[IR] Initial introduction of memset_pattern

llvm/docs/LangRef.rst

@@ -15434,6 +15434,63 @@ The behavior of '``llvm.memset.inline.*``' is equivalent to the behavior of
 '``llvm.memset.*``', but the generated code is guaranteed not to call any
 external functions.
 
+.. _int_experimental_memset_pattern:
+
+'``llvm.experimental.memset.pattern``' Intrinsic
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+Syntax:
+"""""""
+
+This is an overloaded intrinsic. You can use
+``llvm.experimental.memset.pattern`` on any integer bit width and for
+different address spaces. Not all targets support all bit widths however.
+
+::
+
+      declare void @llvm.experimental.memset.pattern.p0.i128.i64(ptr <dest>, i128 <val>,
+                                                                 i64 <count>, i1 <isvolatile>)
+
+Overview:
+"""""""""
+
+The '``llvm.experimental.memset.pattern.*``' intrinsics fill a block of memory
+with a particular value. This may be expanded to an inline loop, a sequence of
+stores, or a libcall depending on what is available for the target and the
+expected performance and code size impact.
+
+Arguments:
+""""""""""
+
+The first argument is a pointer to the destination to fill, the second
+is the value with which to fill it, the third argument is an integer
+argument specifying the number of times to fill the value, and the fourth is a
+boolean indicating a volatile access.
+
+The :ref:`align <attr_align>` parameter attribute can be provided
+for the first argument.
+
+If the ``isvolatile`` parameter is ``true``, the
+``llvm.experimental.memset.pattern`` call is a :ref:`volatile operation
+<volatile>`. The detailed access behavior is not very cleanly specified and it
+is unwise to depend on it.
+
+Semantics:
+""""""""""
+
+The '``llvm.experimental.memset.pattern*``' intrinsic fills memory starting at
+the destination location with the given pattern ``<count>`` times,
+incrementing by the allocation size of the type each time. The stores follow
+the usual semantics of store instructions, including regarding endianness and
+padding. If the argument is known to be aligned to some boundary, this can be
+specified as an attribute on the argument.
+
+If ``<count>`` is 0, it is no-op modulo the behavior of attributes attached to
+the arguments.
+If ``<count>`` is not a well-defined value, the behavior is undefined.
+If ``<count>`` is not zero, ``<dest>`` should be well-defined, otherwise the
+behavior is undefined.
+
 .. _int_sqrt:
 
 '``llvm.sqrt.*``' Intrinsic

llvm/include/llvm/IR/InstVisitor.h

@@ -208,6 +208,9 @@ class InstVisitor {
   RetTy visitDbgInfoIntrinsic(DbgInfoIntrinsic &I){ DELEGATE(IntrinsicInst); }
   RetTy visitMemSetInst(MemSetInst &I)            { DELEGATE(MemIntrinsic); }
   RetTy visitMemSetInlineInst(MemSetInlineInst &I){ DELEGATE(MemSetInst); }
+  RetTy visitMemSetPatternInst(MemSetPatternInst &I) {
+    DELEGATE(IntrinsicInst);
+  }
   RetTy visitMemCpyInst(MemCpyInst &I)            { DELEGATE(MemTransferInst); }
   RetTy visitMemCpyInlineInst(MemCpyInlineInst &I){ DELEGATE(MemCpyInst); }
   RetTy visitMemMoveInst(MemMoveInst &I)          { DELEGATE(MemTransferInst); }
@@ -295,6 +298,8 @@ class InstVisitor {
       case Intrinsic::memset:      DELEGATE(MemSetInst);
       case Intrinsic::memset_inline:
         DELEGATE(MemSetInlineInst);
+      case Intrinsic::experimental_memset_pattern:
+        DELEGATE(MemSetPatternInst);
       case Intrinsic::vastart:     DELEGATE(VAStartInst);
       case Intrinsic::vaend:       DELEGATE(VAEndInst);
       case Intrinsic::vacopy:      DELEGATE(VACopyInst);

llvm/include/llvm/IR/IntrinsicInst.h

@@ -1263,6 +1263,41 @@ class MemSetInlineInst : public MemSetInst {
   }
 };
 
+/// This is the base class for llvm.experimental.memset.pattern
+class MemSetPatternIntrinsic : public MemIntrinsicBase<MemIntrinsic> {
+private:
+  enum { ARG_VOLATILE = 3 };
+
+public:
+  ConstantInt *getVolatileCst() const {
+    return cast<ConstantInt>(const_cast<Value *>(getArgOperand(ARG_VOLATILE)));
+  }
+
+  bool isVolatile() const { return !getVolatileCst()->isZero(); }
+
+  void setVolatile(Constant *V) { setArgOperand(ARG_VOLATILE, V); }
+
+  // Methods for support of type inquiry through isa, cast, and dyn_cast:
+  static bool classof(const IntrinsicInst *I) {
+    return I->getIntrinsicID() == Intrinsic::experimental_memset_pattern;
+  }
+  static bool classof(const Value *V) {
+    return isa<IntrinsicInst>(V) && classof(cast<IntrinsicInst>(V));
+  }
+};
+
+/// This class wraps the llvm.experimental.memset.pattern intrinsic.
+class MemSetPatternInst : public MemSetBase<MemSetPatternIntrinsic> {
+public:
+  // Methods for support type inquiry through isa, cast, and dyn_cast:
+  static bool classof(const IntrinsicInst *I) {
+    return I->getIntrinsicID() == Intrinsic::experimental_memset_pattern;
+  }
+  static bool classof(const Value *V) {
+    return isa<IntrinsicInst>(V) && classof(cast<IntrinsicInst>(V));
+  }
+};
+
 /// This class wraps the llvm.memcpy/memmove intrinsics.
 class MemTransferInst : public MemTransferBase<MemIntrinsic> {
 public:

