[Hexagon] Guard the generation of lookup table

The llvm flag "-hexagon-emit-lookup-tables" guards the generation
of lookup table generated from a switch statement.
Differential Revision: https://reviews.llvm.org/D34819

llvm-svn: 306877

2 files changed, 11 insertions, 0 deletions

diff --git a/llvm/lib/Target/Hexagon/HexagonTargetTransformInfo.cpp b/llvm/lib/Target/Hexagon/HexagonTargetTransformInfo.cpp
index 4135d0cec70..aac810e29fe 100644
--- a/llvm/lib/Target/Hexagon/HexagonTargetTransformInfo.cpp
+++ b/llvm/lib/Target/Hexagon/HexagonTargetTransformInfo.cpp
@@ -21,6 +21,10 @@ using namespace llvm;
 
 #define DEBUG_TYPE "hexagontti"
 
+static cl::opt<bool> EmitLookupTables("hexagon-emit-lookup-tables",
+  cl::init(true), cl::Hidden,
+  cl::desc("Control lookup table emission on Hexagon target"));
+
 TargetTransformInfo::PopcntSupportKind
 HexagonTTIImpl::getPopcntSupport(unsigned IntTyWidthInBit) const {
   // Return Fast Hardware support as every input  < 64 bits will be promoted
@@ -70,3 +74,7 @@ int HexagonTTIImpl::getUserCost(const User *U,
       return TargetTransformInfo::TCC_Free;
   return BaseT::getUserCost(U, Operands);
 }
+
+bool HexagonTTIImpl::shouldBuildLookupTables() const {
+   return EmitLookupTables;
+}
diff --git a/llvm/lib/Target/Hexagon/HexagonTargetTransformInfo.h b/llvm/lib/Target/Hexagon/HexagonTargetTransformInfo.h
index f08a2731057..ab5a6e07d87 100644
--- a/llvm/lib/Target/Hexagon/HexagonTargetTransformInfo.h
+++ b/llvm/lib/Target/Hexagon/HexagonTargetTransformInfo.h
@@ -63,6 +63,9 @@ public:
   /// @}
 
   int getUserCost(const User *U, ArrayRef<const Value *> Operands);
+
+  // Hexagon specific decision to generate a lookup table.
+  bool shouldBuildLookupTables() const;
 };
 
 } // end namespace llvm