[CodeGen] Generate follow-up metadata for loops with more than one transformation.

Before this patch, CGLoop would dump all transformations for a loop into
a single LoopID without encoding any order in which to apply them.
rL348944 added the possibility to encode a transformation order using
followup-attributes.

When a loop has more than one transformation, use the follow-up
attribute define the order in which they are applied. The emitted order
is the defacto order as defined by the current LLVM pass pipeline,
which is:

  LoopFullUnrollPass
  LoopDistributePass
  LoopVectorizePass
  LoopUnrollAndJamPass
  LoopUnrollPass
  MachinePipeliner

This patch should therefore not change the assembly output, assuming
that all explicit transformations can be applied, and no implicit
transformations in-between. In the former case,
WarnMissedTransformationsPass should emit a warning (except for
MachinePipeliner which is not implemented yet). The latter could be
avoided by adding 'llvm.loop.disable_nonforced' attributes.

Because LoopUnrollAndJamPass processes a loop nest, generation of the
MDNode is delayed to after the inner loop metadata have been processed.
A temporary LoopID is therefore used to annotate instructions and
RAUW'ed by the actual LoopID later.

Differential Revision: https://reviews.llvm.org/D57978

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@357415 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 81 insertions, 3 deletions

diff --git a/lib/CodeGen/CGLoopInfo.h b/lib/CodeGen/CGLoopInfo.h
index 115685ebf2..35d0e00527 100644
--- a/lib/CodeGen/CGLoopInfo.h
+++ b/lib/CodeGen/CGLoopInfo.h
@@ -78,10 +78,11 @@ class LoopInfo {
 public:
   /// Construct a new LoopInfo for the loop with entry Header.
   LoopInfo(llvm::BasicBlock *Header, const LoopAttributes &Attrs,
-           const llvm::DebugLoc &StartLoc, const llvm::DebugLoc &EndLoc);
+           const llvm::DebugLoc &StartLoc, const llvm::DebugLoc &EndLoc,
+           LoopInfo *Parent);
 
   /// Get the loop id metadata for this loop.
-  llvm::MDNode *getLoopID() const { return LoopID; }
+  llvm::MDNode *getLoopID() const { return TempLoopID.get(); }
 
   /// Get the header block of this loop.
   llvm::BasicBlock *getHeader() const { return Header; }
@@ -92,15 +93,92 @@ public:
   /// Return this loop's access group or nullptr if it does not have one.
   llvm::MDNode *getAccessGroup() const { return AccGroup; }
 
+  /// Create the loop's metadata. Must be called after its nested loops have
+  /// been processed.
+  void finish();
+
 private:
   /// Loop ID metadata.
-  llvm::MDNode *LoopID;
+  llvm::TempMDTuple TempLoopID;
   /// Header block of this loop.
   llvm::BasicBlock *Header;
   /// The attributes for this loop.
   LoopAttributes Attrs;
   /// The access group for memory accesses parallel to this loop.
   llvm::MDNode *AccGroup = nullptr;
+  /// Start location of this loop.
+  llvm::DebugLoc StartLoc;
+  /// End location of this loop.
+  llvm::DebugLoc EndLoc;
+  /// The next outer loop, or nullptr if this is the outermost loop.
+  LoopInfo *Parent;
+  /// If this loop has unroll-and-jam metadata, this can be set by the inner
+  /// loop's LoopInfo to set the llvm.loop.unroll_and_jam.followup_inner
+  /// metadata.
+  llvm::MDNode *UnrollAndJamInnerFollowup = nullptr;
+
+  /// Create a LoopID without any transformations.
+  llvm::MDNode *
+  createLoopPropertiesMetadata(llvm::ArrayRef<llvm::Metadata *> LoopProperties);
+
+  /// Create a LoopID for transformations.
+  ///
+  /// The methods call each other in case multiple transformations are applied
+  /// to a loop. The transformation first to be applied will use LoopID of the
+  /// next transformation in its followup attribute.
+  ///
+  /// @param Attrs             The loop's transformations.
+  /// @param LoopProperties    Non-transformation properties such as debug
+  ///                          location, parallel accesses and disabled
+  ///                          transformations. These are added to the returned
+  ///                          LoopID.
+  /// @param HasUserTransforms [out] Set to true if the returned MDNode encodes
+  ///                          at least one transformation.
+  ///
+  /// @return A LoopID (metadata node) that can be used for the llvm.loop
+  ///         annotation or followup-attribute.
+  /// @{
+  llvm::MDNode *
+  createPipeliningMetadata(const LoopAttributes &Attrs,
+                           llvm::ArrayRef<llvm::Metadata *> LoopProperties,
+                           bool &HasUserTransforms);
+  llvm::MDNode *
+  createPartialUnrollMetadata(const LoopAttributes &Attrs,
+                              llvm::ArrayRef<llvm::Metadata *> LoopProperties,
+                              bool &HasUserTransforms);
+  llvm::MDNode *
+  createUnrollAndJamMetadata(const LoopAttributes &Attrs,
+                             llvm::ArrayRef<llvm::Metadata *> LoopProperties,
+                             bool &HasUserTransforms);
+  llvm::MDNode *
+  createLoopVectorizeMetadata(const LoopAttributes &Attrs,
+                              llvm::ArrayRef<llvm::Metadata *> LoopProperties,
+                              bool &HasUserTransforms);
+  llvm::MDNode *
+  createLoopDistributeMetadata(const LoopAttributes &Attrs,
+                               llvm::ArrayRef<llvm::Metadata *> LoopProperties,
+                               bool &HasUserTransforms);
+  llvm::MDNode *
+  createFullUnrollMetadata(const LoopAttributes &Attrs,
+                           llvm::ArrayRef<llvm::Metadata *> LoopProperties,
+                           bool &HasUserTransforms);
+  /// @}
+
+  /// Create a LoopID for this loop, including transformation-unspecific
+  /// metadata such as debug location.
+  ///
+  /// @param Attrs             This loop's attributes and transformations.
+  /// @param LoopProperties    Additional non-transformation properties to add
+  ///                          to the LoopID, such as transformation-specific
+  ///                          metadata that are not covered by @p Attrs.
+  /// @param HasUserTransforms [out] Set to true if the returned MDNode encodes
+  ///                          at least one transformation.
+  ///
+  /// @return A LoopID (metadata node) that can be used for the llvm.loop
+  ///         annotation.
+  llvm::MDNode *createMetadata(const LoopAttributes &Attrs,
+                               llvm::ArrayRef<llvm::Metadata *> LoopProperties,
+                               bool &HasUserTransforms);
 };
 
 /// A stack of loop information corresponding to loop nesting levels.