[flang-commits] [flang] [flang] Enable optimizeEmptyElementals for BufferizeHLFIR pass. (PR #124982)

[Slava Zakharin via flang-commits]

https://github.com/vzakhari created https://github.com/llvm/llvm-project/pull/124982

Enable the option under opt-for-speed. Elementals with shapes
like `(0, HUGE)` should run faster.


>From 825a4c2d62fcac72d420754b30572bdb8e6367b8 Mon Sep 17 00:00:00 2001
From: Slava Zakharin <szakharin at nvidia.com>
Date: Tue, 28 Jan 2025 17:21:03 -0800
Subject: [PATCH] [flang] Enable optimizeEmptyElementals for BufferizeHLFIR
 pass.

Enable the option under opt-for-speed. Elementals with shapes
like `(0, HUGE)` should run faster.
---
 flang/lib/Optimizer/Passes/Pipelines.cpp | 10 +++++++++-
 1 file changed, 9 insertions(+), 1 deletion(-)

diff --git a/flang/lib/Optimizer/Passes/Pipelines.cpp b/flang/lib/Optimizer/Passes/Pipelines.cpp
index 1cc3f0b81c20ad..d55ad9e603ffaf 100644
--- a/flang/lib/Optimizer/Passes/Pipelines.cpp
+++ b/flang/lib/Optimizer/Passes/Pipelines.cpp
@@ -245,7 +245,15 @@ void createHLFIRToFIRPassPipeline(mlir::PassManager &pm, bool enableOpenMP,
   }
   pm.addPass(hlfir::createLowerHLFIROrderedAssignments());
   pm.addPass(hlfir::createLowerHLFIRIntrinsics());
-  pm.addPass(hlfir::createBufferizeHLFIR());
+
+  hlfir::BufferizeHLFIROptions bufferizeOptions;
+  // For opt-for-speed, avoid running any of the loops resulting
+  // from hlfir.elemental lowering, if the result is an empty array.
+  // This helps to avoid long running loops for elementals with
+  // shapes like (0, HUGE).
+  if (optLevel.isOptimizingForSpeed())
+    bufferizeOptions.optimizeEmptyElementals = true;
+  pm.addPass(hlfir::createBufferizeHLFIR(bufferizeOptions));
   // Run hlfir.assign inlining again after BufferizeHLFIR,
   // because the latter may introduce new hlfir.assign operations,
   // e.g. for copying an array into a temporary due to