llvm/test/CodeGen/AArch64/sat-trunc-knownbits.ll

; NOTE: Assertions have been autogenerated by utils/update_llc_test_checks.py
; RUN: llc < %s -mtriple=aarch64 | FileCheck %s

;; ============================================================================
;; Tests for canCreateUndefOrPoison = false
;; These verify that freeze operations are correctly eliminated
;; ============================================================================

; TRUNCATE_SSAT_S: No saturation path
define i1 @sqxtn_no_sat_with_freeze(<4 x i32> %x) {
; CHECK-LABEL: sqxtn_no_sat_with_freeze:
; CHECK:       // %bb.0:
; CHECK-NEXT:    movi v1.4s, #100
; CHECK-NEXT:    and v0.16b, v0.16b, v1.16b
; CHECK-NEXT:    sqxtn v0.4h, v0.4s
; CHECK-NEXT:    umov w8, v0.h[0]
; CHECK-NEXT:    and w8, w8, #0xfffc
; CHECK-NEXT:    cmp w8, #200
; CHECK-NEXT:    cset w0, gt
; CHECK-NEXT:    ret
  %masked = and <4 x i32> %x, <i32 100, i32 100, i32 100, i32 100>
  %trunc = call <4 x i16> @llvm.aarch64.neon.sqxtn.v4i16(<4 x i32> %masked)
  %freeze = freeze <4 x i16> %trunc
  %extract = extractelement <4 x i16> %freeze, i32 0
  ; Input is [0,100], so result > 200 is always false
  %cmp = icmp sgt i16 %extract, 200
  ret i1 %cmp
}

; TRUNCATE_SSAT_S: Test specific known bits
define i16 @sqxtn_known_bits(<4 x i32> %x) {
; CHECK-LABEL: sqxtn_known_bits:
; CHECK:       // %bb.0:
; CHECK-NEXT:    mov w0, wzr
; CHECK-NEXT:    ret
  ; Input: [0, 32512] fits in i16 without saturation
  %masked = and <4 x i32> %x, <i32 32512, i32 32512, i32 32512, i32 32512>
  %trunc = call <4 x i16> @llvm.aarch64.neon.sqxtn.v4i16(<4 x i32> %masked)
  %freeze = freeze <4 x i16> %trunc
  %extract = extractelement <4 x i16> %freeze, i32 0
  ; Mask to lower 7 bits - with KnownBits, knows upper bits are already 0
  ; so this AND can be simplified
  %and = and i16 %extract, 127
  ret i16 %and
}

;; ============================================================================
;; Tests for computeKnownBits
;; These verify that known bits analysis enables optimizations
;; TRUNCATE_SSAT_S: Signed to Signed Saturating Truncate (sqxtn)
;; ============================================================================

; Constant 32512 = 0b0111111110000000 has known zero lower bits
; After truncation, ANDing with 127 (lower 7 bits) gives 0
define i16 @sqxtn_known_zero_bits(<4 x i32> %x) {
; CHECK-LABEL: sqxtn_known_zero_bits:
; CHECK:       // %bb.0:
; CHECK-NEXT:    mov w0, wzr
; CHECK-NEXT:    ret
  %masked = and <4 x i32> %x, <i32 32512, i32 32512, i32 32512, i32 32512>
  %trunc = call <4 x i16> @llvm.aarch64.neon.sqxtn.v4i16(<4 x i32> %masked)
  %extract = extractelement <4 x i16> %trunc, i32 0
  %and = and i16 %extract, 127
  ret i16 %and
}

; Input range [0, 256] means result is always non-negative
; Comparison with negative value should fold to false (returns 0)
define i1 @sqxtn_known_nonnegative(<4 x i32> %x) {
; CHECK-LABEL: sqxtn_known_nonnegative:
; CHECK:       // %bb.0:
; CHECK-NEXT:    mov w0, wzr
; CHECK-NEXT:    ret
  %masked = and <4 x i32> %x, <i32 256, i32 256, i32 256, i32 256>
  %trunc = call <4 x i16> @llvm.aarch64.neon.sqxtn.v4i16(<4 x i32> %masked)
  %extract = extractelement <4 x i16> %trunc, i32 0
  %cmp = icmp slt i16 %extract, 0
  ret i1 %cmp
}

;; ============================================================================
;; TRUNCATE_SSAT_U: Signed to Unsigned Saturating Truncate (sqxtun)
;; ============================================================================

define i16 @sqxtun_known_zero_lower_bits(<4 x i32> %x) {
; CHECK-LABEL: sqxtun_known_zero_lower_bits:
; CHECK:       // %bb.0:
; CHECK-NEXT:    mov w0, wzr
; CHECK-NEXT:    ret
  %masked = and <4 x i32> %x, <i32 32512, i32 32512, i32 32512, i32 32512>
  %trunc = call <4 x i16> @llvm.aarch64.neon.sqxtun.v4i16(<4 x i32> %masked)
  %extract = extractelement <4 x i16> %trunc, i32 0
  %and = and i16 %extract, 255
  ret i16 %and
}

define i16 @sqxtun_known_zero_upper_bits(<4 x i32> %x) {
; CHECK-LABEL: sqxtun_known_zero_upper_bits:
; CHECK:       // %bb.0:
; CHECK-NEXT:    mov w0, wzr
; CHECK-NEXT:    ret
  %masked = and <4 x i32> %x, <i32 127, i32 127, i32 127, i32 127>
  %trunc = call <4 x i16> @llvm.aarch64.neon.sqxtun.v4i16(<4 x i32> %masked)
  %extract = extractelement <4 x i16> %trunc, i32 0
  %shift = lshr i16 %extract, 7
  ret i16 %shift
}

;; ============================================================================
;; TRUNCATE_USAT_U: Unsigned to Unsigned Saturating Truncate (uqxtn)
;; ============================================================================

define i8 @uqxtn_known_zero_upper_bits(<8 x i16> %x) {
; CHECK-LABEL: uqxtn_known_zero_upper_bits:
; CHECK:       // %bb.0:
; CHECK-NEXT:    mov w0, wzr
; CHECK-NEXT:    ret
  %masked = and <8 x i16> %x, <i16 63, i16 63, i16 63, i16 63, i16 63, i16 63, i16 63, i16 63>
  %trunc = call <8 x i8> @llvm.aarch64.neon.uqxtn.v8i8(<8 x i16> %masked)
  %extract = extractelement <8 x i8> %trunc, i32 0
  %shift = lshr i8 %extract, 6
  ret i8 %shift
}


declare <4 x i16> @llvm.aarch64.neon.sqxtn.v4i16(<4 x i32>)
declare <4 x i16> @llvm.aarch64.neon.sqxtun.v4i16(<4 x i32>)
declare <8 x i8> @llvm.aarch64.neon.uqxtn.v8i8(<8 x i16>)