[BasicAA] Handle phi with itself as incoming value

We can skip such incoming values. This was already done by
PhiValues if present, but we can also do this without the
additional analysis.

diff --git a/llvm/lib/Analysis/BasicAliasAnalysis.cpp b/llvm/lib/Analysis/BasicAliasAnalysis.cpp
index 2b552bf..6aad258 100644 (file)
--- a/llvm/lib/Analysis/BasicAliasAnalysis.cpp
+++ b/llvm/lib/Analysis/BasicAliasAnalysis.cpp
@@ -1360,6 +1360,10 @@ AliasResult BasicAAResult::aliasPHI(const PHINode *PN, LocationSize PNSize,
     SmallPtrSet<Value *, 4> UniqueSrc;
     Value *OnePhi = nullptr;
     for (Value *PV1 : PN->incoming_values()) {
+      // Skip the phi itself being the incoming value.
+      if (PV1 == PN)
+        continue;
+
       if (isa<PHINode>(PV1)) {
         if (OnePhi && OnePhi != PV1) {
           // To control potential compile time explosion, we choose to be

diff --git a/llvm/test/Analysis/BasicAA/recphi.ll b/llvm/test/Analysis/BasicAA/recphi.ll
index 4d2fa39..3bf621f 100644 (file)
--- a/llvm/test/Analysis/BasicAA/recphi.ll
+++ b/llvm/test/Analysis/BasicAA/recphi.ll
@@ -413,8 +413,7 @@ exit:
   ret void
 }
 
-; NO-PHI-VALUES: MayAlias: i8* %a, i8* %phi
-; PHI-VALUES: MustAlias: i8* %a, i8* %phi
+; CHECK: MustAlias: i8* %a, i8* %phi
 define void @phi_contains_self() {
 entry:
   %a = alloca i32