Add two new pragmas for controlling software pipelining optimizations.

This patch adds #pragma clang loop pipeline and #pragma clang loop pipeline_initiation_interval for debugging or reducing compile time purposes. It is possible to disable SWP for concrete loops to save compilation time or to find bugs by not doing SWP to certain loops. It is possible to set value of initiation interval to concrete number to save compilation time by not doing extra pipeliner passes or to check created schedule for specific initiation interval.

Patch by Alexey Lapshin.

llvm-svn: 350414

2 files changed, 50 insertions, 2 deletions

diff --git a/clang/lib/CodeGen/CGLoopInfo.cpp b/clang/lib/CodeGen/CGLoopInfo.cpp
index 6cbf801ae61..fd0a9c773a2 100644
--- a/clang/lib/CodeGen/CGLoopInfo.cpp
+++ b/clang/lib/CodeGen/CGLoopInfo.cpp
@@ -25,7 +25,8 @@ static MDNode *createMetadata(LLVMContext &Ctx, const LoopAttributes &Attrs,
 
   if (!Attrs.IsParallel && Attrs.VectorizeWidth == 0 &&
       Attrs.InterleaveCount == 0 && Attrs.UnrollCount == 0 &&
-      Attrs.UnrollAndJamCount == 0 &&
+      Attrs.UnrollAndJamCount == 0 && !Attrs.PipelineDisabled &&
+      Attrs.PipelineInitiationInterval == 0 &&
       Attrs.VectorizeEnable == LoopAttributes::Unspecified &&
       Attrs.UnrollEnable == LoopAttributes::Unspecified &&
       Attrs.UnrollAndJamEnable == LoopAttributes::Unspecified &&
@@ -128,6 +129,22 @@ static MDNode *createMetadata(LLVMContext &Ctx, const LoopAttributes &Attrs,
         Ctx, {MDString::get(Ctx, "llvm.loop.parallel_accesses"), AccGroup}));
   }
 
+  if (Attrs.PipelineDisabled) {
+    Metadata *Vals[] = {
+        MDString::get(Ctx, "llvm.loop.pipeline.disable"),
+        ConstantAsMetadata::get(ConstantInt::get(
+            Type::getInt1Ty(Ctx), (Attrs.PipelineDisabled == true)))};
+    Args.push_back(MDNode::get(Ctx, Vals));
+  }
+
+  if (Attrs.PipelineInitiationInterval > 0) {
+    Metadata *Vals[] = {
+        MDString::get(Ctx, "llvm.loop.pipeline.initiationinterval"),
+        ConstantAsMetadata::get(ConstantInt::get(
+            Type::getInt32Ty(Ctx), Attrs.PipelineInitiationInterval))};
+    Args.push_back(MDNode::get(Ctx, Vals));
+  }
+
   // Set the first operand to itself.
   MDNode *LoopID = MDNode::get(Ctx, Args);
   LoopID->replaceOperandWith(0, LoopID);
@@ -139,7 +156,8 @@ LoopAttributes::LoopAttributes(bool IsParallel)
       UnrollEnable(LoopAttributes::Unspecified),
       UnrollAndJamEnable(LoopAttributes::Unspecified), VectorizeWidth(0),
       InterleaveCount(0), UnrollCount(0), UnrollAndJamCount(0),
-      DistributeEnable(LoopAttributes::Unspecified) {}
+      DistributeEnable(LoopAttributes::Unspecified), PipelineDisabled(false),
+      PipelineInitiationInterval(0) {}
 
 void LoopAttributes::clear() {
   IsParallel = false;
@@ -151,6 +169,8 @@ void LoopAttributes::clear() {
   UnrollEnable = LoopAttributes::Unspecified;
   UnrollAndJamEnable = LoopAttributes::Unspecified;
   DistributeEnable = LoopAttributes::Unspecified;
+  PipelineDisabled = false;
+  PipelineInitiationInterval = 0;
 }
 