llvm/include/llvm/IR/Intrinsics.td

@@ -1006,6 +1006,17 @@ def int_memset_inline
        NoCapture<ArgIndex<0>>, WriteOnly<ArgIndex<0>>,
        ImmArg<ArgIndex<3>>]>;
 
+// Memset variant that writes a given pattern.
+def int_experimental_memset_pattern
+    : Intrinsic<[],
+      [llvm_anyptr_ty, // Destination.
+       llvm_anyint_ty, // Pattern value.
+       llvm_anyint_ty, // Count (number of times to fill value).
+       llvm_i1_ty],    // IsVolatile.
+      [IntrWriteMem, IntrArgMemOnly, IntrWillReturn, IntrNoFree, IntrNoCallback,
+       NoCapture<ArgIndex<0>>, WriteOnly<ArgIndex<0>>,
+       ImmArg<ArgIndex<3>>]>;
+
 // FIXME: Add version of these floating point intrinsics which allow non-default
 // rounding modes and FP exception handling.
 

llvm/include/llvm/Transforms/Utils/LowerMemIntrinsics.h

@@ -25,6 +25,7 @@ class Instruction;
 class MemCpyInst;
 class MemMoveInst;
 class MemSetInst;
+class MemSetPatternInst;
 class ScalarEvolution;
 class TargetTransformInfo;
 class Value;
@@ -57,6 +58,9 @@ bool expandMemMoveAsLoop(MemMoveInst *MemMove, const TargetTransformInfo &TTI);
 /// Expand \p MemSet as a loop. \p MemSet is not deleted.
 void expandMemSetAsLoop(MemSetInst *MemSet);
 
+/// Expand \p MemSetPattern as a loop. \p MemSet is not deleted.
+void expandMemSetPatternAsLoop(MemSetPatternInst *MemSet);
+
 /// Expand \p AtomicMemCpy as a loop. \p AtomicMemCpy is not deleted.
 void expandAtomicMemCpyAsLoop(AtomicMemCpyInst *AtomicMemCpy,
                               const TargetTransformInfo &TTI,

llvm/lib/CodeGen/PreISelIntrinsicLowering.cpp

@@ -320,6 +320,13 @@ bool PreISelIntrinsicLowering::expandMemIntrinsicUses(Function &F) const {
       Memset->eraseFromParent();
       break;
     }
+    case Intrinsic::experimental_memset_pattern: {
+      auto *Memset = cast<MemSetPatternInst>(Inst);
+      expandMemSetPatternAsLoop(Memset);
+      Changed = true;
+      Memset->eraseFromParent();
+      break;
+    }
     default:
       llvm_unreachable("unhandled intrinsic");
     }
@@ -339,6 +346,7 @@ bool PreISelIntrinsicLowering::lowerIntrinsics(Module &M) const {
     case Intrinsic::memmove:
     case Intrinsic::memset:
     case Intrinsic::memset_inline:
+    case Intrinsic::experimental_memset_pattern:
       Changed |= expandMemIntrinsicUses(F);
       break;
     case Intrinsic::load_relative:

llvm/lib/IR/Verifier.cpp

@@ -5519,7 +5519,8 @@ void Verifier::visitIntrinsicCall(Intrinsic::ID ID, CallBase &Call) {
   case Intrinsic::memcpy_inline:
   case Intrinsic::memmove:
   case Intrinsic::memset:
-  case Intrinsic::memset_inline: {
+  case Intrinsic::memset_inline:
+  case Intrinsic::experimental_memset_pattern: {
     break;
   }
   case Intrinsic::memcpy_element_unordered_atomic:

llvm/lib/Transforms/Utils/LowerMemIntrinsics.cpp

@@ -970,6 +970,15 @@ void llvm::expandMemSetAsLoop(MemSetInst *Memset) {
                    Memset->isVolatile());
 }
 
+void llvm::expandMemSetPatternAsLoop(MemSetPatternInst *Memset) {
+  createMemSetLoop(/* InsertBefore=*/Memset,
+                   /* DstAddr=*/Memset->getRawDest(),
+                   /* CopyLen=*/Memset->getLength(),
+                   /* SetValue=*/Memset->getValue(),
+                   /* Alignment=*/Memset->getDestAlign().valueOrOne(),
+                   Memset->isVolatile());
+}
+
 void llvm::expandAtomicMemCpyAsLoop(AtomicMemCpyInst *AtomicMemcpy,
                                     const TargetTransformInfo &TTI,
                                     ScalarEvolution *SE) {