[PATCH] Disallow global aliases to bitcast between address spaces

[Matt Arsenault]

Hi eli.friedman,

http://llvm-reviews.chandlerc.com/D1088

Files:
  lib/IR/Verifier.cpp
  test/Bitcode/bitcast-alias-address-space.ll

Index: lib/IR/Verifier.cpp
===================================================================
--- lib/IR/Verifier.cpp
+++ lib/IR/Verifier.cpp
@@ -492,18 +492,29 @@
           "Alias and aliasee types should match!", &GA);
   Assert1(!GA.hasUnnamedAddr(), "Alias cannot have unnamed_addr!", &GA);
 
-  if (!isa<GlobalValue>(GA.getAliasee())) {
-    const ConstantExpr *CE = dyn_cast<ConstantExpr>(GA.getAliasee());
+  Constant *Aliasee = GA.getAliasee();
+
+  if (!isa<GlobalValue>(Aliasee)) {
+    ConstantExpr *CE = dyn_cast<ConstantExpr>(Aliasee);
     Assert1(CE &&
             (CE->getOpcode() == Instruction::BitCast ||
              CE->getOpcode() == Instruction::GetElementPtr) &&
             isa<GlobalValue>(CE->getOperand(0)),
             "Aliasee should be either GlobalValue or bitcast of GlobalValue",
             &GA);
+
+    if (CE->getOpcode() == Instruction::BitCast) {
+      unsigned SrcAS = CE->getOperand(0)->getType()->getPointerAddressSpace();
+      unsigned DstAS = CE->getType()->getPointerAddressSpace();
+
+      Assert1(SrcAS == DstAS,
+              "Alias bitcasts cannot be between different address spaces",
+              &GA);
+    }
   }
 
-  const GlobalValue* Aliasee = GA.resolveAliasedGlobal(/*stopOnWeak*/ false);
-  Assert1(Aliasee,
+  const GlobalValue* Resolved = GA.resolveAliasedGlobal(/*stopOnWeak*/ false);
+  Assert1(Resolved,
           "Aliasing chain should end with function or global variable", &GA);
 
   visitGlobalValue(GA);
Index: test/Bitcode/bitcast-alias-address-space.ll
===================================================================
--- /dev/null
+++ test/Bitcode/bitcast-alias-address-space.ll
@@ -0,0 +1,8 @@
+; XFAIL: *
+; RUN: opt -verify -o - %s | FileCheck %s
+
+target datalayout = "e-p:32:32:32-p1:16:16:16-p2:32:32:32-i1:8:32-i8:8:32-i16:16:32-i32:32:32-i64:32:64-f32:32:32-f64:32:64-v64:32:64-v128:32:128-a0:0:32-n8:16:32"
+
+ at data = addrspace(2) global i32 27
+
+ at illegal_alias_data = alias bitcast (i32 addrspace(2)* @data to i32 addrspace(1)*)
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