[PATCH] Disallow global aliases to bitcast between address spaces

[Eli Friedman]

The test looks a bit weird; can you write it without intentionally
using XFAIL? :)

The code changes look fine.

-Eli

On Wed, Jul 3, 2013 at 1:04 PM, Matt Arsenault
<Matthew.Arsenault at amd.com> wrote:
> 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)*)