From bc302bfbef84bd778a9e5e0a1b5851c6a55c1d9c Mon Sep 17 00:00:00 2001
From: Joseph Tremoulet <jotrem@microsoft.com>
Date: Fri, 7 May 2021 07:48:18 -0700
Subject: [PATCH] BasicAA: Recognize inttoptr as isEscapeSource

Pointers escape when converted to integers, so a pointer produced by
converting an integer to a pointer must not be a local non-escaping
object.

Reviewed By: nikic, nlopes, aqjune

Differential Revision: https://reviews.llvm.org/D101541
---
 llvm/lib/Analysis/BasicAliasAnalysis.cpp      |  8 +++
 .../test/Analysis/BasicAA/noalias-inttoptr.ll | 60 +++++++++++++++++++
 2 files changed, 68 insertions(+)
 create mode 100644 llvm/test/Analysis/BasicAA/noalias-inttoptr.ll

diff --git a/llvm/lib/Analysis/BasicAliasAnalysis.cpp b/llvm/lib/Analysis/BasicAliasAnalysis.cpp
index 963fb1aa9ca3..dec7fcbfb336 100644
--- a/llvm/lib/Analysis/BasicAliasAnalysis.cpp
+++ b/llvm/lib/Analysis/BasicAliasAnalysis.cpp
@@ -129,6 +129,14 @@ static bool isEscapeSource(const Value *V) {
   if (isa<LoadInst>(V))
     return true;
 
+  // The inttoptr case works because isNonEscapingLocalObject considers all
+  // means of converting or equating a pointer to an int (ptrtoint, ptr store
+  // which could be followed by an integer load, ptr<->int compare) as
+  // escaping, and objects located at well-known addresses via platform-specific
+  // means cannot be considered non-escaping local objects.
+  if (isa<IntToPtrInst>(V))
+    return true;
+
   return false;
 }
 
diff --git a/llvm/test/Analysis/BasicAA/noalias-inttoptr.ll b/llvm/test/Analysis/BasicAA/noalias-inttoptr.ll
new file mode 100644
index 000000000000..ee3fd53875b0
--- /dev/null
+++ b/llvm/test/Analysis/BasicAA/noalias-inttoptr.ll
@@ -0,0 +1,60 @@
+; RUN: opt < %s -basic-aa -aa-eval -print-all-alias-modref-info -disable-output 2>&1 | FileCheck %s
+target datalayout = "p:64:64"
+
+declare void @escape(i8* %ptr)
+
+; Verify that unescaped noalias parameter does not alias inttoptr
+define void @test1(i8* noalias %P, i64 %Q_as_int) {
+  ; CHECK-LABEL: Function: test1:
+  ; CHECK: NoAlias:	i8* %P, i8* %Q
+  %Q = inttoptr i64 %Q_as_int to i8*
+  store i8 0, i8* %P
+  store i8 1, i8* %Q
+  ret void
+}
+
+; Verify that unescaped alloca does not alias inttoptr
+define void @test2(i64 %Q_as_int) {
+  ; CHECK-LABEL: Function: test2:
+  ; CHECK: NoAlias:	i8* %P, i8* %Q
+  %P = alloca i8
+  %Q = inttoptr i64 %Q_as_int to i8*
+  store i8 0, i8* %P
+  store i8 1, i8* %Q
+  ret void
+}
+
+; Verify that escaped noalias parameter may alias inttoptr
+define void @test3(i8* noalias %P, i64 %Q_as_int) {
+  ; CHECK-LABEL: Function: test3:
+  ; CHECK: MayAlias:	i8* %P, i8* %Q
+  call void @escape(i8* %P)
+  %Q = inttoptr i64 %Q_as_int to i8*
+  store i8 0, i8* %P
+  store i8 1, i8* %Q
+  ret void
+}
+
+; Verify that escaped alloca may alias inttoptr
+define void @test4(i64 %Q_as_int) {
+  ; CHECK-LABEL: Function: test4:
+  ; CHECK: MayAlias:	i8* %P, i8* %Q
+  %P = alloca i8
+  call void @escape(i8* %P)
+  %Q = inttoptr i64 %Q_as_int to i8*
+  store i8 0, i8* %P
+  store i8 1, i8* %Q
+  ret void
+}
+
+
+; Verify that global may alias inttoptr
+@G = external global i8
+define void @test5(i64 %Q_as_int) {
+  ; CHECK-LABEL: Function: test5:
+  ; CHECK: MayAlias:	i8* %Q, i8* @G
+  %Q = inttoptr i64 %Q_as_int to i8*
+  store i8 0, i8* @G
+  store i8 1, i8* %Q
+  ret void
+}