT:    [[SEL:%.*]] = select i1 [[CMP]], i64 0, i64 [[SUB]]
; CHECK-NEXT:    [[EXTRASUB:%.*]] = sub i64 [[B]], [[A]]
; CHECK-NEXT:    call void @use(i64 [[EXTRASUB]])
; CHECK-NEXT:    ret i64 [[SEL]]
;
  %cmp = icmp ugt i64 %b, %a
  %sub = sub i64 %a, %b
  %sel = select i1 %cmp, i64 0 ,i64 %sub
  %extrasub = sub i64 %b, %a
  call void @use(i64 %extrasub)
  ret i64 %sel
}

; (a < b) ? 0 : a - b -> ((a > b) ? a : b) - b)

define i64 @max_sub_ult_sel_swapped(i64 %a, i64 %b) {
; CHECK-LABEL: @max_sub_ult_sel_swapped(
; CHECK-NEXT:    [[CMP:%.*]] = icmp ult i64 [[A:%.*]], [[B:%.*]]
; CHECK-NEXT:    [[SUB:%.*]] = sub i64 [[A]], [[B]]
; CHECK-NEXT:    [[SEL:%.*]] = select i1 [[CMP]], i64 0, i64 [[SUB]]
; CHECK-NEXT:    ret i64 [[SEL]]
;
  %cmp = icmp ult i64 %a, %b
  %sub = sub i64 %a, %b
  %sel = select i1 %cmp, i64 0 ,i64 %sub
  ret i64 %sel
}

; ((a > b) ? b - a : 0) -> (b - ((a > b) ? a : b))

define i64 @neg_max_sub_ugt(i64 %a, i64 %b) {
; CHECK-LABEL: @neg_max_sub_ugt(
; CHECK-NEXT:    [[CMP:%.*]] = icmp ugt i64 [[A:%.*]], [[B:%.*]]
; CHECK-NEXT:    [[SUB:%.*]] = sub i64 [[B]], [[A]]
; CHECK-NEXT:    [[SEL:%.*]] = select i1 [[CMP]], i64 [[SUB]], i64 0
; CHECK-NEXT:    [[EXTRASUB:%.*]] = sub i64 [[A]], [[B]]
; CHECK-NEXT:    call void @use(i64 [[EXTRASUB]])
; CHECK-NEXT:    ret i64 [[SEL]]
;
  %cmp = icmp ugt i64 %a, %b
  %sub = sub i64 %b, %a
  %sel = select i1 %cmp, i64 %sub ,i64 0
  %extrasub = sub i64 %a, %b
  call void @use(i64 %extrasub)
  ret i64 %sel
}

; ((b < a) ? b - a : 0) -> - ((a > b) ? a : b) - b)

define i64 @neg_max_sub_ult(i64 %a, i64 %b) {
; CHECK-LABEL: @neg_max_sub_ult(
; CHECK-NEXT:    [[CMP:%.*]] = icmp ult i64 [[B:%.*]], [[A:%.*]]
; CHECK-NEXT:    [[SUB:%.*]] = sub i64 [[B]], [[A]]
; CHECK-NEXT:    [[SEL:%.*]] = select i1 [[CMP]], i64 [[SUB]], i64 0
; CHECK-NEXT:    ret i64 [[SEL]]
;
  %cmp = icmp ult i64 %b, %a
  %sub = sub i64 %b, %a
  %sel = select i1 %cmp, i64 %sub ,i64 0
  ret i64 %sel
}

; ((b > a) ? 0 : b - a) -> - ((a > b) ? a : b) - b)

define i64 @neg_max_sub_ugt_sel_swapped(i64 %a, i64 %b) {
; CHECK-LABEL: @neg_max_sub_ugt_sel_swapped(
; CHECK-NEXT:    [[CMP:%.*]] = icmp ugt i64 [[B:%.*]], [[A:%.*]]
; CHECK-NEXT:    [[SUB:%.*]] = sub i64 [[B]], [[A]]
; CHECK-NEXT:    [[SEL:%.*]] = select i1 [[CMP]], i64 0, i64 [[SUB]]
; CHECK-NEXT:    ret i64 [[SEL]]
;
  %cmp = icmp ugt i64 %b, %a
  %sub = sub i64 %b, %a
  %sel = select i1 %cmp, i64 0 ,i64 %sub
  ret i64 %sel
}

; ((a < b) ? 0 : b - a) -> - ((a > b) ? a : b) - b)

define i64 @neg_max_sub_ult_sel_swapped(i64 %a, i64 %b) {
; CHECK-LABEL: @neg_max_sub_ult_sel_swapped(
; CHECK-NEXT:    [[CMP:%.*]] = icmp ult i64 [[A:%.*]], [[B:%.*]]
; CHECK-NEXT:    [[SUB:%.*]] = sub i64 [[B]], [[A]]
; CHECK-NEXT:    [[SEL:%.*]] = select i1 [[CMP]], i64 0, i64 [[SUB]]
; CHECK-NEXT:    [[EXTRASUB:%.*]] = sub i64 [[A]], [[B]]
; CHECK-NEXT:    call void @use(i64 [[EXTRASUB]])
; CHECK-NEXT:    ret i64 [[SEL]]
;
  %cmp = icmp ult i64 %a, %b
  %sub = sub i64 %b, %a
  %sel = select i1 %cmp, i64 0 ,i64 %sub
  %extrasub = sub i64 %a, %b
  call void @use(i64 %extrasub)
  ret i64 %sel
}