[PATCH] Enable partial and runtime loop unrolling for NVPTX

[Mark Heffernan]

Hi jholewinski, broune,

Enable partial and runtime loop unrolling for NVPTX backend via
TTI::UnrollingPreferences with a small threshold. This partially unrolls
small loops which are often unrolled by the PTX to SASS compiler
and unrolling earlier can be beneficial.

REPOSITORY
  rL LLVM

http://reviews.llvm.org/D10855

Files:
  lib/Target/NVPTX/NVPTXTargetTransformInfo.cpp
  lib/Target/NVPTX/NVPTXTargetTransformInfo.h

Index: lib/Target/NVPTX/NVPTXTargetTransformInfo.cpp
===================================================================
--- lib/Target/NVPTX/NVPTXTargetTransformInfo.cpp
+++ lib/Target/NVPTX/NVPTXTargetTransformInfo.cpp
@@ -117,3 +117,15 @@
                                          Opd1PropInfo, Opd2PropInfo);
   }
 }
+
+void NVPTXTTIImpl::getUnrollingPreferences(Loop *L,
+                                           TTI::UnrollingPreferences &UP) {
+  BaseT::getUnrollingPreferences(L, UP);
+
+  // Enable partial unrolling and runtime unrolling, but reduce the
+  // threshold.  This partially unrolls small loops which are often
+  // unrolled by the PTX to SASS compiler and unrolling earlier can be
+  // beneficial.
+  UP.Partial = UP.Runtime = true;
+  UP.PartialThreshold = UP.Threshold / 4;
+}
Index: lib/Target/NVPTX/NVPTXTargetTransformInfo.h
===================================================================
--- lib/Target/NVPTX/NVPTXTargetTransformInfo.h
+++ lib/Target/NVPTX/NVPTXTargetTransformInfo.h
@@ -69,6 +69,8 @@
       TTI::OperandValueKind Opd2Info = TTI::OK_AnyValue,
       TTI::OperandValueProperties Opd1PropInfo = TTI::OP_None,
       TTI::OperandValueProperties Opd2PropInfo = TTI::OP_None);
+
+  void getUnrollingPreferences(Loop *L, TTI::UnrollingPreferences &UP);
 };
 
 } // end namespace llvm

EMAIL PREFERENCES
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