[PATCH] D128782: [CodeGen] Keep track of decls that were deferred and have been emitted.

[Jun Zhang via Phabricator via cfe-commits]

junaire created this revision.
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This patch adds a new field called EmittedDeferredDecls in CodeGenModule
that keeps track of decls that were deferred and have been emitted.

The intention of this patch is to solve issues in the incremental c++,
we'll lose info of decls that are lazily emitted when we undo their
usage.

See example below:

clang-repl> inline int foo() { return 42;}
clang-repl> int bar = foo();
clang-repl> %undo
clang-repl> int baz = foo();
JIT session error: Symbols not found: [ _Z3foov ]
error: Failed to materialize symbols: { (main, { baz, $.incr_module_2.__inits.0,
__orc_init_func.incr_module_2 }) }

Signed-off-by: Jun Zhang <jun at junz.org>


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D128782

Files:
  clang/lib/CodeGen/CodeGenModule.cpp
  clang/lib/CodeGen/CodeGenModule.h
  clang/test/Interpreter/code-undo.cpp


Index: clang/test/Interpreter/code-undo.cpp
===================================================================
--- clang/test/Interpreter/code-undo.cpp
+++ clang/test/Interpreter/code-undo.cpp
@@ -20,4 +20,11 @@
 auto r3 = printf("foo() = %d\n", foo());
 // CHECK-NEXT: foo() = 2
 
+inline int bar() { return 42;}
+auto r4 = printf("r4 = %d\n", bar());
+// CHECK-NEXT: r4 = 42
+%undo
+auto r5 = printf("r5 = %d\n", bar());
+// CHECK-NEXT: r5 = 42
+
 %quit
Index: clang/lib/CodeGen/CodeGenModule.h
===================================================================
--- clang/lib/CodeGen/CodeGenModule.h
+++ clang/lib/CodeGen/CodeGenModule.h
@@ -344,6 +344,20 @@
   std::vector<GlobalDecl> DeferredDeclsToEmit;
   void addDeferredDeclToEmit(GlobalDecl GD) {
     DeferredDeclsToEmit.emplace_back(GD);
+    addEmittedDeferredDecl(GD);
+  }
+
+  /// Decls that were DeferredDecls and have now been emitted.
+  llvm::DenseMap<llvm::StringRef, GlobalDecl> EmittedDeferredDecls;
+
+  void addEmittedDeferredDecl(GlobalDecl GD) {
+    if (!llvm::isa<FunctionDecl>(GD.getDecl()))
+      return;
+    llvm::GlobalVariable::LinkageTypes L = getFunctionLinkage(GD);
+    if (llvm::GlobalValue::isLinkOnceLinkage(L) ||
+        llvm::GlobalValue::isWeakLinkage(L)) {
+      EmittedDeferredDecls[getMangledName(GD)] = GD;
+    }
   }
 
   /// List of alias we have emitted. Used to make sure that what they point to
@@ -1516,6 +1530,10 @@
     NewBuilder->WeakRefReferences = std::move(WeakRefReferences);
 
     NewBuilder->TBAA = std::move(TBAA);
+    assert(NewBuilder->EmittedDeferredDecls.empty() &&
+           "Still have (unmerged) EmittedDeferredDecls deferred decls");
+
+    NewBuilder->EmittedDeferredDecls = std::move(EmittedDeferredDecls);
   }
 
 private:
Index: clang/lib/CodeGen/CodeGenModule.cpp
===================================================================
--- clang/lib/CodeGen/CodeGenModule.cpp
+++ clang/lib/CodeGen/CodeGenModule.cpp
@@ -445,6 +445,7 @@
 
 void CodeGenModule::clear() {
   DeferredDeclsToEmit.clear();
+  EmittedDeferredDecls.clear();
   if (OpenMPRuntime)
     OpenMPRuntime->clear();
 }
@@ -510,6 +511,9 @@
 
 void CodeGenModule::Release() {
   EmitDeferred();
+  DeferredDecls.insert(EmittedDeferredDecls.begin(),
+                       EmittedDeferredDecls.end());
+  EmittedDeferredDecls.clear();
   EmitVTablesOpportunistically();
   applyGlobalValReplacements();
   applyReplacements();


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