musttail-call.ll | Explore in Territory

; NOTE: Assertions have been autogenerated by utils/update_test_checks.py UTC_ARGS: --function-signature
; RUN: opt < %s -passes=ipsccp -S | FileCheck %s
; PR36485
; musttail call result can\'t be replaced with a constant, unless the call
; can be removed

declare i32 @external()

define ptr @start(i8 %v) {
; CHECK-LABEL: define {{[^@]+}}@start
; CHECK-SAME: (i8 [[V:%.*]]) {
; CHECK-NEXT:    [[C1:%.*]] = icmp eq i8 [[V]], 0
; CHECK-NEXT:    br i1 [[C1]], label [[TRUE:%.*]], label [[FALSE:%.*]]
; CHECK:       true:
; CHECK-NEXT:    [[CA:%.*]] = musttail call ptr @side_effects(i8 0)
; CHECK-NEXT:    ret ptr [[CA]]
; CHECK:       false:
; CHECK-NEXT:    [[C2:%.*]] = icmp eq i8 [[V]], 1
; CHECK-NEXT:    br i1 [[C2]], label [[C2_TRUE:%.*]], label [[C2_FALSE:%.*]]
; CHECK:       c2_true:
; CHECK-NEXT:    ret ptr null
; CHECK:       c2_false:
; CHECK-NEXT:    [[CA2:%.*]] = musttail call ptr @dont_zap_me(i8 [[V]])
; CHECK-NEXT:    ret ptr [[CA2]]
;
  %c1 = icmp eq i8 %v, 0
  br i1 %c1, label %true, label %false
true:
  %ca = musttail call ptr @side_effects(i8 %v)
  ret ptr %ca
false:
  %c2 = icmp eq i8 %v, 1
  br i1 %c2, label %c2_true, label %c2_false
c2_true:
  %ca1 = musttail call ptr @no_side_effects(i8 %v)
  ret ptr %ca1
c2_false:
  %ca2 = musttail call ptr @dont_zap_me(i8 %v)
  ret ptr %ca2
}

define internal ptr @side_effects(i8 %v) {
; CHECK-LABEL: define {{[^@]+}}@side_effects
; CHECK-SAME: (i8 [[V:%.*]]) {
; CHECK-NEXT:    [[I1:%.*]] = call i32 @external()
; CHECK-NEXT:    [[CA:%.*]] = musttail call ptr @start(i8 0)
; CHECK-NEXT:    ret ptr [[CA]]
;
  %i1 = call i32 @external()

  ; since this goes back to `start` the SCPP should be see that the return value
  ; is always `null`.
  ; The call can't be removed due to `external` call above, though.

  %ca = musttail call ptr @start(i8 %v)

  ; Thus the result must be returned anyway
  ret ptr %ca
}

; The call to this function is removed, so the return value must be zapped
define internal ptr @no_side_effects(i8 %v) readonly nounwind willreturn {
; CHECK-LABEL: define {{[^@]+}}@no_side_effects
; CHECK-SAME: (i8 [[V:%.*]]) #[[ATTR0:[0-9]+]] {
; CHECK-NEXT:    ret ptr poison
;
  ret ptr null
}

; The call to this function cannot be removed due to side effects. Thus the
; return value should stay as it is, and should not be zapped.
define internal ptr @dont_zap_me(i8 %v) {
; CHECK-LABEL: define {{[^@]+}}@dont_zap_me
; CHECK-SAME: (i8 [[V:%.*]]) {
; CHECK-NEXT:    [[I1:%.*]] = call i32 @external()
; CHECK-NEXT:    ret ptr null
;
  %i1 = call i32 @external()
  ret ptr null
}
llvm/llvm/test/Transforms/SCCP/musttail-call.ll
