[clang][llvm][aarch64][win] Add a clang flag and module attribute for import call optimization, and remove LLVM flag (#122831)

Switches import call optimization from being enabled by an LLVM flag to
instead using a module attribute, and creates a new Clang flag that will
set that attribute. This addresses the concern raised in the original
PR:
<https://github.com/llvm/llvm-project/pull/121516#discussion_r1911763991>

This change also only creates the Called Global info if the module
attribute is present, addressing this concern:
<https://github.com/llvm/llvm-project/pull/122762#pullrequestreview-2547595934>

1 files changed, 5 insertions, 0 deletions

diff --git a/clang/lib/CodeGen/CodeGenModule.cpp b/clang/lib/CodeGen/CodeGenModule.cpp
index a015d64..05879cd 100644
--- a/clang/lib/CodeGen/CodeGenModule.cpp
+++ b/clang/lib/CodeGen/CodeGenModule.cpp
@@ -1293,6 +1293,11 @@ void CodeGenModule::Release() {
   if (LangOpts.EHAsynch)
     getModule().addModuleFlag(llvm::Module::Warning, "eh-asynch", 1);
 
+  // Emit Import Call section.
+  if (CodeGenOpts.ImportCallOptimization)
+    getModule().addModuleFlag(llvm::Module::Warning, "import-call-optimization",
+                              1);
+
   // Indicate whether this Module was compiled with -fopenmp
   if (getLangOpts().OpenMP && !getLangOpts().OpenMPSimd)
     getModule().addModuleFlag(llvm::Module::Max, "openmp", LangOpts.OpenMP);