[llvm] r311387 - [IR] AutoUpgrade ModuleFlagBehavior for PIC and PIE level

[Hans Wennborg via llvm-commits]

I will merge this to 5.0 once it has baked in the tree a little bit.

On Mon, Aug 21, 2017 at 2:49 PM, Steven Wu via llvm-commits
<llvm-commits at lists.llvm.org> wrote:
> Author: steven_wu
> Date: Mon Aug 21 14:49:13 2017
> New Revision: 311387
>
> URL: http://llvm.org/viewvc/llvm-project?rev=311387&view=rev
> Log:
> [IR] AutoUpgrade ModuleFlagBehavior for PIC and PIE level
>
> Summary:
> From r303590, ModuleFlagBehavior for PIC and PIE level is changed from
> Error to Max. This will cause bitcode compatibility issue when linking
> against a bitcode static archive built with old compiler.
> Add an auto-ugprade path to upgrade the the ModuleFlagBehavior in the
> old bitcode to match the new one so IRLinker can link them.
>
> Reviewers: tejohnson, mehdi_amini, dexonsmith
>
> Reviewed By: dexonsmith
>
> Subscribers: hans, llvm-commits
>
> Differential Revision: https://reviews.llvm.org/D36556
>
> Modified:
>     llvm/trunk/lib/IR/AutoUpgrade.cpp
>     llvm/trunk/test/Bitcode/upgrade-module-flag.ll
>     llvm/trunk/test/Linker/module-flags-pic-1-a.ll
>
> Modified: llvm/trunk/lib/IR/AutoUpgrade.cpp
> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/IR/AutoUpgrade.cpp?rev=311387&r1=311386&r2=311387&view=diff
> ==============================================================================
> --- llvm/trunk/lib/IR/AutoUpgrade.cpp (original)
> +++ llvm/trunk/lib/IR/AutoUpgrade.cpp Mon Aug 21 14:49:13 2017
> @@ -2284,14 +2284,14 @@ bool llvm::UpgradeDebugInfo(Module &M) {
>  }
>
>  bool llvm::UpgradeModuleFlags(Module &M) {
> -  const NamedMDNode *ModFlags = M.getModuleFlagsMetadata();
> +  NamedMDNode *ModFlags = M.getModuleFlagsMetadata();
>    if (!ModFlags)
>      return false;
>
> -  bool HasObjCFlag = false, HasClassProperties = false;
> +  bool HasObjCFlag = false, HasClassProperties = false, Changed = false;
>    for (unsigned I = 0, E = ModFlags->getNumOperands(); I != E; ++I) {
>      MDNode *Op = ModFlags->getOperand(I);
> -    if (Op->getNumOperands() < 2)
> +    if (Op->getNumOperands() != 3)
>        continue;
>      MDString *ID = dyn_cast_or_null<MDString>(Op->getOperand(1));
>      if (!ID)
> @@ -2300,7 +2300,24 @@ bool llvm::UpgradeModuleFlags(Module &M)
>        HasObjCFlag = true;
>      if (ID->getString() == "Objective-C Class Properties")
>        HasClassProperties = true;
> +    // Upgrade PIC/PIE Module Flags. The module flag behavior for these two
> +    // field was Error and now they are Max.
> +    if (ID->getString() == "PIC Level" || ID->getString() == "PIE Level") {
> +      if (auto *Behavior =
> +              mdconst::dyn_extract_or_null<ConstantInt>(Op->getOperand(0))) {
> +        if (Behavior->getLimitedValue() == Module::Error) {
> +          Type *Int32Ty = Type::getInt32Ty(M.getContext());
> +          Metadata *Ops[3] = {
> +              ConstantAsMetadata::get(ConstantInt::get(Int32Ty, Module::Max)),
> +              MDString::get(M.getContext(), ID->getString()),
> +              Op->getOperand(2)};
> +          ModFlags->setOperand(I, MDNode::get(M.getContext(), Ops));
> +          Changed = true;
> +        }
> +      }
> +    }
>    }
> +
>    // "Objective-C Class Properties" is recently added for Objective-C. We
>    // upgrade ObjC bitcodes to contain a "Objective-C Class Properties" module
>    // flag of value 0, so we can correclty downgrade this flag when trying to
> @@ -2309,9 +2326,10 @@ bool llvm::UpgradeModuleFlags(Module &M)
>    if (HasObjCFlag && !HasClassProperties) {
>      M.addModuleFlag(llvm::Module::Override, "Objective-C Class Properties",
>                      (uint32_t)0);
> -    return true;
> +    Changed = true;
>    }
> -  return false;
> +
> +  return Changed;
>  }
>
>  static bool isOldLoopArgument(Metadata *MD) {
>
> Modified: llvm/trunk/test/Bitcode/upgrade-module-flag.ll
> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Bitcode/upgrade-module-flag.ll?rev=311387&r1=311386&r2=311387&view=diff
> ==============================================================================
> --- llvm/trunk/test/Bitcode/upgrade-module-flag.ll (original)
> +++ llvm/trunk/test/Bitcode/upgrade-module-flag.ll Mon Aug 21 14:49:13 2017
> @@ -1,9 +1,13 @@
>  ; RUN: llvm-as < %s | llvm-dis | FileCheck %s
>  ; RUN: verify-uselistorder < %s
>
> -!llvm.module.flags = !{!0}
> +!llvm.module.flags = !{!0, !1, !2}
>
> -!0 = !{i32 1, !"Objective-C Image Info Version", i32 0}
> +!0 = !{i32 1, !"PIC Level", i32 1}
> +!1 = !{i32 1, !"PIE Level", i32 1}
> +!2 = !{i32 1, !"Objective-C Image Info Version", i32 0}
>
> -; CHECK: !0 = !{i32 1, !"Objective-C Image Info Version", i32 0}
> -; CHECK: !1 = !{i32 4, !"Objective-C Class Properties", i32 0}
> +; CHECK: !0 = !{i32 7, !"PIC Level", i32 1}
> +; CHECK: !1 = !{i32 7, !"PIE Level", i32 1}
> +; CHECK: !2 = !{i32 1, !"Objective-C Image Info Version", i32 0}
> +; CHECK: !3 = !{i32 4, !"Objective-C Class Properties", i32 0}
>
> Modified: llvm/trunk/test/Linker/module-flags-pic-1-a.ll
> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Linker/module-flags-pic-1-a.ll?rev=311387&r1=311386&r2=311387&view=diff
> ==============================================================================
> --- llvm/trunk/test/Linker/module-flags-pic-1-a.ll (original)
> +++ llvm/trunk/test/Linker/module-flags-pic-1-a.ll Mon Aug 21 14:49:13 2017
> @@ -2,8 +2,8 @@
>
>  ; test linking modules with specified and default PIC levels
>
> -!0 = !{ i32 1, !"PIC Level", i32 1 }
> +!0 = !{ i32 7, !"PIC Level", i32 1 }
>
>  !llvm.module.flags = !{!0}
>  ; CHECK: !llvm.module.flags = !{!0}
> -; CHECK: !0 = !{i32 1, !"PIC Level", i32 1}
> +; CHECK: !0 = !{i32 7, !"PIC Level", i32 1}
>
>
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