[PATCH] D127892: [LoopIdiom] Set `elementtype` attribute for generated memory intrinsic if required.

[Denis Antrushin via Phabricator via llvm-commits]

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Some garbage collectors require load and/or store barriers when
reading/storing object pointers. The only way to differentiate object
pointer from scalar type of the same size when using memory intrinsics
is `elementtype` attribute. Set it when we created new memcpy call
in function which has GCStrategy requiring barriers.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D127892

Files:
  llvm/include/llvm/IR/GCStrategy.h
  llvm/lib/Transforms/Scalar/LoopIdiomRecognize.cpp


Index: llvm/lib/Transforms/Scalar/LoopIdiomRecognize.cpp
===================================================================
--- llvm/lib/Transforms/Scalar/LoopIdiomRecognize.cpp
+++ llvm/lib/Transforms/Scalar/LoopIdiomRecognize.cpp
@@ -68,6 +68,7 @@
 #include "llvm/IR/DebugLoc.h"
 #include "llvm/IR/DerivedTypes.h"
 #include "llvm/IR/Dominators.h"
+#include "llvm/IR/GCStrategy.h"
 #include "llvm/IR/GlobalValue.h"
 #include "llvm/IR/GlobalVariable.h"
 #include "llvm/IR/IRBuilder.h"
@@ -1503,6 +1504,16 @@
   }
   NewCall->setDebugLoc(TheStore->getDebugLoc());
 
+  const auto *F = TheStore->getFunction();
+  if (F->hasGC())
+    if (auto GC = llvm::getGCStrategy(F->getGC()))
+      if (GC->requiresBarriers()) {
+        LLVMContext &Ctx = NewCall->getContext();
+        Type *ET = TheLoad->getType();
+        NewCall->addParamAttr(0, Attribute::get(Ctx, Attribute::ElementType, ET));
+        NewCall->addParamAttr(1, Attribute::get(Ctx, Attribute::ElementType, ET));
+      }
+
   if (MSSAU) {
     MemoryAccess *NewMemAcc = MSSAU->createMemoryAccessInBB(
         NewCall, nullptr, NewCall->getParent(), MemorySSA::BeforeTerminator);
Index: llvm/include/llvm/IR/GCStrategy.h
===================================================================
--- llvm/include/llvm/IR/GCStrategy.h
+++ llvm/include/llvm/IR/GCStrategy.h
@@ -74,6 +74,10 @@
 
   bool NeededSafePoints = false;    ///< if set, calls are inferred to be safepoints
   bool UsesMetadata = false;     ///< If set, backend must emit metadata tables.
+  bool RequiresLoadBarriers = false; ///< If set, GC requires read barriers on object
+                                     ///  pointer loads
+  bool RequiresStoreBarriers = false; ///< If set, GC requires store barriers on object
+                                      ///  pointer stores.
 
 public:
   GCStrategy();
@@ -87,6 +91,17 @@
   /// and false otherwise.
   bool useStatepoints() const { return UseStatepoints; }
 
+  /// Returns true if GC requires load barriers on object pointers.
+  bool requiresLoadBarriers() const { return RequiresLoadBarriers; }
+
+  /// Returns true if GC requires store barriers on object pointers.
+  bool requiresStoreBarriers() const { return RequiresStoreBarriers; }
+
+  /// Returns true if GC requires load and/or store barriers on object pointers.
+  bool requiresBarriers() const {
+    return RequiresLoadBarriers || RequiresStoreBarriers;
+  }
+
   /** @name Statepoint Specific Properties */
   ///@{
 


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