[flang-commits] [flang] [mlir] [OpenMP] [MLIR] [Flang] Replace all uses of variables in ALLOCATE directive to use new value which is created. (PR #212361)

[Sairudra More via flang-commits]

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@@ -2437,6 +2439,60 @@ SmallVector<llvm::Value *> ModuleTranslation::lookupValues(ValueRange values) {
   return remapped;
 }
 
+static void remapConstantPointerUses(
+    llvm::Constant *oldPtr, llvm::Value *newPtr, llvm::IRBuilderBase &builder,
+    llvm::DenseMap<llvm::Constant *, llvm::Value *> &replacements) {
+  for (llvm::Use &use : llvm::make_early_inc_range(oldPtr->uses())) {
+    if (auto *constantExpr =
+            llvm::dyn_cast<llvm::ConstantExpr>(use.getUser())) {
+      if (constantExpr->getOpcode() == llvm::Instruction::GetElementPtr) {
+        auto *gep = llvm::cast<llvm::GEPOperator>(constantExpr);
+        llvm::SmallVector<llvm::Value *, 4> indices;
+        for (unsigned i = 1, e = constantExpr->getNumOperands(); i < e; ++i)
+          indices.push_back(constantExpr->getOperand(i));
+        llvm::Value *newGEP =
+            builder.CreateGEP(gep->getSourceElementType(), newPtr, indices);
+        replacements[constantExpr] = newGEP;
+        constantExpr->replaceAllUsesWith(newGEP);
+        continue;
+      }
+      llvm::Instruction *newInst = constantExpr->getAsInstruction();
+      builder.Insert(newInst);
+      replacements[constantExpr] = newInst;
+      constantExpr->replaceAllUsesWith(newInst);
+      continue;
+    }
+    use.set(newPtr);
+  }
+}
+
+void ModuleTranslation::remapAllValuesWith(llvm::Value *oldValue,
+                                           llvm::Value *newValue,
+                                           llvm::IRBuilderBase *builder) {
+  if (oldValue == newValue)
+    return;
+
+  llvm::DenseMap<llvm::Constant *, llvm::Value *> constantReplacements;
+  if (auto *constant = llvm::dyn_cast<llvm::Constant>(oldValue)) {
+    assert(builder &&
+           "IRBuilder required when remapping constant storage pointers");
+    remapConstantPointerUses(constant, newValue, *builder,
+                             constantReplacements);
+  } else {
+    oldValue->replaceAllUsesWith(newValue);
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Saieiei wrote:

`replaceAllUsesWith` also rewrites LLVM users emitted before `omp.allocate_dir`. In a verifier-valid use-before-directive case, this makes an earlier use reference the newly allocated value defined later, producing non-dominating IR. Could this update only the mapping for subsequent translations and add a regression test?

https://github.com/llvm/llvm-project/pull/212361