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
diff --git a/lib/Analysis/BasicAliasAnalysis.cpp b/lib/Analysis/BasicAliasAnalysis.cpp
index 131b9d6..4bb93ee 100644
--- a/lib/Analysis/BasicAliasAnalysis.cpp
+++ b/lib/Analysis/BasicAliasAnalysis.cpp
@@ -58,12 +58,12 @@
// then it has not escaped before entering the function. Check if it escapes
// inside the function.
if (const Argument *A = dyn_cast<Argument>(V))
- if (A->hasByValAttr() || A->hasNoAliasAttr()) {
- // Don't bother analyzing arguments already known not to escape.
- if (A->hasNoCaptureAttr())
- return true;
+ if (A->hasByValAttr() || A->hasNoAliasAttr())
+ // Note even if the argument is marked nocapture we still need to check
+ // for copies made inside the function. The nocapture attribute only
+ // specifies that there are no copies made that outlive the function.
return !PointerMayBeCaptured(V, false, /*StoreCaptures=*/true);
- }
+
return false;
}
diff --git a/test/Analysis/BasicAA/nocapture.ll b/test/Analysis/BasicAA/nocapture.ll
index a8658ec..ffc0a09 100644
--- a/test/Analysis/BasicAA/nocapture.ll
+++ b/test/Analysis/BasicAA/nocapture.ll
@@ -13,3 +13,24 @@
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
+}