From 77a614a6e154fe97d4eb8ea976d95f1aa44cdde2 Mon Sep 17 00:00:00 2001
From: Michael Kruse <llvm@meinersbur.de>
Date: Mon, 11 Feb 2019 19:45:44 +0000
Subject: Refactor setAlreadyUnrolled() and setAlreadyVectorized().

Loop::setAlreadyUnrolled() and
LoopVectorizeHints::setLoopAlreadyUnrolled() both add loop metadata that
stops the same loop from being transformed multiple times. This patch
merges both implementations.

In doing so we fix 3 potential issues:

 * setLoopAlreadyUnrolled() kept the llvm.loop.vectorize/interleave.*
   metadata even though it will not be used anymore. This already caused
   problems such as http://llvm.org/PR40546. Change the behavior to the
   one of setAlreadyUnrolled which deletes this loop metadata.

 * setAlreadyUnrolled() used to create a new LoopID by calling
   MDNode::get with nullptr as the first operand, then replacing it by
   the returned references using replaceOperandWith. It is possible
   that MDNode::get would instead return an existing node (due to
   de-duplication) that then gets modified. To avoid, use a fresh
   TempMDNode that does not get uniqued with anything else before
   replacing it with replaceOperandWith.

 * LoopVectorizeHints::matchesHintMetadataName() only compares the
   suffix of the attribute to set the new value for. That is, when
   called with "enable", would erase attributes such as
   "llvm.loop.unroll.enable", "llvm.loop.vectorize.enable" and
   "llvm.loop.distribute.enable" instead of the one to replace.
   Fortunately, function was only called with "isvectorized".

Differential Revision: https://reviews.llvm.org/D57566

llvm-svn: 353738
---
 .../Vectorize/LoopVectorizationLegality.cpp        | 70 ++++++----------------
 1 file changed, 19 insertions(+), 51 deletions(-)

(limited to 'llvm/lib/Transforms/Vectorize/LoopVectorizationLegality.cpp')

diff --git a/llvm/lib/Transforms/Vectorize/LoopVectorizationLegality.cpp b/llvm/lib/Transforms/Vectorize/LoopVectorizationLegality.cpp
index 60aaa315a3c..1d030944815 100644
--- a/llvm/lib/Transforms/Vectorize/LoopVectorizationLegality.cpp
+++ b/llvm/lib/Transforms/Vectorize/LoopVectorizationLegality.cpp
@@ -104,6 +104,25 @@ LoopVectorizeHints::LoopVectorizeHints(const Loop *L,
              << "LV: Interleaving disabled by the pass manager\n");
 }
 
+void LoopVectorizeHints::setAlreadyVectorized() {
+  LLVMContext &Context = TheLoop->getHeader()->getContext();
+
+  MDNode *IsVectorizedMD = MDNode::get(
+      Context,
+      {MDString::get(Context, "llvm.loop.isvectorized"),
+       ConstantAsMetadata::get(ConstantInt::get(Context, APInt(32, 1)))});
+  MDNode *LoopID = TheLoop->getLoopID();
+  MDNode *NewLoopID =
+      makePostTransformationMetadata(Context, LoopID,
+                                     {Twine(Prefix(), "vectorize.").str(),
+                                      Twine(Prefix(), "interleave.").str()},
+                                     {IsVectorizedMD});
+  TheLoop->setLoopID(NewLoopID);
+
+  // Update internal cache.
+  IsVectorized.Value = 1;
+}
+
 bool LoopVectorizeHints::allowVectorization(
     Function *F, Loop *L, bool VectorizeOnlyWhenForced) const {
   if (getForce() == LoopVectorizeHints::FK_Disabled) {
@@ -231,57 +250,6 @@ void LoopVectorizeHints::setHint(StringRef Name, Metadata *Arg) {
   }
 }
 
-MDNode *LoopVectorizeHints::createHintMetadata(StringRef Name,
-                                               unsigned V) const {
-  LLVMContext &Context = TheLoop->getHeader()->getContext();
-  Metadata *MDs[] = {
-      MDString::get(Context, Name),
-      ConstantAsMetadata::get(ConstantInt::get(Type::getInt32Ty(Context), V))};
-  return MDNode::get(Context, MDs);
-}
-
-bool LoopVectorizeHints::matchesHintMetadataName(MDNode *Node,
-                                                 ArrayRef<Hint> HintTypes) {
-  MDString *Name = dyn_cast<MDString>(Node->getOperand(0));
-  if (!Name)
-    return false;
-
-  for (auto H : HintTypes)
-    if (Name->getString().endswith(H.Name))
-      return true;
-  return false;
-}
-
-void LoopVectorizeHints::writeHintsToMetadata(ArrayRef<Hint> HintTypes) {
-  if (HintTypes.empty())
-    return;
-
-  // Reserve the first element to LoopID (see below).
-  SmallVector<Metadata *, 4> MDs(1);
-  // If the loop already has metadata, then ignore the existing operands.
-  MDNode *LoopID = TheLoop->getLoopID();
-  if (LoopID) {
-    for (unsigned i = 1, ie = LoopID->getNumOperands(); i < ie; ++i) {
-      MDNode *Node = cast<MDNode>(LoopID->getOperand(i));
-      // If node in update list, ignore old value.
-      if (!matchesHintMetadataName(Node, HintTypes))
-        MDs.push_back(Node);
-    }
-  }
-
-  // Now, add the missing hints.
-  for (auto H : HintTypes)
-    MDs.push_back(createHintMetadata(Twine(Prefix(), H.Name).str(), H.Value));
-
-  // Replace current metadata node with new one.
-  LLVMContext &Context = TheLoop->getHeader()->getContext();
-  MDNode *NewLoopID = MDNode::get(Context, MDs);
-  // Set operand 0 to refer to the loop id itself.
-  NewLoopID->replaceOperandWith(0, NewLoopID);
-
-  TheLoop->setLoopID(NewLoopID);
-}
-
 bool LoopVectorizationRequirements::doesNotMeet(
     Function *F, Loop *L, const LoopVectorizeHints &Hints) {
   const char *PassName = Hints.vectorizeAnalysisPassName();
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