test/Transforms/InstCombine/trivial-dse-calls.ll

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

declare void @llvm.lifetime.start.p0(i64 immarg, ptr nocapture)
declare void @llvm.lifetime.end.p0(i64 immarg, ptr nocapture)

declare void @unknown()
declare void @f(ptr)
declare void @f2(ptr, ptr)
declare ptr @f3(ptr, ptr)

; Basic case for DSEing a trivially dead writing call
define void @test_dead() {
; CHECK-LABEL: @test_dead(
; CHECK-NEXT:    ret void
;
  %a = alloca i32, align 4
  call void @f(ptr writeonly nocapture %a) argmemonly nounwind willreturn
  ret void
}

; Add in canonical lifetime intrinsics
define void @test_lifetime() {
; CHECK-LABEL: @test_lifetime(
; CHECK-NEXT:    ret void
;
  %a = alloca i32, align 4
  call void @llvm.lifetime.start.p0(i64 4, ptr %a)
  call void @f(ptr writeonly nocapture %a) argmemonly nounwind willreturn
  call void @llvm.lifetime.end.p0(i64 4, ptr %a)
  ret void
}

; Add some unknown calls just to point out that this is use based, not
; instruction order sensitive
define void @test_lifetime2() {
; CHECK-LABEL: @test_lifetime2(
; CHECK-NEXT:    call void @unknown()
; CHECK-NEXT:    call void @unknown()
; CHECK-NEXT:    ret void
;
  %a = alloca i32, align 4
  call void @llvm.lifetime.start.p0(i64 4, ptr %a)
  call void @unknown()
  call void @f(ptr writeonly nocapture %a) argmemonly nounwind willreturn
  call void @unknown()
  call void @llvm.lifetime.end.p0(i64 4, ptr %a)
  ret void
}

; As long as the result is unused, we can even remove reads of the alloca
; itself since the write will be dropped.
define void @test_dead_readwrite() {
; CHECK-LABEL: @test_dead_readwrite(
; CHECK-NEXT:    ret void
;
  %a = alloca i32, align 4
  call void @f(ptr nocapture %a) argmemonly nounwind willreturn
  ret void
}

define i32 @test_neg_read_after() {
; CHECK-LABEL: @test_neg_read_after(
; CHECK-NEXT:    [[A:%.*]] = alloca i32, align 4
; CHECK-NEXT:    call void @f(ptr nocapture nonnull writeonly [[A]]) #[[ATTR3:[0-9]+]]
; CHECK-NEXT:    [[RES:%.*]] = load i32, ptr [[A]], align 4
; CHECK-NEXT:    ret i32 [[RES]]
;
  %a = alloca i32, align 4
  call void @f(ptr writeonly nocapture %a) argmemonly nounwind willreturn
  %res = load i32, ptr %a
  ret i32 %res
}


define void @test_neg_infinite_loop() {
; CHECK-LABEL: @test_neg_infinite_loop(
; CHECK-NEXT:    [[A:%.*]] = alloca i32, align 4
; CHECK-NEXT:    call void @f(ptr nocapture nonnull writeonly [[A]]) #[[ATTR4:[0-9]+]]
; CHECK-NEXT:    ret void
;
  %a = alloca i32, align 4
  call void @f(ptr writeonly nocapture %a) argmemonly nounwind
  ret void
}

define void @test_neg_throw() {
; CHECK-LABEL: @test_neg_throw(
; CHECK-NEXT:    [[A:%.*]] = alloca i32, align 4
; CHECK-NEXT:    call void @f(ptr nocapture nonnull writeonly [[A]]) #[[ATTR5:[0-9]+]]
; CHECK-NEXT:    ret void
;
  %a = alloca i32, align 4
  call void @f(ptr writeonly nocapture %a) argmemonly willreturn
  ret void
}

define void @test_neg_extra_write() {
; CHECK-LABEL: @test_neg_extra_write(
; CHECK-NEXT:    [[A:%.*]] = alloca i32, align 4
; CHECK-NEXT:    call void @f(ptr nocapture nonnull writeonly [[A]]) #[[ATTR6:[0-9]+]]
; CHECK-NEXT:    ret void
;
  %a = alloca i32, align 4
  call void @f(ptr writeonly nocapture %a) nounwind willreturn
  ret void
}

; In this case, we can't remove a1 because we need to preserve the write to
; a2, and if we leave the call around, we need memory to pass to the first arg.
define void @test_neg_unmodeled_write() {
; CHECK-LABEL: @test_neg_unmodeled_write(
; CHECK-NEXT:    [[A:%.*]] = alloca i32, align 4
; CHECK-NEXT:    [[A2:%.*]] = alloca i32, align 4
; CHECK-NEXT:    call void @f2(ptr nocapture nonnull writeonly [[A]], ptr nonnull [[A2]]) #[[ATTR3]]
; CHECK-NEXT:    ret void
;
  %a = alloca i32, align 4
  %a2 = alloca i32, align 4
  call void @f2(ptr nocapture writeonly %a, ptr %a2) argmemonly nounwind willreturn
  ret void
}

