[Mlir-commits] [llvm] [mlir] [Flang][OpenMP][OpenMPIRBuilder] Implement module scope declare target use rewrite mechanism (PR #212920)

[llvmlistbot at llvm.org]

================
@@ -1051,6 +1054,73 @@ void OpenMPIRBuilder::finalize(Function *Fn) {
 
 bool OpenMPIRBuilder::isFinalized() { return IsFinalized; }
 
+void OpenMPIRBuilder::registerDeclareTargetGlobalReplacement(
+    GlobalValue *Original, GlobalValue *Replacement) {
+  assert(Original && Replacement &&
+         "Null values provided to registerDeclareTargetGlobalReplacement");
+  DeclareTargetGlobalReplacements.push_back({Original, Replacement});
+}
+
+void OpenMPIRBuilder::applyDeclareTargetGlobalReplacements() {
+  for (DeclareTargetGlobalReplacement &R : DeclareTargetGlobalReplacements) {
+    GlobalValue *OldGV = R.Original;
+    GlobalValue *NewGV = R.Replacement;
+    if (!OldGV || !NewGV)
+      continue;
+
+    // The replacement global is a reference pointer that holds the
+    // address of the device-resident storage. Every use must load the
+    // reference pointer first and use the loaded address.
+    //
+    // Constant expression users (e.g. a constant GEP embedded in another
+    // global's initializer or in an instruction) cannot have a load inserted
+    // in place, so first expand any constant-expression users that live inside
+    // functions into instructions. Any remaining constant users are handled
+    // via a direct constant rewrite below as we cannot materialize a load
+    // there.
+    //
+    // NOTE: We extend the constant rewrite to module scope, as we replace all
+    // usages.
+    if (auto *OldConst = dyn_cast<Constant>(OldGV))
+      convertUsersOfConstantsToInstructions(OldConst,
+                                            /*RestrictToFunc=*/nullptr,
+                                            /*RemoveDeadConstants=*/false);
+
+    IRBuilderBase::InsertPointGuard Guard(Builder);
+    SmallVector<User *, 16> Users(OldGV->users());
+    for (User *U : Users) {
+      auto *Insn = dyn_cast<Instruction>(U);
+      if (!Insn)
+        continue;
+
+      Builder.SetInsertPoint(Insn);
----------------
agozillon wrote:

Sounds good, do you have a bit of Flang or MLIR handy that can trigger this, I can likely recreate with the explanation, just a lot easier to make sure I fix the original trigger if you provide it :-)

https://github.com/llvm/llvm-project/pull/212920