From 4bf804fe0d352ea5a69beb0962d99c333beabd32 Mon Sep 17 00:00:00 2001
From: Nick Lewycky <nicholas@mxc.ca>
Date: Tue, 20 May 2014 05:13:21 +0000
Subject: 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).

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@209193 91177308-0d34-0410-b5e6-96231b3b80d8
---
 lib/Analysis/ValueTracking.cpp          |  5 +++++
 test/Transforms/InstSimplify/compare.ll | 17 +++++++++++++++++
 2 files changed, 22 insertions(+)

diff --git a/lib/Analysis/ValueTracking.cpp b/lib/Analysis/ValueTracking.cpp
index 280f15b509..4f48753578 100644
--- a/lib/Analysis/ValueTracking.cpp
+++ b/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;
diff --git a/test/Transforms/InstSimplify/compare.ll b/test/Transforms/InstSimplify/compare.ll
index 1a62e27dd8..105e244ed8 100644
--- a/test/Transforms/InstSimplify/compare.ll
+++ b/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
+}
+
-- 
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