llvm/test/Transforms/InstCombine/dead-alloc-elim.ll

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

declare noalias ptr @calloc(i32, i32) nounwind allockind("alloc,zeroed") allocsize(0,1) "alloc-family"="malloc"
declare void @free(ptr) allockind("free") "alloc-family"="malloc"

; Test load from uninitialized alloca - should be removed and replaced with undef
define i32 @test_load_uninitialized_alloca() {
; CHECK-LABEL: @test_load_uninitialized_alloca(
; CHECK-NEXT:    ret i32 undef
;
  %a = alloca i32
  %v = load i32, ptr %a
  ret i32 %v
}

; Test load from zero-initialized malloc - should be removed and replaced with zero
define i32 @test_load_zero_initialized_malloc() {
; CHECK-LABEL: @test_load_zero_initialized_malloc(
; CHECK-NEXT:    ret i32 0
;
  %a = call ptr @calloc(i32 1, i32 4)
  %v = load i32, ptr %a
  call void @free(ptr %a)
  ret i32 %v
}

; Test memcpy from uninitialized source - should be removed
define void @test_memcpy_from_uninitialized_alloca(ptr %dest) {
; CHECK-LABEL: @test_memcpy_from_uninitialized_alloca(
; CHECK-NEXT:    ret void
;
  %src = alloca i32, align 1
  call void @llvm.memcpy.p0.p0.i32(ptr %src, ptr %src, i32 4, i1 false)
  call void @llvm.memcpy.p0.p0.i32(ptr %dest, ptr %src, i32 4, i1 false)
  ret void
}

; Test memcpy from zeroed source - should transform to memset with zero
define void @test_memcpy_from_uninitialized_calloc(ptr %dest) {
; CHECK-LABEL: @test_memcpy_from_uninitialized_calloc(
; CHECK-NEXT:    call void @llvm.memset.p0.i32(ptr noundef nonnull align 1 dereferenceable(16) [[DEST:%.*]], i8 0, i32 16, i1 false)
; CHECK-NEXT:    ret void
;
  %src = call ptr @calloc(i32 1, i32 16)
  call void @llvm.memcpy.p0.p0.i32(ptr %dest, ptr %src, i32 16, i1 false)
  call void @free(ptr %src)
  ret void
}

; Test mixed read/write pattern - should not be removable due to write before read
define i32 @test_write_then_read_alloca() {
; CHECK-LABEL: @test_write_then_read_alloca(
; CHECK-NEXT:    [[A:%.*]] = alloca i32, align 4
; CHECK-NEXT:    store i8 42, ptr [[A]], align 1
; CHECK-NEXT:    [[V:%.*]] = load i32, ptr [[A]], align 4
; CHECK-NEXT:    ret i32 [[V]]
;
  %a = alloca i32
  store i8 42, ptr %a
  %v = load i32, ptr %a
  ret i32 %v
}

; Test read then write pattern - should not be removable due to conflicting access
define void @test_read_then_write_alloca() {
; CHECK-LABEL: @test_read_then_write_alloca(
; CHECK-NEXT:    [[A:%.*]] = alloca i32, align 4
; CHECK-NEXT:    [[V:%.*]] = load i32, ptr [[A]], align 4
; CHECK-NEXT:    [[V8:%.*]] = trunc i32 [[V]] to i8
; CHECK-NEXT:    store i8 [[V8]], ptr [[A]], align 1
; CHECK-NEXT:    ret void
;
  %a = alloca i32
  %v = load i32, ptr %a
  %v8 = trunc i32 %v to i8
  store i8 %v8, ptr %a
  ret void
}

; Test load through GEP from uninitialized alloca
define i8 @test_load_gep_uninitialized_alloca() {
; CHECK-LABEL: @test_load_gep_uninitialized_alloca(
; CHECK-NEXT:    ret i8 undef
;
  %a = alloca [4 x i8]
  %gep = getelementptr [4 x i8], ptr %a, i32 0, i32 2
  %v = load i8, ptr %gep
  ret i8 %v
}

; Test load through bitcast from uninitialized alloca
define i16 @test_load_bitcast_uninitialized_alloca() {
; CHECK-LABEL: @test_load_bitcast_uninitialized_alloca(
; CHECK-NEXT:    ret i16 undef
;
  %a = alloca i32
  %bc = bitcast ptr %a to ptr
  %v = load i16, ptr %bc
  ret i16 %v
}

; Test memmove from zero-initialized malloc
define void @test_memmove_from_zero_initialized_malloc(ptr %dest) {
; CHECK-LABEL: @test_memmove_from_zero_initialized_malloc(
; CHECK-NEXT:    call void @llvm.memset.p0.i32(ptr noundef nonnull align 1 dereferenceable(32) [[DEST:%.*]], i8 0, i32 32, i1 false)
; CHECK-NEXT:    ret void
;
  %src = call ptr @calloc(i32 8, i32 4)
  call void @llvm.memmove.p0.p0.i32(ptr %dest, ptr %src, i32 32, i1 false)
  call void @free(ptr %src)
  ret void
}

; Test multiple loads from same uninitialized alloca
define { i32, i32 } @test_multiple_loads_uninitialized_alloca() {
; CHECK-LABEL: @test_multiple_loads_uninitialized_alloca(
; CHECK-NEXT:    ret { i32, i32 } undef
;
  %a = alloca [2 x i32]
  %gep1 = getelementptr [2 x i32], ptr %a, i32 0, i32 0
  %gep2 = getelementptr [2 x i32], ptr %a, i32 0, i32 1
  %v1 = load i32, ptr %gep1
  %v2 = load i32, ptr %gep2
  %ret = insertvalue { i32, i32 } { i32 undef, i32 poison }, i32 %v1, 0
  %ret2 = insertvalue { i32, i32 } %ret, i32 %v2, 1
  ret { i32, i32 } %ret2
}

; Test that volatile operations prevent removal
define i32 @test_volatile_load_prevents_removal() {
; CHECK-LABEL: @test_volatile_load_prevents_removal(
; CHECK-NEXT:    [[A:%.*]] = alloca i32, align 4
; CHECK-NEXT:    [[V:%.*]] = load volatile i32, ptr [[A]], align 4
; CHECK-NEXT:    ret i32 [[V]]
;
  %a = alloca i32
  %v = load volatile i32, ptr %a
  ret i32 %v
}