Fix: CFLAA -- Mark no-args returns as unknown

Prior to this patch, we hadn't been marking StratifiedSets with the
appropriate StratifiedAttrs when handling the result of no-args call
instructions. This caused us to report NoAlias when handed, for
example, an escaped alloca and a result from an opaque function. Now we
properly mark the return value of said functions.

Thanks again to Chandler, Richard, and Nick for pinging me about this.

Differential review: http://reviews.llvm.org/D12408

llvm-svn: 246240

1 files changed, 20 insertions, 0 deletions

diff --git a/llvm/test/Analysis/CFLAliasAnalysis/opaque-call-alias.ll b/llvm/test/Analysis/CFLAliasAnalysis/opaque-call-alias.ll
new file mode 100644
index 00000000000..8d602ebb90a
--- /dev/null
+++ b/llvm/test/Analysis/CFLAliasAnalysis/opaque-call-alias.ll
@@ -0,0 +1,20 @@
+; We previously had a case where we would put results from a no-args call in
+; its own stratified set. This would make cases like the one in @test say that
+; nothing (except %Escapes and %Arg) can alias
+
+; RUN: opt < %s -cfl-aa -aa-eval -print-may-aliases -disable-output 2>&1 | FileCheck %s
+
+; CHECK:     Function: test
+; CHECK:     MayAlias: i8* %Arg, i8* %Escapes
+; CHECK:     MayAlias: i8* %Arg, i8* %Retrieved
+; CHECK:     MayAlias: i8* %Escapes, i8* %Retrieved
+define void @test(i8* %Arg) {
+  %Noalias = alloca i8
+  %Escapes = alloca i8
+  call void @set_thepointer(i8* %Escapes)
+  %Retrieved = call i8* @get_thepointer()
+  ret void
+}
+
+declare void @set_thepointer(i8* %P)
+declare i8* @get_thepointer()