DI: Reverse direction of subprogram -> function edge.

Previously, subprograms contained a metadata reference to the function they
described. Because most clients need to get or set a subprogram for a given
function rather than the other way around, this created unneeded inefficiency.

For example, many passes needed to call the function llvm::makeSubprogramMap()
to build a mapping from functions to subprograms, and the IR linker needed to
fix up function references in a way that caused quadratic complexity in the IR
linking phase of LTO.

This change reverses the direction of the edge by storing the subprogram as
function-level metadata and removing DISubprogram's function field.

Since this is an IR change, a bitcode upgrade has been provided.

Fixes PR23367. An upgrade script for textual IR for out-of-tree clients is
attached to the PR.

Differential Revision: http://reviews.llvm.org/D14265

llvm-svn: 252219

1 files changed, 8 insertions, 19 deletions

diff --git a/llvm/lib/IR/DebugInfoMetadata.cpp b/llvm/lib/IR/DebugInfoMetadata.cpp
index 7ba51f66b79..cead10652e0 100644
--- a/llvm/lib/IR/DebugInfoMetadata.cpp
+++ b/llvm/lib/IR/DebugInfoMetadata.cpp
@@ -342,34 +342,28 @@ DISubprogram *DISubprogram::getImpl(
     MDString *LinkageName, Metadata *File, unsigned Line, Metadata *Type,
     bool IsLocalToUnit, bool IsDefinition, unsigned ScopeLine,
     Metadata *ContainingType, unsigned Virtuality, unsigned VirtualIndex,
-    unsigned Flags, bool IsOptimized, Metadata *Function,
-    Metadata *TemplateParams, Metadata *Declaration, Metadata *Variables,
-    StorageType Storage, bool ShouldCreate) {
+    unsigned Flags, bool IsOptimized, Metadata *TemplateParams,
+    Metadata *Declaration, Metadata *Variables, StorageType Storage,
+    bool ShouldCreate) {
   assert(isCanonical(Name) && "Expected canonical MDString");
   assert(isCanonical(LinkageName) && "Expected canonical MDString");
   DEFINE_GETIMPL_LOOKUP(DISubprogram,
                         (Scope, getString(Name), getString(LinkageName), File,
                          Line, Type, IsLocalToUnit, IsDefinition, ScopeLine,
                          ContainingType, Virtuality, VirtualIndex, Flags,
-                         IsOptimized, Function, TemplateParams, Declaration,
-                         Variables));
-  Metadata *Ops[] = {File,           Scope,       Name,           Name,
-                     LinkageName,    Type,        ContainingType, Function,
-                     TemplateParams, Declaration, Variables};
+                         IsOptimized, TemplateParams, Declaration, Variables));
+  Metadata *Ops[] = {File,        Scope,    Name,           Name,
+                     LinkageName, Type,     ContainingType, TemplateParams,
+                     Declaration, Variables};
   DEFINE_GETIMPL_STORE(DISubprogram,
                        (Line, ScopeLine, Virtuality, VirtualIndex, Flags,
                         IsLocalToUnit, IsDefinition, IsOptimized),
                        Ops);
 }
 
-Function *DISubprogram::getFunction() const {
-  // FIXME: Should this be looking through bitcasts?
-  return dyn_cast_or_null<Function>(getFunctionConstant());
-}
-
 bool DISubprogram::describes(const Function *F) const {
   assert(F && "Invalid function");
-  if (F == getFunction())
+  if (F->getSubprogram() == this)
     return true;
   StringRef Name = getLinkageName();
   if (Name.empty())
@@ -377,11 +371,6 @@ bool DISubprogram::describes(const Function *F) const {
   return F->getName() == Name;
 }
 
-void DISubprogram::replaceFunction(Function *F) {
-  replaceFunction(F ? ConstantAsMetadata::get(F)
-                    : static_cast<ConstantAsMetadata *>(nullptr));
-}
-
 DILexicalBlock *DILexicalBlock::getImpl(LLVMContext &Context, Metadata *Scope,
                                         Metadata *File, unsigned Line,
                                         unsigned Column, StorageType Storage,