Don't infer whether a value is captured in the current function from the

'nocapture' attribute.

The nocapture attribute only specifies that no copies are made that
outlive the function. This isn't the same as there being no copies at all.
This fixes PR14045.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@167381 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 21 insertions, 0 deletions

diff --git a/test/Analysis/BasicAA/nocapture.ll b/test/Analysis/BasicAA/nocapture.ll
index a8658ec801..ffc0a09a07 100644
--- a/test/Analysis/BasicAA/nocapture.ll
+++ b/test/Analysis/BasicAA/nocapture.ll
@@ -13,3 +13,24 @@ define i32 @test2() {
        ret i32 %c
 }
 
+declare void @test3(i32** %p, i32* %q) nounwind
+
+define i32 @test4(i32* noalias nocapture %p) nounwind {
+; CHECK: call void @test3
+; CHECK: store i32 0, i32* %p
+; CHECK: store i32 1, i32* %x
+; CHECK: %y = load i32* %p
+; CHECK: ret i32 %y
+entry:
+       %q = alloca i32*
+       ; Here test3 might store %p to %q. This doesn't violate %p's nocapture
+       ; attribute since the copy doesn't outlive the function.
+       call void @test3(i32** %q, i32* %p) nounwind
+       store i32 0, i32* %p
+       %x = load i32** %q
+       ; This store might write to %p and so we can't eliminate the subsequent
+       ; load
+       store i32 1, i32* %x
+       %y = load i32* %p
+       ret i32 %y
+}