3 files changed, 24 insertions, 6 deletions

diff --git a/llvm/lib/IR/DebugInfo.cpp b/llvm/lib/IR/DebugInfo.cpp
index a2d58fca67a..6bb69bad37a 100644
--- a/llvm/lib/IR/DebugInfo.cpp
+++ b/llvm/lib/IR/DebugInfo.cpp
@@ -47,11 +47,6 @@ void DICompileUnit::replaceGlobalVariables(DIArray GlobalVariables) {
   get()->replaceGlobalVariables(MDGlobalVariableArray(GlobalVariables));
 }
 
-unsigned DILocation::computeNewDiscriminator(LLVMContext &Ctx) {
-  std::pair<const char *, unsigned> Key(getFilename().data(), getLineNumber());
-  return ++Ctx.pImpl->DiscriminatorTable[Key];
-}
-
 DIVariable llvm::createInlinedVariable(MDNode *DV, MDNode *InlinedScope,
                                        LLVMContext &VMContext) {
   return cast<MDLocalVariable>(DV)
diff --git a/llvm/lib/IR/DebugInfoMetadata.cpp b/llvm/lib/IR/DebugInfoMetadata.cpp
index ed6206264b0..1ad09dafa4e 100644
--- a/llvm/lib/IR/DebugInfoMetadata.cpp
+++ b/llvm/lib/IR/DebugInfoMetadata.cpp
@@ -66,6 +66,23 @@ MDLocation *MDLocation::getImpl(LLVMContext &Context, unsigned Line,
                    Storage, Context.pImpl->MDLocations);
 }
 
+unsigned MDLocation::computeNewDiscriminator() const {
+  // FIXME: This seems completely wrong.
+  //
+  //  1. If two modules are generated in the same context, then the second
+  //     Module will get different discriminators than it would have if it were
+  //     generated in its own context.
+  //  2. If this function is called after round-tripping to bitcode instead of
+  //     before, it will give a different (and potentially incorrect!) return.
+  //
+  // The discriminator should instead be calculated from local information
+  // where it's actually needed.  This logic should be moved to
+  // AddDiscriminators::runOnFunction(), where it doesn't pollute the
+  // LLVMContext.
+  std::pair<const char *, unsigned> Key(getFilename().data(), getLine());
+  return ++getContext().pImpl->DiscriminatorTable[Key];
+}
+
 unsigned DebugNode::getFlag(StringRef Flag) {
   return StringSwitch<unsigned>(Flag)
 #define HANDLE_DI_FLAG(ID, NAME) .Case("DIFlag" #NAME, Flag##NAME)
diff --git a/llvm/lib/Transforms/Utils/AddDiscriminators.cpp b/llvm/lib/Transforms/Utils/AddDiscriminators.cpp
index 4197e35f267..2cbe93e30aa 100644
--- a/llvm/lib/Transforms/Utils/AddDiscriminators.cpp
+++ b/llvm/lib/Transforms/Utils/AddDiscriminators.cpp
@@ -195,7 +195,13 @@ bool AddDiscriminators::runOnFunction(Function &F) {
         StringRef Filename = FirstDIL.getFilename();
         DIScope Scope = FirstDIL.getScope();
         DIFile File = Builder.createFile(Filename, Scope.getDirectory());
-        unsigned Discriminator = FirstDIL.computeNewDiscriminator(Ctx);
+
+        // FIXME: Calculate the discriminator here, based on local information,
+        // and delete MDLocation::computeNewDiscriminator().  The current
+        // solution gives different results depending on other modules in the
+        // same context.  All we really need is to discriminate between
+        // FirstDIL and LastDIL -- a local map would suffice.
+        unsigned Discriminator = FirstDIL->computeNewDiscriminator();
         DILexicalBlockFile NewScope =
             Builder.createLexicalBlockFile(Scope, File, Discriminator);
         DILocation NewDIL =