[PATCH] D36556: [IR] AutoUpgrade ModuleFlagBehavior for PIC and PIE level

[Steven Wu via Phabricator via llvm-commits]

steven_wu created this revision.

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.


https://reviews.llvm.org/D36556

Files:
  lib/IR/AutoUpgrade.cpp
  test/Bitcode/upgrade-module-flag.ll
  test/Linker/module-flags-pic-1-a.ll


Index: test/Linker/module-flags-pic-1-a.ll
===================================================================
--- test/Linker/module-flags-pic-1-a.ll
+++ test/Linker/module-flags-pic-1-a.ll
@@ -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}
Index: test/Bitcode/upgrade-module-flag.ll
===================================================================
--- test/Bitcode/upgrade-module-flag.ll
+++ test/Bitcode/upgrade-module-flag.ll
@@ -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}
Index: lib/IR/AutoUpgrade.cpp
===================================================================
--- lib/IR/AutoUpgrade.cpp
+++ lib/IR/AutoUpgrade.cpp
@@ -2260,12 +2260,30 @@
   return RetCode;
 }
 
+static bool replaceModuleFlagBehavior(Metadata *M,
+                                      Module::ModFlagBehavior After,
+                                      Module::ModFlagBehavior Before,
+                                      LLVMContext &Context) {
+  auto *MD = dyn_cast<MDNode>(M);
+  assert(MD->getNumOperands() > 2 && "Module Flag need to have at least 3 Ops");
+  if (ConstantInt *Behavior =
+          mdconst::dyn_extract_or_null<ConstantInt>(MD->getOperand(0))) {
+    if (Behavior->getLimitedValue() == Before) {
+      Type *Int32Ty = Type::getInt32Ty(Context);
+      MD->replaceOperandWith(
+          0, ConstantAsMetadata::get(ConstantInt::get(Int32Ty, After)));
+      return true;
+    }
+  }
+  return false;
+}
+
 bool llvm::UpgradeModuleFlags(Module &M) {
   const 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)
@@ -2277,6 +2295,11 @@
       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")
+      Changed |= replaceModuleFlagBehavior(Op, Module::Max, Module::Error,
+                                           M.getContext());
   }
   // "Objective-C Class Properties" is recently added for Objective-C. We
   // upgrade ObjC bitcodes to contain a "Objective-C Class Properties" module
@@ -2286,9 +2309,10 @@
   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) {


-------------- next part --------------
A non-text attachment was scrubbed...
Name: D36556.110489.patch
Type: text/x-patch
Size: 3714 bytes
Desc: not available
URL: <http://lists.llvm.org/pipermail/llvm-commits/attachments/20170809/aa63949c/attachment.bin>