DebugInfo: Move DILocation::computeNewDiscriminators()

As documented in PR23200 (and the FIXMEs I've added to the code here),
this logic is fairly broken: it modifies the `LLVMContext` in a way that
affects other modules and cannot be serialized to assembly/bitcode.  For
now, move it over to `MDLocation::computeNewDiscriminators()` anyway.

llvm-svn: 234825

1 files changed, 17 insertions, 0 deletions

diff --git a/llvm/lib/IR/DebugInfoMetadata.cpp b/llvm/lib/IR/DebugInfoMetadata.cpp
index ed62062..1ad09da 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)