llvm/test/Transforms/InstCombine/sext-of-trunc-nsw.ll

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

; Iff we know that trunc only chops off the sign bits,
; and not all of them, then we can bypass said trunc
; for the purpose of sign extension.

declare void @use8(i8)
declare void @use4(i4)
declare void @usevec(<2 x i8>)

define i16 @t0(i8 %x) {
; CHECK-LABEL: @t0(
; CHECK-NEXT:    [[A:%.*]] = ashr i8 [[X:%.*]], 5
; CHECK-NEXT:    call void @use8(i8 [[A]])
; CHECK-NEXT:    [[C:%.*]] = sext i8 [[A]] to i16
; CHECK-NEXT:    ret i16 [[C]]
;
  %a = ashr i8 %x, 5
  call void @use8(i8 %a)
  %b = trunc i8 %a to i4
  %c = sext i4 %b to i16
  ret i16 %c
}

define i16 @t1(i8 %x) {
; CHECK-LABEL: @t1(
; CHECK-NEXT:    [[A:%.*]] = ashr i8 [[X:%.*]], 4
; CHECK-NEXT:    call void @use8(i8 [[A]])
; CHECK-NEXT:    [[C:%.*]] = sext i8 [[A]] to i16
; CHECK-NEXT:    ret i16 [[C]]
;
  %a = ashr i8 %x, 4
  call void @use8(i8 %a)
  %b = trunc i8 %a to i4
  %c = sext i4 %b to i16
  ret i16 %c
}

; Here we don't know that %a has any sign bits from %x left
define i16 @n2(i8 %x) {
; CHECK-LABEL: @n2(
; CHECK-NEXT:    [[A:%.*]] = ashr i8 [[X:%.*]], 3
; CHECK-NEXT:    call void @use8(i8 [[A]])
; CHECK-NEXT:    [[B:%.*]] = trunc i8 [[A]] to i4
; CHECK-NEXT:    [[C:%.*]] = sext i4 [[B]] to i16
; CHECK-NEXT:    ret i16 [[C]]
;
  %a = ashr i8 %x, 3
  call void @use8(i8 %a)
  %b = trunc i8 %a to i4
  %c = sext i4 %b to i16
  ret i16 %c
}

define <2 x i16> @t3_vec(<2 x i8> %x) {
; CHECK-LABEL: @t3_vec(
; CHECK-NEXT:    [[A:%.*]] = ashr <2 x i8> [[X:%.*]], <i8 4, i8 4>
; CHECK-NEXT:    call void @usevec(<2 x i8> [[A]])
; CHECK-NEXT:    [[C:%.*]] = sext <2 x i8> [[A]] to <2 x i16>
; CHECK-NEXT:    ret <2 x i16> [[C]]
;
  %a = ashr <2 x i8> %x, <i8 4, i8 4>
  call void @usevec(<2 x i8> %a)
  %b = trunc <2 x i8> %a to <2 x i4>
  %c = sext <2 x i4> %b to <2 x i16>
  ret <2 x i16> %c
}

define <2 x i16> @t4_vec_nonsplat(<2 x i8> %x) {
; CHECK-LABEL: @t4_vec_nonsplat(
; CHECK-NEXT:    [[A:%.*]] = ashr <2 x i8> [[X:%.*]], <i8 4, i8 3>
; CHECK-NEXT:    call void @usevec(<2 x i8> [[A]])
; CHECK-NEXT:    [[B:%.*]] = trunc <2 x i8> [[A]] to <2 x i4>
; CHECK-NEXT:    [[C:%.*]] = sext <2 x i4> [[B]] to <2 x i16>
; CHECK-NEXT:    ret <2 x i16> [[C]]
;
  %a = ashr <2 x i8> %x, <i8 4, i8 3>
  call void @usevec(<2 x i8> %a)
  %b = trunc <2 x i8> %a to <2 x i4>
  %c = sext <2 x i4> %b to <2 x i16>
  ret <2 x i16> %c
}

define i16 @t5_extrause(i8 %x) {
; CHECK-LABEL: @t5_extrause(
; CHECK-NEXT:    [[A:%.*]] = ashr i8 [[X:%.*]], 5
; CHECK-NEXT:    call void @use8(i8 [[A]])
; CHECK-NEXT:    [[B:%.*]] = trunc i8 [[A]] to i4
; CHECK-NEXT:    call void @use4(i4 [[B]])
; CHECK-NEXT:    [[C:%.*]] = sext i8 [[A]] to i16
; CHECK-NEXT:    ret i16 [[C]]
;
  %a = ashr i8 %x, 5
  call void @use8(i8 %a)
  %b = trunc i8 %a to i4
  call void @use4(i4 %b)
  %c = sext i4 %b to i16
  ret i16 %c
}

define i64 @narrow_source_matching_signbits(i32 %x) {
; CHECK-LABEL: @narrow_source_matching_signbits(
; CHECK-NEXT:    [[M:%.*]] = and i32 [[X:%.*]], 7
; CHECK-NEXT:    [[A:%.*]] = shl nsw i32 -1, [[M]]
; CHECK-NEXT:    [[C:%.*]] = sext i32 [[A]] to i64
; CHECK-NEXT:    ret i64 [[C]]
;
  %m = and i32 %x, 7
  %a = shl nsw i32 -1, %m
  %b = trunc i32 %a to i8
  %c = sext i8 %b to i64
  ret i64 %c
}

