[PATCH] D120079: [OpenMP] Add an option to limit shared memory usage in OpenMPOpt

[Joseph Huber via Phabricator via llvm-commits]

jhuber6 updated this revision to Diff 409766.
jhuber6 added a comment.

Fixing nits


Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D120079/new/

https://reviews.llvm.org/D120079

Files:
  llvm/lib/Transforms/IPO/OpenMPOpt.cpp
  llvm/test/Transforms/OpenMP/replace_globalization.ll


Index: llvm/test/Transforms/OpenMP/replace_globalization.ll
===================================================================
--- llvm/test/Transforms/OpenMP/replace_globalization.ll
+++ llvm/test/Transforms/OpenMP/replace_globalization.ll
@@ -1,6 +1,7 @@
 ; NOTE: Assertions have been autogenerated by utils/update_test_checks.py UTC_ARGS: --function-signature --check-attributes --check-globals --include-generated-funcs
 ; RUN: opt -S -passes='openmp-opt' < %s | FileCheck %s
 ; RUN: opt -passes=openmp-opt -pass-remarks=openmp-opt -disable-output < %s 2>&1 | FileCheck %s -check-prefix=CHECK-REMARKS
+; RUN: opt -passes=openmp-opt -pass-remarks=openmp-opt -pass-remarks-missed=openmp-opt -disable-output -openmp-opt-shared-limit=4 < %s 2>&1 | FileCheck %s -check-prefix=CHECK-LIMIT
 target datalayout = "e-i64:64-i128:128-v16:16-v32:32-n16:32:64"
 target triple = "nvptx64"
 
@@ -8,6 +9,8 @@
 ; CHECK-REMARKS: remark: replace_globalization.c:5:7: Replaced globalized variable with 16 bytes of shared memory
 ; CHECK-REMARKS: remark: replace_globalization.c:5:14: Replaced globalized variable with 4 bytes of shared memory
 ; CHECK-REMARKS-NOT: 6 bytes
+; CHECK-LIMIT: remark: replace_globalization.c:5:14: Replaced globalized variable with 4 bytes of shared memory
+; CHECK-LIMIT: remark: replace_globalization.c:5:7: Found thread data sharing on the GPU. Expect degraded performance due to data globalization
 ; UTC_ARGS: --enable
 
 %struct.ident_t = type { i32, i32, i32, i32, i8* }
Index: llvm/lib/Transforms/IPO/OpenMPOpt.cpp
===================================================================
--- llvm/lib/Transforms/IPO/OpenMPOpt.cpp
+++ llvm/lib/Transforms/IPO/OpenMPOpt.cpp
@@ -129,6 +129,11 @@
                           cl::desc("Maximal number of attributor iterations."),
                           cl::init(256));
 
+static cl::opt<unsigned>
+    SharedMemoryLimit("openmp-opt-shared-limit", cl::Hidden,
+                      cl::desc("Maximum amount of shared memory to use."),
+                      cl::init(std::numeric_limits<unsigned>::max()));
+
 STATISTIC(NumOpenMPRuntimeCallsDeduplicated,
           "Number of OpenMP runtime calls deduplicated");
 STATISTIC(NumOpenMPParallelRegionsDeleted,
@@ -3000,6 +3005,14 @@
 
       auto *AllocSize = cast<ConstantInt>(CB->getArgOperand(0));
 
+      if (AllocSize->getZExtValue() + SharedMemoryUsed > SharedMemoryLimit) {
+        LLVM_DEBUG(dbgs() << TAG << "Cannot replace call " << *CB
+                          << " with shared memory."
+                          << " Shared memory usage is limited to "
+                          << SharedMemoryLimit << " bytes\n");
+        continue;
+      }
+
       LLVM_DEBUG(dbgs() << TAG << "Replace globalization call " << *CB
                         << " with " << AllocSize->getZExtValue()
                         << " bytes of shared memory\n");
@@ -3034,7 +3047,8 @@
       A.deleteAfterManifest(*CB);
       A.deleteAfterManifest(*FreeCalls.front());
 
-      NumBytesMovedToSharedMemory += AllocSize->getZExtValue();
+      SharedMemoryUsed += AllocSize->getZExtValue();
+      NumBytesMovedToSharedMemory = SharedMemoryUsed;
       Changed = ChangeStatus::CHANGED;
     }
 
@@ -3070,6 +3084,8 @@
   SmallSetVector<CallBase *, 4> MallocCalls;
   /// Collection of potentially removed free calls in a function.
   SmallPtrSet<CallBase *, 4> PotentialRemovedFreeCalls;
+  /// The total amount of shared memory that has been used for HeapToShared.
+  unsigned SharedMemoryUsed = 0;
 };
 
 struct AAKernelInfo : public StateWrapper<KernelInfoState, AbstractAttribute> {


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