define i32 @test_neg_captured_by_call() {
; CHECK-LABEL: @test_neg_captured_by_call(
; CHECK-NEXT:    [[A:%.*]] = alloca i32, align 4
; CHECK-NEXT:    [[A2:%.*]] = alloca ptr, align 4
; CHECK-NEXT:    call void @f2(ptr nonnull writeonly [[A]], ptr nonnull [[A2]]) #[[ATTR3]]
; CHECK-NEXT:    [[A_COPY_CAST:%.*]] = load ptr, ptr [[A2]], align 8
; CHECK-NEXT:    [[RES:%.*]] = load i32, ptr [[A_COPY_CAST]], align 4
; CHECK-NEXT:    ret i32 [[RES]]
;
  %a = alloca i32, align 4
  %a2 = alloca ptr, align 4
  call void @f2(ptr writeonly %a, ptr %a2) argmemonly nounwind willreturn
  %a_copy_cast = load ptr, ptr %a2
  %res = load i32, ptr %a_copy_cast
  ret i32 %res
}

define i32 @test_neg_captured_before() {
; CHECK-LABEL: @test_neg_captured_before(
; CHECK-NEXT:    [[A:%.*]] = alloca i32, align 4
; CHECK-NEXT:    call void @f(ptr nocapture nonnull writeonly [[A]]) #[[ATTR3]]
; CHECK-NEXT:    [[RES:%.*]] = load i32, ptr [[A]], align 4
; CHECK-NEXT:    ret i32 [[RES]]
;
  %a = alloca i32, align 4
  %a2 = alloca ptr, align 4
  store ptr %a, ptr %a2
  call void @f(ptr writeonly nocapture %a) argmemonly nounwind willreturn
  %a_copy_cast = load ptr, ptr %a2
  %res = load i32, ptr %a_copy_cast
  ret i32 %res
}

; Show that reading from unrelated memory is okay
define void @test_unreleated_read() {
; CHECK-LABEL: @test_unreleated_read(
; CHECK-NEXT:    ret void
;
  %a = alloca i32, align 4
  %a2 = alloca i32, align 4
  call void @f2(ptr nocapture writeonly %a, ptr nocapture readonly %a2) argmemonly nounwind willreturn
  ret void
}

; Removing a capture is also okay. The capture can only be in the return value
; (which is unused) or written into the dead out parameter.
define void @test_unrelated_capture() {
; CHECK-LABEL: @test_unrelated_capture(
; CHECK-NEXT:    ret void
;
  %a = alloca i32, align 4
  %a2 = alloca i32, align 4
  call ptr @f3(ptr nocapture writeonly %a, ptr readonly %a2) argmemonly nounwind willreturn
  ret void
}

; Cannot remove call, as %a2 is captured via the return value.
define i8 @test_neg_unrelated_capture_used_via_return() {
; CHECK-LABEL: @test_neg_unrelated_capture_used_via_return(
; CHECK-NEXT:    [[A:%.*]] = alloca i32, align 4
; CHECK-NEXT:    [[A2:%.*]] = alloca i32, align 4
; CHECK-NEXT:    [[CAPTURE:%.*]] = call ptr @f3(ptr nocapture nonnull writeonly [[A]], ptr nonnull readonly [[A2]]) #[[ATTR3]]
; CHECK-NEXT:    [[V:%.*]] = load i8, ptr [[CAPTURE]], align 1
; CHECK-NEXT:    ret i8 [[V]]
;
  %a = alloca i32, align 4
  %a2 = alloca i32, align 4
  %capture = call ptr @f3(ptr nocapture writeonly %a, ptr readonly %a2) argmemonly nounwind willreturn
  %v = load i8, ptr %capture
  ret i8 %v
}

; As long as the result is unused, we can even remove reads of the alloca
; itself since the write will be dropped.
define void @test_self_read() {
; CHECK-LABEL: @test_self_read(
; CHECK-NEXT:    ret void
;
  %a = alloca i32, align 4
  call void @f2(ptr nocapture writeonly %a, ptr nocapture readonly %a) argmemonly nounwind willreturn
  ret void
}


declare void @removable_readnone() readnone nounwind willreturn
declare void @removable_ro() readonly nounwind willreturn

define void @test_readnone() {
; CHECK-LABEL: @test_readnone(
; CHECK-NEXT:    ret void
;
  call void @removable_readnone()
  ret void
}

define void @test_readnone_with_deopt() {
; CHECK-LABEL: @test_readnone_with_deopt(
; CHECK-NEXT:    ret void
;
  call void @removable_readnone() [ "deopt"() ]
  ret void
}

define void @test_readonly() {
; CHECK-LABEL: @test_readonly(
; CHECK-NEXT:    ret void
;
  call void @removable_ro()
  ret void
}

define void @test_readonly_with_deopt() {
; CHECK-LABEL: @test_readonly_with_deopt(
; CHECK-NEXT:    ret void
;
  call void @removable_ro() [ "deopt"() ]
  ret void
}