test/Transforms/EarlyCSE/basic.ll

; RUN: opt < %s -S -early-cse | FileCheck %s
; RUN: opt < %s -S -basicaa -early-cse-memssa | FileCheck %s
; RUN: opt < %s -S -passes=early-cse | FileCheck %s

declare void @llvm.assume(i1) nounwind

; CHECK-LABEL: @test1(
define void @test1(i8 %V, i32 *%P) {
  %A = bitcast i64 42 to double  ;; dead
  %B = add i32 4, 19             ;; constant folds
  store i32 %B, i32* %P
  ; CHECK-NEXT: store i32 23, i32* %P
  
  %C = zext i8 %V to i32
  %D = zext i8 %V to i32  ;; CSE
  store volatile i32 %C, i32* %P
  store volatile i32 %D, i32* %P
  ; CHECK-NEXT: %C = zext i8 %V to i32
  ; CHECK-NEXT: store volatile i32 %C
  ; CHECK-NEXT: store volatile i32 %C
  
  %E = add i32 %C, %C
  %F = add i32 %C, %C
  store volatile i32 %E, i32* %P
  store volatile i32 %F, i32* %P
  ; CHECK-NEXT: %E = add i32 %C, %C
  ; CHECK-NEXT: store volatile i32 %E
  ; CHECK-NEXT: store volatile i32 %E

  %G = add nuw i32 %C, %C
  store volatile i32 %G, i32* %P
  ; CHECK-NEXT: store volatile i32 %E
  ret void
}


;; Simple load value numbering.
; CHECK-LABEL: @test2(
define i32 @test2(i32 *%P) {
  %V1 = load i32, i32* %P
  %V2 = load i32, i32* %P
  %Diff = sub i32 %V1, %V2
  ret i32 %Diff
  ; CHECK: ret i32 0
}

; CHECK-LABEL: @test2a(
define i32 @test2a(i32 *%P, i1 %b) {
  %V1 = load i32, i32* %P
  tail call void @llvm.assume(i1 %b)
  %V2 = load i32, i32* %P
  %Diff = sub i32 %V1, %V2
  ret i32 %Diff
  ; CHECK: ret i32 0
}

;; Cross block load value numbering.
; CHECK-LABEL: @test3(
define i32 @test3(i32 *%P, i1 %Cond) {
  %V1 = load i32, i32* %P
  br i1 %Cond, label %T, label %F
T:
  store i32 4, i32* %P
  ret i32 42
F:
  %V2 = load i32, i32* %P
  %Diff = sub i32 %V1, %V2
  ret i32 %Diff
  ; CHECK: F:
  ; CHECK: ret i32 0
}

; CHECK-LABEL: @test3a(
define i32 @test3a(i32 *%P, i1 %Cond, i1 %b) {
  %V1 = load i32, i32* %P
  br i1 %Cond, label %T, label %F
T:
  store i32 4, i32* %P
  ret i32 42
F:
  tail call void @llvm.assume(i1 %b)
  %V2 = load i32, i32* %P
  %Diff = sub i32 %V1, %V2
  ret i32 %Diff
  ; CHECK: F:
  ; CHECK: ret i32 0
}

;; Cross block load value numbering stops when stores happen.
; CHECK-LABEL: @test4(
define i32 @test4(i32 *%P, i1 %Cond) {
  %V1 = load i32, i32* %P
  br i1 %Cond, label %T, label %F
T:
  ret i32 42
F:
  ; Clobbers V1
  store i32 42, i32* %P
  
  %V2 = load i32, i32* %P
  %Diff = sub i32 %V1, %V2
  ret i32 %Diff
  ; CHECK: F:
  ; CHECK: ret i32 %Diff
}

declare i32 @func(i32 *%P) readonly

;; Simple call CSE'ing.
; CHECK-LABEL: @test5(
define i32 @test5(i32 *%P) {
  %V1 = call i32 @func(i32* %P)
  %V2 = call i32 @func(i32* %P)
  %Diff = sub i32 %V1, %V2
  ret i32 %Diff
  ; CHECK: ret i32 0
}

;; Trivial Store->load forwarding
; CHECK-LABEL: @test6(
define i32 @test6(i32 *%P) {
  store i32 42, i32* %P
  %V1 = load i32, i32* %P
  ret i32 %V1
  ; CHECK: ret i32 42
}

; CHECK-LABEL: @test6a(
define i32 @test6a(i32 *%P, i1 %b) {
  store i32 42, i32* %P
  tail call void @llvm.assume(i1 %b)
  %V1 = load i32, i32* %P
  ret i32 %V1
  ; CHECK: ret i32 42
}

;; Trivial dead store elimination.
; CHECK-LABEL: @test7(
define void @test7(i32 *%P) {
  store i32 42, i32* %P
  store i32 45, i32* %P
  ret void
  ; CHECK-NEXT: store i32 45
  ; CHECK-NEXT: ret void
}

