[flang-commits] [flang] [flang] Erase `fir.local` ops before lowering `fir` to `llvm` (PR #143687)

[Kareem Ergawy via flang-commits]

https://github.com/ergawy updated https://github.com/llvm/llvm-project/pull/143687

>From b6cdce86b8e62968a82943db776cd06ef68cff80 Mon Sep 17 00:00:00 2001
From: ergawy <kareem.ergawy at amd.com>
Date: Wed, 11 Jun 2025 06:38:14 -0500
Subject: [PATCH 1/2] [flang] Erase `fir.local` ops before lowering `fir` to
 `llvm`

`fir.local` ops are not supposed to have any uses at this point (i.e. during
lowering to LLVM). In case of serialization, the `fir.do_concurrent` users are
expected to have been lowered to `fir.do_loop` nests. In case of parallelization,
the `fir.do_concurrent` users are expected to have been lowered to the target
parallel model (e.g. OpenMP).
---
 flang/lib/Optimizer/CodeGen/CodeGen.cpp | 41 +++++++++++++++++++------
 flang/test/Fir/local.fir                | 10 ++++++
 2 files changed, 42 insertions(+), 9 deletions(-)
 create mode 100644 flang/test/Fir/local.fir

diff --git a/flang/lib/Optimizer/CodeGen/CodeGen.cpp b/flang/lib/Optimizer/CodeGen/CodeGen.cpp
index 82d960a6fc61e..ecce5c6f9d159 100644
--- a/flang/lib/Optimizer/CodeGen/CodeGen.cpp
+++ b/flang/lib/Optimizer/CodeGen/CodeGen.cpp
@@ -3294,6 +3294,29 @@ struct LoadOpConversion : public fir::FIROpConversion<fir::LoadOp> {
   }
 };
 
+struct LocalitySpecifierOpConversion
+    : public fir::FIROpConversion<fir::LocalitySpecifierOp> {
+  using FIROpConversion::FIROpConversion;
+  llvm::LogicalResult
+  matchAndRewrite(fir::LocalitySpecifierOp localizer, OpAdaptor adaptor,
+                  mlir::ConversionPatternRewriter &rewriter) const override {
+    auto uses = mlir::SymbolTable::getSymbolUses(
+        localizer, localizer->getParentOfType<mlir::ModuleOp>());
+
+    // `fir.local` ops are not supposed to have any uses at this point (i.e.
+    // during lowering to LLVM). In case of serialization, the
+    // `fir.do_concurrent` users are expected to have been lowered to
+    // `fir.do_loop` nests. In case of parallelization, the `fir.do_concurrent`
+    // users are expected to have been lowered to the target parallel model
+    // (e.g. OpenMP).
+    if (!uses || !uses->empty())
+      return mlir::failure();
+
+    rewriter.eraseOp(localizer);
+    return mlir::success();
+  }
+};
+
 /// Lower `fir.no_reassoc` to LLVM IR dialect.
 /// TODO: how do we want to enforce this in LLVM-IR? Can we manipulate the fast
 /// math flags?
@@ -4249,15 +4272,15 @@ void fir::populateFIRToLLVMConversionPatterns(
       FieldIndexOpConversion, FirEndOpConversion, FreeMemOpConversion,
       GlobalLenOpConversion, GlobalOpConversion, InsertOnRangeOpConversion,
       IsPresentOpConversion, LenParamIndexOpConversion, LoadOpConversion,
-      MulcOpConversion, NegcOpConversion, NoReassocOpConversion,
-      SelectCaseOpConversion, SelectOpConversion, SelectRankOpConversion,
-      SelectTypeOpConversion, ShapeOpConversion, ShapeShiftOpConversion,
-      ShiftOpConversion, SliceOpConversion, StoreOpConversion,
-      StringLitOpConversion, SubcOpConversion, TypeDescOpConversion,
-      TypeInfoOpConversion, UnboxCharOpConversion, UnboxProcOpConversion,
-      UndefOpConversion, UnreachableOpConversion, XArrayCoorOpConversion,
-      XEmboxOpConversion, XReboxOpConversion, ZeroOpConversion>(converter,
-                                                                options);
+      LocalitySpecifierOpConversion, MulcOpConversion, NegcOpConversion,
+      NoReassocOpConversion, SelectCaseOpConversion, SelectOpConversion,
+      SelectRankOpConversion, SelectTypeOpConversion, ShapeOpConversion,
+      ShapeShiftOpConversion, ShiftOpConversion, SliceOpConversion,
+      StoreOpConversion, StringLitOpConversion, SubcOpConversion,
+      TypeDescOpConversion, TypeInfoOpConversion, UnboxCharOpConversion,
+      UnboxProcOpConversion, UndefOpConversion, UnreachableOpConversion,
+      XArrayCoorOpConversion, XEmboxOpConversion, XReboxOpConversion,
+      ZeroOpConversion>(converter, options);
 
   // Patterns that are populated without a type converter do not trigger
   // target materializations for the operands of the root op.
diff --git a/flang/test/Fir/local.fir b/flang/test/Fir/local.fir
new file mode 100644
index 0000000000000..006f5ca944670
--- /dev/null
+++ b/flang/test/Fir/local.fir
@@ -0,0 +1,10 @@
+// RUN: fir-opt --fir-to-llvm-ir %s | FileCheck %s
+
+// Tests that `fir.local` ops are dropped from the module before LLVM lowering.
+
+fir.local {type = local} @local_privatizer : i32
+func.func @foo() {
+  return
+}
+
+// CHECK-NOT: fir.local

>From 1709ab1360758bbe813e5e7eea4b455def8ecbe4 Mon Sep 17 00:00:00 2001
From: ergawy <kareem.ergawy at amd.com>
Date: Wed, 11 Jun 2025 07:52:18 -0500
Subject: [PATCH 2/2] use expensive_checks

---
 flang/lib/Optimizer/CodeGen/CodeGen.cpp | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/flang/lib/Optimizer/CodeGen/CodeGen.cpp b/flang/lib/Optimizer/CodeGen/CodeGen.cpp
index ecce5c6f9d159..a3de3ae9d116a 100644
--- a/flang/lib/Optimizer/CodeGen/CodeGen.cpp
+++ b/flang/lib/Optimizer/CodeGen/CodeGen.cpp
@@ -3300,6 +3300,7 @@ struct LocalitySpecifierOpConversion
   llvm::LogicalResult
   matchAndRewrite(fir::LocalitySpecifierOp localizer, OpAdaptor adaptor,
                   mlir::ConversionPatternRewriter &rewriter) const override {
+#ifdef EXPENSIVE_CHECKS
     auto uses = mlir::SymbolTable::getSymbolUses(
         localizer, localizer->getParentOfType<mlir::ModuleOp>());
 
@@ -3309,8 +3310,8 @@ struct LocalitySpecifierOpConversion
     // `fir.do_loop` nests. In case of parallelization, the `fir.do_concurrent`
     // users are expected to have been lowered to the target parallel model
     // (e.g. OpenMP).
-    if (!uses || !uses->empty())
-      return mlir::failure();
+    assert(uses && uses->empty());
+#endif
 
     rewriter.eraseOp(localizer);
     return mlir::success();