[CodeGen] Track DeferredDecls that have been emitted

[junaire]

Summary

If we run into a first usage or definition of a mangled name, and
there's a DeferredDecl that associated with it, we should remember it we
need to emit it later on.

Without this patch, clang-repl hits a JIT symbol not found error:
clang-repl> extern "C" int printf(const char *, ...);
clang-repl> auto l1 = []() { printf("ONE\n"); return 42; };
clang-repl> auto l2 = []() { printf("TWO\n"); return 17; };
clang-repl> auto r1 = l1();
ONE
clang-repl> auto r2 = l2();
TWO
clang-repl> auto r3 = l2();
JIT session error: Symbols not found: [ l2 ]
error: Failed to materialize symbols: { (main,
{ r3, orc_init_func.incr_module_5, $.incr_module_5.inits.0 }) }

[v.g.vassilev]

This looks good to me but let’s add more reviewers.

[junaire]

gentle ping :)

[v.g.vassilev]

Let's move forward with this patch and rely on a post-commit review if necessary.

clang/lib/CodeGen/CodeGenModule.cpp

void CodeGenModule::EmitGlobal(GlobalDecl GD) {
   StringRef MangledName = getMangledName(GD);
   if (GetGlobalValue(MangledName) != nullptr) {
     // The value has already been used and should therefore be emitted.
     addDeferredDeclToEmit(GD);
   } else if (MustBeEmitted(Global)) {
     // The value must be emitted, but cannot be emitted eagerly.
     assert(!MayBeEmittedEagerly(Global));
     addDeferredDeclToEmit(GD);
+    EmittedDeferredDecls[MangledName] = GD;
   } else {
     // Otherwise, remember that we saw a deferred decl with this name.  The
     // first use of the mangled name will cause it to move into
     // DeferredDeclsToEmit.
     DeferredDecls[MangledName] = GD;
   }
 }
 
if (!DontDefer) {
     // deferred decl with this name, remember that we need to emit it at the end
     // of the file.
     auto DDI = DeferredDecls.find(MangledName);
     if (DDI != DeferredDecls.end()) {
       // Move the potentially referenced deferred decl to the
       // DeferredDeclsToEmit list, and remove it from DeferredDecls (since we
       // don't need it anymore).
       addDeferredDeclToEmit(DDI->second);
+      EmittedDeferredDecls[DDI->first] = DDI->second;
       DeferredDecls.erase(DDI);
 
       // Otherwise, there are cases we have to worry about where we're
       // using a declaration for which we must emit a definition but where
       // we might not find a top-level definition:
       //   - member functions defined inline in their classes
       //   - friend functions defined inline in some class
       //   - special member functions with implicit definitions
CodeGenModule::GetOrCreateLLVMGlobal(StringRef MangledName, llvm::Type *Ty,
   // This is the first use or definition of a mangled name.  If there is a
   // deferred decl with this name, remember that we need to emit it at the end
   // of the file.
   auto DDI = DeferredDecls.find(MangledName);
   if (DDI != DeferredDecls.end()) {
     // Move the potentially referenced deferred decl to the DeferredDeclsToEmit
     // list, and remove it from DeferredDecls (since we don't need it anymore).
     addDeferredDeclToEmit(DDI->second);
+    EmittedDeferredDecls[DDI->first] = DDI->second;
     DeferredDecls.erase(DDI);
   }
 
   // Handle things which are present even on external declarations.
   if (D) {
     if (LangOpts.OpenMP && !LangOpts.OpenMPSimd)
       getOpenMPRuntime().registerTargetGlobalVariable(D, GV);
 

clang/test/Interpreter/lambda.cpp

+// RUN: clang-repl "int x = 10;" "int y=7; err;" "int y = 10;"
+// RUN: clang-repl "int i = 10;" 'extern "C" int printf(const char*,...);' \
+// RUN:            'auto r1 = printf("i = %d\n", i);' | FileCheck --check-prefix=CHECK-DRIVER %s
+// REQUIRES: host-supports-jit
+// UNSUPPORTED: system-aix
+// CHECK-DRIVER: i = 10
+// RUN: cat %s | clang-repl | FileCheck %s
+// RUN: cat %s | clang-repl -Xcc -O2 | FileCheck %s
+extern "C" int printf(const char *, ...);
+
+auto l1 = []() { printf("ONE\n"); return 42; };
+auto l2 = []() { printf("TWO\n"); return 17; };
+
+auto r1 = l1();
+// CHECK: ONE
+auto r2 = l2();
+// CHECK: TWO
+auto r3 = l2();
+// CHECK: TWO
+
+%quit