;; Readnone functions aren't invalidated by stores.
; CHECK-LABEL: @test8(
define i32 @test8(i32 *%P) {
  %V1 = call i32 @func(i32* %P) readnone
  store i32 4, i32* %P
  %V2 = call i32 @func(i32* %P) readnone
  %Diff = sub i32 %V1, %V2
  ret i32 %Diff
  ; CHECK: ret i32 0
}

;; Trivial DSE can't be performed across a readonly call.  The call
;; can observe the earlier write.
; CHECK-LABEL: @test9(
define i32 @test9(i32 *%P) {
  store i32 4, i32* %P
  %V1 = call i32 @func(i32* %P) readonly
  store i32 5, i32* %P        
  ret i32 %V1
  ; CHECK: store i32 4, i32* %P        
  ; CHECK-NEXT: %V1 = call i32 @func(i32* %P)
  ; CHECK-NEXT: store i32 5, i32* %P        
  ; CHECK-NEXT: ret i32 %V1
}

;; Trivial DSE can be performed across a readnone call.
; CHECK-LABEL: @test10
define i32 @test10(i32 *%P) {
  store i32 4, i32* %P
  %V1 = call i32 @func(i32* %P) readnone
  store i32 5, i32* %P        
  ret i32 %V1
  ; CHECK-NEXT: %V1 = call i32 @func(i32* %P)
  ; CHECK-NEXT: store i32 5, i32* %P        
  ; CHECK-NEXT: ret i32 %V1
}

;; Trivial dead store elimination - should work for an entire series of dead stores too.
; CHECK-LABEL: @test11(
define void @test11(i32 *%P) {
  store i32 42, i32* %P
  store i32 43, i32* %P
  store i32 44, i32* %P
  store i32 45, i32* %P
  ret void
  ; CHECK-NEXT: store i32 45
  ; CHECK-NEXT: ret void
}

; CHECK-LABEL: @test12(
define i32 @test12(i1 %B, i32* %P1, i32* %P2) {
  %load0 = load i32, i32* %P1
  %1 = load atomic i32, i32* %P2 seq_cst, align 4
  %load1 = load i32, i32* %P1
  %sel = select i1 %B, i32 %load0, i32 %load1
  ret i32 %sel
  ; CHECK: load i32, i32* %P1
  ; CHECK: load i32, i32* %P1
}

define void @dse1(i32 *%P) {
; CHECK-LABEL: @dse1
; CHECK-NOT: store
  %v = load i32, i32* %P
  store i32 %v, i32* %P
  ret void
}

define void @dse2(i32 *%P) {
; CHECK-LABEL: @dse2
; CHECK-NOT: store
  %v = load atomic i32, i32* %P seq_cst, align 4
  store i32 %v, i32* %P
  ret void
}

define void @dse3(i32 *%P) {
; CHECK-LABEL: @dse3
; CHECK-NOT: store
  %v = load atomic i32, i32* %P seq_cst, align 4
  store atomic i32 %v, i32* %P unordered, align 4
  ret void
}

define i32 @dse4(i32 *%P, i32 *%Q) {
; CHECK-LABEL: @dse4
; CHECK-NOT: store
; CHECK: ret i32 0
  %a = load i32, i32* %Q
  %v = load atomic i32, i32* %P unordered, align 4
  store atomic i32 %v, i32* %P unordered, align 4
  %b = load i32, i32* %Q
  %res = sub i32 %a, %b
  ret i32 %res
}

; Note that in this example, %P and %Q could in fact be the same
; pointer.  %v could be different than the value observed for %a
; and that's okay because we're using relaxed memory ordering.  
; The only guarantee we have to provide is that each of the loads 
; has to observe some value written to that location.  We  do 
; not have to respect the order in which those writes were done.  
define i32 @dse5(i32 *%P, i32 *%Q) {
; CHECK-LABEL: @dse5
; CHECK-NOT: store
; CHECK: ret i32 0
  %v = load atomic i32, i32* %P unordered, align 4
  %a = load atomic i32, i32* %Q unordered, align 4
  store atomic i32 %v, i32* %P unordered, align 4
  %b = load atomic i32, i32* %Q unordered, align 4
  %res = sub i32 %a, %b
  ret i32 %res
}


define void @dse_neg1(i32 *%P) {
; CHECK-LABEL: @dse_neg1
; CHECK: store
  %v = load i32, i32* %P
  store i32 5, i32* %P
  ret void
}

; Could remove the store, but only if ordering was somehow
; encoded.
define void @dse_neg2(i32 *%P) {
; CHECK-LABEL: @dse_neg2
; CHECK: store
  %v = load i32, i32* %P
  store atomic i32 %v, i32* %P seq_cst, align 4
  ret void
}

@c = external global i32, align 4
declare i32 @reads_c(i32 returned)
define void @pr28763() {
entry:
; CHECK-LABEL: @pr28763(
; CHECK: store i32 0, i32* @c, align 4
; CHECK: call i32 @reads_c(i32 0)
; CHECK: store i32 2, i32* @c, align 4
  %load = load i32, i32* @c, align 4
  store i32 0, i32* @c, align 4
  %call = call i32 @reads_c(i32 0)
  store i32 2, i32* @c, align 4
  ret void
}