[llvm] r279248 - [Hexagon] Consider zext/sext of a load to i32 to be free

[Krzysztof Parzyszek via llvm-commits]

Author: kparzysz
Date: Fri Aug 19 09:22:07 2016
New Revision: 279248

URL: http://llvm.org/viewvc/llvm-project?rev=279248&view=rev
Log:
[Hexagon] Consider zext/sext of a load to i32 to be free

Modified:
    llvm/trunk/lib/Target/Hexagon/HexagonTargetTransformInfo.cpp
    llvm/trunk/lib/Target/Hexagon/HexagonTargetTransformInfo.h

Modified: llvm/trunk/lib/Target/Hexagon/HexagonTargetTransformInfo.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Target/Hexagon/HexagonTargetTransformInfo.cpp?rev=279248&r1=279247&r2=279248&view=diff
==============================================================================
--- llvm/trunk/lib/Target/Hexagon/HexagonTargetTransformInfo.cpp (original)
+++ llvm/trunk/lib/Target/Hexagon/HexagonTargetTransformInfo.cpp Fri Aug 19 09:22:07 2016
@@ -14,6 +14,7 @@
 //===----------------------------------------------------------------------===//
 
 #include "HexagonTargetTransformInfo.h"
+#include "llvm/IR/Instructions.h"
 #include "llvm/Support/Debug.h"
 
 using namespace llvm;
@@ -44,3 +45,27 @@ unsigned HexagonTTIImpl::getPrefetchDist
 unsigned HexagonTTIImpl::getCacheLineSize() const {
   return getST()->getL1CacheLineSize();
 }
+
+int HexagonTTIImpl::getUserCost(const User *U) {
+  auto isCastFoldedIntoLoad = [] (const CastInst *CI) -> bool {
+    if (!CI->isIntegerCast())
+      return false;
+    const LoadInst *LI = dyn_cast<const LoadInst>(CI->getOperand(0));
+    // Technically, this code could allow multiple uses of the load, and
+    // check if all the uses are the same extension operation, but this
+    // should be sufficient for most cases.
+    if (!LI || !LI->hasOneUse())
+      return false;
+
+    // Only extensions from an integer type shorter than 32-bit to i32
+    // can be folded into the load.
+    unsigned SBW = CI->getSrcTy()->getIntegerBitWidth();
+    unsigned DBW = CI->getDestTy()->getIntegerBitWidth();
+    return DBW == 32 && (SBW < DBW);
+  };
+
+  if (const CastInst *CI = dyn_cast<const CastInst>(U))
+    if (isCastFoldedIntoLoad(CI))
+      return TargetTransformInfo::TCC_Free;
+  return BaseT::getUserCost(U);
+}

Modified: llvm/trunk/lib/Target/Hexagon/HexagonTargetTransformInfo.h
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Target/Hexagon/HexagonTargetTransformInfo.h?rev=279248&r1=279247&r2=279248&view=diff
==============================================================================
--- llvm/trunk/lib/Target/Hexagon/HexagonTargetTransformInfo.h (original)
+++ llvm/trunk/lib/Target/Hexagon/HexagonTargetTransformInfo.h Fri Aug 19 09:22:07 2016
@@ -67,6 +67,8 @@ public:
   unsigned getNumberOfRegisters(bool vector) const;
 
   /// @}
+
+  int getUserCost(const User *U);
 };
 
 } // end namespace llvm