llvm/test/Transforms/GVN/invariant-load.ll

; Test if the !invariant.load metadata is maintained by GVN.
; RUN: opt -basicaa -gvn -S < %s | FileCheck %s

define i32 @test1(i32* nocapture %p, i8* nocapture %q) {
; CHECK-LABEL: test1
; CHECK: %x = load i32, i32* %p, align 4, !invariant.load !0
; CHECK-NOT: %y = load
entry:
  %x = load i32, i32* %p, align 4, !invariant.load !0
  %conv = trunc i32 %x to i8
  store i8 %conv, i8* %q, align 1
  %y = load i32, i32* %p, align 4, !invariant.load !0
  %add = add i32 %y, 1
  ret i32 %add
}

define i32 @test2(i32* nocapture %p, i8* nocapture %q) {
; CHECK-LABEL: test2
; CHECK-NOT: !invariant.load
; CHECK-NOT: %y = load
entry:
  %x = load i32, i32* %p, align 4
  %conv = trunc i32 %x to i8
  store i8 %conv, i8* %q, align 1
  %y = load i32, i32* %p, align 4, !invariant.load !0
  %add = add i32 %y, 1
  ret i32 %add
}

; With the invariant.load metadata, what would otherwise
; be a case for PRE becomes a full redundancy.
define i32 @test3(i1 %cnd, i32* %p, i32* %q) {
; CHECK-LABEL: test3
; CHECK-NOT: load
entry:
  %v1 = load i32, i32* %p
  br i1 %cnd, label %bb1, label %bb2

bb1:
  store i32 5, i32* %q
  br label %bb2

bb2:
  %v2 = load i32, i32* %p, !invariant.load !0
  %res = sub i32 %v1, %v2
  ret i32 %res
}

; This test is here to document a case which doesn't optimize
; as well as it could.  
define i32 @test4(i1 %cnd, i32* %p, i32* %q) {
; CHECK-LABEL: test4
; %v2 is redundant, but GVN currently doesn't catch that
entry:
  %v1 = load i32, i32* %p, !invariant.load !0
  br i1 %cnd, label %bb1, label %bb2

bb1:
  store i32 5, i32* %q
  br label %bb2

bb2:
  %v2 = load i32, i32* %p
  %res = sub i32 %v1, %v2
  ret i32 %res
}

!0 = !{ }