 LoopInfo::LoopInfo(BasicBlock *Header, const LoopAttributes &Attrs,
@@ -230,10 +250,14 @@ void LoopInfoStack::push(BasicBlock *Header, clang::ASTContext &Ctx,
       case LoopHintAttr::Distribute:
         setDistributeState(false);
         break;
+      case LoopHintAttr::PipelineDisabled:
+        setPipelineDisabled(true);
+        break;
       case LoopHintAttr::UnrollCount:
       case LoopHintAttr::UnrollAndJamCount:
       case LoopHintAttr::VectorizeWidth:
       case LoopHintAttr::InterleaveCount:
+      case LoopHintAttr::PipelineInitiationInterval:
         llvm_unreachable("Options cannot be disabled.");
         break;
       }
@@ -257,6 +281,8 @@ void LoopInfoStack::push(BasicBlock *Header, clang::ASTContext &Ctx,
       case LoopHintAttr::UnrollAndJamCount:
       case LoopHintAttr::VectorizeWidth:
       case LoopHintAttr::InterleaveCount:
+      case LoopHintAttr::PipelineDisabled:
+      case LoopHintAttr::PipelineInitiationInterval:
         llvm_unreachable("Options cannot enabled.");
         break;
       }
@@ -276,6 +302,8 @@ void LoopInfoStack::push(BasicBlock *Header, clang::ASTContext &Ctx,
       case LoopHintAttr::VectorizeWidth:
       case LoopHintAttr::InterleaveCount:
       case LoopHintAttr::Distribute:
+      case LoopHintAttr::PipelineDisabled:
+      case LoopHintAttr::PipelineInitiationInterval:
         llvm_unreachable("Options cannot be used to assume mem safety.");
         break;
       }
@@ -295,6 +323,8 @@ void LoopInfoStack::push(BasicBlock *Header, clang::ASTContext &Ctx,
       case LoopHintAttr::VectorizeWidth:
       case LoopHintAttr::InterleaveCount:
       case LoopHintAttr::Distribute:
+      case LoopHintAttr::PipelineDisabled:
+      case LoopHintAttr::PipelineInitiationInterval:
         llvm_unreachable("Options cannot be used with 'full' hint.");
         break;
       }
@@ -313,11 +343,15 @@ void LoopInfoStack::push(BasicBlock *Header, clang::ASTContext &Ctx,
       case LoopHintAttr::UnrollAndJamCount:
         setUnrollAndJamCount(ValueInt);
         break;
+      case LoopHintAttr::PipelineInitiationInterval:
+        setPipelineInitiationInterval(ValueInt);
+        break;
       case LoopHintAttr::Unroll:
       case LoopHintAttr::UnrollAndJam:
       case LoopHintAttr::Vectorize:
       case LoopHintAttr::Interleave:
       case LoopHintAttr::Distribute:
+      case LoopHintAttr::PipelineDisabled:
         llvm_unreachable("Options cannot be assigned a value.");
         break;
       }
diff --git a/clang/lib/CodeGen/CGLoopInfo.h b/clang/lib/CodeGen/CGLoopInfo.h
index 201cbb7894b..84ba03bfb00 100644
--- a/clang/lib/CodeGen/CGLoopInfo.h
+++ b/clang/lib/CodeGen/CGLoopInfo.h
@@ -66,6 +66,12 @@ struct LoopAttributes {
 
   /// Value for llvm.loop.distribute.enable metadata.
   LVEnableState DistributeEnable;
+
+  /// Value for llvm.loop.pipeline.disable metadata.
+  bool PipelineDisabled;
+
+  /// Value for llvm.loop.pipeline.iicount metadata.
+  unsigned PipelineInitiationInterval;
 };
 
 /// Information used when generating a structured loop.
@@ -171,6 +177,14 @@ public:
   /// \brief Set the unroll count for the next loop pushed.
   void setUnrollAndJamCount(unsigned C) { StagedAttrs.UnrollAndJamCount = C; }
 
+  /// Set the pipeline disabled state.
+  void setPipelineDisabled(bool S) { StagedAttrs.PipelineDisabled = S; }
+
+  /// Set the pipeline initiation interval.
+  void setPipelineInitiationInterval(unsigned C) {
+    StagedAttrs.PipelineInitiationInterval = C;
+  }
+
 private:
   /// Returns true if there is LoopInfo on the stack.
   bool hasInfo() const { return !Active.empty(); }