Teach isKnownNonNull that a nonnull return is not null. Add a test for this case as well as the case of a nonnull attribute (already handled but not tested).

llvm-svn: 209193

lib/Analysis/ValueTracking.cpp

@@ -16,6 +16,7 @@
 #include "llvm/ADT/SmallPtrSet.h"
 #include "llvm/Analysis/InstructionSimplify.h"
 #include "llvm/Analysis/MemoryBuiltins.h"
+#include "llvm/IR/CallSite.h"
 #include "llvm/IR/ConstantRange.h"
 #include "llvm/IR/Constants.h"
 #include "llvm/IR/DataLayout.h"
@@ -2073,6 +2074,10 @@ bool llvm::isKnownNonNull(const Value *V, const TargetLibraryInfo *TLI) {
   if (const GlobalValue *GV = dyn_cast<GlobalValue>(V))
     return !GV->hasExternalWeakLinkage();
 
+  if (ImmutableCallSite CS = V)
+    if (CS.paramHasAttr(0, Attribute::NonNull))
+      return true;
+
   // operator new never returns null.
   if (isOperatorNewLikeFn(V, TLI, /*LookThroughBitCast=*/true))
     return true;

test/Transforms/InstSimplify/compare.ll

@@ -866,3 +866,20 @@ define i1 @exact_ashr_sgt_false(i32 %a) {
 ; CHECK-LABEL: @exact_ashr_sgt_false
 ; CHECK-NEXT: ret i1 false
 }
+
+define i1 @nonnull_arg(i32* nonnull %i) {
+  %cmp = icmp eq i32* %i, null
+  ret i1 %cmp
+; CHECK-LABEL: @nonnull_arg
+; CHECK: ret i1 false
+}
+
+declare nonnull i32* @returns_nonnull_helper()
+define i1 @returns_nonnull() {
+  %call = call nonnull i32* @returns_nonnull_helper()
+  %cmp = icmp eq i32* %call, null
+  ret i1 %cmp
+; CHECK-LABEL: @returns_nonnull
+; CHECK: ret i1 false
+}
+