; negative test - not enough sign-bits

define i64 @narrow_source_not_matching_signbits(i32 %x) {
; CHECK-LABEL: @narrow_source_not_matching_signbits(
; CHECK-NEXT:    [[M:%.*]] = and i32 [[X:%.*]], 8
; CHECK-NEXT:    [[A:%.*]] = shl nsw i32 -1, [[M]]
; CHECK-NEXT:    [[B:%.*]] = trunc i32 [[A]] to i8
; CHECK-NEXT:    [[C:%.*]] = sext i8 [[B]] to i64
; CHECK-NEXT:    ret i64 [[C]]
;
  %m = and i32 %x, 8
  %a = shl nsw i32 -1, %m
  %b = trunc i32 %a to i8
  %c = sext i8 %b to i64
  ret i64 %c
}

define i24 @wide_source_matching_signbits(i32 %x) {
; CHECK-LABEL: @wide_source_matching_signbits(
; CHECK-NEXT:    [[M:%.*]] = and i32 [[X:%.*]], 7
; CHECK-NEXT:    [[A:%.*]] = shl nsw i32 -1, [[M]]
; CHECK-NEXT:    [[C:%.*]] = trunc i32 [[A]] to i24
; CHECK-NEXT:    ret i24 [[C]]
;
  %m = and i32 %x, 7
  %a = shl nsw i32 -1, %m
  %b = trunc i32 %a to i8
  %c = sext i8 %b to i24
  ret i24 %c
}

; negative test - not enough sign-bits

define i24 @wide_source_not_matching_signbits(i32 %x) {
; CHECK-LABEL: @wide_source_not_matching_signbits(
; CHECK-NEXT:    [[M2:%.*]] = and i32 [[X:%.*]], 8
; CHECK-NEXT:    [[A:%.*]] = shl nsw i32 -1, [[M2]]
; CHECK-NEXT:    [[B:%.*]] = trunc i32 [[A]] to i8
; CHECK-NEXT:    [[C:%.*]] = sext i8 [[B]] to i24
; CHECK-NEXT:    ret i24 [[C]]
;
  %m2 = and i32 %x, 8
  %a = shl nsw i32 -1, %m2
  %b = trunc i32 %a to i8
  %c = sext i8 %b to i24
  ret i24 %c
}

define i32 @same_source_matching_signbits(i32 %x) {
; CHECK-LABEL: @same_source_matching_signbits(
; CHECK-NEXT:    [[M:%.*]] = and i32 [[X:%.*]], 7
; CHECK-NEXT:    [[A:%.*]] = shl nsw i32 -1, [[M]]
; CHECK-NEXT:    ret i32 [[A]]
;
  %m = and i32 %x, 7
  %a = shl nsw i32 -1, %m
  %b = trunc i32 %a to i8
  %c = sext i8 %b to i32
  ret i32 %c
}

; negative test - not enough sign-bits

define i32 @same_source_not_matching_signbits(i32 %x) {
; CHECK-LABEL: @same_source_not_matching_signbits(
; CHECK-NEXT:    [[M2:%.*]] = and i32 [[X:%.*]], 8
; CHECK-NEXT:    [[TMP1:%.*]] = shl i32 -16777216, [[M2]]
; CHECK-NEXT:    [[C:%.*]] = ashr exact i32 [[TMP1]], 24
; CHECK-NEXT:    ret i32 [[C]]
;
  %m2 = and i32 %x, 8
  %a = shl nsw i32 -1, %m2
  %b = trunc i32 %a to i8
  %c = sext i8 %b to i32
  ret i32 %c
}

define i32 @same_source_matching_signbits_extra_use(i32 %x) {
; CHECK-LABEL: @same_source_matching_signbits_extra_use(
; CHECK-NEXT:    [[M:%.*]] = and i32 [[X:%.*]], 7
; CHECK-NEXT:    [[A:%.*]] = shl nsw i32 -1, [[M]]
; CHECK-NEXT:    [[B:%.*]] = trunc i32 [[A]] to i8
; CHECK-NEXT:    call void @use8(i8 [[B]])
; CHECK-NEXT:    ret i32 [[A]]
;
  %m = and i32 %x, 7
  %a = shl nsw i32 -1, %m
  %b = trunc i32 %a to i8
  call void @use8(i8 %b)
  %c = sext i8 %b to i32
  ret i32 %c
}

define i32 @same_source_not_matching_signbits_extra_use(i32 %x) {
; CHECK-LABEL: @same_source_not_matching_signbits_extra_use(
; CHECK-NEXT:    [[M2:%.*]] = and i32 [[X:%.*]], 8
; CHECK-NEXT:    [[A:%.*]] = shl nsw i32 -1, [[M2]]
; CHECK-NEXT:    [[B:%.*]] = trunc i32 [[A]] to i8
; CHECK-NEXT:    call void @use8(i8 [[B]])
; CHECK-NEXT:    [[C:%.*]] = sext i8 [[B]] to i32
; CHECK-NEXT:    ret i32 [[C]]
;
  %m2 = and i32 %x, 8
  %a = shl nsw i32 -1, %m2
  %b = trunc i32 %a to i8
  call void @use8(i8 %b)
  %c = sext i8 %b to i32
  ret i32 %c
}